Specification for Structural Steel Buildings ______

______Specification for Structural Steel Buildings ______

PUBLIC REVIEW DRAFT DATED March 2, 2015

Supersedes the Specification for Structural Steel Buildings dated June 22, 2010 and all previous versions of this specification.

Approved by the AISC Committee on Specifications

AMERICAN INSTITUTE OF STEEL CONSTRUCTION One East Wacker Drive, Suite 700 Chicago, Illinois 60601-1802

American Institute of Steel Construction

The information presented in this publication has been prepared in accordance with recognized engineering principles and is for general information only. While it is believed to be accurate, this information should not be used or relied upon for any specific application without competent professional examination and verification of its accuracy, suitability, and applicability by a licensed professional engineer, designer, or architect. The publication of the material contained herein is not intended as a representation or warranty on the part of the American Institute of Steel Construction or of any other person named herein, that this information is suitable for any general or particular use or of freedom from infringement of any patent or patents. Anyone making use of this information assumes all liability arising from such use.

Caution must be exercised when relying upon other specifications and codes developed by other bodies and incorporated by reference herein since such material may be modified or amended from time to time subsequent to the printing of this edition. The Institute bears no responsibility for such material other than to refer to it and incorporate it by reference at the time of the initial publication of this edition.

Printed in the United States of America

1 Symbols 2 3 Some definitions in the list below have been simplified in the interest of 4 brevity. In all cases, the definitions given in the body of the Specification 5 govern. Symbols without text definitions, used only in one location and 6 defined at that location are omitted in some cases. The section or table 7 number in the righthand column refers to the Section where the symbol is 8 first used. 9 10 Symbol Definition Section 11 2 2 12 ABM Cross-sectional area of the base metal, in. (mm ) ...... J2.4 2 2 13 Ab Nominal unthreaded body area of bolt or threaded part, in. (mm )J3.6 2 2 14 Abi Cross-sectional area of the overlapping branch, in. (mm )Table K3.2 2 2 15 Abj Cross-sectional area of the overlapped branch, in. (mm )Table K3.2 2 2 16 Ac Area of concrete, in. (mm ) ...... I2.1b 2 2 17 Ac Area of concrete slab within effective width, in. (mm ) ...... I3.2d 2 2 18 Ae Effective net area, in. (mm ) ...... D2 19 Ae Summation of the effective areas of the cross section based on the 2 2 20 reduced effective width, be, in. (mm ) ...... E7.2 2 2 21 Afc Area of compression flange, in. (mm ) ...... G3.1 2 2 22 Afg Gross area of tension flange, in. (mm ) ...... F13.1 2 2 23 Afn Net area of tension flange, in. (mm ) ...... F13.1 2 2 24 Aft Area of tension flange, in. (mm ) ...... G3.1 2 2 25 Ag Gross cross-sectional area of member, in. (mm ) ...... B3.3 2 2 26 Ag Gross area of composite member, in. (mm ) ...... I2.1 2 2 27 Agv Gross area subject to shear, in. (mm ) ...... J4.2 2 2 28 An Net area of member, in. (mm ) ...... B4.3 2 2 29 An Area of the directly connected elements, in. (mm ) ...... Table D3.1 2 2 30 Ant Net area subject to tension, in. (mm ) ...... J4.3 2 2 31 Anv Net area subject to shear, in. (mm ) ...... J4.2 2 2 32 Apb Projected area in bearing, in. (mm ) ...... J7 2 2 33 As Cross-sectional area of steel section, in. (mm ) ...... I2.1b 2 2 34 Asa Cross-sectional area of steel headed stud anchor, in. (mm ) ... I8.2a 2 2 35 Asf Area on the shear failure path, in. (mm ) ...... D5.1 2 2 36 Asr Area of continuous reinforcing bars, in. (mm ) ...... I2.1 37 Asr Area of adequately developed longitudinal reinforcing steel within 38 the effective width of the concrete slab, in.2 (mm2) ...... I3.2d 2 2 39 At Net area in tension, in. (mm ) ...... App. 3.4 40 Aw Area of web, the overall depth times the web thickness, dtw, 41 in.2 (mm2) ...... G2.1 2 2 42 Awe Effective area of the weld, in. (mm ) ...... J2.4 2 2 43 A1 Loaded area of concrete, in. (mm ) ...... I6.3a 44 A1 Area of steel concentrically bearing on a concrete support, 45 in.2 (mm2) ...... J8 46 A2 Maximum area of the portion of the supporting surface that is 47 geometrically similar to and concentric with the loaded area, in.2 48 (mm2) ...... J8

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

49 B Overall width of rectangular HSS member, measured 90 to the 50 plane of the connection, in. (mm) ...... Table D3.1 51 Bb Overall width of rectangular HSS branch member or plate, 52 measured 90 to the plane of the connection, in. (mm) ...... K1.1 53 Be Effective width of rectangular HSS branch or plate, measured 90 54 to the plane of the connection, in. (mm)………………………K1.2 55 Bei Effective width of the overlapping branch, in. (mm)...…Table K3.2 56 Bej Effective width of the overlapping branch, in. (mm)...…Table K3.2 57 Bbi Overall width of the overlapping branch, in. (mm) ...... K3.2 58 Bbj Overall width of the overlapped branch, in. (mm) ...... K3.2 59 Bp Width of plate, measured 90 to the plane of the connection, 60 in. (mm) ...... Table K2.2 61 B1 Multiplier to account for P- effects ...... App.8.2 62 B2 Multiplier to account for P- effects ...... App.8.2 63 C HSS torsional constant ...... H3.1 64 Cb Lateral-torsional buckling modification factor for nonuniform 65 moment diagrams ...... F1 66 Cd Coefficient accounting for increased required bracing stiffness at 67 inflection point ...... App. 6.3.1a 68 Cf Constant from Table A-3.1 for the fatigue category ...... App. 3.3 69 Cm Coefficient accounting for non-uniform moment ...... App. 8.2.1 70 Cp Ponding flexibility coefficient for primary member in a 71 flat roof ...... App. 2.1 72 Cr Coefficient for web sidesway buckling ...... J10.4 73 74 Cs Ponding flexibility coefficient for secondary member in a 75 flat roof ...... App. 2.1 76 CvB Web shear buckling coefficient ...... G2.1 77 CvPB Web shear post buckling strength coefficient………………. . ..G2.1 6 6 78 Cw Warping constant, in. (mm ) ...... E4 79 C1 Coefficient for calculation of effective rigidity of encased 80 composite compression member ...... I2.1b 81 C2 Edge distance increment ...... Table J3.5 82 C3 Coefficient for calculation of effective rigidity of filled composite 83 compression member ...... I2.2b 84 D Outside diameter of round HSS, in. (mm) ...... Table B4.1 85 D Outside diameter of round HSS main member, in. (mm) ...... K1.1 86 D Nominal dead load, kips (N) ...... B3.9 87 Db Outside diameter of round HSS branch member, in. (mm) ...... K1.1 88 Du In slip-critical connections, a multiplier that reflects the ratio of the 89 mean installed bolt pretension to the specified minimum bolt 90 pretension ...... J3.8 91 E Modulus of elasticity of steel = 29,000 ksi (200 000 MPa) ...... 92 ...... Table B4.1 1.5 1.5 93 Ec Modulus of elasticity of concrete = wfcc , ksi ( 0.043wfcc , 94 MPa) ...... I2.1b 95 Es Modulus of elasticity of steel = 29,000 ksi (200 000 MPa) ..... I2.1b

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

96 97 2 2 98 EIeff Effective stiffness of composite section, kip-in. (N-mm ) ...... I2.1b 99 Fc Available stress, ksi (MPa) ...... K1.1 100 Fca Available axial stress at the point of consideration, ksi (MPa)..... H2 101 Fcbw,Fcbz Available flexural stress at the point of consideration, ksi (MPa) H2 102 Fcr Critical stress, ksi (MPa) ...... E3 103 Fe Elastic buckling stress, ksi (MPa) ...... E3 104 Fex Flexural elastic buckling stress about the major principal axis, ksi 105 (MPa) ...... E4 106 FEXX Filler metal classification strength, ksi (MPa) ...... J2.4 107 Fey Flexural elastic buckling stress about the major principal axis, ksiE4 108 Fez Torsional elastic buckling stress, ksi (MPa) ...... E4 109 FL Magnitude of flexural stress in compression flange at which flange 110 local buckling or lateral-torsional buckling is influenced by 111 yielding, ksi (MPa) ...... Table B4.1 112 Fn Nominal stress, ksi (MPa)...... H3.3 113 Fn Nominal tensile stress Fnt, or shear stress, Fnv, from Table J3.2, ksi 114 (MPa) ...... J3.6 115 FnBM Nominal stress of the base metal, ksi (MPa) ...... J2.4 116 Fnt Nominal tensile stress from Table J3.2, ksi (MPa) ...... J3.7 117 Fnt Nominal tensile stress modified to include the effects of shear 118 stress, ksi (MPa) ...... J3.7 119 Fnv Nominal shear stress from Table J3.2, ksi (MPa) ...... J3.7 120 Fnw Nominal stress of the weld metal, ksi (MPa) ...... J2.4 121 Fnw Nominal stress of the weld metal (Chapter J) with no increase in 122 strength due to directionality of load, ksi (MPa) ...... K5 123 FSR Allowable stress range, ksi (MPa) ...... App. 3.3 124 FTH Threshold allowable stress range, maximum stress range for 125 indefinite design life from Table A-3.1, ksi (MPa) ...... App. 3.3 126 Fu Specified minimum tensile strength, ksi (MPa) ...... D2 127 Fy Specified minimum yield stress, ksi (MPa). As used in this 128 Specification, “yield stress” denotes either the specified minimum 129 yield point (for those steels that have a yield point) or specified 130 yield strength (for those steels that do not have a yield point) .. B3.3 131 Fyb Specified minimum yield stress of HSS branch member or plate 132 material, ksi (MPa) ...... K1.1 133 Fybi Specified minimum yield stress of the overlapping branch material, 134 ksi (MPa) ...... Table K3.2 135 Fybj Specified minimum yield stress of the overlapped branch material, 136 ksi (MPa) ...... Table K3.2 137 Fyf Specified minimum yield stress of the flange, ksi (MPa) ...... J10.1 138 Fyp Specified minimum yield stress of plate, ksi (MPa) ...... Table K2.2 139 Fysr Specified minimum yield stress of reinforcing bars, ksi (MPa) I2.1b 140 Fyst Specified minimum yield stress of the stiffener material, ksi 141 (MPa) ...... G3.2 142 Fyw Specified minimum yield stress of the web material, ksi (MPa)G3.2 143 G Shear modulus of elasticity of steel = 11,200 ksi (77 200 MPa) .. E4

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

144 H Flexural constant ...... E4 145 H Story shear, in the direction of translation being considered, 146 produced by the lateral forces used to compute H, kips (N) 147 ...... App. 8.2.2 148 H Overall height of rectangular HSS member, measured in the plane 149 of the connection, in. (mm) ...... Table D3.1 150 Hb Overall height of rectangular HSS branch member, measured in the 151 plane of the connection, in. (mm) ...... K1.1 152 Hbi Overall depth of the overlapping branch, in. (mm) ...... Table K3.2 153 I Moment of inertia, in.4 (mm4) ...... App. 8.2.1 154 Ic Moment of inertia of the concrete section about the elastic neutral 155 axis of the composite section, in.4 (mm4) ...... I2.1b 156 Id Moment of inertia of the steel deck supported on secondary 157 members, in.4 (mm4) ...... App. 2.1 4 4 158 Ip Moment of inertia of primary members, in. (mm ) ...... App. 2.1 4 4 159 Is Moment of inertia of secondary members, in. (mm ) ...... App. 2.1 160 Is Moment of inertia of steel shape about the elastic neutral axis of 161 the composite section, in.4 (mm4) ...... I2.1b 162 Isr Moment of inertia of reinforcing bars about the elastic neutral axis 163 of the composite section, in.4 (mm4) ...... I2.1b 164 Ist Moment of inertia of transverse stiffeners about an axis in the web 165 center for stiffener pairs, or about the face in contact with the web 166 plate for single stiffeners, in.4 (mm4) ...... G2.2 167 Ist1 Minimum moment of inertia of transverse stiffeners required for 168 development of the full web shear resistance without tension field 169 action in Section G2.2, in.4 (mm4) ...... G3.2 170 Ist2 Minimum moment of inertia of transverse stiffeners required for 171 development of the full tension field resistance of the stiffened web 4 4 172 panels, Vr = Vc2, in. (mm ) ...... G3.2 4 4 173 Ix, Iy Moment of inertia about the principal axes, in. (mm ) ...... E4 174 4 4 175 Iyeff Effective out-of-plane moment of inertia, in. (mm )… App. 6.3.2a 4 176 Iyc Moment of inertia of the compression flange about the y-axis, in. 177 (mm4) ...... F4.2 4 4 178 Iyt Moment of inertia of the tension flange about the y-axis, in. (mm ) 179 ...... App. 6.3.2a 4 4 180 Iz Minor principal axis moment of inertia, in. (mm ) ...... F10.2 181 J Torsional constant, in.4 (mm4) ...... E4 182 K Effective length factor ...... E2 183 Kx Effective length factor for flexural buckling about x-axis ...... E4 184 Ky Effective length factor for flexural buckling about y-axis ...... E4 185 Kz Effective length factor for torsional buckling ...... E4 186 Lc1 Effective length in the plane of bending, calculated based on the 187 assumption of no lateral translation at the member ends, set equal 188 to the member’s unbraced length unless analysis justifies a smaller 189 value, in. (mm) ...... App. 8.2.1 190 L Height of story, in. (mm) ...... App. 7.3.2 191 L Length of member, in. (mm)...... H3.1

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

192 L Nominal occupancy live load ...... B3.9 193 L Laterally unbraced length of member, in. (mm) ...... E2 194 L Length of span, in. (mm) ...... App. 6.3.2a 195 L Length of member between work points at truss chord centerlines, 196 in. (mm) ...... E5 197 Lb Length between points that are either braced against lateral 198 displacement of compression flange or braced against twist of the 199 cross section, in. (mm) ...... F2.2 200 Lb Distance between braces, in. (mm) ...... App. 6.1 201 Lb Largest laterally unbraced length along either flange at the point of 202 load, in. (mm) ...... J10.4 203 Lbr Flange unbraced length, in. (mm)……………..………….App. 6.1 204 Lm Limiting laterally unbraced length for eligibility for moment 205 redistribution in beams ...... F13.5 206 Lp Limiting laterally unbraced length for the limit state of yielding, in. 207 (mm) ...... F2.2 208 Lp Length of primary members, ft (m) ...... App. 2.1 209 Lpd Limiting laterally unbraced length for plastic analysis, in. 210 (mm) ...... App. 1.2.2c 211 Lr Limiting laterally unbraced length for the limit state of inelastic 212 lateral-torsional buckling, in. (mm) ...... F2.2 213 Ls Length of secondary members, ft (m) ...... App. 2.1 214 Lv Distance from maximum to zero shear force, in. (mm) ...... G6 215 MA Absolute value of moment at quarter point of the unbraced 216 segment, kip-in. (N-mm) ...... F1 217 Ma Required flexural strength using ASD load combinations, kip-in. 218 (N-mm) ...... J10.4 219 MB Absolute value of moment at centerline of the unbraced segment, 220 kip-in. (N-mm) ...... F1 221 MC Absolute value of moment at three-quarter point of the unbraced 222 segment, kip-in. (N-mm) ...... F1 223 Mcx,Mcy Available flexural strength determined in accordance with Chapter 224 F, kip-in. (N-mm) ...... H1.1 225 Mcx Available lateral-torsional strength for strong axis flexure 226 determined in accordance with Chapter F using Cb = 1.0, kip-in. 227 (N-mm) ...... H1.1 228 Mcx Available flexural strength about the x-axis for the limit state of 229 tensile rupture of the flange, kip-in. (N-mm) ...... H4 230 Mlt First-order moment using LRFD or ASD load combinations, due to 231 lateral translation of the structure only, kip-in. (N-mm) App. 8.2 232 Mmax Absolute value of maximum moment in the unbraced segment, 233 kip-in. (N-mm) ...... F1 234 Mmid Moment at the middle of the unbraced length, kip-in. (N-mm) 235 ...... App. 1.2.2c 236 Mn Nominal flexural strength, kip-in. (N-mm) ...... F1

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

237 Mn-ip Nominal flexural strength for in-plane bending Table K4.1

238 Mn-op Nominal flexural strength for out-of-plane bending Table K4.1

239 Mnt First-order moment using LRFD or ASD load combinations, with 240 the structure restrained against lateral translation, kip-in. (N-mm) ... 241 ...... App. 8.2 242 Mp Plastic flexural strength, kip-in. (N-mm) ...... Table B4.1 243 Mp Moment corresponding to plastic stress distribution over the 244 composite cross-section, kip-in. (N-mm) ...... I3.4b 245 Mr Required second-order flexural strength under LRFD or ASD load 246 combinations, kip-in. (N-mm) ...... App. 8.2 247 Mr Required flexural strength using LRFD or ASD load combinations, 248 kip-in. (N-mm) ...... H1.1 249 Mr Required flexural strength of the beam within the panel under 250 consideration using LRFD or ASD load combinations, kip-in. (N- 251 mm) ...... App. 6.3.1a 252 Mr Largest of the required flexural strengths of the beam within the 253 unbraced lengths adjacent to the point brace using LRFD or ASD 254 load combinations, kip-in. (N-mm)…………………….App. 6.3.1b 255 Mbr Required flexural strength of the brace, kip-in. (N-mm) App. 6.3.2a 256 Mro Required flexural strength in chord at a joint, on the side of joint 257 with lower compression stress, kips (N) ...... Table K2.1 258 Mr-ip Required in-plane flexural strength in branch using LRFD or ASD 259 load combinations, kip-in. (N-mm) ...... Table K4.1 260 Mr-op Required out-of-plane flexural strength in branch using LRFD or 261 ASD load combinations, kip-in. (N-mm) ...... Table K4.1 262 Mrx,Mry Required flexural strength, kip-in. (N-mm) ...... H1.1 263 Mrx Required flexural strength at the location of the bolt holes; positive 264 for tension in the flange under consideration, negative for 265 compression, kip-in. (N-mm) ...... H4 266 Mu Required flexural strength using LRFD load combinations, kip-in. 267 (N-mm) ...... J10.4 268 My Moment at yielding of the extreme fiber, kip-in. (N-mm)Table B4.1 269 My Yield moment about the axis of bending, kip-in. (N-mm) ...... F9.1 270 Myc Moment at yielding of the extreme fiber in the compression flange, 271 kip-in. (N-mm) ...... F4.2 272 Myt Moment at yielding of the extreme fiber in the tension flange, kip- 273 in. (N-mm) ...... F4.4 274 M1 Effective moment at the end of the unbraced length opposite from 275 M2, kip-in. (N-mm) ...... App. 1.2.2b 276 M1 Smaller moment at end of unbraced length, kip-in. 277 (N-mm) ...... F13.5 278 M2 Larger moment at end of unbraced length, kip-in. 279 (N-mm) ...... F13.5 280 Ni Notional load applied at level i, kips (N) ...... C2.2b 281 Ni Additional lateral load, kips (N) ...... App. 7.3.2 282 Ov Overlap connection coefficient ...... K3.1 283 Pa Required axial strength in chord using ASD load combinations,

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

284 kips (N) ...... Table K2.1 285 Pc Available axial strength, kips (N) ...... H1.1 286 Pcy Available axial compressive strength out of the plane of bending, 287 kips (N) ...... H1.1 288 Pe Elastic critical buckling load determined in accordance with 289 Chapter C or Appendix 7, kips (N) ...... I2.1b 290 Pns Nominal cross-section compressive strength, kips (N)…...... C2.3 291 Pe story Elastic critical buckling strength for the story in the direction of 292 translation being considered, kips (N) ...... App 8.2.2 293 Pey Elastic critical buckling load for buckling about the weak axis, kips 294 (kN) ...... H1.2 295 Pe1 Elastic critical buckling strength of the member in the plane of 296 bending, kips (N) ...... App. 8.2.1 297 Plt First-order axial force using LRFD or ASD load combinations, due 298 to lateral translation of the structure only, kips (N) ...... App. 8.2 299 Pmf Total vertical load in columns in the story that are part of moment 300 frames, if any, in the direction of translation being considered, kips 301 (N) ...... App. 8.2.2 302 Pn Nominal axial strength, kips (N) ...... D2 303 Pn Nominal axial compressive strength, kips (N)...... E1 304 Pno Nominal axial compressive strength of zero length, doubly 305 symmetric, axially loaded composite member, kips (N) ...... I2.1b 306 Pnt First-order axial force using LRFD and ASD load combinations, 307 with the structure restrained against lateral translation, 308 kips (N) ...... App. 8.2 309 Pp Nominal bearing strength, kips (N) ...... J8 310 Pr Required second-order axial strength using LRFD or ASD load 311 combinations, kips (N) ...... App. 8.2 312 Pr Required axial compressive strength using LRFD or ASD load 313 combinations, kips (N) ...... C2.3 314 Pr Required axial strength using LRFD or ASD load combinations, 315 kips (N) ...... H1.1 316 Pr Required axial strength of the member at the location of the bolt 317 holes; positive in tension, negative in compression, kips (N) ...... H4 318 Pr required external force applied to the composite member, kips 319 (N) ...... I6.2a 320 Pbr Required end and intermediate point brace strength using LRFD or 321 ASD load combinations, kips (N) ...... App. 6.2.2 322 Pro Required axial strength in chord at a joint, on the side of joint with 323 lower compression stress, kips (N) ...... Table K2.1 324 Pstory Total vertical load supported by the story using LRFD or ASD 325 load combinations, as applicable, including loads in columns that 326 are not part of the lateral force resisting system, kips (N) App. 8.2.2 327 Pu Required axial strength in chord using LRFD load combinations, 328 kips (N) ...... Table K2.1 329 Pu Required axial strength using LRFD load combinations, 330 kips (N) ...... App. 1.2.2b 331 Qct Available tensile strength, kips (N) ...... I8.3c

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

332 Qcv Available shear strength, kips (N) ...... I8.3c 333 Qf Chord-stress interaction parameter ...... Table K2.1 334 Qg Gapped truss joint parameter accounting for geometric effects 335 ...... Table K3.1 336 Qn Nominal strength of one steel headed stud or steel channel 337 connector, kips (N) ...... I3.2d 338 Qnt Nominal tensile strength of steel headed stud anchor, kips (N) I8.3b 339 Qnv Nominal shear strength of steel headed stud anchor, kips (N) . I8.3a 340 Qrt Required tensile strength, kips (N) ...... I8.3c 341 Qrv Required shear strength, kips (N) ...... I8.3c 342 R Radius of joint surface, in. (mm) ...... Table J2.2 343 R Seismic response modification coefficient ...... A1.1 344 Ra Required strength using ASD load combinations ...... B3.2 345 RFIL Reduction factor for joints using a pair of transverse fillet welds 346 only ...... App. 3.3 347 Rg Coefficient to account for group effect ...... I8.2a 348 RM Coefficient to account for influence of P- on P- ...... App. 8.2.2 349 Rn Nominal strength, specified in Chapters B through K ...... B3.2 350 Rn Nominal slip resistance, kips (N) ...... J3.8 351 Rn Nominal strength of the applicable force transfer mechanism, kips 352 (N) ...... I6.3 353 Rnwl Total nominal strength of longitudinally loaded fillet welds, as 354 determined in accordance with Table J2.5, kips (N) ...... J2.4 355 Rnwt Total nominal strength of transversely loaded fillet welds, as 356 determined in accordance with Table J2.5 without the alternate in 357 Section J2.4(a), kips (N) ...... J2.4 358 Rp Position effect factor for shear studs ...... I8.2a 359 Rpc Web plastification factor...... F4.1 360 Rpg Bending strength reduction factor ...... F5.2 361 RPJP Reduction factor for reinforced or nonreinforced transverse partial- 362 joint-penetration (PJP) groove welds ...... App. 3.3 363 Rpt Web plastification factor corresponding to the tension flange 364 yielding limit state ...... F4.4 365 Ru Required strength using LRFD load combinations ...... B3.2 366 S Elastic section modulus, in.3 (mm3) ...... F8.2 367 S Spacing of secondary members, ft (m) ...... App. 2.1 368 Sc Elastic section modulus to the toe in compression relative to the 369 axis of bending, in.3 (mm3)...... F10.3 3 3 370 Se Effective section modulus about major axis, in. (mm ) ...... F7.2 371 Sip Effective elastic section modulus of welds for in-plane bending 372 (Table K5.1), in.3 (mm3) ...... K5 3 373 Smin Lowest elastic section modulus relative to the axis of bending, in. 374 (mm3) ...... F12 375 Sop Effective elastic section modulus of welds for out-of-plane bending 376 (Table K5.1), in.3 (mm3) ...... K5 377 Sxc, Sxt Elastic section modulus referred to compression and tension 378 flanges, respectively, in.3 (mm3) ...... Table B4.1 3 3 379 Sx Elastic section modulus taken about the x-axis, in. (mm ) ...... F2.2

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

380 Sy Elastic section modulus taken about the y-axis. For a channel, the 381 minimum section modulus, in.3 (mm3) ...... F6.2 382 Ta Required tension force using ASD load combinations, 383 kips (kN) ...... J3.9 384 Tb Minimum fastener tension given in Table J3.1 or J3.1M, 385 kips (kN) ...... J3.8 386 Tc Available torsional strength, kip-in. (N-mm) ...... H3.2 387 Tn Nominal torsional strength, kip-in. (N-mm) ...... H3.1 388 Tr Required torsional strength using LRFD or ASD load 389 combinations, kip-in. (N-mm) ...... H3.2 390 Tu Required tension force using LRFD load combinations, 391 kips (kN) ...... J3.9 392 U Shear lag factor ...... D3 393 U Utilization ratio ...... Table K2.1 394 Ubs Reduction coefficient, used in calculating block shear rupture 395 strength ...... J4.3 396 Up Stress index for primary members ...... App. 2.2 397 Us Stress index for secondary members ...... App. 2.2 398 V  Nominal shear force between the steel beam and the concrete slab 399 transferred by steel anchors, kips (N) ...... I3.2d 400 Vc Available shear strength, kips (N) ...... H3.2 401 Vc1 Available shear strength without tension field action calculated 402 with Vn as defined in Section G2.1, kips (N) ...... G3.2 403 Vc2 Available shear strength with tension field action calculated with 404 Vn as defined in Section G3.2, kips (N) ...... G3.2 405 Vn Nominal shear strength, kips (N) ...... G1 406 Vr Larger of the required shear strengths in the adjacent panels, kips 407 (N) ...... G3.2 408 Vr Required shear strength using LRFD or ASD load combinations, 409 kips (N) ...... H3.2

410 Vr Required longitudinal shear force to be transferred to the steel or 411 concrete, kips (N) ...... I6.2 412 Yi Gravity load applied at level i from the LRFD load combination or 413 ASD load combination, as applicable, kips (N) ...... C2.2b 414 Z Plastic section modulus about the axis of bending, in.3 (mm3) .. F7.1 3 415 Zb Plastic section modulus of branch about the axis of bending, in. 416 (mm3) ...... K4.1 3 3 417 Zx Plastic section modulus about the x-axis, in. (mm ) ...... F2.1 3 3 418 Zy Plastic section modulus about the y-axis, in. (mm ) ...... F6.1 419 a Clear distance between transverse stiffeners, in. (mm) ...... F13.2 420 a Distance between connectors, in. (mm) ...... E6.1 421 a Shortest distance from edge of pin hole to edge of member 422 measured parallel to the direction of force, in. (mm) ...... D5.1 423 a Half the length of the nonwelded root face in the direction of the 424 thickness of the tension-loaded plate, in. (mm) ...... App. 3.3 425 a Weld length along both edges of the cover plate termination to the 426 beam or girder, in. (mm) ...... F13.3

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

427 aw Ratio of two times the web area in compression due to application 428 of major axis bending moment alone to the area of the compression 429 flange components ...... F4.2 430 b Full width of leg in compression, in. (mm) ...... F10.3 431 b For flanges of I-shaped members, half the full-flange width, bf ; for 432 flanges of channels, the full nominal dimension of the flange, in. 433 (mm) ...... F6.2 434 b Full width of longest leg, in. (mm) ...... E7.1 435 b Width of unstiffened compression element; width of stiffened 436 compression element, in. (mm) ...... B4.1 437 b Width of the leg resisting the shear force or depth of tee stem, in. 438 (mm) ...... G4 439 bcf Width of column flange, in. (mm) ...... J10.6 440 be Reduced effective width, in. (mm) ...... E7.2 441 be Effective edge distance for calculation of tensile rupture strength 442 of pin-connected member, in. (mm) ...... D5.1 443 bf Width of flange, in. (mm) ...... B4.1 444 bfc Width of compression flange, in. (mm) ...... F4.2 445 bft Width of tension flange, in. (mm) ...... G3.1 446 bl Length of longer leg of angle, in. (mm) ...... E5 447 bs Length of shorter leg of angle, in. (mm) ...... E5 448 bs Stiffener width for one-sided stiffeners, in. (mm) ...... App. 6.3.2a 449 d Nominal fastener diameter, in. (mm) ...... J3.3 450 d Nominal bolt diameter, in. (mm) ...... J3.10 451 d Full nominal depth of the section, in. (mm) ...... B4.1, J10.3 452 d Depth of rectangular bar, in. (mm) ...... F11.2 453 d Diameter, in. (mm) ...... J7 454 d Diameter of pin, in. (mm) ...... D5.1 455 db Depth of beam, in. (mm) ...... J10.6 456 db Nominal diameter (body or shank diameter), in. (mm) ...... App. 3.4 457 dc Depth of column, in. (mm) ...... J10.6 458 dsa Diameter of steel headed stud anchor shank, in. (mm)……….. I8.1 459 e Eccentricity in a truss connection, positive being away from the 460 branches, in. (mm) ...... K3.1 461 emid-ht Distance from the edge of steel headed stud anchor shank to the 462 steel deck web, in. (mm) ...... I8.2a 463 fc Specified compressive strength of concrete, ksi (MPa) ...... I1.2a 464 fo Stress due to D + R (D = nominal dead load, R = nominal load due 465 to rainwater or snow exclusive of the ponding contribution), ksi 466 (MPa) ...... App. 2.2 467 fra Required axial stress at the point of consideration using LRFD or 468 ASD load combinations, ksi (MPa) ...... H2 469 frbw. frbz Required flexural stress at the point of consideration using LRFD 470 or ASD load combinations, ksi (MPa) ...... H2 471 frv Required shear stress using LRFD or ASD load combinations, ksi 472 (MPa) ...... J3.7 473 g Transverse center-to-center spacing (gage) between fastener gage 474 lines, in. (mm) ...... B4.3

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

475 g Gap between toes of branch members in a gapped K-connection, 476 neglecting the welds, in. (mm) ...... K3.1 477 h Width of stiffened compression element, in. (mm) ...... B4.1 478 h Height of shear element, in. (mm) ...... G2.1b 479 h Width resisting the shear force, taken as the clear distance between 480 the flanges less the inside corner radius on each side, 481 in. (mm) ...... G5 482 h Clear distance between flanges less the fillet or corner radius for 483 rolled shapes; distance between adjacent lines of fasteners or the 484 clear distance between flanges when welds are used for built-up 485 shapes, in. (mm) ...... J10.4 486 hc Twice the distance from the center of gravity to the following: the 487 inside face of the compression flange less the fillet or corner 488 radius, for rolled shapes; the nearest line of fasteners at the 489 compression flange or the inside faces of the compression flange 490 when welds are used, for built-up sections, in. (mm) ...... B4.1 491 ho Distance between flange centroids, in. (mm) ...... F2.2 492 hp Twice the distance from the plastic neutral axis to the nearest line 493 of fasteners at the compression flange or the inside face of the 494 compression flange when welds are used, in. (mm) ...... B4.1 495 hr Nominal height of rib, in. (mm) ...... I8.2a 496 k Distance from outer face of flange to the web toe of fillet, in. 497 (mm) ...... J10.2 498 kc Coefficient for slender unstiffened elements ...... Table B4.1 499 ksc Slip-critical combined tension and shear coefficient ...... J3.9 500 kv Web plate shear buckling coefficient ...... G2.1 501 l Actual length of end-loaded weld, in. (mm) ...... J2.2 502 l Length of connection, in. (mm) ...... Table D3.1 503 lb Length of bearing, in. (mm) ...... J7 504 la Length of channel anchor, in. (mm) ...... I8.2b 505 lc Clear distance, in the direction of the force, between the edge of 506 the hole and the edge of the adjacent hole or edge of the material, 507 in. (mm) ...... J3.10 508 le Total effective weld length of groove and fillet welds to 509 rectangular HSS for weld strength calculations, in. (mm) ...... K5 510 lend Distance from the near side of the connecting branch or plate to the 511 end of the chord, in. (mm)………………………………….…K1.1 512 lov Overlap length measured along the connecting face of the chord 513 beneath the two branches, in. (mm) ...... K3.1 514 lp Projected length of the overlapping branch on the chord, 515 in. (mm) ...... K3.1 516 n Number of braced points within the span ...... App. 6.3.2a 517 n Threads per inch (per mm) ...... App. 3.4 518 nb Number of bolts carrying the applied tension ...... J3.9 519 ns Number of slip planes required to permit the connection to slip J3.8 520 nSR Number of stress range fluctuations in design life ...... App. 3.3 521 p Pitch, in. per thread (mm per thread) ...... App. 3.4 522 r Radius of gyration, in. (mm)...... E2

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

523 ra Radius of gyration about the geometric axis parallel to the 524 connected leg, in. (mm) ...... E5 525 ri Minimum radius of gyration of individual component, in. (mm)E6.1

526 ro Polar radius of gyration about the shear center, in. (mm) ...... E4

527 rt Radius of gyration of the flange components in flexural 528 compression plus one-third of the web area in compression due to 529 application of major axis bending moment alone, in. (mm) ...... F4.2 530 rts Effective radius of gyration, in. (mm) ...... F2.2 531 rx Radius of gyration about the x-axis, in. (mm) ...... E4 532 ry Radius of gyration about y-axis, in. (mm) ...... E4 533 ryf Radius of gyration of the flange about its principal axis parallel to 534 the plane of the web, in. (mm)…………………………… . App. 6.1 535 rz Radius of gyration about the minor principal axis, in. (mm) ...... E5 536 s Longitudinal center-to-center spacing (pitch) of any two 537 consecutive holes, in. (mm) ...... B4.3 538 t Thickness of wall, in. (mm) ...... E7.2 539 t Thickness of angle leg, in. (mm) ...... F10.2 540 t Width of rectangular bar parallel to axis of bending, in. (mm) F11.2 541 t Thickness of connected material, in. (mm) ...... J3.10 542 t Thickness of plate, in. (mm) ...... D5.1 543 t Total thickness of fillers, in. (mm) ...... J5.2 544 t Design wall thickness of HSS member, in. (mm)...... B4.1 545 tb Design wall thickness of HSS branch member or thickness of 546 plate, in. (mm) ...... K1.1 547 tbi Thickness of overlapping branch, in. (mm) ...... Table K3.2 548 tbj Thickness of overlapped branch, in. (mm) ...... Table K3.2 549 tcf Thickness of column flange, in. (mm) ...... J10.6 550 tf Thickness of flange, in. (mm) ...... F6.2 551 tf Thickness of loaded flange, in. (mm) ...... J10.1 552 tf Thickness of flange of channel anchor, in. (mm) ...... I8.2b 553 tfc Thickness of compression flange, in. (mm) ...... F4.2 554 tp Thickness of tension loaded plate, in. (mm) ...... App. 3.3 555 tst Thickness of web stiffener, in. (mm) ...... App. 6.3.2a 556 tw Thickness of web, in. (mm) ...... Table B4.1 557 tw Smallest effective weld throat thickness around the perimeter of 558 branch or plate, in. (mm) ...... K5 559 tw Thickness of channel anchor web, in. (mm) ...... I8.2b 560 w Width of cover plate, in. (mm) ...... F13.3 561 w Size of weld leg, in. (mm) ...... J2.2 562 w Subscript relating symbol to major principal axis bending ...... H2 563 w Width of plate, in. (mm) ...... Table D3.1 564 w Leg size of the reinforcing or contouring fillet, if any, in the 565 direction of the thickness of the tension-loaded plate, 566 in. (mm) ...... App. 3.3 3 567 wc Weight of concrete per unit volume (90 ≤ wc ≤ 155 lbs / ft or 1500 3 568 ≤ wc ≤ 2500 kg/m ) ...... I2.1 569 wr Average width of concrete rib or haunch, in. (mm) ...... I3.2c 570 x Subscript relating symbol to strong axis bending ...... H1.1

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

571 xo, yo Coordinates of the shear center with respect to the centroid, in. 572 (mm) ...... E4 573 x Eccentricity of connection, in. (mm) ...... Table D3.1 574 y Subscript relating symbol to weak axis bending ...... H1.1 575 z Subscript relating symbol to minor principal axis bending ...... H2 576  ASD/LRFD force level adjustment factor ...... C2.3 577  Reduction factor given by Equation J2-1 ...... J2.2 578  Width ratio; the ratio of branch diameter to chord diameter for 579 round HSS; the ratio of overall branch width to chord width for 580 rectangular HSS ...... K3.1 581 T Overall brace system required stiffness, kip-in./rad (N-mm/rad) 582 ...... App. 6.3.2a 583 br Required shear stiffness of the bracing system, kips/in. (N/mm) ...... 584 ...... App. 6.2.1 585 eff Effective width ratio; the sum of the perimeters of the two branch 586 members in a K-connection divided by eight times the chord 587 width ...... K3.1 588 eop Effective outside punching parameter ...... Table K3.2 589 Lbr Required lateral brace stiffness, kip/in. (N/mm) ...... App. 6.3.3 590 Lbro Base required lateral brace stiffness given by Eq. A-6-6 for panel 591 bracing or Eq. A-6-8 for point bracing, kip/in. (N/mm)...App. 6.3.3 592 sec Web distortional stiffness, including the effect of web transverse 593 stiffeners, if any, kip-in./rad (N-mm/rad) ...... App. 6.3.2a 594 Tbr Required torsional brace stiffness, kip-in./rad 595 (N-mm/rad) ...... App. 6.3.3 596 Tbro Base required torsional brace stiffness given by Eq. A-6-10, kip- 597 in./rad (N-mm/rad)...... App. 6.3.3 598 w Section property for unequal leg angles, positive for short legs in 599 compression and negative for long legs in compression ...... F10.2 600  First-order story drift due to the LRFD or ASD load combinations, 601 in. (mm) ...... App. 7.3.2 602 H First-order story drift due to lateral forces, in. (mm) ...... App. 8.2.2 603 Δc Temperature above room temperature (68 °F or 20 °C).App. 4.2.3b 604  Chord slenderness ratio; the ratio of one-half the diameter to the 605 wall thickness for round HSS; the ratio of one-half the width to 606 wall thickness for rectangular HSS ...... K3.1 607  Gap ratio; the ratio of the gap between the branches of a gapped K- 608 connection to the width of the chord for rectangular HSS ...... K3.1 609  Load length parameter, applicable only to rectangular HSS; the 610 ratio of the length of contact of the branch with the chord in the 611 plane of the connection to the chord width ...... K3.1 612  Slenderness parameter ...... F3.2 613 p Limiting slenderness parameter for compact element ...... B4 614 pd Limiting slenderness parameter for plastic design ...... App. 1.2.2b 615 pf Limiting slenderness parameter for compact flange ...... F3.2 616 pw Limiting slenderness parameter for compact web ...... F4

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

617 r Limiting slenderness parameter for noncompact element ...... B4 618 rf Limiting slenderness parameter for noncompact flange ...... F3.2 619 rw Limiting slenderness parameter for noncompact web ...... F4.2 620  Mean slip coefficient for class A or B surfaces, as applicable, or as 621 established by tests ...... J3.8 622  Resistance factor ...... B3.1 623 B Resistance factor for bearing on concrete ...... I6.3a 624 b Resistance factor for flexure ...... F1 625 c Resistance factor for compression ...... E1 626 c Resistance factor for axially loaded composite columns ...... I2.1b 627 t Resistance factor for steel headed stud anchor in tension ...... I8.3b 628 sf Resistance factor for shear on the failure path ...... D5.1 629 T Resistance factor for torsion ...... H3.1 630 t Resistance factor for tension ...... D2 631 v Resistance factor for shear ...... G1 632 v Resistance factor for steel headed stud anchor in shear ...... I8.3a 633 Ω Safety factor ...... B3.2 634 ΩB Safety factor for bearing on concrete ...... I6.3a 635 Ωb Safety factor for flexure ...... F1 636 Ωc Safety factor for compression ...... E1 637 Ωc Safety factor for axially loaded composite columns ...... I2.1b 638 Ωt Safety factor for steel headed stud anchor in tension ...... I8.3b 639 Ωsf Safety factor for shear on the failure path ...... D5.1 640 ΩT Safety factor for torsion ...... H3.1 641 Ωt Safety factor for tension...... D2 642 Ωv Safety factor for shear ...... G1 643 Ωv Safety factor for steel headed stud anchor in shear ...... I8.3a 644 sr Minimum reinforcement ratio for longitudinal reinforcing ...... I2.1 645 st The larger of Fyw/Fyst and 1.0 ...... G3.2 646  Angle of loading measured from the weld longitudinal axis, 647 degrees ...... J2.4 648  Acute angle between the branch and chord, degrees ...... K3.1 649 b Stiffness reduction parameter ...... C2.3 650 651

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

1 2 3 4 GLOSSARY 5 6 7 Notes: 8 (1) Terms designated with † are common AISI-AISC terms that are coordinated between the two standards 9 development organizations. 10 (2) Terms designated with * are usually qualified by the type of load effect, for example, nominal tensile 11 strength, available compressive strength, and design flexural strength. 12 (3) Terms designated with ** are usually qualified by the type of component, for example, web local 13 buckling, and flange local bending. 14 15 Active fire protection. Building materials and systems that are activated by a fire to mitigate adverse 16 effects or to notify people to take some action to mitigate adverse effects.

17 Allowable strength*†. Nominal strength divided by the safety factor, Rn/. 18 Allowable stress*. Allowable strength divided by the appropriate section property, such as section 19 modulus or cross-section area. 20 Applicable building code†. Building code under which the structure is designed. 21 ASD (allowable strength design)†. Method of proportioning structural components such that the 22 allowable strength equals or exceeds the required strength of the component under the action of the 23 ASD load combinations. 24 ASD load combination†. Load combination in the applicable building code intended for allowable 25 strength design (allowable stress design). 26 Authority having jurisdiction (AHJ). Organization, political subdivision, office or individual charged 27 with the responsibility of administering and enforcing the provisions of this Standard. 28 Available strength*†. Design strength or allowable strength, as appropriate. 29 Available stress*. Design stress or allowable stress, as appropriate. 30 Average rib width. In a formed steel deck, average width of the rib of a corrugation. 31 32 Beam. NominallyDRAFT horizontal structural member that has the primary function of resisting bending 33 moments. 34 Beam-column. Structural member that resists both axial force and bending moment. 35 Bearing†. In a connection, limit state of shear forces transmitted by the mechanical fastener to the 36 connection elements. 37 Bearing (local compressive yielding)†. Limit state of local compressive yielding due to the action of a 38 member bearing against another member or surface. 39 Bearing-type connection. Bolted connection where shear forces are transmitted by the bolt bearing 40 against the connection elements. 41 Block shear rupture†. In a connection, limit state of tension rupture along one path and shear yielding or 42 shear rupture along another path. 43 Box section. Square or rectangular, doubly symmetric member made with four plates welded together at 44 the corners such that it behaves as a single member. 45 Braced frame†. Essentially vertical truss system that provides resistance to lateral forces and provides 46 stability for the structural system. 47 Bracing. Member or system that provides stiffness and strength to limit the out-of-plane movement of 48 another member at a brace point. 49 Branch member. In an HSS connection, member that terminates at a chord member or main member. 50 Buckling†. Limit state of sudden change in the geometry of a structure or any of its elements under a 51 critical loading condition. 52 Buckling strength. Strength for instability limit states. 53 Built-up member, cross section, section, shape. Member, cross section, section or shape fabricated from 54 structural steel elements that are welded or bolted together. 55 Camber. Curvature fabricated into a beam or truss so as to compensate for deflection induced by loads.

Specification for Structural Steel Buildings, PUBLIC REVIEW draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

56 Charpy V-notch impact test. Standard dynamic test measuring notch toughness of a specimen. 57 Chord member. In an HSS connection, primary member that extends through a truss connection. 58 Cladding. Exterior covering of structure. 59 Cold-formed steel structural member†. Shape manufactured by press-braking blanks sheared from sheets, 60 cut lengths of coils or plates, or by roll forming cold- or hot-rolled coils or sheets; both forming 61 operations being performed at ambient room temperature, that is, without manifest addition of heat 62 such as would be required for hot forming. 63 Collector. Also known as drag strut; member that serves to transfer loads between floor diaphragms and 64 the members of the lateral force resisting system. 65 Column. Nominally vertical structural member that has the primary function of resisting axial 66 compressive force. 67 Column base. Assemblage of structural shapes, plates, connectors, bolts and rods at the base of a column 68 used to transmit forces between the steel superstructure and the foundation. 69 Compact section. Section capable of developing a fully plastic stress distribution and possessing a 70 rotation capacity of approximately three before the onset of local buckling. 71 Compartmentation. Enclosure of a building space with elements that have a specific fire endurance. 72 Complete-joint-penetration (CJP) groove weld. Groove weld in which weld metal extends through the 73 joint thickness, except as permitted for HSS connections. 74 Composite. Condition in which steel and concrete elements and members work as a unit in the 75 distribution of internal forces. 76 Composite beam. Structural steel beam in contact with and acting compositely with a reinforced concrete 77 slab. 78 Composite component. Member, connecting element or assemblage in which steel and concrete elements 79 work as a unit in the distribution of internal forces, with the exception of the special case of compo- 80 site beams where steel anchors are embedded in a solid concrete slab or in a slab cast on formed 81 steel deck. 82 Concrete breakout surface. The surface delineating a volume of concrete surrounding a steel headed stud 83 anchor that separates from the remaining concrete. 84 Concrete crushing. Limit state of compressive failure in concrete having reached the ultimate strain. 85 Concrete haunch. In a composite floor system constructed using a formed steel deck, the section of solid 86 concrete that results from stopping the deck on each side of the girder. 87 Concrete-encasedDRAFT beam. Beam totally encased in concrete cast integrally with the slab. 88 Connection†. Combination of structural elements and joints used to transmit forces between two or more 89 members. 90 Construction documents. Written, graphic and pictorial documents prepared or assembled for describing 91 the design (including the structural system), location and physical characteristics of the elements of a 92 building necessary to obtain a building permit and construct a building. 93 Cope. Cutout made in a structural member to remove a flange and conform to the shape of an intersecting 94 member. 95 Cover plate. Plate welded or bolted to the flange of a member to increase cross-sectional area, section 96 modulus or moment of inertia. 97 Cross connection. HSS connection in which forces in branch members or connecting elements transverse 98 to the main member are primarily equilibrated by forces in other branch members or connecting 99 elements on the opposite side of the main member. 100 Design. The process of establishing the physical and other properties of a structure for the purpose of 101 achieving the desired strength, serviceability, durability, constructability, economy and other desired 102 characteristics. Design for strength, as used in this Specification, includes analysis to determine 103 required strength and proportioning to have adequate available strength. 104 Design-basis fire. Set of conditions that define the development of a fire and the spread of combustion 105 products throughout a building or portion thereof. 106 Design drawings. Graphic and pictorial documents showing the design, location and dimensions of the 107 work. These documents generally include plans, elevations, sections, details, schedules, diagrams 108 and notes. 109 Design load†. Applied load determined in accordance with either LRFD load combinations or ASD load 110 combinations, whichever is applicable.

111 Design strength*†. Resistance factor multiplied by the nominal strength, Rn.

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

112 Design wall thickness. HSS wall thickness assumed in the determination of section properties. 113 Diagonal stiffener. Web stiffener at column panel zone oriented diagonally to the flanges, on one or both 114 sides of the web. 115 Diaphragm†. Roof, floor or other membrane or bracing system that transfers in-plane forces to the lateral 116 force resisting system. 117 Diaphragm plate. Plate possessing in-plane shear stiffness and strength, used to transfer forces to the 118 supporting elements. 119 Direct bond interaction. In a composite section, mechanism by which force is transferred between steel 120 and concrete by bond stress. 121 Distortional failure. Limit state of an HSS truss connection based on distortion of a rectangular HSS 122 chord member into a rhomboidal shape. 123 Distortional stiffness. Out-of-plane flexural stiffness of web. 124 Double curvature. Deformed shape of a beam with one or more inflection points within the span. 125 Double-concentrated forces. Two equal and opposite forces applied normal to the same flange, forming a 126 couple. 127 Doubler. Plate added to, and parallel with, a beam or column web to increase strength at locations of 128 concentrated forces. 129 Drift. Lateral deflection of structure. 130 Effective length factor, K. Ratio between the effective length and the unbraced length of the member. 131 Effective length. Length of an otherwise identical column with the same strength when analyzed with 132 pinned end conditions. 133 Effective net area. Net area modified to account for the effect of shear lag. 134 Effective section modulus. Section modulus reduced to account for buckling of slender compression 135 elements. 136 Effective width. Reduced width of a plate or slab with an assumed uniform stress distribution which 137 produces the same effect on the behavior of a structural member as the actual plate or slab width 138 with its nonuniform stress distribution. 139 Elastic analysis. Structural analysis based on the assumption that the structure returns to its original 140 geometry on removal of the load. 141 Elevated temperatures. Heating conditions experienced by building elements or structures as a result of 142 fire which are in excess of the anticipated ambient conditions. 143 Encased compositeDRAFT member. Composite member consisting of a structural concrete member and one or 144 more embedded steel shapes. 145 End panel. Web panel with an adjacent panel on one side only. 146 End return. Length of fillet weld that continues around a corner in the same plane. 147 Engineer of record. Licensed professional responsible for sealing the design drawings and specifications. 148 Expansion rocker. Support with curved surface on which a member bears that can tilt to accommodate 149 expansion. 150 Expansion roller. Round steel bar on which a member bears that can roll to accommodate expansion. 151 Eyebar. Pin-connected tension member of uniform thickness, with forged or thermally cut head of 152 greater width than the body, proportioned to provide approximately equal strength in the head and 153 body. 154 Factored load †. Product of a load factor and the nominal load. 155 Fastener. Generic term for bolts, rivets, or other connecting devices. 156 Fatigue†.Limit state of crack initiation and growth resulting from repeated application of live loads. 157 Faying surface. Contact surface of connection elements transmitting a shear force. 158 Filled composite member. Composite member consisting of an HSS or box section filled with structural 159 concrete. 160 Filler metal. Metal or alloy added in making a welded joint. 161 Filler. Plate used to build up the thickness of one component. 162 Fillet weld reinforcement. Fillet welds added to groove welds. 163 Fillet weld. Weld of generally triangular cross section made between intersecting surfaces of elements. 164 Finished surface. Surfaces fabricated with a roughness height value measured in accordance with 165 ANSI/ASME B46.1 that is equal to or less than 500. 166 Fire. Destructive burning, as manifested by any or all of the following: light, flame, heat, or smoke.

Specification for Structural Steel Buildings, PUBLIC REVIEW draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

167 Fire barrier. Element of construction formed of fire-resisting materials and tested in accordance with an 168 approved standard fire resistance test, to demonstrate compliance with the applicable building code. 169 Fire resistance. Property of assemblies that prevents or retards the passage of excessive heat, hot gases or 170 flames under conditions of use and enables them to continue to perform a stipulated function. 171 First-order analysis. Structural analysis in which equilibrium conditions are formulated on the 172 undeformed structure; second-order effects are neglected. 173 Fitted bearing stiffener. Stiffener used at a support or concentrated load that fits tightly against one or 174 both flanges of a beam so as to transmit load through bearing. 175 Flare bevel groove weld. Weld in a groove formed by a member with a curved surface in contact with a 176 planar member. 177 Flare V-groove weld. Weld in a groove formed by two members with curved surfaces. 178 Flashover. Transition to a state of total surface involvement in a fire of combustible materials within an 179 enclosure. 180 Flat width. Nominal width of rectangular HSS minus twice the outside corner radius. In the absence of 181 knowledge of the corner radius, the flat width may be taken as the total section width minus three 182 times the thickness. 183 Flexural buckling†. Buckling mode in which a compression member deflects laterally without twist or 184 change in cross-sectional shape. 185 Flexural-torsional buckling†. Buckling mode in which a compression member bends and twists 186 simultaneously without change in cross-sectional shape. 187 Force. Resultant of distribution of stress over a prescribed area. 188 Formed steel deck. In composite construction, steel cold formed into a decking profile used as a 189 permanent concrete form. 190 Fully-restrained moment connection. Connection capable of transferring moment with negligible rotation 191 between connected members. 192 Gage. Transverse center-to-center spacing of fasteners. 193 Gapped connection. HSS truss connection with a gap or space on the chord face between intersecting 194 branch members. 195 Geometric axis. Axis parallel to web, flange or angle leg. 196 Girder filler. In a composite floor system constructed using a formed steel deck, narrow piece of sheet 197 steel used as a fill between the edge of a deck sheet and the flange of a girder. 198 Girder. See BeamDRAFT. 199 Gouge. Relatively smooth surface groove or cavity resulting from plastic deformation or removal of 200 material. 201 Gravity load. Load acting in the downward direction, such as dead and live loads. 202 Grip (of bolt). Thickness of material through which a bolt passes. 203 Groove weld. Weld in a groove between connection elements. See also AWS D1.1. 204 Gusset plate. Plate element connecting truss members or a strut or brace to a beam or column. 205 Heat flux. Radiant energy per unit surface area. 206 Heat release rate. Rate at which thermal energy is generated by a burning material. 207 High-strength bolt. Fastener in compliance with ASTM A325, A325M, A490, A490M, F1852, F2280 or 208 an alternate fastener as permitted in Section J3.1. 209 Horizontal shear. In a composite beam, force at the interface between steel and concrete surfaces. 210 HSS (hollow structural section). Square, rectangular or round hollow structural steel section produced in 211 accordance with one of the product specifications in Section A3.1a(b). 212 Inelastic analysis. Structural analysis that takes into account inelastic material behavior, including plastic 213 analysis. 214 In-plane instability†. Limit state involving buckling in the plane of the frame or the member. 215 Instability†. Limit state reached in the loading of a structural component, frame or structure in which a 216 slight disturbance in the loads or geometry produces large displacements. 217 Introduction length. The length along which the required longitudinal shear force is assumed to be 218 transferred into or out of the steel shape in an encased or filled composite column. 219 Joint†. Area where two or more ends, surfaces, or edges are attached. Categorized by type of fastener or 220 weld used and method of force transfer. 221 Joint eccentricity. In an HSS truss connection, perpendicular distance from chord member center of 222 gravity to intersection of branch member work points.

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

223 k-area. The region of the web that extends from the tangent point of the web and the flange-web fillet 224 (AISC k dimension) a distance 12 in. (38 mm) into the web beyond the k dimension. 225 K-connection. HSS connection in which forces in branch members or connecting elements transverse to 226 the main member are primarily equilibriated by forces in other branch members or connecting 227 elements on the same side of the main member. 228 Lacing. Plate, angle or other steel shape, in a lattice configuration, that connects two steel shapes 229 together. 230 Lap joint. Joint between two overlapping connection elements in parallel planes. 231 Lateral bracing. Member or system that is designed to inhibit lateral buckling or lateral-torsional 232 buckling of structural members. 233 Lateral force resisting system. Structural system designed to resist lateral loads and provide stability for 234 the structure as a whole. 235 Lateral load. Load acting in a lateral direction, such as wind or earthquake effects. 236 Lateral-torsional buckling†. Buckling mode of a flexural member involving deflection out of the plane of 237 bending occurring simultaneously with twist about the shear center of the cross-section. 238 Leaning column. Column designed to carry gravity loads only, with connections that are not intended to 239 provide resistance to lateral loads. 240 Length effects. Consideration of the reduction in strength of a member based on its unbraced length. 241 Lightweight concrete. Structural concrete with an equilibrium density of 115 lb/ft3 (1840 kg/m3) or less 242 as determined by ASTM C567. 243 Limit state†. Condition in which a structure or component becomes unfit for service and is judged either 244 to be no longer useful for its intended function (serviceability limit state) or to have reached its 245 ultimate load-carrying capacity (strength limit state). 246 Load†. Force or other action that results from the weight of building materials, occupants and their 247 possessions, environmental effects, differential movement, or restrained dimensional changes. 248 Load effect†. Forces, stresses and deformations produced in a structural component by the applied loads. 249 Load factor. Factor that accounts for deviations of the nominal load from the actual load, for 250 uncertainties in the analysis that transforms the load into a load effect and for the probability that 251 more than one extreme load will occur simultaneously. 252 Load transfer region. Region of a composite member over which force is directly applied to the member, 253 such as the depth of a connection plate. 254 Local bending**DRAFT †. Limit state of large deformation of a flange under a concentrated transverse force. 255 Local buckling**. Limit state of buckling of a compression element within a cross section. 256 Local yielding**†. Yielding that occurs in a local area of an element. 257 LRFD (load and resistance factor design)†. Method of proportioning structural components such that the 258 design strength equals or exceeds the required strength of the component under the action of the 259 LRFD load combinations. 260 LRFD load combination†. Load combination in the applicable building code intended for strength design 261 (load and resistance factor design). 262 Main member. In an HSS connection, chord member, column or other HSS member to which branch 263 members or other connecting elements are attached. 264 Mechanism. Structural system that includes a sufficient number of real hinges, plastic hinges or both, so 265 as to be able to articulate in one or more rigid body modes. 266 Mill scale. Oxide surface coating on steel formed by the hot rolling process. 267 Moment connection. Connection that transmits bending moment between connected members. 268 Moment frame†. Framing system that provides resistance to lateral loads and provides stability to the 269 structural system, primarily by shear and flexure of the framing members and their connections. 270 Negative flexural strength. Flexural strength of a composite beam in regions with tension due to flexure 271 on the top surface. 272 Net area. Gross area reduced to account for removed material. 273 Nominal dimension. Designated or theoretical dimension, as in tables of section properties. 274 Nominal load†. Magnitude of the load specified by the applicable building code. 275 Nominal rib height. In a formed steel deck, height of deck measured from the underside of the lowest 276 point to the top of the highest point. 277 Nominal strength*†. Strength of a structure or component (without the resistance factor or safety factor 278 applied) to resist load effects, as determined in accordance with this Specification.

Specification for Structural Steel Buildings, PUBLIC REVIEW draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

279 Noncompact section. Section that can develop the yield stress in its compression elements before local 280 buckling occurs, but cannot develop a rotation capacity of three. 281 Nondestructive testing. Inspection procedure wherein no material is destroyed and the integrity of the 282 material or component is not affected. 283 Notch toughness. Energy absorbed at a specified temperature as measured in the Charpy V-notch impact 284 test. 285 Notional load. Virtual load applied in a structural analysis to account for destabilizing effects that are not 286 otherwise accounted for in the design provisions. 287 Out-of-plane buckling†. Limit state of a beam, column or beam-column involving lateral or lateral- 288 torsional buckling. 289 Overlapped connection. HSS truss connection in which intersecting branch members overlap. 290 Panel brace. Brace that controls the relative movement of two adjacent brace points along the length of a 291 beam or column or the relative lateral displacement of two stories in a frame (see point brace). 292 Panel zone. Web area of beam-to-column connection delineated by the extension of beam and column 293 flanges through the connection, transmitting moment through a shear panel. 294 Partial-joint-penetration (PJP) groove weld. Groove weld in which the penetration is intentionally less 295 than the complete thickness of the connected element. 296 Partially-restrained moment connection. Connection capable of transferring moment with rotation 297 between connected members that is not negligible. 298 Percent elongation. Measure of ductility, determined in a tensile test as the maximum elongation of the 299 gage length divided by the original gage length expressed as a percentage. 300 Pipe. See HSS. 301 Pitch. Longitudinal center-to-center spacing of fasteners. Center-to-center spacing of bolt threads along 302 axis of bolt. 303 Plastic analysis. Structural analysis based on the assumption of rigid-plastic behavior, that is, that 304 equilibrium is satisfied and the stress is at or below the yield stress throughout the structure. 305 Plastic hinge. Fully yielded zone that forms in a structural member when the plastic moment is attained. 306 Plastic moment. Theoretical resisting moment developed within a fully yielded cross section. 307 Plastic stress distribution method. In a composite member, method for determining stresses assuming 308 that the steel section and the concrete in the cross section are fully plastic. 309 Plastification. In an HSS connection, limit state based on an out-of-plane flexural yield line mechanism 310 in the chordDRAFT at a branch member connection. 311 Plate girder. Built-up beam. 312 Plug weld. Weld made in a circular hole in one element of a joint fusing that element to another element. 313 Point brace. Brace that prevents lateral movement or twist independently of other braces at adjacent 314 brace points (see panel brace). 315 Ponding. Retention of water due solely to the deflection of flat roof framing. 316 Positive flexural strength. Flexural strength of a composite beam in regions with compression due to 317 flexure on the top surface. 318 Pretensioned bolt. Bolt tightened to the specified minimum pretension. 319 Pretensioned joint. Joint with high-strength bolts tightened to the specified minimum pretension. 320 Properly developed. Reinforcing bars detailed to yield in a ductile manner before crushing of the 321 concrete occurs. Bars meeting the provisions of ACI 318 insofar as development length, spacing and 322 cover, are deemed to be properly developed. 323 Prying action. Amplification of the tension force in a bolt caused by leverage between the point of 324 applied load, the bolt and the reaction of the connected elements. 325 Punching load. In an HSS connection, component of branch member force perpendicular to a chord. 326 P-δ effect. Effect of loads acting on the deflected shape of a member between joints or nodes. 327 P-Δ effect. Effect of loads acting on the displaced location of joints or nodes in a structure. In tiered 328 building structures, this is the effect of loads acting on the laterally displaced location of floors and 329 roofs. 330 Quality assurance. Monitoring and inspection tasks to ensure that the material provided and work 331 performed by the fabricator and erector meet the requirements of the approved construction docu- 332 ments and referenced standards. Quality assurance includes those tasks designated “special inspec- 333 tion” by the applicable building code.

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

334 Quality assurance inspector (QAI). Individual designated to provide quality assurance inspection for the 335 work being performed. 336 Quality assurance plan (QAP). Program in which the agency or firm responsible for quality assurance 337 maintains detailed monitoring and inspection procedures to ensure conformance with the approved 338 construction documents and referenced standards. 339 Quality control. Controls and inspections implemented by the fabricator or erector, as applicable, to 340 ensure that the material provided and work performed meet the requirements of the approved 341 construction documents and referenced standards. 342 Quality control inspector (QCI). Individual designated to perform quality control inspection tasks for the 343 work being performed. 344 Quality control program (QCP). Program in which the fabricator or erector, as applicable, maintains 345 detailed fabrication or erection and inspection procedures to ensure conformance with the approved 346 design drawings, specifications, and referenced standards. 347 Reentrant. In a cope or weld access hole, a cut at an abrupt change in direction in which the exposed 348 surface is concave. 349 Required strength*†. Forces, stresses and deformations acting on a structural component, determined by 350 either structural analysis, for the LRFD or ASD load combinations, as appropriate, or as specified by 351 this Specification or Standard. 352 Resistance factor †. Factor that accounts for unavoidable deviations of the nominal strength from the 353 actual strength and for the manner and consequences of failure. 354 Restrained construction. Floor and roof assemblies and individual beams in buildings where the 355 surrounding or supporting structure is capable of resisting substantial thermal expansion throughout 356 the range of anticipated elevated temperatures. 357 Reverse curvature. See double curvature. 358 Root of joint. Portion of a joint to be welded where the members are closest to each other. 359 Rotation capacity. Incremental angular rotation defined as the ratio of the inelastic rotation attained to the 360 idealized elastic rotation at first yield prior to excessive load shedding. 361 Rupture strength†. Strength limited by breaking or tearing of members or connecting elements. 362 Safety factor, †. Factor that accounts for deviations of the actual strength from the nominal strength, 363 deviations of the actual load from the nominal load, uncertainties in the analysis that transforms the 364 load into a load effect, and for the manner and consequences of failure. 365 Second-order effect.DRAFT Effect of loads acting on the deformed configuration of a structure; includes P-δ 366 effect and P-Δ effect. 367 Seismic force resisting system. That part of the structural system that has been considered in the design to 368 provide the required resistance to the seismic forces prescribed in ASCE/SEI 7. 369 Seismic response modification factor. Factor that reduces seismic load effects to strength level. 370 Service load combination. Load combination under which serviceability limit states are evaluated. 371 Service load†. Load under which serviceability limit states are evaluated. 372 Serviceability limit state†. Limiting condition affecting the ability of a structure to preserve its 373 appearance, maintainability, durability or the comfort of its occupants or function of machinery, 374 under normal usage. 375 Shear buckling†. Buckling mode in which a plate element, such as the web of a beam, deforms under 376 pure shear applied in the plane of the plate. 377 Shear lag. Non-uniform tensile stress distribution in a member or connecting element in the vicinity of a 378 connection. 379 Shear wall†. Wall that provides resistance to lateral loads in the plane of the wall and provides stability 380 for the structural system. 381 Shear yielding (punching). In an HSS connection, limit state based on out-of-plane shear strength of the 382 chord wall to which branch members are attached. 383 Sheet steel. In a composite floor system, steel used for closure plates or miscellaneous trimming in a 384 formed steel deck. 385 Shim. Thin layer of material used to fill a space between faying or bearing surfaces. 386 Sidesway buckling (frame). Stability limit state involving lateral sideway instability of a frame. 387 Simple connection. Connection that transmits negligible bending moment between connected members. 388 Single-concentrated force. Tensile or compressive force applied normal to the flange of a member. 389 Single curvature. Deformed shape of a beam with no inflection point within the span.

Specification for Structural Steel Buildings, PUBLIC REVIEW draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

390 Slender-element section. Cross section possessing plate components of sufficient slenderness such that 391 local buckling in the elastic range will occur. 392 Slip. In a bolted connection, limit state of relative motion of connected parts prior to the attainment of the 393 available strength of the connection. 394 Slip-critical connection. Bolted connection designed to resist movement by friction on the faying surface 395 of the connection under the clamping force of the bolts. 396 Slot weld. Weld made in an elongated hole fusing an element to another element. 397 Snug-tightened joint. Joint with the connected plies in firm contact as specified in Chapter J. 398 Specifications. Written documents containing the requirements for materials, standards and workman- 399 ship. 400 Specified minimum tensile strength. Lower limit of tensile strength specified for a material as defined by 401 ASTM. 402 Specified minimum yield stress†. Lower limit of yield stress specified for a material as defined by ASTM. 403 Splice. Connection between two structural elements joined at their ends to form a single, longer element. 404 Stability. Condition in the loading of a structural component, frame or structure in which a slight 405 disturbance in the loads or geometry does not produce large displacements. 406 Statically loaded. Not subject to fatigue stresses. 407 Steel anchor. Headed stud or hot rolled channel welded to a steel member and embodied in concrete of a 408 composite member to transmit shear, tension or a combination of shear and tension at the interface 409 of the two materials. 410 Stiffened element. Flat compression element with adjoining out-of-plane elements along both edges 411 parallel to the direction of loading. 412 Stiffener. Structural element, usually an angle or plate, attached to a member to distribute load, transfer 413 shear or prevent buckling. 414 Stiffness. Resistance to deformation of a member or structure, measured by the ratio of the applied force 415 (or moment) to the corresponding displacement (or rotation). 416 Story drift. The horizontal deflection at the top of the story relative to the bottom of the story. 417 Story drift ratio. The story drift divided by the story height. 418 Strain compatibility method. In a composite member, method for determining the stresses considering the 419 stress-strain relationships of each material and its location with respect to the neutral axis of the 420 cross section. 421 Strength limit stateDRAFT†. Limiting condition in which the maximum strength of a structure or its components 422 is reached. 423 Stress. Force per unit area caused by axial force, moment, shear or torsion. 424 Stress concentration. Localized stress considerably higher than average due to abrupt changes in 425 geometry or localized loading 426 . 427 Strong axis. Major principal centroidal axis of a cross section. 428 Structural analysis†. Determination of load effects on members and connections based on principles of 429 structural mechanics. 430 Structural component†. Member, connector, connecting element or assemblage. 431 Structural Integrity. A performance characteristic of a structure indicating resistance to catastrophic 432 failure. 433 Structural steel. Steel elements as defined in Section 2.1 of the AISC Code of Standard Practice for Steel 434 Buildings and Bridges. 435 Structural system. An assemblage of load-carrying components that are joined together to provide 436 interaction or interdependence. 437 T-connection. HSS connection in which the branch member or connecting element is perpendicular to the 438 main member and in which forces transverse to the main member are primarily equilibriated by 439 shear in the main member. 440 Tensile strength (of material) †. Maximum tensile stress that a material is capable of sustaining as 441 defined by ASTM. 442 Tensile strength (of member). Maximum tension force that a member is capable of sustaining. 443 Tension and shear rupture†. In a bolt or other type of mechanical fastener, limit state of rupture due to 444 simultaneous tension and shear force.

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

445 Tension field action. Behavior of a panel under shear in which diagonal tensile forces develop in the web 446 and compressive forces develop in the transverse stiffeners in a manner similar to a Pratt truss. 447 Thermally cut. Cut with gas, plasma or laser. 448 Tie plate. Plate element used to join two parallel components of a built-up column, girder or strut rigidly 449 connected to the parallel components and designed to transmit shear between them. 450 Toe of fillet. Junction of a fillet weld face and base metal. Tangent point of a fillet in a rolled shape. 451 Torsional bracing. Bracing resisting twist of a beam or column. 452 Torsional buckling†. Buckling mode in which a compression member twists about its shear center axis. 453 Transverse reinforcement. In an encased composite column, steel reinforcement in the form of closed ties 454 or welded wire fabric providing confinement for the concrete surrounding the steel shape. 455 Transverse stiffener. Web stiffener oriented perpendicular to the flanges, attached to the web. 456 Tubing. See HSS. 457 Turn-of-nut method. Procedure whereby the specified pretension in high-strength bolts is controlled by 458 rotating the fastener component a predetermined amount after the bolt has been snug tightened. 459 Unbraced length. Distance between braced points of a member, measured between the centers of gravity 460 of the bracing members. 461 Uneven load distribution. In an HSS connection, condition in which the load is not distributed through 462 the cross section of connected elements in a manner that can be readily determined. 463 Unframed end. The end of a member not restrained against rotation by stiffeners or connection elements. 464 Unstiffened element. Flat compression element with an adjoining out-of-plane element along one edge 465 parallel to the direction of loading. 466 Unrestrained construction. Floor and roof assemblies and individual beams in buildings that are assumed 467 to be free to rotate and expand throughout the range of anticipated elevated temperatures. 468 Weak axis. Minor principal centroidal axis of a cross section. 469 Weathering steel. High-strength, low-alloy steel that, with suitable precautions, can be used in normal 470 atmospheric exposures (not marine) without protective paint coating. 471 Web crippling†. Limit state of local failure of web plate in the immediate vicinity of a concentrated load 472 or reaction. 473 Web sidesway buckling. Limit state of lateral buckling of the tension flange opposite the location of a 474 concentrated compression force. 475 Weld metal. Portion of a fusion weld that has been completely melted during welding. Weld metal has 476 elements ofDRAFT filler metal and base metal melted in the weld thermal cycle. 477 Weld root. See root of joint. 478 Y-connection. HSS connection in which the branch member or connecting element is not perpendicular to 479 the main member and in which forces transverse to the main member are primarily equilibriated by 480 shear in the main member. 481 Yield moment†. In a member subjected to bending, the moment at which the extreme outer fiber first 482 attains the yield stress. 483 Yield point†. First stress in a material at which an increase in strain occurs without an increase in stress 484 as defined by ASTM. 485 Yield strength†. Stress at which a material exhibits a specified limiting deviation from the proportionality 486 of stress to strain as defined by ASTM. 487 Yield stress†. Generic term to denote either yield point or yield strength, as appropriate for the material. 488 Yielding†. Limit state of inelastic deformation that occurs when the yield stress is reached. 489 Yielding (plastic moment)†. Yielding throughout the cross section of a member as the bending moment 490 reaches the plastic moment. 491 Yielding (yield moment)†. Yielding at the extreme fiber on the cross section of a member when the 492 bending moment reaches the yield moment. 493

Specification for Structural Steel Buildings, PUBLIC REVIEW draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

1 ACRONYMS AND ABBREVIATIONS 2 3 The following acronyms appear in the AISC Specification for Structural Steel Buildings. The acronyms are written 4 out where they first appear within a Section. 5 6 ABC (applicable building code) 7 ACI (American Concrete Institute) 8 AHJ (authority having jurisdiction) 9 AISC (American Institute of Steel Construction) 10 AISI (American Iron and Steel Institute) 11 ANSI (American National Standards Institute) 12 ASCE (American Society of Civil Engineers) 13 ASD (allowable strength design) 14 ASME (American Society of Mechanical Engineers) 15 ASNT (American Society for Nondestructive Testing) 16 AWI (associate welding inspector) 17 AWS (American Welding Society) 18 CJP (complete joint penetration) 19 CVN (Charpy V-notch) 20 EOR (engineer of record) 21 ERW (electric resistance welded) 22 FCAW (flux cored arc welding) 23 FR (fully restrained) 24 GMAW (gas metal arc welding) 25 HSLA (high-strength low-alloy) 26 HSS (hollow structural section) 27 LRFD (load and resistance factor design) 28 MT (magnetic particle testing) 29 NDT (nondestructive testing) 30 OSHA (Occupational Safety and Health Administration) 31 PJP (partial joint penetration) 32 PQR (procedure qualification record) 33 PR (partially restrained) 34 PT (penetrant testing) 35 QA (quality assurance) 36 QAI (quality assurance inspector) 37 QAP (quality assurance plan) 38 QC (quality control) 39 QCI (quality control inspector) 40 QCP (quality control program) 41 RCSC (Research Council on Structural Connections) 42 RT (radiographic testing) 43 SAW (submerged arc welding) 44 SEI (Structural Engineering Institute) 45 SFPE (Society of Fire Protection Engineers) 46 SMAW (shielded metal arc welding) 47 SWI (senior welding inspector) 48 UNC (Unified National Coarse) 49 UT (ultrasonic testing) 50 WI (welding inspector) 51 WPQR (welder performance qualification records) 52 WPS (welding procedure specification) 53

Specification for Structural Steel Buildings, public review draft dated March 2, 2015

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1 CHAPTER A

2 GENERAL PROVISIONS 3 4 This chapter states the scope of this Specification, lists referenced specifications, 5 codes and standards, and provides requirements for materials and structural design 6 documents. 7 8 The chapter is organized as follows: 9 10 A1. Scope 11 A2. Referenced Specifications, Codes and Standards 12 A3. Material 13 A4. Structural Design Drawings and Specifications 14 15 A1. SCOPE 16 17 The Specification for Structural Steel Buildings (ANSI/AISC 360), hereafter 18 referred to as the Specification, shall apply to the design, fabrication and 19 erection of the structural steel system or systems with structural steel acting 20 compositely with reinforced concrete, where the steel elements are defined in 21 Section 2.1 of the AISC Code of Standard Practice for Steel Buildings and 22 Bridges (AISC 303), hereafter referred to as the Code of Standard Practice. 23 24 The Specification includes the Symbols, the Glossary, Chapters A through N, 25 and Appendices 1 through 9. The Commentary to the Specification and the 26 User Notes interspersed throughout are not part of the Specification. The 27 phrases “is permitted” and “are permitted” in this document identify 28 provisions that comply with the Specification, but are not mandatory. 29 DRAFT 30 User Note: User notes are intended to provide concise and practical guidance 31 in the application of the Specification provisions. 32 33 The Specification sets forth criteria for the design, fabrication and erection of 34 structural steel buildings and other structures, where other structures are 35 defined as structures designed, fabricated and erected in a manner similar to 36 buildings, with building-like vertical and lateral load resisting-elements.

37 Wherever the Specification refers to the applicable building code and there is 38 none, the loads, load combinations, system limitations, and general design 39 requirements shall be those in ASCE Minimum Design Loads for Buildings 40 and Other Structures (ASCE/SEI 7). 41 42 Where conditions are not covered by the Specification, designs are permitted 43 to be based on tests or analysis, subject to the approval by the authority having 44 jurisdiction. Alternative methods of analysis and design are permitted, 45 provided such alternative methods or criteria are acceptable to the authority 46 having jurisdiction. 47 48 User Note: For the design of cold-formed steel structural members, the 49 provisions in the AISI North American Specification for the Design of Cold- 50 Formed Steel Structural Members (AISI S100) are recommended, except for 51 cold-formed hollow structural sections (HSS), which are designed in 52 accordance with this Specification.

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53 54 1. Seismic Applications 55 56 The Seismic Provisions for Structural Steel Buildings (ANSI/AISC 341) shall 57 apply to the design of seismic force resisting systems of structural steel or of 58 structural steel acting compositely with reinforced concrete, unless 59 specifically exempted by the applicable building code. 60 61 User Note: ASCE/SEI 7 (Table 12.2-1, Item H) specifically exempts 62 structural steel systems in seismic design categories B and C from the 63 requirements in the Seismic Provisions for Structural Steel Buildings if they 64 are designed according to the Specification and the seismic loads are 65 computed using a seismic response modification factor, R, of 3; composite 66 systems are not covered by this exemption. The Seismic Provisions for 67 Structural Steel Buildings do not apply in seismic design category A. 68 69 70 2. Nuclear Applications 71 72 The design, fabrication and erection of nuclear structures shall comply with 73 the provisions of this Specification as modified by the requirements of the 74 Specification for Safety-Related Steel Structures for Nuclear Facilities 75 (ANSI/AISC N690). 76 77 A2. REFERENCED SPECIFICATIONS, CODES AND STANDARDS 78 79 The following specifications, codes and standards are referenced in this 80 Specification: 81 82 (a) ACI International (ACI) 83 84 ACI 318-14DRAFT Building Code Requirements for Structural Concrete and 85 Commentary 86 ACI 349-13 Code Requirements for Nuclear Safety-Related Concrete 87 Structures and Commentary 88 89 (b) American Institute of Steel Construction (AISC) 90 91 AISC 303-16 Code of Standard Practice for Steel Buildings and Bridges 92 ANSI/AISC 341-16 Seismic Provisions for Structural Steel Buildings 93 ANSI/AISC N690-12 Specification for Safety-Related Steel Structures for 94 Nuclear Facilities 95 ANSI/AISC N690-12s1 Specification for Safety-Related Steel Structures 96 for Nuclear Facilities, Supplement No. 1 97 98 (c) American Society of Civil Engineers (ASCE) 99 100 ASCE/SEI 7-16 Minimum Design Loads for Buildings and Other Struc- 101 tures 102 ASCE/SEI/SFPE 29-05 Standard Calculation Methods for Structural Fire 103 Protection 104 105 (d) American Society of Mechanical Engineers (ASME) 106 107 ASME B18.2.6-10 Fasteners for Use in Structural Applications

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108 ASME B46.1-09 Surface Texture, Surface Roughness, Waviness, and 109 Lay 110 111 (e) American Society for Nondestructive Testing (ASNT) 112 113 ANSI/ASNT CP-189-2011 Standard for Qualification and Certification 114 of Nondestructive Testing Personnel 115 Recommended Practice No. SNT-TC-1A-2011 Personnel Qualification 116 and Certification in Nondestructive Testing 117 118 (f) ASTM International (ASTM) 119 120 A6/A6M-14 Standard Specification for General Requirements for Rolled 121 Structural Steel Bars, Plates, Shapes, and Sheet Piling 122 A36/A36M-14 Standard Specification for Carbon Structural Steel 123 A53/A53M-12 Standard Specification for Pipe, Steel, Black and Hot- 124 Dipped, Zinc-Coated, Welded and Seamless 125 A193/A193M-14 Standard Specification for Alloy-Steel and Stainless 126 Steel Bolting Materials for High Temperature or High Pressure 127 Service and Other Special Purpose Applications 128 A194/A194M-14 Standard Specification for Carbon and Alloy Steel 129 Nuts for Bolts for High Pressure or High Temperature Service, or 130 Both 131 A216/A216M-14 Standard Specification for Steel Castings, Carbon, 132 Suitable for Fusion Welding, for High Temperature Service 133 A242/A242M-13 Standard Specification for High-Strength Low-Alloy 134 Structural Steel 135 A283/A283M-13 Standard Specification for Low and Intermediate 136 Tensile Strength Carbon Steel Plates 137 A307-14 Standard Specification for Carbon Steel Bolts and Studs, 138 60,000 PSI Tensile Strength 139 A354-07aDRAFT Standard Specification for Quenched and Tempered Alloy 140 Steel Bolts, Studs, and Other Externally Threaded Fasteners 141 A370-14 Standard Test Methods and Definitions for Mechanical Testing 142 of Steel Products 143 A449-14 Standard Specification for Hex Cap Screws, Bolts and Studs, 144 Steel, Heat Treated, 120/105/90 ksi Minimum Tensile Strength, 145 General Use 146 A500/A500M-13 Standard Specification for Cold-Formed Welded and 147 Seamless Carbon Steel Structural Tubing in Rounds and Shapes 148 A501-14 Standard Specification for Hot-Formed Welded and Seamless 149 Carbon Steel Structural Tubing 150 A502-03(2009) Standard Specification for Rivets, Steel, Structural 151 A514/A514M-14 Standard Specification for High-Yield Strength, 152 Quenched and Tempered Alloy Steel Plate, Suitable for Welding 153 A529/A529M-14 Standard Specification for High-Strength Carbon- 154 Manganese Steel of Structural Quality 155 A563-07a(2014) Standard Specification for Carbon and Alloy Steel Nuts 156 A563M-07(2013) Standard Specification for Carbon and Alloy Steel 157 Nuts [Metric] 158 A568/A568M-14 Standard Specification for Steel, Sheet, Carbon, 159 Structural, and High-Strength, Low-Alloy, Hot-Rolled and Cold- 160 Rolled, General Requirements for 161 A572/A572M-13a Standard Specification for High-Strength Low-Alloy 162 Columbium-Vanadium Structural Steel

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163 A588/A588M-10 Standard Specification for High-Strength Low-Alloy 164 Structural Steel, up to 50 ksi [345 MPa] Minimum Yield Point, with 165 Atmospheric Corrosion Resistance 166 A606/A606M-09a Standard Specification for Steel, Sheet and Strip, 167 High-Strength, Low-Alloy, Hot-Rolled and Cold-Rolled, with Im- 168 proved Atmospheric Corrosion Resistance 169 A618/A618M-04(2010) Standard Specification for Hot-Formed Welded 170 and Seamless High-Strength Low-Alloy Structural Tubing 171 A668/A668M-14 Standard Specification for Steel Forgings, Carbon and 172 Alloy, for General Industrial Use 173 A673/A673M-07(2012) Standard Specification for Sampling Procedure 174 for Impact Testing of Structural Steel 175 A709/A709M-13a Standard Specification for Structural Steel for Bridg- 176 es 177 A751-14a Standard Test Methods, Practices, and Terminology for 178 Chemical Analysis of Steel Products 179 A847/A847M-14 Standard Specification for Cold-Formed Welded and 180 Seamless High-Strength, Low-Alloy Structural Tubing with Im- 181 proved Atmospheric Corrosion Resistance 182 A852/A852M-03(2007) Standard Specification for Quenched and 183 Tempered Low-Alloy Structural Steel Plate with 70 ksi [485 MPa] 184 Minimum Yield Strength to 4 in. [100 mm] Thick 185 A913/A913M-14a Standard Specification for High-Strength Low-Alloy 186 Steel Shapes of Structural Quality, Produced by Quenching and 187 Self-Tempering Process (QST) 188 A992/A992M-11 Standard Specification for Structural Steel Shapes 189 190 User Note: ASTM A992 is the most commonly referenced specification 191 for W-shapes. 192 193 A1011/A1011M-14 Standard Specification for Steel, Sheet and Strip, 194 Hot-Rolled,DRAFT Carbon, Structural, High-Strength Low-Alloy, High- 195 Strength Low-Alloy with Improved Formability, and Ultra-High 196 Strength 197 A1043/A1043M-14 Standard Specification for Structural Steel with Low 198 Yield to Tensile Ratio for Use in Buildings 199 A1065/A1065M-09(2014) Standard Specification for Cold-Formed 200 Electric-Fusion (Arc) Welded High-Strength Low-Alloy Structural 201 Tubing, with 50 ksi Minimum Yield Point 202 A1066/A1066M-11 Standard Specification for High-Strength Low-Alloy 203 Structural Steel Plate Produced by Thermo-Mechanical Controlled 204 Process (TMCP) 205 A1085/A1085M-13 Standard Specification for Cold-Formed Welded 206 Carbon Steel Hollow Structural Sections (HSS) 207 C567/C567M-14 Standard Test Method for Determining Density of 208 Structural Lightweight Concrete 209 E119-14 Standard Test Methods for Fire Tests of Building Construction 210 and Materials 211 E165/E165M-12 Standard Practice for Liquid Penetrant Examination 212 for General Industry 213 E709-14 Standard Guide for Magnetic Particle Examination 214 F436-11 Standard Specification for Hardened Steel Washers 215 F436M-11 Standard Specification for Hardened Steel Washers (Metric) 216 F606-14 Standard Test Methods for Determining the Mechanical Prop- 217 erties of Externally and Internally Threaded Fasteners, Washers, 218 Direct Tension Indicators, and Rivets

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219 F606M-14 Standard Test Methods for Determining the Mechanical 220 Properties of Externally and Internally Threaded Fasteners, Wash- 221 ers, and Rivets (Metric) 222 F844-07a(2013) Standard Specification for Washers, Steel, Plain (Flat), 223 Unhardened for General Use 224 F959-13 Standard Specification for Compressible-Washer-Type Direct 225 Tension Indicators for Use with Structural Fasteners 226 F959M-13 Standard Specification for Compressible-Washer-Type Direct 227 Tension Indicators for Use with Structural Fasteners (Metric) 228 F1554-07ae1 Standard Specification for Anchor Bolts, Steel, 36, 55, and 229 105 ksi Yield Strength 230 231 User Note: ASTM F1554 is the most commonly referenced specifica- 232 tion for anchor rods. Grade and weldability must be specified. 233 234 235 F3043-14 Standard Specification for “Twist Off” Type Tension Control 236 Structural Bolt/Nut/Washer Assemblies, Alloy Steel, Heat Treated, 237 200 ksi Minimum Tensile Strength 238 F3111-14 Specification for Heavy Hex Structural Bolt/Nut/Washer 239 Assemblies, Steel, Heat Treated, 200-ksi Minimum Tensile Strength 240 F3125-15 Specification for High Strength Structural Bolts, Steel and 241 Alloy Steel, Heat Treated, 120ksi (830MPa) and 150ksi (1040MPa) 242 Minimum Tensile Strength, Inch and Metric Dimensions 243 244 (g) American Welding Society (AWS) 245 246 AWS A5.1/A5.1M:2012 Specification for Carbon Steel Electrodes for 247 Shielded Metal Arc Welding 248 AWS A5.5/A5.5M:2014 Specification for Low-Alloy Steel Electrodes for 249 Shielded Metal Arc Welding 250 AWS A5.17/A5.17M:1997DRAFT (R2007) Specification for Carbon Steel 251 Electrodes and Fluxes for Submerged Arc Welding 252 AWS A5.18/A5.18M:2005 Specification for Carbon Steel Electrodes 253 and Rods for Gas Shielded Arc Welding 254 AWS A5.20/A5.20M:2005 Specification for Carbon Steel Electrodes for 255 Flux Cored Arc Welding 256 AWS A5.23/A5.23M:2011 Specification for Low-Alloy Steel Electrodes 257 and Fluxes for Submerged Arc Welding 258 AWS A5.25/A5.25M:1997 (R2009) Specification for Carbon and Low- 259 Alloy Steel Electrodes and Fluxes for Electroslag Welding 260 AWS A5.26/A5.26M:1997 (R2009) Specification for Carbon and Low- 261 Alloy Steel Electrodes for Electrogas Welding 262 AWS A5.28/A5.28M:2005 Specification for Low-Alloy Steel Electrodes 263 and Rods for Gas Shielded Arc Welding 264 AWS A5.29/A5.29M:2010 Specification for Low-Alloy Steel Electrodes 265 for Flux Cored Arc Welding 266 AWS A5.32/A5.32M:2011 Welding Consumables – Gases and Gas 267 Mixtures for Fusion Welding and Allied Processes 268 AWS A5.36/A5.36M:2012 Specification for Carbon and Low-Alloy 269 Steel Flux Cored Electrodes for Flux Cored Arc Welding and Metal 270 Cored Electrodes for Gas Metal Arc Welding. 271 AWS B5.1:2013-AMD1 Specification for the Qualification of Welding 272 Inspectors 273 AWS D1.1/D1.1M:2015 Structural Welding Code—Steel 274 AWS D1.3:2008 Structural Welding Code—Sheet Steel

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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275 276 (h) Research Council on Structural Connections (RCSC) 277 278 Specification for Structural Joints Using High-Strength Bolts, 2014 279 280 (i) Steel Deck Insitute (SDI) 281 282 ANSI/SDI QA/QC-2011 Standard for Quality Control and Quality 283 Assurance for Installation of Steel Deck 284 285 A3. MATERIAL 286 287 1. Structural Steel Materials 288 289 Material test reports or reports of tests made by the fabricator or a testing 290 laboratory shall constitute sufficient evidence of conformity with one of the 291 ASTM standards listed in Section A3.1a. For hot-rolled structural shapes, 292 plates, and bars, such tests shall be made in accordance with ASTM 293 A6/A6M; for sheets, such tests shall be made in accordance with ASTM 294 A568/A568M; for tubing and pipe, such tests shall be made in accordance 295 with the requirements of the applicable ASTM standards listed above for 296 those product forms. 297 298 1a. ASTM Designations 299 300 Structural steel material conforming to one of the following ASTM 301 specifications is approved for use under this Specification: 302 303 (a) Hot-rolled structural shapes 304 305 ASTM A36/A36M 306 ASTM A529/A529MDRAFT 307 ASTM A572/A572M 308 ASTM A588/A588M 309 ASTM A709/A709M 310 ASTM A913/A913M 311 ASTM A992/ A992M 312 ASTM A1043/A1043M 313 314 (b) Hollow Structural Sections (HSS) 315 316 ASTM A500 317 ASTM A501 318 ASTM A618/A618M 319 ASTM A847/A847M 320 ASTM A1065/A1065M 321 ASTM A1085/A1085M 322 ASTM A53/A53M, Gr. B 323 324 (c) Plates 325 326 ASTM A36/A36M 327 ASTM A242/A242M 328 ASTM A283/A283M 329 ASTM A514/A514M 330 ASTM A529/A529M

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331 ASTM A572/A572M 332 ASTM A588/A588M 333 ASTM A709/A709M 334 ASTM A852/A852M 335 ASTM A1043/A1043M 336 ASTM A1066/A1066M 337 338 (d) Bars 339 340 ASTM A36/A36M 341 ASTM A529/A529M 342 ASTM A572/A572M 343 ASTM A709/A709M 344 345 (e) Sheets 346 347 ASTM A606/A606M 348 ASTM A1011/A1011M SS, HSLAS, AND HSLAS-F 349 350 1b. Unidentified Steel 351 352 Unidentified steel, free of injurious defects, is permitted to be used only for 353 members or details whose failure will not reduce the strength of the structure, 354 either locally or overall. Such use shall be subject to the approval of the 355 engineer of record. 356 357 User Note: Unidentified steel may be used for details where the precise 358 mechanical properties and weldability are not of concern. These are 359 commonly curb plates, shims and other similar pieces. 360 361 1c. Rolled Heavy Shapes 362 DRAFT 363 ASTM A6/A6M hot-rolled shapes with a flange thickness exceeding 2 in. (50 364 mm) are considered to be rolled heavy shapes. Rolled heavy shapes used as 365 members subject to primary (computed) tensile forces due to tension or 366 flexure and spliced or connected using complete-joint-penetration groove 367 welds that fuse through the thickness of the flange or the flange and the web, 368 shall be specified as follows. The structural design documents shall require 369 that such shapes be supplied with Charpy V-notch (CVN) impact test results 370 in accordance with ASTM A6/A6M, Supplementary Requirement S30, 371 Charpy V-Notch Impact Test for Structural Shapes—Alternate Core 372 Location. The impact test shall meet a minimum average value of 20 ft-lb 373 (27 J) absorbed energy at a maximum temperature of +70 F (+21 C). 374 375 The above requirements do not apply if the splices and connections are made 376 by bolting. Where a rolled heavy shape is welded to the surface of another 377 shape using groove welds, the requirement above applies only to the shape 378 that has weld metal fused through the cross section. 379 380 User Note: Additional requirements for joints in heavy rolled members are 381 given in Sections J1.5, J1.6, J2.6 and M2.2. 382 383 384 1d. Built-Up Heavy Shapes 385

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386 Built-up cross sections consisting of plates with a thickness exceeding 2 in. 387 (50 mm) are considered built-up heavy shapes. Built-up heavy shapes used as 388 members subject to primary (computed) tensile forces due to tension or 389 flexure and spliced or connected to other members using complete-joint- 390 penetration groove welds that fuse through the thickness of the plates, shall 391 be specified as follows. The structural design documents shall require that 392 the steel be supplied with Charpy V-notch impact test results in accordance 393 with ASTM A6/A6M, Supplementary Requirement S5, Charpy V-Notch 394 Impact Test. The impact test shall be conducted in accordance with ASTM 395 A673/A673M, Frequency P, and shall meet a minimum average value of 20 396 ft-lb (27 J) absorbed energy at a maximum temperature of +70 F (+21 C). 397 398 When a built-up heavy shape is welded to the face of another member using 399 groove welds, the requirement above applies only to the shape that has weld 400 metal fused through the cross section. 401 402 User Note: Additional requirements for joints in heavy built-up members 403 are given in Sections J1.5, J1.6, J2.6 and M2.2. 404 405 2. Steel Castings and Forgings 406 407 Steel castings and forgings shall conform to an ASTM standard intended for 408 structural applications and shall provide strength, ductility, weldability and 409 toughness adequate for the purpose. Test reports produced in accordance with 410 the ASTM reference standards shall constitute sufficient evidence of 411 conformity with such standards. 412 413 3. Bolts, Washers and Nuts 414 415 Bolt, washer and nut material conforming to one of the following ASTM 416 specifications is approved for use under this Specification: 417 DRAFT 418 (a) Bolts 419 420 ASTM A307 421 ASTM A354 422 ASTM A449 423 ASTM F3043 424 ASTM F3111 425 ASTM F3125 426 427 (b) Nuts 428 429 ASTM A194/A194M 430 ASTM A563 431 ASTM A563M 432 433 (c) Washers 434 435 ASTM F436 436 ASTM F436M 437 ASTM F844 438 439 (d) Compressible-Washer-Type Direct Tension Indicators 440 441 ASTM F959

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442 ASTM F959M 443 444 Manufacturer’s certification shall constitute sufficient evidence of conformity 445 with the standards. 446 447 4. Anchor Rods and Threaded Rods 448 449 Anchor rod and threaded rod material conforming to one of the following 450 ASTM specifications is approved for use under this Specification: 451 452 ASTM A36/A36M 453 ASTM A193/A193M 454 ASTM A354 455 ASTM A449 456 ASTM A572/A572M 457 ASTM A588/A588M 458 ASTM F1554 459 460 User Note: ASTM F1554 is the preferred material specification for anchor 461 rods. 462 463 ASTM A449 material is permitted for high-strength anchor rods and threaded 464 rods of any diameter. 465 466 Threads on anchor rods and threaded rods shall conform to the Unified 467 Standard Series of ASME B18.2.6 and shall have Class 2A tolerances. 468 469 Manufacturer’s certification shall constitute sufficient evidence of conformity 470 with the standards. 471 472 5. Consumables for Welding 473 DRAFT 474 Filler metals and fluxes shall conform to one of the following specifications 475 of the American Welding Society: 476 AWS A5.1/A5.1M 477 AWS A5.5/A5.5M 478 AWS A5.17/A5.17M 479 AWS A5.18/A5.18M 480 AWS A5.20/A5.20M 481 AWS A5.23/A5.23M 482 AWS A5.25/A5.25M 483 AWS A5.26/A5.26M 484 AWS A5.28/A5.28M 485 AWS A5.29/A5.29M 486 AWS A5.32/A5.32M 487 AWS A5.36/A5.36M 488 489 Manufacturer’s certification shall constitute sufficient evidence of conformity 490 with the standards. 491 492 6. Headed Stud Anchors 493 494 Steel headed stud anchors shall conform to the requirements of the Structural 495 Welding Code—Steel (AWS D1.1/D1.1M). 496

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497 Manufacturer’s certification shall constitute sufficient evidence of conformity 498 with AWS D1.1/D1.1M. 499 500 A4. STRUCTURAL DESIGN DRAWINGS AND SPECIFICATIONS 501 502 The structural design drawings and specifications shall meet the requirements 503 of the Code of Standard Practice. 504 505 User Note: Provisions in this Specification contain information that is to be 506 shown on design drawings. These include: 507 508  Section A3.1c Rolled heavy shapes where alternate core Charpy V- 509 notch toughness (CVN) is required 510  Section A3.1d Built-up heavy shapes where CVN toughness is 511 required 512  Section J3.1 Locations of connections using pretensioned bolts 513 514 Other information needed by the fabricator or erector should be shown on 515 design drawings, including: 516 517 • Fatigue details requiring nondestructive testing 518 • Risk category (Chapter N) 519 • Indication of complete-joint-penetration (CJP) groove welds subject 520 to tension (Chapter N). DRAFT

Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

1 CHAPTER B

2 DESIGN REQUIREMENTS 3 4 5 6 This chapter addresses general requirements for the design of steel structures 7 applicable to all chapters of the Specification. 8 9 The chapter is organized as follows: 10 11 B1. General Provisions 12 B2. Loads and Load Combinations 13 B3. Design Basis 14 B4. Member Properties 15 B5. Fabrication and Erection 16 B6. Quality Control and Quality Assurance 17 B7. Evaluation of Existing Structures 18 19 B1. GENERAL PROVISIONS 20 The design of members and connections shall be consistent with the intended 21 behavior of the framing system and the assumptions made in the structural 22 analysis. 23 B2. LOADS AND LOAD COMBINATIONS 24 The loads, nominal loads and load combinations shall be those stipulated by 25 the applicable building code. In the absence of a building code, the loads, 26 nominal loadsDRAFT and load combinations shall be those stipulated in Minimum 27 Design Loads for Buildings and Other Structures (ASCE/SEI 7). 28 User Note: When using ASCE/SEI 7, for design according to Section B3.1 29 (LRFD), the load combinations in ASCE/SEI 7, Section 2.3 apply. For 30 design according to Section B3.2 (ASD), the load combinations in 31 ASCE/SEI 7, Section 2.4 apply. 32 33 B3. DESIGN BASIS 34 35 Design shall be such that no applicable strength or serviceability limit state 36 shall be exceeded when the structure is subjected to all applicable load 37 combinations. 38 39 Design for strength shall be performed according to the provisions for load 40 and resistance factor design (LRFD) or to the provisions for allowable 41 strength design (ASD). 42 User Note: The term “design” as used in this Specification is the process of 43 establishing the physical and other properties of a structure for the purpose of 44 achieving the desired strength, serviceability, durability, constructability, 45 economy and other desired characteristics. Design for strength includes 46 analysis to determine required strength and proportioning to have adequate 47 available strength.

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

48 1. Design for Strength Using Load and Resistance Factor Design (LRFD) 49 50 Design according to the provisions for LRFD satisfies the requirements of 51 the Specification when the design strength of each structural component 52 equals or exceeds the required strength determined on the basis of the LRFD 53 load combinations. All provisions of the Specification, except for those in 54 Section B3.2, shall apply. 55 Design shall be performed in accordance with Equation B3-1:

56 Ru  Rn (B3-1) 57 where

58 Ru = required strength using LRFD load combinations 59 Rn = nominal strength 60  = resistance factor

61 Rn = design strength 62

63 The nominal strength, Rn, and the resistance factor, , for the applicable limit 64 states are specified in Chapters D through K. 65 66 2. Design for Strength Using Allowable Strength Design (ASD) 67 68 Design according to the provisions for ASD satisfies the requirements of the 69 Specification when the allowable strength of each structural component 70 equals or exceeds the required strength determined on the basis of the ASD 71 load combinations. All provisions of the Specification, except those of 72 Section B3.1, shall apply. 73 Design shall be performed in accordance with Equation B3-2: 74 DRAFT Ra  Rn/ (B3-2) 75 where

76 Ra = required strength using ASD load combinations 77 Rn = nominal strength 78  = safety factor

79 Rn/ = allowable strength 80

81 The nominal strength, Rn, and the safety factor, , for the applicable limit 82 states are specified in Chapters D through K. 83 84 3. Required Strength 85 86 The required strength of structural members and connections shall be 87 determined by structural analysis for the applicable load combinations as 88 stipulated in Section B2. 89 Design by elastic or inelastic analysis is permitted. Requirements for 90 analysis are stipulated in Chapter C and Appendix 1. 91 The required flexural strength of indeterminate beams composed of compact 92 sections, as defined in Section B4.1, carrying gravity loads only, and 93 satisfying the unbraced length requirements of Section F13.5 is permitted to 94 be taken as nine-tenths of the negative moments at the points of support, 95 produced by the gravity loading and determined by an elastic analysis 96 satisfying the requirements of Chapter C, provided that the maximum

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

97 positive moment is increased by one-tenth of the average negative moment 98 determined by an elastic analysis. This moment redistribution is not 99 permitted for moments in members with Fy exceeding 65 ksi (450 MPa), for 100 moments produced by loading on cantilevers, for design using partially 101 restrained (PR) moment connections, or for design by inelastic analysis using 102 the provisions of Appendix 1. This moment redistribution is permitted for 103 design according to Section B3.1 (LRFD) and for design according to

104 Section B3.2 (ASD). The required axial strength shall not exceed 0.15cFyAg 105 for LRFD or 0.15FyAg/c for ASD, where c and c are determined from 2 2 106 Section E1, Ag = gross area of member, in. (mm ), and Fy = specified 107 minimum yield stress, ksi (MPa). 108 109 4. Design of Connections and Supports 110 111 Connection elements shall be designed in accordance with the provisions of 112 Chapters J and K. The forces and deformations used in design of the 113 connections shall be consistent with the intended performance of the 114 connection and the assumptions used in the design of the structure. Self- 115 limiting inelastic deformations of the connections are permitted. At points of 116 support, beams, girders, and trusses shall be restrained against rotation about 117 their longitudinal axis unless it can be shown by analysis that the restraint is 118 not required. 119 User Note: Section 3.1.2 of the Code of Standard Practice addresses 120 communication of necessary information for the design of connections. 121 4a. Simple Connections 122 A simple connection transmits a negligible moment. In the analysis of the 123 structure, simple connections may be assumed to allow unrestrained relative 124 rotation between the framing elements being connected. A simple 125 connection shall have sufficient rotation capacity to accommodate the 126 required rotationDRAFT determined by the analysis of the structure. 127 4b. Moment Connections 128 Two types of moment connections, fully restrained and partially restrained, 129 are permitted, as specified below. 130 (a) Fully Restrained (FR) Moment Connections 131 A fully restrained (FR) moment connection transfers moment with a 132 negligible rotation between the connected members. In the analysis of 133 the structure, the connection may be assumed to allow no relative rota- 134 tion. An FR connection shall have sufficient strength and stiffness to 135 maintain the initial angle between the connected members at the strength 136 limit states. 137 (b) Partially Restrained (PR) Moment Connections 138 Partially restrained (PR) moment connections transfer moments, but the 139 rotation between connected members is not negligible. In the analysis of 140 the structure, the force-deformation response characteristics of the 141 connection shall be included. The response characteristics of a PR 142 connection shall be documented in the technical literature or established 143 by analytical or experimental means. The component elements of a PR 144 connection shall have sufficient strength, stiffness and deformation 145 capacity at the strength limit states. 146

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

147 5. Design of Diaphragms and Collectors 148 149 Diaphragms and collectors shall be designed for forces that result from loads 150 as stipulated in Section B2. They shall be designed in conformance with the 151 provisions of Chapters C through K, as applicable. 152 153 6. Design of Anchorages to Concrete 154 155 Anchorage between steel and concrete acting compositely shall be designed 156 in accordance with Chapter I. The design of column bases and anchor rods 157 shall be in accordance with Chapter J. 158 159 7. Design for Stability 160 161 The structure and its elements shall be designed for stability in accordance 162 with Chapter C. 163 164 8. Design for Serviceability 165 166 The overall structure and the individual members and connections shall be 167 evaluated for the serviceability limit states stipulated in Chapter L. 168 169 9. Design for Structural Integrity 170 171 When design for structural integrity is required by the applicable building 172 code, the requirements in this section shall be met. 173 174 (a) Column splices shall have a nominal strength in tension equal to or 175 greater than D+L for the area tributary to the column between the splice 176 and the splice or base immediately below. 177 DRAFT 178 (b) Beam and girder end connections shall have a minimum nominal axial 179 tensile strength equal to (i) two-thirds of the required vertical shear 180 strength for design according to Section B3.1 (LRFD) or (ii) the re- 181 quired vertical shear strength for design according to Section B3.2 182 (ASD), but not less than 10 kips in either case. 183 184 (c) End connections of members bracing columns shall have a nominal 185 tensile strength equal to or greater than (i) 1% of two-thirds of the 186 required column axial strength at that level for design according to 187 Section B3.1 (LRFD) or (ii) 1% of the required column axial strength at 188 that level for design according to Section B3.2 (ASD). 189 190 The strength requirements for structural integrity in this section shall be 191 evaluated independently of other strength requirements. For the purpose of 192 satisfying these requirements, bearing bolts in connections with short-slotted 193 holes parallel to the direction of the tension force and inelastic deformation 194 of the connection are permitted.

195 10. Design for Ponding 196

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

197 The roof system shall be investigated through structural analysis to assure 198 strength and stability under ponding conditions, unless the roof surface is 199 configured to prevent the accumulation of water. 200 Methods of evaluating stability and strength under ponding conditions are 201 provided in Appendix 2. 202 11. Design for Fatigue 203 204 Fatigue shall be considered in accordance with Appendix 3, Design for 205 Fatigue, for members and their connections subject to repeated loading. 206 Fatigue need not be considered for seismic effects or for the effects of wind 207 loading on typical building lateral force resisting systems and building 208 enclosure components. 209 210 12. Design for Fire Conditions 211 212 Two methods of design for fire conditions are provided in Appendix 4, 213 Structural Design for Fire Conditions: by Analysis and by Qualification 214 Testing. Compliance with the fire protection requirements in the applicable 215 building code shall be deemed to satisfy the requirements of Appendix 4. 216 217 This section is not intended to create or imply a contractual requirement for 218 the engineer of record responsible for the structural design or any other 219 member of the design team. 220 User Note: Design by qualification testing is the prescriptive method 221 specified in most building codes. Traditionally, on most projects where the 222 architect is the prime professional, the architect has been the responsible 223 party to specify and coordinate fire protection requirements. Design by 224 analysis is a new engineering approach to fire protection. Designation of the 225 person(s) responsible for designing for fire conditions is a contractual matter 226 to be addressedDRAFT on each project. 227 13. Design for Corrosion Effects 228 Where corrosion could impair the strength or serviceability of a structure, 229 structural components shall be designed to tolerate corrosion or shall be 230 protected against corrosion. 231 B4. MEMBER PROPERTIES 232 233 1. Classification of Sections for Local Buckling 234 235 For members subject to axial compression, sections are classified as 236 nonslender element or slender-element sections. For a nonslender element 237 section, the width-to-thickness ratios of its compression elements shall not

238 exceed r from Table B4.1a. If the width-to-thickness ratio of any 239 compression element exceeds r, the section is a slender-element section. 240 241 For members subject to flexure, sections are classified as compact, 242 noncompact or slender-element sections. For a section to qualify as compact, 243 its flanges must be continuously connected to the web or webs and the width- 244 to-thickness ratios of its compression elements shall not exceed the limiting

245 width-to-thickness ratios, p, from Table B4.1b. If the width-to-thickness 246 ratio of one or more compression elements exceeds p, but does not exceed 247 r from Table B4.1b, the section is noncompact. If the width-to-thickness

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

248 ratio of any compression element exceeds r, the section is a slender-element 249 section. 250 251 1a. Unstiffened Elements 252 253 For unstiffened elements supported along only one edge parallel to the 254 direction of the compression force, the width shall be taken as follows: 255 256 (a) For flanges of I-shaped members and tees, the width, b, is one-half the 257 full-flange width, bf. 258 259 (b) For legs of angles and flanges of channels and zees, the width, b, is the 260 full leg or flange width. 261 262 (c) For plates, the width, b, is the distance from the free edge to the first row 263 of fasteners or line of welds. 264 265 (d) For stems of tees, d is the full depth of the section. 266 267 User Note: Refer to Table B4.1 for the graphic representation of unstiffened 268 element dimensions. 269 270 1b. Stiffened Elements 271 272 For stiffened elements supported along two edges parallel to the direction of 273 the compression force, the width shall be taken as follows: 274 275 (a) For webs of rolled sections, h is the clear distance between flanges less 276 the fillet at each flange; hc is twice the distance from the centroid to the 277 inside face of the compression flange less the fillet or corner radius. 278 DRAFT 279 (b) For webs of built-up sections, h is the distance between adjacent lines of 280 fasteners or the clear distance between flanges when welds are used, and 281 hc is twice the distance from the centroid to the nearest line of fasteners 282 at the compression flange or the inside face of the compression flange 283 when welds are used; hp is twice the distance from the plastic neutral 284 axis to the nearest line of fasteners at the compression flange or the 285 inside face of the compression flange when welds are used. 286 287 (c) For flange or diaphragm plates in built-up sections, the width, b, is the 288 distance between adjacent lines of fasteners or lines of welds. 289 290 (d) For flanges of rectangular hollow structural sections (HSS), the width, b, 291 is the clear distance between webs less the inside corner radius on each 292 side. For webs of rectangular HSS, h is the clear distance between the 293 flanges less the inside corner radius on each side. If the corner radius is 294 not known, b and h shall be taken as the corresponding outside dimen- 295 sion minus three times the thickness. The thickness, t, shall be taken as 296 the design wall thickness, per Section B4.2. 297 298 (e) For flanges or webs of box sections and other stiffened elements, the 299 width, b, is the clear distance between the elements providing stiffening. 300

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

301 (f) For perforated cover plates, b is the transverse distance between the 302 nearest line of fasteners, and the net area of the plate is taken at the 303 widest hole. 304 305 User Note: Refer to Table B4.1 for the graphic representation of stiffened 306 element dimensions. 307 308 For tapered flanges of rolled sections, the thickness is the nominal value 309 halfway between the free edge and the corresponding face of the web. 310 311 2. Design Wall Thickness for HSS 312 313 The design wall thickness, t, shall be used in calculations involving the wall 314 thickness of hollow structural sections (HSS). The design wall thickness, t, 315 shall be taken equal to the nominal thickness for box sections and HSS 316 produced according to ASTM A1065 or ASTM A1085. For HSS produced 317 according to other standards approved for use under this Specification, the 318 design wall thickness, t, shall be taken equal to 0.93 times the nominal wall 319 thickness. 320 User Note: A pipe can be designed using the provisions of the Specification 321 for round HSS sections as long as the pipe conforms to ASTM A53 Class B 322 and the appropriate limitations of the Specification are used. 323 324 3. Gross and Net Area Determination 325 326 3a. Gross Area 327 328 The gross area, Ag, of a member is the total cross-sectional area. 329 330 3b. Net Area DRAFT 331 332 The net area, An, of a member is the sum of the products of the thickness and 333 the net width of each element computed as follows: 334 335 In computing net area for tension and shear, the width of a bolt hole shall be 336 taken as z in. (2 mm) greater than the nominal dimension of the hole. 337 338 For a chain of holes extending across a part in any diagonal or zigzag line, 339 the net width of the part shall be obtained by deducting from the gross width 340 the sum of the diameters or slot dimensions as provided in this section, of all 341 holes in the chain, and adding, for each gage space in the chain, the quantity 342 s2/ 4g, 343 344 where 345 346 s = longitudinal center-to-center spacing (pitch) of any two 347 consecutive holes, in. (mm) 348 g = transverse center-to-center spacing (gage) between fastener gage 349 lines, in. (mm) 350 351 For angles, the gage for holes in opposite adjacent legs shall be the sum of 352 the gages from the back of the angles less the thickness. 353

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

354 For slotted HSS welded to a gusset plate, the net area, An, is the gross area 355 minus the product of the thickness and the total width of material that is 356 removed to form the slot. 357 358 In determining the net area across plug or slot welds, the weld metal shall not 359 be considered as adding to the net area. 360 361 For members without holes, the net area, An, is equal to the gross area, Ag. 362 363 364

DRAFT

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

365 TABLE B4.1a

Width-to-Thickness Ratios: Compression Elements Members Subject to Axial Compression

Limiting Width- Width-to-Thickness to- Ratio Thick- λ Case r Description of ness (nonslender / Element Ratio slender) Examples 1 Flanges of rolled I- b/t E shaped sections, 0.56 plates projecting Fy from rolled I-shaped sections; outstanding legs of pairs of angles connected with continuous contact, flanges of channels, and flanges of tees DRAFT

2 Flanges of built-up b/t [a] I-shaped sections and plates or angle kEc 0.64 legs projecting from F built-up I-shaped y

Unstiffened Elements sections

3 Legs of single b/t E angles, legs of 0.45 double angles with Fy separators, and all other unstiffened elements

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

4 Stems of tees d/t E 0.75 Fy

5 Webs of doubly- h/tw E symmetric rolled 1.49 and built-up I- Fy shaped sections and channels

6 Walls of rectangular b/t E HSS 1.40 Fy

7 Flange cover plates b/t E and diaphragm 1.40 plates between Fy lines of fasteners or welds

Stiffened Elements 8 All other stiffened b/t E elements 1.49 F DRAFTy 9 Round HSS D/t E 0.11 Fy

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

B-11

TABLE B4.1b Width-to-Thickness Ratios: Compression Elements Members Subject to Flexure

Width-to- Limiting Width-to-Thickness Ratios

Thick- λ r Description ness λ (noncompact / Case p of Element Ratio (compact / noncompact) slender) Examples 10 Flanges of b/t E E rolled I- 0.38 1.0 shaped Fy Fy sections, channels, and tees

11 Flanges of b/t E [a] [b] doubly and 0.38 singly kEc Fy 0.95 symmetric I- F shaped built- L up sections

12 Legs of single b/t E E angles 0.54 0.91 Fy Fy Unstiffened Elements 13 Flanges of all b/t E E I-shaped DRAFT0.38 1.0 sections and Fy Fy channels in flexure about the weak axis

14 Stems of tees d/t E E 0.84 1.52 Fy Fy 15 Webs of h/tw E E doubly- 3.76 5.70 symmetric I- Fy Fy shaped sections and channels

16 Webs of hc/tw [c] hEc E singly- 5.70 symmetric I- hFpy   Fy shaped 2 r  sections Mp Stiffened Elements 0.54 0.09 M y

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

B-12

17 Flanges of b/t E E rectangular 1.12 1.40 HSS Fy Fy

18 Flange cover b/t E E plates and 1.12 1.40 diaphragm Fy Fy plates between lines of fasteners or welds 19 Webs of h/t E E rectangular 2.42 5.70 HSS and box Fy Fy sections

20 Round HSS D/t E E 0.07 0.31 F F DRAFTy y

21 Flanges of b/t E E box sections 1.12 1.49 Fy Fy

4 [a] kc  but shall not be taken less than 0.35 nor greater than 0.76 for calculation purposes. ht/ w

[b] FL = 0.7Fy for slender web I-shaped members and major axis bending of compact and noncompact web built-up I-shaped members with Sxt/Sxc ≥ 0.7; and FL = FySxt/Sxc ≥ 0.5Fy for major-axis bending of compact and noncompact web built-up I-shaped members with Sxt/Sxc < 0.7. [c] My is the moment at yielding of the extreme fiber. Mp = FyZx, plastic bending moment, kip-in. (N-mm) E = modulus of elasticity of steel = 29,000 ksi (200 000 MPa) Fy = specified minimum yield stress, ksi (MPa) 366

Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

B-13

367 B5. FABRICATION AND ERECTION 368 369 Shop drawings, fabrication, shop painting and erection shall satisfy the 370 requirements stipulated in Chapter M, Fabrication and Erection. 371 372 B6. QUALITY CONTROL AND QUALITY ASSURANCE 373 374 Quality control and quality assurance activities shall satisfy the requirements 375 stipulated in Chapter N, Quality Control and Quality Assurance. 376 377 B7. EVALUATION OF EXISTING STRUCTURES 378 379 The evaluation of existing structures shall satisfy the requirements stipulated 380 in Appendix 5, Evaluation of Existing Structures. 381 B8. STRUCTURAL DESIGN FOR COLD OPERATING 382 TEMPERATURES 383 384 Members and connections subject to cold atmospheric or service tempera- 385 tures during normal operation shall satisfy the requirements stipulated in 386 Appendix 9, Structural Design for Cold Operating Temperatures. 387 DRAFT

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

C-1

2 CHAPTER C

3 DESIGN FOR STABILITY 4 5 6 7 This chapter addresses requirements for the design of structures for stability. 8 The direct analysis method is presented herein, with extensions for including 9 member imperfections and/or inelasticity presented in Appendix 1; 10 alternative methods to the direct analysis method are presented in Appendix 11 7. 12 13 The chapter is organized as follows: 14 15 C1. General Stability Requirements 16 C2. Calculation of Required Strengths 17 C3. Calculation of Available Strengths 18 19 C1. GENERAL STABILITY REQUIREMENTS 20 21 Stability shall be provided for the structure as a whole and for each of 22 its elements. The effects of all of the following on the stability of the 23 structure and its elements shall be considered: (a) flexural, shear, and 24 axial member deformations, and all other component and connection 25 deformations that contribute to the displacements of the structure; (b) 26 second-orderDRAFT effects (including P-∆ and P-δ effects); (c) geometric 27 imperfections; (d) stiffness reductions due to inelasticity, including 28 the effect of partial yielding of the cross section which may be 29 accentuated by the presence of residual stresses; and (e) uncertainty in 30 system, member, and connection strength and stiffness. All load- 31 dependent effects shall be calculated at a level of loading correspond- 32 ing to LRFD load combinations or 1.6 times ASD load combinations. 33 34 Any rational method of design for stability that considers all of the 35 listed effects is permitted; this includes the methods identified in 36 Sections C1.1 and C1.2. 37 38 User Note: See Commentary Section C1 and Table C-C1.1 for an 39 explanation of how requirements (a) through (e) of Section C1 are 40 satisfied in the methods of design listed in Sections C1.1 and C1.2. 41 42 1. Direct Analysis Method of Design 43 44 The direct analysis method of design is permitted for all structures, 45 and can be based on either elastic or inelastic analysis. For design by 46 elastic analysis, required strengths shall be calculated in accordance 47 with Section C2 and the calculation of available strengths in

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION C-2

48 accordance with Section C3. For design by inelastic analysis, the 49 provisions of Section 1.2 of Appendix 1 shall be satisfied. 50 51 2. Alternative Methods of Design 52 53 The effective length method and the first-order analysis method, both 54 defined in Appendix 7, are based on elastic analysis and are permitted 55 as alternatives to the direct analysis method for structures that satisfy 56 the limitations specified in that appendix. 57 58 C2. CALCULATION OF REQUIRED STRENGTHS 59 60 For the direct analysis method of design, the required strengths of 61 components of the structure shall be determined from an elastic 62 analysis conforming to Section C2.1. The analysis shall include 63 consideration of initial imperfections in accordance with Section C2.2 64 and adjustments to stiffness in accordance with Section C2.3. 65 66 1. General Analysis Requirements 67 68 The analysis of the structure shall conform to the following require- 69 ments: 70 71 (a) The analysis shall consider flexural, shear and axial member 72 deformations, and all other component and connection defor- 73 mations that contribute to displacements of the structure. The 74 analysis shall incorporate reductions in all stiffnesses that are 75 considered to contribute to the stability of the structure, as spec- 76 ified inDRAFT Section C2.3. 77 78 (b) The analysis shall be a second-order analysis that considers 79 both P-Δ and P-δ effects, except that it is permissible to neglect 80 the effect of P-δ on the response of the structure when the fol- 81 lowing conditions are satisfied: (1) The structure supports grav- 82 ity loads primarily through nominally-vertical columns, walls or 83 frames; (2) the ratio of maximum second-order drift to maxi- 84 mum first-order drift (both determined for LRFD load combina- 85 tions or 1.6 times ASD load combinations, with stiffnesses ad- 86 justed as specified in Section C2.3) in all stories is equal to or 87 less than 1.7; and (3) no more than one-third of the total gravity 88 load on the structure is supported by columns that are part of 89 moment-resisting frames in the direction of translation being 90 considered. It is necessary in all cases to consider P-δ effects in 91 the evaluation of individual members subject to compression 92 and flexure. 93 94 User Note: A P-Δ-only second-order analysis (one that ne- 95 glects the effects of P-δ on the response of the structure) is per- 96 mitted under the conditions listed. The requirement for consid- 97 ering P-δ effects in the evaluation of individual members can be

Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION C-3

98 satisfied by applying the B1 multiplier defined in Appendix 8 to 99 the required flexural strength of the member. 100 101 Use of the approximate method of second-order analysis pro- 102 vided in Appendix 8 is permitted. 103 104 (c) The analysis shall consider all gravity and other applied loads 105 that may influence the stability of the structure. 106 107 User Note: It is important to include in the analysis all gravity 108 loads, including loads on leaning columns and other elements 109 that are not part of the lateral force resisting system. 110 111 (d) For design by LRFD, the second-order analysis shall be carried 112 out under LRFD load combinations. For design by ASD, the 113 second-order analysis shall be carried out under 1.6 times the 114 ASD load combinations, and the results shall be divided by 1.6 115 to obtain the required strengths of components. 116 117 2. Consideration of Initial Imperfections 118 119 The effect of initial imperfections in the position of points of 120 intersection of members on the stability of the structure shall be taken 121 into account either by direct modeling of these imperfections in the 122 analysis as specified in Section C2.2a or by the application of notional 123 loads as specified in Section C2.2b. 124 125 User Note: The imperfections required to be considered in this 126 section are imperfectionsDRAFT in the locations of points of intersection of 127 members. In typical building structures, the important imperfection of 128 this type is the out-of-plumbness of columns. Consideration of initial 129 out-of-straightness of individual members (member imperfections) is 130 not required in the structural analysis when using the provisions of 131 this section; it is accounted for in the compression member design 132 provisions of Chapter E and need not be considered explicitly in the 133 analysis as long as it is within the limits specified in the AISC Code of 134 Standard Practice for Steel Buildings and Bridges. As permitted (but 135 not required), Section 1.1 of Appendix 1 provides an extension to the 136 direct analysis method that includes modeling member imperfections 137 (initial out-of-straightness) within the structural analysis. 138 139 2a. Direct Modeling of Imperfections 140 141 In all cases, it is permissible to account for the effect of initial 142 imperfections by including the imperfections directly in the analysis. 143 The structure shall be analyzed with points of intersection of members 144 displaced from their nominal locations. The magnitude of the initial 145 displacements shall be the maximum amount considered in the design; 146 the pattern of initial displacements shall be such that it provides the 147 greatest destabilizing effect.

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION C-4

148 149 User Note: Initial displacements similar in configuration to both 150 displacements due to loading and anticipated buckling modes should 151 be considered in the modeling of imperfections. The magnitude of the 152 initial displacements should be based on permissible construction 153 tolerances, as specified in the Code of Standard Practice for Steel 154 Buildings and Bridges or other governing requirements, or on actual 155 imperfections if known. 156 157 In the analysis of structures that support gravity loads primarily 158 through nominally-vertical columns, walls or frames, where the ratio 159 of maximum second-order story drift to maximum first-order story 160 drift (both determined for LRFD load combinations or 1.6 times ASD 161 load combinations, with stiffnesses adjusted as specified in Section 162 C2.3) in all stories is equal to or less than 1.7, it is permissible to 163 include initial imperfections in the analysis for gravity-only load 164 combinations and not in the analysis for load combinations that 165 include applied lateral loads. 166 167 2b. Use of Notional Loads to Represent Imperfections 168 169 For structures that support gravity loads primarily through nominally- 170 vertical columns, walls or frames, it is permissible to use notional 171 loads to represent the effects of initial imperfections in the position of 172 points of intersection of members in accordance with the requirements 173 of this section. The notional load shall be applied to a model of the 174 structure based on its nominal geometry. 175 176 User Note: DRAFT In general, the notional load concept is applicable to all 177 types of structures and to imperfections in the positions of both points 178 of intersection of members and points along members, but the specific 179 requirements in Sections C2.2b(a) through C2.2b(d) are applicable 180 only for the particular class of structure and type of imperfection 181 identified above. 182 183 (a) Notional loads shall be applied as lateral loads at all levels. The 184 notional loads shall be additive to other lateral loads and shall 185 be applied in all load combinations, except as indicated in (d), 186 below. The magnitude of the notional loads shall be: 187

188 Ni = 0.002Yi (C2-1) 189 190 where 191  = 1.0 (LRFD);  = 1.6 (ASD) 192 Ni = notional load applied at level i, kips (N) 193 Yi = gravity load applied at level i from the LRFD load 194 combination or ASD load combination, as applicable, 195 kips (N) 196

Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION C-5

197 User Note: The use of notional loads can lead to additional 198 (generally small) fictitious base shears in the structure. The cor- 199 rect horizontal reactions at the foundation may be obtained by 200 applying an additional horizontal force at the base of the struc- 201 ture, equal and opposite in direction to the sum of all notional 202 loads, distributed among vertical load-carrying elements in the 203 same proportion as the gravity load supported by those ele- 204 ments. The notional loads can also lead to additional overturn- 205 ing effects, which are not fictitious. 206 207 (b) The notional load at any level, Ni, shall be distributed over that 208 level in the same manner as the gravity load at the level. The 209 notional loads shall be applied in the direction that provides the 210 greatest destabilizing effect. 211 212 User Note: For most building structures, the requirement re- 213 garding notional load direction may be satisfied as follows: For 214 load combinations that do not include lateral loading, consider 215 two alternative orthogonal directions of notional load applica- 216 tion, in a positive and a negative sense in each of the two direc- 217 tions, in the same direction at all levels; for load combinations 218 that include lateral loading, apply all notional loads in the direc- 219 tion of the resultant of all lateral loads in the combination. 220 221 (c) The notional load coefficient of 0.002 in Equation C2-1 is based 222 on a nominal initial story out-of-plumbness ratio of 1/500; 223 where the use of a different maximum out-of-plumbness is justi- 224 fied, it is permissible to adjust the notional load coefficient pro- 225 portionally.DRAFT 226 227 User Note: An out-of-plumbness of 1/500 represents the max- 228 imum tolerance on column plumbness specified in the AISC 229 Code of Standard Practice for Steel buildings and Bridges. In 230 some cases, other specified tolerances such as those on plan lo- 231 cation of columns will govern and will require a tighter plumb- 232 ness tolerance. 233 234 (d) For structures in which the ratio of maximum second-order drift 235 to maximum first-order drift (both determined for LRFD load 236 combinations or 1.6 times ASD load combinations, with stiff- 237 nesses adjusted as specified in Section C2.3) in all stories is 238 equal to or less than 1.7, it is permissible to apply the notional 239 load, Ni, only in gravity-only load combinations and not in 240 combinations that include other lateral loads. 241 242 3. Adjustments to Stiffness 243 244 The analysis of the structure to determine the required strengths of 245 components shall use reduced stiffnesses, as follows: 246

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION C-6

247 (a) A factor of 0.80 shall be applied to all stiffnesses that are 248 considered to contribute to the stability of the structure. It is 249 permissible to apply this reduction factor to all stiffnesses in the 250 structure. 251 252 User Note: Applying the stiffness reduction to some members 253 and not others can, in some cases, result in artificial distortion 254 of the structure under load and possible unintended redistribu- 255 tion of forces. This can be avoided by applying the reduction to 256 all members, including those that do not contribute to the stabil- 257 ity of the structure. 258 259 (b) An additional factor, τb, shall be applied to the flexural 260 stiffnesses of all members whose flexural stiffnesses are consid- 261 ered to contribute to the stability of the structure. For non- 262 composite members, τb shall be defined as follows (see Chapter 263 I for the definition of τb for composite members): 264

265 (1) When Pr/Pns  0.5 266

267  b = 1.0 (C2-2a) 268

269 (2) When Pr/Pns > 0.5 270

271 b = 4(Pr/Pns)[1-(Pr/Pns)] (C2-2b) 272 where 273  = 1.0 (LRFD);  = 1.6 (ASD) 274 Pr = required axial compressive strength using LRFD or 275 DRAFTASD load combinations, kips (N) 276 Pns = cross-section compressive strength; for nonslender- 277 element sections, Pns = FyAg, and for slender-element 278 sections, Pns = FyAe, where Ae is as defined in Section 279 E7, kips (N) 280 281 User Note: Taken together, Sections (a) and (b) require the use

282 of 0.8b times the nominal elastic flexural stiffness and 0.8 times 283 other nominal elastic stiffnesses for structural steel members in 284 the analysis. 285 286 (c) In structures to which Section C2.2b is applicable, in lieu of

287 using b < 1.0, where Pr/Pns > 0.5, it is permissible to use b = 288 1.0 for all noncomposite members if a notional load of 0.001Yi 289 [where Yi is as defined in Section C2.2b(a)] is applied at all lev- 290 els, in the direction specified in Section C2.2b(b), in all load 291 combinations. These notional loads shall be added to those, if 292 any, used to account for the effects of initial imperfections in 293 the position of points of intersection of members and shall not 294 be subject to Section C2.2b(d). 295

Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION C-7

296 (d) Where components comprised of materials other than structural 297 steel are considered to contribute to the stability of the structure 298 and the governing codes and specifications for the other materi- 299 als require greater reductions in stiffness, such greater stiffness 300 reductions shall be applied to those components. 301 302 C3. CALCULATION OF AVAILABLE STRENGTHS 303 304 For the direct analysis method of design, the available strengths of 305 members and connections shall be calculated in accordance with the 306 provisions of Chapters D, E, F, G, H, I, J and K, as applicable, with no 307 further consideration of overall structure stability. The effective 308 length for flexural buckling of all members shall be taken as the 309 unbraced length unless a smaller value is justified by rational analysis. 310 311 Bracing intended to define the unbraced lengths of members shall 312 have sufficient stiffness and strength to control member movement at 313 the braced points. 314 315 User Note: Methods of satisfying this bracing requirement are 316 provided in Appendix 6. The requirements of Appendix 6 are not 317 applicable to bracing that is included in the analysis of the overall 318 structure as partDRAFT of the overall force-resisting system.

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION D-1

1 CHAPTER D

2 DESIGN OF MEMBERS FOR TENSION 3 4 5 This chapter applies to members subject to axial tension caused by static forces acting through the 6 centroidal axis. 7 The chapter is organized as follows: 8 D1. Slenderness Limitations 9 D2. Tensile Strength 10 D3. Effective Net Area 11 D4. Built-Up Members 12 D5. Pin-Connected Members 13 D6. Eyebars 14 15 User Note: For cases not included in this chapter the following sections apply: 16  B3.11 Members subject to fatigue 17  Chapter H Members subject to combined axial tension and flexure 18  J3 Threaded rods 19  J4.1 Connecting elements in tension 20  J4.3 Block shear rupture strength at end connections of tension members 21 22 D1. SLENDERNESS LIMITATIONS 23 24 There is no maximum slenderness limit for members in tension. 25 26 User Note: For members designed on the basis of tension, the slenderness ratio, L/r, preferably 27 should notDRAFT exceed 300. This suggestion does not apply to rods or hangers in tension. 28 29 D2. TENSILE STRENGTH 30 31 The design tensile strength, tPn, and the allowable tensile strength, Pn/t, of tension members shall 32 be the lower value obtained according to the limit states of tensile yielding in the gross section and 33 tensile rupture in the net section. 34 35 (a) For tensile yielding in the gross section: 36 37 Pn = Fy Ag (D2-1)

38 t = 0.90 (LRFD) t = 1.67 (ASD) 39 40 (b) For tensile rupture in the net section: 41 Pn = Fu Ae (D2-2) 42

43 t = 0.75 (LRFD) t = 2.00 (ASD) 44 45 where 2 2 46 Ae = effective net area, in. (mm ) 2 2 47 Ag = gross area of member, in. (mm )

48 Fy = specified minimum yield stress, ksi (MPa)

49 Fu = specified minimum tensile strength, ksi (MPa) 50 Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

D-2

51 Where connections use plug, slot or fillet welds in holes or slots, the effective net area through the 52 holes shall be used in Equation D2-2. 53 54 D3. EFFECTIVE NET AREA 55 56 The gross area, Ag, and net area, An, of tension members shall be determined in accordance with the 57 provisions of Section B4.3. 58 59 The effective net area of tension members shall be determined as 60 61 Ae = An U (D3-1) 62 63 where U, the shear lag factor, is determined as shown in Table D3.1. 64 65 For open cross sections such as W, M, S, C, or HP shapes, WTs, STs, and single and double angles, 66 the shear lag factor, U, need not be less than the ratio of the gross area of the connected element(s) 67 to the member gross area. This provision does not apply to closed sections, such as HSS sections, 68 nor to plates. 69 70 DRAFT

Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

D-3

71 TABLE D3.1 72 Shear Lag Factors for Connections 73 to Tension Members

Case Description of Element Shear Lag Factor, U Example 1 All tension members where the tension load is transmitted directly to each of the cross-sectional elements by fasteners or U = 1.0 ______welds. (except as in Cases 4, 5 and 6).

2 All tension members, except HSS, where the tension load is transmitted to some but not all of the cross-sectional elements U 1 x by fasteners or by longitudinal welds in combination with l transverse welds. Alternatively, Case 7 is permitted for W, M, S and HP shapes. (For angles, Case 8 is permitted to be used.)

3 All tension members where the tension load is transmitted only U = 1.0 by transverse welds to some but not all of the cross-sectional and elements. An = area of the directly connected elements _____

4[a] Plates, angles, channels with welds at heels, tees, and W- 3l 2 shapes with connected elements, where the tension load is   x U 1 transmitted by longitudinal welds only. 3lw22 l  See Case 2 for definition of x . DRAFT 5 Round HSS with a single concentric gusset plate l  1.3D ……U = 1.0 x Dl<1.3D U 1 l D x   6 Rectangular HSS with a single concentric gusset l  H …U 1 x plate l BBH2  2 x  4()BH

with two side gusset plates l  H....… U 1 x l B2 x  4()BH

7 W, M, S or HP Shapes with flange connected with 3 or bf 2/3 d…U = 0.90 or Tees cut from these more fasteners per line in the bf <2/3 d…U = 0.85 ____ shapes. direction of loading (If U is calculated per Case with web connected with 4 or more 2, the larger value is fasteners per line in the direction U = 0.70 ____ permitted to be used.) of loading 8 Single and double angles with 4 or more fasteners per line in U = 0.80 ____ (If U is calculated per Case the direction of loading Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

D-4

2, the larger value is with 3 fasteners per line in the U = 0.60 ____ permitted to be used.) direction of loading (with fewer than 3 fasteners per line in the direction of loading, use Case 2) l = length of connection, in. (mm); w = plate width, in. (mm); x = eccentricity of connection, in. (mm); B = overall width of rectangular HSS member, measured 90 to the plane of the connection, in. (mm); H = overall height of rectangular HSS member, measured in the plane of the connection, in. (mm)

[a] ll12 l  , where l1 and l2 shall not be less than 4 times the weld size. 2 74 75 76 77 D4. BUILT-UP MEMBERS 78 79 For limitations on the longitudinal spacing of connectors between elements in continuous contact 80 consisting of a plate and a shape or two plates, see Section J3.5. 81 82 Lacing, perforated cover plates or tie plates without lacing are permitted to be used on the open sides 83 of built-up tension members. Tie plates shall have a length not less than two-thirds the distance 84 between the lines of welds or fasteners connecting them to the components of the member. The 85 thickness of such tie plates shall not be less than one-fiftieth of the distance between these lines. The 86 longitudinal spacing of intermittent welds or fasteners at tie plates shall not exceed 6 in. (150 mm). 87 88 User Note: The longitudinal spacing of connectors between components should preferably limit the 89 slenderness ratio in any component between the connectors to 300. 90 91 D5. PIN-CONNECTED MEMBERS 92 93 1. Tensile Strength 94 95 The designDRAFT tensile strength, tPn, and the allowable tensile strength, Pn/t, of pin-connected 96 members, shall be the lower value determined according to the limit states of tensile rupture, shear 97 rupture, bearing and yielding. 98 99 (a) For tensile rupture on the net effective area: 100 101 Pn = Fu (2tbe) (D5-1) 102 103 t = 0.75 (LRFD) t = 2.00 (ASD) 104 105 (b) For shear rupture on the effective area: 106 107 Pn = 0.6FuAsf (D5-2) 108

109 sf = 0.75 (LRFD) sf = 2.00 (ASD) 110 111 where 2 2 112 Asf = area on the shear failure path = 2t(a + d / 2), in. (mm ) 113 a = shortest distance from edge of the pin hole to the edge of the member measured parallel 114 to the direction of the force, in. (mm) 115 be = 2t + 0.63, in. (= 2t + 16, mm), but not more than the actual distance from the edge of the 116 hole to the edge of the part measured in the direction normal to the applied force, in. 117 (mm) 118 d = diameter of pin, in. (mm) 119 t = thickness of plate, in. (mm) Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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120 121 (c) For bearing on the projected area of the pin, use Section J7. 122 123 (d) For yielding on the gross section, use Section D2(a). 124 125 2. Dimensional Requirements 126 127 Pin connected members shall meet the following requirements: 128 129 (a)The pin hole shall be located midway between the edges of the member in the direction normal to 130 the applied force. 131 132 (b)When the pin is expected to provide for relative movement between connected parts while under 133 full load, the diameter of the pin hole shall not be more than Q in. (1 mm) greater than the 134 diameter of the pin. 135 136 (c)The width of the plate at the pin hole shall not be less than 2be + d and the minimum extension, a, 137 beyond the bearing end of the pin hole, parallel to the axis of the member, shall not be less than 138 1.33be. 139 140 (d)The corners beyond the pin hole are permitted to be cut at 45 to the axis of the member, provided 141 the net area beyond the pin hole, on a plane perpendicular to the cut, is not less than that required 142 beyond the pin hole parallel to the axis of the member. 143 144 D6. EYEBARS 145 146 1. Tensile Strength 147 148 The available tensile strength of eyebars shall be determined in accordance with Section D2, with Ag 149 taken as the cross-sectional area of the body. 150 151 For calculationDRAFT purposes, the width of the body of the eyebars shall not exceed eight times its 152 thickness. 153 154 2. Dimensional Requirements 155 156 Eyebars shall meet the following requirements: 157 158 (a)Eyebars shall be of uniform thickness, without reinforcement at the pin holes, and have circular 159 heads with the periphery concentric with the pin hole. 160 161 (b)The radius of transition between the circular head and the eyebar body shall not be less than the 162 head diameter. 163 164 (c)The pin diameter shall not be less than seven-eighths times the eyebar body width, and the pin 165 hole diameter shall not be more than Q in. (1 mm) greater than the pin diameter. 166 167 (d)For steels having Fy greater than 70 ksi (485 MPa), the hole diameter shall not exceed five times 168 the plate thickness, and the width of the eyebar body shall be reduced accordingly. 169 170 (e) A thickness of less than 2 in. (13 mm) is permissible only if external nuts are provided to tighten 171 pin plates and filler plates into snug contact. The width from the hole edge to the plate edge 172 perpendicular to the direction of applied load shall be greater than two-thirds and, for the purpose 173 of calculation, not more than three-fourths times the eyebar body width. 174

Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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3 CHAPTER E

4 DESIGN OF MEMBERS FOR COMPRESSION 5 6 This chapter addresses members subject to axial compression. 7 The chapter is organized as follows: 8 9 E1. General Provisions 10 E2. Effective Length 11 E3. Flexural Buckling of Members without Slender Elements 12 E4. Torsional and Flexural-Torsional Buckling of Members without Slender Elements 13 E5. Single Angle Compression Members 14 E6. Built-Up Members 15 E7. Members with Slender Elements 16 17 User Note: For cases not included in this chapter the following sections apply: 18  H1–H2 Members subject to combined axial compression and flexure 19  H3 Members subject to axial compression and torsion 20  I2 Composite axially loaded members 21  J4.4 Compressive strength of connecting elements 22 23 E1. GENERAL PROVISIONS 24

25 The design compressive strength, cPn, and the allowable compressive strength, Pn /c, are 26 determinedDRAFT as follows. 27 The nominal compressive strength, Pn, shall be the lowest value obtained based on the applicable 28 limit states of flexural buckling, torsional buckling, and flexural-torsional buckling. 29

30 c = 0.90 (LRFD) c= 1.67 (ASD) 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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46 47 48 49 50 51 52 53 TABLE USER NOTE E1.1 54 Selection Table for the Application of 55 Chapter E Sections Without Slender With Slender Elements Elements Cross Section Sections in Limit Sections in Limit Chapter E States Chapter E States E3 FB E7 LB E4 TB FB TB

E3 FB E7 LB E4 FTB FB FTB

E3 FB E7 LB FB

E3 FB E7 LB E4 FTB FB FTB

E6 E6 DRAFTE3 FB E7 LB E4 FTB FB FTB

E5 E5

E3 FB N/A N/A

Unsymmetrical shapes E4 FTB E7 LB other than single FTB angles FB = flexural buckling, TB = torsional buckling, FTB = flexural-torsional buckling, LB = local buckling 56

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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57 58 E2. EFFECTIVE LENGTH 59 The effective length, Lc, for calculation of member slenderness, Lc/r, shall be determined in 60 accordance with Chapter C or Appendix 7, 61 62 63 where 64 K = effective length factor 65 Lc = KL = effective length, in. (mm) 66 L = laterally unbraced length of the member, in. (mm) 67 r = radius of gyration, in. (mm) 68 69 User Note: For members designed on the basis of compression, the effective slenderness ratio, Lc/r, 70 preferably should not exceed 200. 71 72 User Note: The effective length, Lc, can be derived through methods other than those using the 73 effective length factor, K. 74 75 E3. FLEXURAL BUCKLING OF MEMBERS WITHOUT SLENDER ELEMENTS 76 77 This section applies to nonslender element compression members as defined in Section B4.1 for 78 elements in axial compression. 79 80 User Note: When the torsional effective length is larger than the lateral effective length, Section E4 81 may control the design of wide flange and similarly shaped columns. 82 83 The nominal compressive strength, Pn, shall be determined based on the limit state of flexural 84 buckling: 85 86 Pn = Fcr Ag (E3-1) 87 88 The critical stress, Fcr, is determined as follows: 89

L E Fy 90 (a) When c  4.71 (or  2.25) r Fy Fe 91 DRAFT 92  Fy  93 F  0.658 Fe  F (E3-2) cr   y   94

L E Fy 95 (b) When c > 4.71 (or  2.25) r Fy Fe 96

97 Fcr  0.877Fe (E3-3) 98 99 where 100 Fe = elastic buckling stress determined according to Equation E3-4, as specified in Appendix 101 Section 7.2.3(b), or through an elastic buckling analysis, as applicable, ksi (MPa)

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2 E 102 F  (E3-4) e 2 Lc  r 103 104 Lc = KL = effective length of member, in. (mm)

105 User Note: The two inequalities for calculating the limits and applicability of Sections E3(a) and 106 E3(b), one based on Lc/r and one based on Fy/Fe, provide the same result. 107 108 E4. TORSIONAL AND FLEXURAL-TORSIONAL BUCKLING OF MEMBERS WITHOUT 109 SLENDER ELEMENTS 110 111 This section applies to singly symmetric and unsymmetric members and certain doubly symmetric 112 members, such as cruciform or built-up columns without slender elements, as defined in Section 113 B4.1 for elements in axial compression. In addition, this section applies to all doubly symmetric 114 members without slender elements when the torsional unbraced length exceeds the lateral unbraced 115 length. These provisions are required for single angles with bt 20 .

116 The nominal compressive strength, Pn, shall be determined based on the limit states of torsional and 117 flexural-torsional buckling: 118 119 Pn = FcrAg (E4-1) 120 121 The critical stress, Fcr, shall be determined according to Equation E3-2 or E3-3, using the torsional 122 or flexural-torsional elastic buckling stress, Fe, determined as follows: 123 124 (a) For doubly symmetric members twisting about the shear center: 125 126 2 EC 1 127 FGJw (E4-2) e 2 I  I Lcz x y 128 129 130 131 (b) ForDRAFT singly symmetric members twisting about the shear center where y is the axis of 132 symmetry: 133   FFey ez 4 FFHey ez 134 Fe 11  (E4-3) 2H  ()FF 2   ey ez  135 136 User Note: For singly symmetric members with the x-axis as the axis of symmetry, such as 137 channels, Equation E4-5 is applicable with Fey replaced by Fex. 138 139 (c) For unsymmetric members twisting about the shear center, Fe is the lowest root of the cubic 140 equation: 141 22 22xyoo  142 ()()()()FFFFFFeexeeyeezeeey FFF  FFF eeex ()   0 (E4-4) rroo  143 144 where 145 Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

E-5

2 2 146 Ag = gross cross-sectional area of member, in. (mm ) 6 6 147 Cw = warping constant, in. (mm ) 2 E 148 F = (E4-5) ex 2 L cx rx 2 E 149 F = (E4-6) ey 2 L cy  ry 2  ECw 1 150 Fez =  GJ (E4-7) 2 A r 2 Lcz g o 151 G = shear modulus of elasticity of steel = 11,200 ksi (77 200 MPa) x22 y 152 H = 1 oo (E4-8) 2 ro 4 4 153 Ix, Iy = moment of inertia about the principal axes, in. (mm ) 154 J = torsional constant, in.4 (mm4) 155 Kx = effective length factor for flexural buckling about x-axis 156 Ky = effective length factor for flexural buckling about y-axis 157 Kz = effective length factor for torsional buckling about the longitudinal axis 158 Lcx = KxLx,= effective length of member for buckling about x-axis, in. (mm) 159 Lcy = KyLy, = effective length of member for buckling about y-axis, in. 160 (mm)Lcz = KzLz, = effective length of member for buckling about the 161 longitudinal axis, in. (mm) 162 ro = polar radius of gyration about the shear center, in. (mm)

2 22IIx  y 163 ro = xyoo (E4-9) Ag

164 rx = radius of gyration about x-axis, in. (mm) 165 ry = radius of gyration about y-axis, in. (mm) 166 xo, yo = coordinates of the shear center with respect to the centroid, in. (mm) 167 2 168 User Note: For doubly symmetric I-shaped sections, Cw may be taken as Iyho /4, where ho is the 169 distance DRAFTbetween flange centroids, in lieu of a more precise analysis. For tees and double angles, 170 omit the term with Cw when computing Fez and take xo as 0. 171 172 (d) For members with lateral bracing offset from the shear center, the elastic buckling stress, 173 Fe, shall be determined by analysis. 174 175 User Note: Sections with lateral bracing offset from the shear center are susceptible to 176 constrained-axis torsional buckling, which is discussed in the Commentary. 177 178 179 E5. SINGLE ANGLE COMPRESSION MEMBERS 180 181 The nominal compressive strength, Pn, of single angle members with bt 20 shall be determined 182 based on the limit state of flexural buckling in accordance with Section E3 or Section E7, as 183 applicable. For single angles with bt 20 , the nominal compressive strength, Pn, shall be the lowest 184 value based on the limit states of flexural buckling in accordance with Section E7 or flexural- 185 torsional buckling in accordance with Section E4.

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186 The effects of eccentricity on single angle members are permitted to be neglected and the member 187 evaluated as axially loaded using one of the effective slenderness ratios specified in Section E5(a) or 188 E5(b), provided that the following requirements are met: 189 190 191 (a)members are loaded at the ends in compression through the same one leg, 192 (b)members are attached by welding or by connections with a minimum of two bolts, 193 (c)there are no intermediate transverse loads, and 194 (d) Lc/r as determined in this section does not exceed 200. 195 (e) For unequal leg angles, the ratio of long leg width to short leg width is less than 1.7, 196 197 Single angle members that do not meet these requirements or the requirements described in Section 198 E5(a) or (b), shall be evaluated for combined axial load and flexure using the provisions of Chapter 199 H. 200 (a) For angles that are individual members or are web members of planar trusses with adjacent web 201 members attached to the same side of the gusset plate or chord: 202 (1) For equal-leg angles or unequal-leg angles connected through the longer leg L 203 (i) When  80 : ra L L 204 c 72 0.75 (E5-1) rra L 205 (ii) When  80 : ra 206 L L 207 c 32 1.25 (E5-2) rra

208 (2) For unequal-leg angles connected through the shorter leg, Lc/r from Equations E5-1 and E5- 2 209 2 shall be increased by adding 4[(bl/bs) –1], but Lc/r of the members shall not be taken as 210 less than 0.95L/rz 211 212 (b) For angles that are web members of box or space trusses with adjacent web members attached to 213 the same side of the gusset plate or chord: 214 (1) ForDRAFT equal-leg angles or unequal-leg angles connected through the longer leg L 215 (i) When  75 : ra L L 216 c 60 0.8 (E5-3) rra L 217 (ii) When  75 : ra

218 L L 219 c  45  (E5-4) rra 220 (2) For unequal-leg angles with leg length ratios less than 1.7 and connected through the shorter 2 221 leg, Lc/r from Equations E5-3 and E5-4 shall be increased by adding 6[(bl/bs) –1], but Lc/r of 222 the member shall not be taken as less than 0.82L/rz, 223 224 where 225 L = length of member between work points at truss chord centerlines, in. (mm)

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226 Lc = effective length of the member for buckling about the weak axis, in. (mm) 227 bl = length of longer leg of angle, in. (mm) 228 bs = length of shorter leg of angle, in. (mm) 229 ra = radius of gyration about the geometric axis parallel to the connected leg, in. (mm) 230 rz = radius of gyration about the minor principal axis, in. (mm) 231 232 E6. BUILT-UP MEMBERS 233 234 1. Compressive Strength 235 236 This section applies to built-up members composed of two shapes either (a) interconnected by bolts 237 or welds or (b) with at least one open side interconnected by perforated cover plates or lacing with 238 tie plates. The end connection shall be welded or connected by means of pretensioned bolts with 239 Class A or B faying surfaces. 240 User Note: It is acceptable to design a bolted end connection of a built-up compression member for 241 the full compressive load with bolts in bearing and bolt design based on the shear strength; however, 242 the bolts must be pretensioned. In built-up compression members, such as double-angle struts in 243 trusses, a small relative slip between the elements can significantly reduce the compressive strength 244 of the strut. Therefore, the connection between the elements at the ends of built-up members should 245 be designed to resist slip. 246 247 The nominal compressive strength of built-up members composed of two shapes that are 248 interconnected by bolts or welds shall be determined in accordance with Sections E3, E4 or E7 249 subject to the following modification. In lieu of more accurate analysis, if the buckling mode 250 involves relative deformations that produce shear forces in the connectors between individual 251 shapes, L c / r is replaced by (Lc/ r)m determined as follows: 252 (a) For intermediate connectors that are bolted snug-tight: 253 2 2 LLcc a 254   (E6-1) rrrmo i 255 256 (b) For intermediate connectors that are welded or are connected by means of pretensioned bolts 257 with ClassDRAFT A or B faying surfaces: a 258 (1) When  40 ri

LLcc  259   (E6-2a) rrmo  260 a 261 (2) When  40 ri 262

2 2 LLKacci  263   (E6-2b) rrrmo i 264 265 where 266

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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Lc 267  = modified slenderness ratio of built-up member r m Lc 268  = slenderness ratio of built-up member acting as a unit in the buckling direction r o 269 being addressed 270 Lc = effective length of built-up member, in. (mm) 271 Ki = 0.50 for angles back-to-back 272 = 0.75 for channels back-to-back 273 = 0.86 for all other cases 274 a = distance between connectors, in. (mm) 275 ri = minimum radius of gyration of individual component, in. (mm) 276 277 2. Dimensional Requirements 278 279 Built-up members shall meet the following requirements: 280 (a) Individual components of compression members composed of two or more shapes shall be 281 connected to one another at intervals, a, such that the slenderness ratio, a/ri, of each of the 282 component shapes between the fasteners does not exceed three-fourths times the governing 283 slenderness ratio of the built-up member. The least radius of gyration, ri, shall be used in 284 computing the slenderness ratio of each component part. 285 (b) At the ends of built-up compression members bearing on base plates or finished surfaces, all 286 components in contact with one another shall be connected by a weld having a length not less 287 than the maximum width of the member or by bolts spaced longitudinally not more than four 288 diameters apart for a distance equal to 1½ times the maximum width of the member. 289 Along the length of built-up compression members between the end connections required above, 290 longitudinal spacing for intermittent welds or bolts shall be adequate to providethe required 291 strength. For limitations on the longitudinal spacing of fasteners between elements in continuous 292 contact consisting of a plate and a shape or two plates, see Section J3.5. Where a component of 293 a built-up compression member consists of an outside plate, the maximum spacing shall not

294 exceed the thickness of the thinner outside plate times 075./EFy , nor 12 in. (305 mm), when 295 intermittent welds are provided along the edges of the components or when fasteners are 296 provided on all gage lines at each section. When fasteners are staggered, the maximum spacing 297 of fastenersDRAFT on each gage line shall not exceed the thickness of the thinner outside plate times 298 112./EFy nor 18 in. (460 mm).

299 (c) Open sides of compression members built up from plates or shapes shall be provided with 300 continuous cover plates perforated with a succession of access holes. The unsupported width of 301 such plates at access holes, as defined in Section B4.1, is assumed to contribute to the available 302 strength provided the following requirements are met: 303 (1) The width-to-thickness ratio shall conform to the limitations of Section B4.1. 304 User Note: It is conservative to use the limiting width-to-thickness ratio for Case 7 in Table 305 B4.1a with the width, b, taken as the transverse distance between the nearest lines of 306 fasteners. The net area of the plate is taken at the widest hole. In lieu of this approach, the 307 limiting width-to-thickness ratio may be determined through analysis. 308 (2) The ratio of length (in direction of stress) to width of hole shall not exceed 2. 309 (3) The clear distance between holes in the direction of stress shall be not less than the 310 transverse distance between nearest lines of connecting fasteners or welds. 311 (4) The periphery of the holes at all points shall have a minimum radius of 1½ in. (38 mm).

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312 (d) As an alternative to perforated cover plates, lacing with tie plates is permitted at each end and at 313 intermediate points if the lacing is interrupted. Tie plates shall be as near the ends as practicable. 314 In members providing available strength, the end tie plates shall have a length of not less than 315 the distance between the lines of fasteners or welds connecting them to the components of the 316 member. Intermediate tie plates shall have a length not less than one-half of this distance. The 317 thickness of tie plates shall be not less than one-fiftieth of the distance between lines of welds or 318 fasteners connecting them to the segments of the members. In welded construction, the welding 319 on each line connecting a tie plate shall total not less than one-third the length of the plate. In 320 bolted construction, the spacing in the direction of stress in tie plates shall be not more than six 321 diameters and the tie plates shall be connected to each segment by at least three fasteners. 322 (e) Lacing, including flat bars, angles, channels or other shapes employed as lacing, shall be so 323 spaced that L/r of the flange element included between their connections shall not exceed three- 324 fourths times the governing slenderness ratio for the member as a whole. Lacing shall be 325 proportioned to provide a shearing strength normal to the axis of the member equal to 2% of the 326 available compressive strength of the member. For lacing bars arranged in single systems, L/r 327 shall not exceed 140. For double lacing this ratio shall not exceed 200. Double lacing bars shall 328 be joined at the intersections. For lacing bars in compression, L is permitted to be taken as the 329 unsupported length of the lacing bar between welds or fasteners connecting it to the components 330 of the built-up member for single lacing, and 70% of that distance for double lacing. 331 User Note: The inclination of lacing bars to the axis of the member shall preferably be not less 332 than 60º for single lacing and 45º for double lacing. When the distance between the lines of 333 welds or fasteners in the flanges is more than 15 in. (380 mm), the lacing shall preferably be 334 double or be made of angles. 335 For additional spacing requirements, see Section J3.5. 336 337 E7. MEMBERS WITH SLENDER ELEMENTS 338 339 This section applies to slender-element compression members, as defined in Section B4.1 for 340 elements in axial compression. 341 342 The nominal compressive strength, Pn, shall be the lowest value based on the applicable limit states 343 of flexural buckling, torsional buckling, and flexural-torsional buckling in interaction with local 344 buckling. 345 346 DRAFT Pn = FcrAe (E7-1) 347 where 348 Ae = summation of the effective areas of the cross section based on reduced effective widths, be, 2 2 349 de or he, in. (mm ), or the area as given by Equations E7-5 or E7-6 350 Fcr = critical stress determined in accordance with Section E3 or E4. For single angles determine 351 Fcr in accordance with Section E3 only. 352 353 User Note: The effective area, Ae, may be determined by deducting from the gross area, Ag, the 354 reduction in area of each slender element determined as (b – be)t. 355 356 1. Slender Element Members Excluding Round HSS 357 358 The effective width, be, (for tees, this is de; for webs this is he), for slender elements is determined as 359 follows: 360

Fy 361 (a) When r Fcr

362 bbe  (E7-2)

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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363

Fy 364 (b) When r Fcr 365

FelF el 366 bbe 1 c1 (E7-3) FcrF cr 367 368 where 369 b = width of the element (for tees this is d; for webs this is h), in. (mm) 370 c1 = effective width imperfection adjustment factor determined from Table E7-1 371 ccc211114    2 372 λ = width-to-thickness ratio for the element as defined in Section B4.1 373 λr = limiting width-to-thickness ratio as defined in Table B4.1a 374 Fel = elastic local buckling stress determined according to Equation E7-4 or an elastic 375 local buckling analysis, ksi (MPa) 2 r 376  cF2 y (E7-4)  377 378 379 Table E7-1 380 Effective Width Imperfection Adjustment Factor, c1 and c2 Factor Case Slender Element c1 c2 (a) Stiffened elements except flanges of square and rectangular HSS 0.18 1.31 (b) Flanges of square and rectangular HSS 0.20 1.38 (c) All other elements 0.22 1.49 381 382 2. Round HSS 383 384 The effective area, Ae, is determined as follows 385 DE 386 (a) When  0.11 tFy 387 DRAFT

388 Aeg A (E7-5) 389 E D E 390 (b) When 0.11 < < 0.45 Fy t Fy 391 392 0.038E 2 393 A A (E7-6) eg FDty (/)3 394 where 395 D = outside diameter of round HSS, in. (mm) 396 t = thickness of wall, in. (mm) 397

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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1 CHAPTER F

2 DESIGN OF MEMBERS FOR FLEXURE 3 4 This chapter applies to members subject to simple bending about one principal axis. For simple bending, 5 the member is loaded in a plane parallel to a principal axis that passes through the shear center or is 6 restrained against twisting at load points and supports. 7 8 The chapter is organized as follows: 9 10 F1. General Provisions 11 F2. Doubly Symmetric Compact I-Shaped Members and Channels Bent about Their Major Axis 12 F3. Doubly Symmetric I-Shaped Members with Compact Webs and Noncompact or Slender 13 Flanges Bent about Their Major Axis 14 F4. Other I-Shaped Members with Compact or Noncompact Webs Bent about Their Major Axis 15 F5. Doubly Symmetric and Singly Symmetric I-Shaped Members with Slender Webs Bent about 16 Their Major Axis 17 F6. I-Shaped Members and Channels Bent about Their Minor Axis 18 F7. Square and Rectangular HSS and Box-Sections 19 F8. Round HSS 20 F9. Tees and Double Angles Loaded in the Plane of Symmetry 21 F10. Single Angles 22 F11. Rectangular Bars and Rounds 23 F12. Unsymmetrical Shapes 24 F13. Proportions of Beams and Girders 25 26 User Note: For cases not included in this chapter the following sections apply: 27  Chapter G Design provisions for shear 28  H1–H3 Members subject to biaxial flexure or to combined flexure and axial force 29  H3 Members subject to flexure and torsion 30  Appendix 3 Members subject to fatigue 31 32 For guidance in determining the appropriate sections of this chapter to apply, Table User Note F1.1 may be 33 used. 34 DRAFT

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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35 36 TABLE USER NOTE F1.1 37 Selection Table for the Application of Chapter F Sections 38 Section Cross Section Flange Web Limit in Slenderness Slenderness States Chapter F F2 C C Y, LTB

F3 NC, S C LTB, FLB

F4 C, NC, S C, NC Y,LTB, FLB, TFY

F5 C, NC, S S Y,LTB, FLB, TFY

F6 C, NC, S N/A Y FLB F7 C, NC, S C, NC Y, FLB, WLB

F8 N/A N/A Y, LB

F9 C, NC, S N/A Y, LTB, FLB

F10 N/A N/A Y, LTB, LLB F11 N/A N/A Y, LTB

F12 Unsymmetrical shapes, N/A N/A All other than single angles limit DRAFTstates Y = yielding, LTB = lateral-torsional buckling, FLB = flange local buckling, WLB = web local buckling, TFY = tension flange yielding, LLB = leg local buckling, LB = local buckling, C = compact, NC = noncompact, S = slender

39 40 F1. GENERAL PROVISIONS 41

42 The design flexural strength, bMn, and the allowable flexural strength, Mn/b, shall be determined as 43 follows: 44

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45 (a) For all provisions in this chapter

46 b = 0.90 (LRFD) b = 1.67 (ASD) 47 48 and the nominal flexural strength, Mn, shall be determined according to Sections F2 through 49 F13. 50 (b) The provisions in this chapter are based on the assumption that points of support for beams and 51 girders are restrained against rotation about their longitudinal axis. 52 53 (c) For singly symmetric members in single curvature and all doubly symmetric members: 54 55 Cb, the lateral-torsional buckling modification factor for nonuniform moment diagrams when 56 both ends of the segment are braced is determined as follows: 57

12.5M max 58 Cb  (F1-1) 2.5M max 3MMM A 4 B 3 C 59 where 60 Mmax = absolute value of maximum moment in the unbraced segment, kip-in. (N-mm) 61 MA = absolute value of moment at quarter point of the unbraced segment, kip-in. (N- 62 mm) 63 MB = absolute value of moment at centerline of the unbraced segment, kip-in. (N- 64 mm) 65 MC = absolute value of moment at three-quarter point of the unbraced segment, kip- 66 in. (N-mm) 67 68 69 70 User Note: For doubly symmetric members with no transverse loading between brace points, 71 Equation F1-1 reduces to 1.0 for the case of equal end moments of opposite sign (uniform 72 moment), 2.27 for the case of equal end moments of the same sign (reverse curvature bending), 73 and to 1.67 when one end moment equals zero. For singly symmetric members, a more detailed 74 analysis for Cb is presented in the Commentary. The Commentary provides additional equations 75 for Cb that provide improved characterization of the effects of a variety of member boundary 76 conditions. 77 78 For cantilevers where warping is prevented at the support and where the free end is unbraced, Cb 79 = 1.0. 80 81 (d) In singly symmetric members subject to reverse curvature bending, the lateral-torsional buckling 82 strength shall be checked for both flanges. The available flexural strength shall be greater than 83 or equal to the maximum required moment causing compression within the flange under 84 consideration. 85 86 F2. DOUBLY SYMMETRICDRAFT COMPACT I-SHAPED MEMBERS AND CHANNELS 87 FORBENT ABOUTCOMMITTEE THEIR MAJOR AXIS USE ONLY 88 89 This section applies to doubly symmetric I-shaped members and channels bent about their major 90 axis, having compact webs and compact flanges as defined in Section B4.1 for flexure. 91 92 User Note: All current ASTM A6 W, S, M, C and MC shapes except W21×48, W14×99, W14×90, 93 W12×65, W10×12, W8×31, W8×10, W6×15, W6×9, W6×8.5 and M4×6 have compact flanges for

94 Fy  50 ksi (345 MPa); all current ASTM A6 W, S, M, HP, C and MC shapes have compact webs

95 at Fy < 65 ksi (450 MPa).

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96 The nominal flexural strength, Mn, shall be the lower value obtained according to the limit states of 97 yielding (plastic moment) and lateral-torsional buckling. 98 1. Yielding 99 100 Mn = Mp=FyZx (F2-1) 101 102 where 103 Fy = specified minimum yield stress of the type of steel being used, ksi (MPa) 3 3 104 Zx = plastic section modulus about the x-axis, in. (mm ) 105 106 2. Lateral-Torsional Buckling 107

108 (a) When LLbp , the limit state of lateral-torsional buckling does not apply.

109 (b) When LLLpbr  110 LLbp (F2-2) M nbpCM M p0.7 FS yxM p  LLrp 111 (c) When Lb > Lr

112   MSFM pxcrn (F2-3) 113 where 114 Lb = length between points that are either braced against lateral displacement of the 115 compression flange or braced against twist of the cross section, in. (mm) 116 Fcr = the critical stress, ksi (MPa), is: 117 2 2 CEbb JcL 118 Fcr 10.078 (F2-4) 2 Sh r Lb xo ts  rts 119 120 E = modulus of elasticity of steel = 29,000 ksi (200 000 MPa) 121 J = torsional constant, in.4 (mm4) 3 3 122 Sx = elastic section modulus taken about the x-axis, in. (mm ) 123 ho = distance between the flange centroids, in. (mm) 124 125 User Note: The square root term in Equation F2-4 may be conservatively taken equal to 1.0. 126 127 User Note: Equations F2-3 and F2-4 provide identical solutions to the following expression for 128 lateral-torsional buckling of doubly symmetric sections that has been presented in past editions of 129 the AISC LRFD Specification: 2 E 130 DRAFTM crCEIGJIC b y y w  LLbb 131 The advantage of Equations F2-3 and F2-4 is that the form is very similar to the expression for 132 lateral-torsional buckling of singly symmetric sections given in Equations F4-4 and F4-5. 133 134 and where 135 136 Lp , the limiting laterally unbraced length for the limit state of yielding, in. (mm) is: 137 138

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139 E (F2-5) Lrpy1.76 Fy

140 Lr, the limiting unbraced length for the limit state of inelastic lateral-torsional buckling, in. 141 (mm) is: 142

2 2 EJcJc 0.7Fy 143 Lrrts1.95 6.76 (F2-6) 0.7FShyxo Sh xo  E

144 where

CI 2 wy 145 rts  (F2-7) S x 146 and the coefficient c is determined as follows: 147 (1) For doubly symmetric I-shapes: c = 1 (F2-8a) h I 148 (2) For channels: c  o y (F2-8b) 2 Cw 149 User Note:

2 Ihy o 150 For doubly symmetric I-shapes with rectangular flanges, Cw  and thus Equation F2-7 becomes 4

2 Ihy o 151 rts  2Sx

152 rts may be approximated accurately and conservatively as the radius of gyration of the compression 153 flange plus one-sixth of the web: bf 154 rts = 1 htw 12 1 6 btff 155 156 F3. DOUBLY SYMMETRIC I-SHAPED MEMBERS WITH COMPACT WEBS AND 157 NONCOMPACT OR SLENDER FLANGES BENT ABOUT THEIR MAJOR AXIS 158 159 ThisFOR section appliesCOMMITTEE to doubly symmetric I-shaped USE members ONLY bent about their major axis having 160 compact webs and noncompact or slender flanges as defined in Section B4.1 for flexure. 161 162 User Note: The followingDRAFT shapes have noncompact flanges for F  50 ksi (345 MPa): W21×48, y 163 W14×99, W14×90, W12×65, W10×12, W8×31, W8×10, W6×15, W6×9, W6×8.5 and M4×6. All

164 other ASTM A6 W, S and M shapes have compact flanges for Fy  50 ksi (345 MPa). 165 166 The nominal flexural strength, Mn, shall be the lower value obtained according to the limit states of 167 lateral-torsional buckling and compression flange local buckling. 168 169 1. Lateral-Torsional Buckling 170 171 For lateral-torsional buckling, the provisions of Section F2.2 shall apply. Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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172 2. Compression Flange Local Buckling 173 174 (a) For sections with noncompact flanges   175 MM M 0.7 FS pf (F3-1) np p yx rf pf 176

177 (b) For sections with slender flanges 178 0.9EkScx 179 M n  (F3-2) 2 180 where 181 b 182 f 2t f

183 pf = p is the limiting slenderness for a compact flange, Table B4.1b 184 rf = r is the limiting slenderness for a noncompact flange, Table B4.1b 4 185 kc  and shall not be taken less than 0.35 nor greater than 0.76 for calculation purposes htw 186 h = distance as defined in Section B4.1b, in. (mm) 187 188 F4. OTHER I-SHAPED MEMBERS WITH COMPACT OR NONCOMPACT WEBS 189 BENT ABOUT THEIR MAJOR AXIS 190 191 This section applies to doubly symmetric I-shaped members bent about their major axis with 192 noncompact webs and singly symmetric I-shaped members with webs attached to the mid-width of 193 the flanges, bent about their major axis, with compact or noncompact webs, as defined in Section 194 B4.1 for flexure. 195 196 User Note: I-shaped members for which this section is applicable may be designed conservatively 197 using Section F5. 198 199 The nominal flexural strength, Mn, shall be the lowest value obtained according to the limit states of 200 compression flange yielding, lateral-torsional buckling, compression flange local buckling, and 201 tension flange yielding. 202 203 1. Compression Flange Yielding 204 205 Mn = RpcMyc (F4-1) 206 where DRAFT 207 Myc = FySxc , yield moment in the compression flange, kip-in. (N-mm) 3 3 208 Sxc = elastic section modulus referred to compression flange, in. (mm ) 209 210 2. Lateral-Torsional Buckling

211 (a) When LLbp , the limit state of lateral-torsional buckling does not apply.

212 (b) When LLLp br

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LLbp 213 M nCRM b pc yc RM pc yc FS L xc RM pc yc (F4-2) LL rp

214 (c) When Lb > Lr

215  xccrn  MRSFM ycpc (F4-3) 216 where

217 (1) Myc, the yield moment in the compression flange, kip-in. (N-mm) is:

218 Myc =FySxc (F4-4) 219 220 (2) Fcr, the critical stress, ksi (MPa) is: 221 2 2 CEbb J L 222 Fcr 10.078 (F4-5) 2 Sh r Lb xc o t  rt 223 I 224 For yc  0.23 , J shall be taken as zero I y 225 where 4 4 226 Iyc = moment of inertia of the compression flange about the y-axis, in. (mm ) 227 228 (3) FL, nominal compression flange stress above which the inelastic buckling limit states apply, 229 ksi (MPa), is determined as follows: 230 S 231 (i) When xt  0.7 Sxc 232 F  0.7F (F4-6a) Ly 233 S 234 (ii) When xt  0.7 Sxc S 235 F FFxt 0.5 (F4-6b) LyS y xc 236 where 3 3 237 Sxt = elastic section modulus referred to tension flange, in. (mm ) 238 239 (4) Lp, the limiting laterally unbraced length for the limit state of yielding, in. (mm) is:

E 240 DRAFT 11 r.L tp (F4-7) Fy

241 242 (5) Lr, the limiting unbraced length for the limit state of inelastic lateral-torsional buckling, in. 243 (mm), is: 244 245

2 2 EJ J FL 246 Lrrt1.95 6.76 (F4-8) FShLxco Sh xco  E 247 Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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248 (6) Rpc, the web plastification factor is determined as follows: 249 250 (i) When Iyc/Iy > 0.23 hc 251 (a) When pw tw

M p 252 Rpc  (F4-9a) M yc

hc 253 (b) When pw tw M MM 254 R p pp1 wp  (F4-9b) pc M MM yc yc rw pw yc

255 (ii) When Iyc/Iy ≤ 0.23 256 257 Rpc = 1.0 (F4-10) 258 259 where

260 Mp = FyZx  1.6FySxc 261 h 262  c tw 263 pw = p, the limiting slenderness for a compact web, Table B4.1b 264 rw = r, the limiting slenderness for a noncompact web, Table B4.1b 265 hc = twice the distance from the centroid to the following: the inside face of the 266 compression flange less the fillet or corner radius, for rolled shapes; the nearest line 267 of fasteners at the compression flange or the inside faces of the compression flange 268 when welds are used, for built-up sections, in. (mm) 269 270 (7) rt, the effective radius of gyration for lateral-torsional buckling, in. (mm) is determined as 271 follows: 272 (i) For I-shapes with a rectangular compression flange 273 bfc 274 rt  (F4-11) 1 12 1 aw 6 275 where

th wc 276 aw  (F4-12) tb fcfc

277 bfc DRAFT= width of compression flange, in. (mm) 278 tfc = compression flange thickness, in. (mm) 279 280 (ii) For I-shapes with a channel cap or a cover plate attached to the compression flange 281 282 rt = radius of gyration of the flange components in flexural compression plus one- 283 third of the web area in compression due to application of major axis bending 284 moment alone, in. (mm) 285 286 3. Compression Flange Local Buckling 287 288 (a) For sections with compact flanges, the limit state of local buckling does not apply. Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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289 (b) For sections with noncompact flanges

 pf 290 MRMRMFSn pcycpcycLxc  (F4-13) rf pf

291 (c) For sections with slender flanges

0.9Ekcxc S 292 M n  (F4-14) 2 293 where 294 F L is defined in Equations F4-6a and F4-6b 295 Rpc is the web plastification factor, determined by Equations F4-9 296 4 297 kc  and shall not be taken less than 0.35 nor greater than 0.76 for calculation purposes htw b 298  fc 2t fc 299 pf = p, the limiting slenderness for a compact flange, Table B4.1b 300 rf = r, the limiting slenderness for a noncompact flange, Table B4.1b 301 302 4. Tension Flange Yielding 303 304 (a) When Sxt > Sxc, the limit state of tension flange yielding does not apply. 305 306 (b) When Sxt < Sxc 307 308 Mn = RptMyt (F4-15) 309 where 310 M yt FS y xt = yield moment in the tension flange, kip-in. (N-mm) 3 3 311 Sxt = elastic section modulus referred to tension flange, in. (mm ) 312 313 Rpt, the web plastification factor corresponding to the tension flange yielding limit state, is 314 determined as follows: hc 315 (1) When pw tw

M p 316 Rpt  (F4-16a) M yt

hc 317 (2) When pw tw

M MM 318 p ppwp (F4-16b) Rpt DRAFT1  M MM yt yt rw pw yt 319 where h 320  c tw

321 pw = p, the limiting slenderness for a compact web, defined in Table B4.1b 322 rw = r, the limiting slenderness for a noncompact web, defined in Table B4.1b 323 324 F5. DOUBLY SYMMETRIC AND SINGLY SYMMETRIC I-SHAPED MEMBERS WITH 325 SLENDER WEBS BENT ABOUT THEIR MAJOR AXIS

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326 327 This section applies to doubly symmetric and singly symmetric I-shaped members with slender webs 328 attached to the mid-width of the flanges and bent about their major axis as defined in Section B4.1 329 for flexure. 330 331 The nominal flexural strength, Mn, shall be the lowest value obtained according to the limit states of 332 compression flange yielding, lateral-torsional buckling, compression flange local buckling, and 333 tension flange yielding. 334 335 1. Compression Flange Yielding 336 337 M npgyxc RFS (F5-1) 338 339 2. Lateral-Torsional Buckling 340 341 M npgcrxc RFS (F5-2)

342 (a) When LLbp , the limit state of lateral-torsional buckling does not apply. 343 (b) When LLL pbr LL 344 bp (F5-3) FCFcr b y0.3 F yF y LL rp 345 (c) When Lb > Lr 346 2 CEb 347 F   F (F5-4) cr 2 y Lb  rt 348 349 where 350 Lp is defined by Equation F4-7 351 E 352 Lrrt (F5-5) 0.7Fy

353 rt is the effective radius of gyration for lateral-torsional buckling as defined in Section F4 354 355 Rpg, the bending strength reduction factor is ahE 356 R 15wc .7 1.0 (F5-6) pg 1200 300at F ww y 357 where 358 aw is defined by Equation F4-12 but shall not exceed 10 359 DRAFT 360 361 362 3. Compression Flange Local Buckling

363 M npgcrxc RFS (F5-7)

364 (a) For sections with compact flanges, the limit state of compression flange local buckling does not 365 apply. 366 (b) For sections with noncompact flanges

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  pf 367 FFcr y0.3 F y  (F5-8)  rf pf 368

369 (c) For sections with slender flanges

0.9Ekc 370 Fcr  2 (F5-9) bf  2t f 371 where 4 372 and shall not be taken less than 0.35 nor greater than 0.76 for calculation kc  htw 373 purposes 374 b 375 fc 2t fc 376 pf = p, the limiting slenderness for a compact flange, Table B4.1b 377 rf = r, the limiting slenderness for a noncompact flange, Table B4.1b 378 379 4. Tension Flange Yielding 380 381 (a) When Sxt > Sxc, the limit state of tension flange yielding does not apply. 382 383 (b) When Sxt < Sxc 384 Mn = FySxt (F5-10) 385 386 F6. I-SHAPED MEMBERS AND CHANNELS BENT ABOUT THEIR MINOR AXIS 387 388 This section applies to I-shaped members and channels bent about their minor axis. 389 390 The nominal flexural strength, Mn, shall be the lower value obtained according to the limit states of 391 yielding (plastic moment) and flange local buckling. 392 393 1. Yielding 394 395 Mn =Mp= FyZy  1.6FSyy (F6-1)

396 397 2. Flange Local Buckling 398 (a) For sections withDRAFT compact flanges the limit state of flange local buckling does not apply. 399 User Note: All current ASTM A6 W, S, M, C and MC shapes except W21x48, W14x99, 400 W14x90, W12x65, W10x12, W8x31, W8x10, W6x15, W6x9, W6x8.5 and M4x6 have compact

401 flanges at Fy  50 ksi (345 MPa).

402 (b) For sections with noncompact flanges

   pf  403 MMMnpp 0.7 FS yy (F6-2)   rf pf  404 (c) For sections with slender flanges

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405 M ncry FS (F6-3) 406 where 0.69E 407 Fcr  2 (F6-4) b  t f b 408  t f

409 pf = p, the limiting slenderness for a compact flange, Table B4.1b 410 rf = r, the limiting slenderness for a noncompact flange, Table B4.1b 411 b = for flanges of I-shaped members, half the full-flange width, bf; for flanges of channels, 412 the full nominal dimension of the flange, in. (mm) 413 tf = thickness of the flange, in. (mm) 3 3 414 Sy = elastic section modulus taken about the y-axis, in. (mm ); for a channel, the minimum 415 section modulus 416 417 F7. SQUARE AND RECTANGULAR HSS AND BOX SECTIONS 418 419 This section applies to square and rectangular HSS, and box sections bent about either axis, having 420 compact or noncompact webs and compact, noncompact or slender flanges as defined in Section 421 B4.1 for flexure.

422 The nominal flexural strength, Mn, shall be the lowest value obtained according to the limit states of 423 yielding (plastic moment), flange local buckling and web local buckling under pure flexure. 424 User Note: Very long rectangular HSS bent about the major axis are subject to lateral-torsional 425 buckling; however, the Specification provides no strength equation for this limit state since beam 426 deflection will control for all reasonable cases. 427 428 1. Yielding 429 Mn Mp = FyZ (F7-1) 430 431 where 432 Z = plastic section modulus about the axis of bending, in.3 (mm3) 433 434 2. Flange Local Buckling 435 436 (a) For compact sections, the limit state of flange local buckling does not apply. 437 (b) For sections with noncompact flanges  b Fy 438 M npMMFS py  3.57 4.0 Mp (F7-2) tE f 439 where DRAFT3 3 440 S = elastic section modulus about the axis of bending, in. (mm ) 441 442 (c) For sections with slender flanges 443 444 Mn = FySe (F7-3) 445 446 where 447 Se = effective section modulus determined with the effective width, be, of the compression 448 flange taken as: 449 450 (1) for HSS

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451 EE0.38 452 btef 1.92 1 b (F7-4) FbtFyfy/ 453 454 (2) for box sections EE0.34 455 btef 1.92 1 b (F7-5) FbtFyfy/ 456 3. Web Local Buckling 457 458 (a) For compact sections, the limit state of web local buckling does not apply. 459 (b) For sections with noncompact webs 460  h Fy 461 M npMMFS py  0.305 0.738 Mp (F7-6) tE w 462 F8. ROUND HSS 0.45E 463 This section applies to round HSS having D/t ratios of less than . Fy

464 The nominal flexural strength, Mn, shall be the lower value obtained according to the limit states of 465 yielding (plastic moment) and local buckling. 466 1. Yielding 467 Mn Mp = FyZ (F8-1) 468 469 2. Local Buckling 470 471 (a) For compact sections, the limit state of flange local buckling does not apply. 472 (b) For noncompact sections    021.0 E  473 M    SF (F8-2) n  D y     t  474 (c) For sections with slender walls 475 Mn = FcrS (F8-3) 476 where 33.0 E 477 F  (F8-4) cr D t 478 S = elastic section modulus,DRAFT in.3 (mm3) 479 t = thickness of wall, in. (mm) 480 481 F9. TEES AND DOUBLE ANGLES LOADED IN THE PLANE OF SYMMETRY 482 483 This section applies to tees and double angles loaded in the plane of symmetry. 484 485 The nominal flexural strength, Mn, shall be the lowest value obtained according to the limit states of 486 yielding (plastic moment), lateral-torsional buckling, flange local buckling, and local buckling of tee 487 stems and double angle web legs. 488 Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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489 1. Yielding 490

491 Mn Mp (F9-1) 492 where 493 494 (a) For tee stems and web legs in tension 495

496 M p FZyx1.6 M y (F9-2) 497 498 where 499 My = FySx; yield moment about the axis of bending, kip-in. (N-mm) 500 501 (b) For tee stems in compression 502

503 M py M (F9-3) 504 (c) For double angles with web legs in compression 505 506 M py1.5M (F9-4) 507 2. Lateral-Torsional Buckling 508 509 (a) For stems and web legs in tension 510 511 (1) When LLbp the limit state of lateral-torsional buckling does not apply 512 513 (2) When LLLpbr 514 515

 LLbp  516 MMnp MM py    (F9-5) LL  rp 517 518 (3) When Lbr L 519 520 Mncr M (F9-6) 521 where E 522 Lrpy 1.76 (F9-7) Fy

EdSIJy Fy x 523 Lr 1.95 2.36 1 (F9-8) FSyx  EJ 1.95EDRAFT2  524 Mcr IJy B1 B (F9-9) Lb  525 526

d I y 527 B  2.3 (F9-10) LJb 528 529 (b) For stems and web legs in compression anywhere along the unbraced length 530 531 Mcr is given by Equation F9-9 with

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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532

d I y 533 B 2.3 (F9-11) LJb 534 (1) For tee stems

535 M ncry MM (F9-12)

536 (2) For double angle web legs, Mn shall be determined using Equations F10-2 and F10-3 with Mcr 537 determined using Equation F9-9. 538 539 3. Flange Local Buckling of Tees and Double Angle Legs 540 541 (a) For Tee flanges 542 543 (1) For sections with a compact flange in flexural compression, the limit state of flange local 544 buckling does not apply. 545 546 (2) For sections with a noncompact flange in flexural compression 547   pf  548  70 SF.MMM    61 M. (F9-13) pn p xcy   y   pfrf  549 (3) For sections with a slender flange in flexural compression 550 0.7ESxc 551 M n  (F9-14) 2 bf  2t f 552 553 where 3 3 554 Sxc = elastic section modulus referred to the compression flange, in. (mm ) bf 555  2t f

556 pf = p, the limiting slenderness for a compact flange, Table B4.1b 557 rf = r, the limiting slenderness for a noncompact flange, Table B4.1b 558 559 560 (b) For double angle flange legs 561 562 The nominal moment strength, Mn, for double angles with the web legs in compression shall be 563 determined in accordance with Section F10.3 564 565 4. Local Buckling of Tee Stems and double angle leg webs in Flexural Compression 566 DRAFT 567 Mncrx FS (F9-15) 568 569 where 3 3 570 Sx = elastic section modulus, in. (mm ) 571 572 Fcr, the critical stress is determined as follows: 573 574 (a) For tee stems 575

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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dE 576 (1) When  0.84 tFwy 577

578 Fcr F y (F9-16) Ed E 579 (2) When 0.84 1.52 FywtF y 580 581

 d Fy  582 Fcr1.43 0.515  F y (F9-17)  tEw  583 dE 584 (3) When  1.52 tFwy 585 586 1.52E 587 F  (F9-18) cr 2 d  tw 588 589 (b) For double angle web legs 590 591 The nominal moment strength, Mn, for double angles with the web legs in compression shall be 592 determined in accordance with Section F10.3 593 594 F10. SINGLE ANGLES 595 596 This section applies to single angles with and without continuous lateral restraint along their 597 length. 598 Single angles with continuous lateral-torsional restraint along the length are permitted to be 599 designed on the basis of geometric axis (x, y) bending. Single angles without continuous lateral- 600 torsional restraint along the length shall be designed using the provisions for principal axis 601 bending except where the provision for bending about a geometric axis is permitted. 602 If the moment resultant has components about both principal axes, with or without axial load, or 603 the moment is about one principal axis and there is axial load, the combined stress ratio shall be 604 determined using the provisions of Section H2. 605 User Note: For geometric axis design, use section properties computed about the x- and y-axis of 606 the angle, parallel andDRAFT perpendicular to the legs. For principal axis design, use section properties 607 computed about the major and minor principal axes of the angle.

608 The nominal flexural strength, Mn, shall be the lowest value obtained according to the limit states 609 of yielding (plastic moment), lateral-torsional buckling, and leg local buckling. 610 User Note: For bending about the minor principal axis, only the limit states of yielding and leg 611 local buckling apply. 612 1. Yielding 613

614 Mn My (F10-1) 615 616 Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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617 618 2. Lateral-Torsional Buckling 619 620 For single angles without continuous lateral-torsional restraint along the length M 621 (a) When y  1.0 Mcr M 622 M 1.92 1.17 y MM 1.5 (F10-2) nyyM cr 623 M 624 (b) When y  1.0 Mcr 0.17M 625 M 0.92 cr M (F10-3) ncr M y 626 627 where 628 Mcr , the elastic lateral-torsional buckling moment, is determined as follows: 629 630 (1) For bending about the major principal axis of single angles: 631 632 2 9EArz tC bwzrβwz r 633 M cr 14.4 4.4 (F10-4) 8LLbbbtLt  634 where 635 Cb is computed using Equation F1-1 with a maximum value of 1.5 636 A = cross-sectional area of angle, in.2 (mm2) 637 Lb = laterally unbraced length of member, in. (mm) 638 rz = radius of gyration about the minor principal axis, in. (mm) 639 t = thickness of angle leg, in. (mm) 640 w = section property for single angles about major principal axis, in. (mm). w is 641 positive with short legs in compression and negative with long legs in 642 compression for unequal-leg angles, and zero for equal-leg angles. If the long 643 leg is in compression anywhere along the unbraced length of the member, the 644 negative value of w shall be used. 645 646 User Note: The equation for w and values for common angle sizes are listed in the 647 Commentary. 648 649 (2) For bending about one of the geometric axes of an equal-leg angle with no axial 650 compressionDRAFT 651 652 (i) With no lateral-torsional restraint: 653 654 (a) With maximum compression at the toe 655

4 2 0.58Eb tCbbL t 656 M cr  10.88 1 (F10-5a) Lb22 b  657 (b) With maximum tension at the toe 658 Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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659 4 2 0.58Eb tCbbL t 660 Mcr  10.88 1 (F10-5b) Lb22 b 

661 My shall be taken as 0.80 times the yield moment calculated using the geometric 662 section modulus. 663 664 (ii)With lateral-torsional restraint at the point of maximum moment only: 665 666 Mcr shall be taken as 1.25 times Mcr computed using Equation F10-5a or F10-5b. 667 My shall be taken as the yield moment calculated using the geometric section 668 modulus. 669 670 671 User Note: Mn may be taken as My for single angles with their vertical leg toe in compression, and 2 1.64Et Fy 672 having a span-to-depth ratio less than or equal to 1.4 . Fby  E 673 674 3. Leg Local Buckling 675 676 The limit state of leg local buckling applies when the toe of the leg is in compression. 677 678 (a) For compact sections, the limit state of leg local buckling does not apply. 679 (b) For sections with noncompact legs:  b Fy 680 MFS2.43 1.72 (F10-6) nyctE  681 682 (c) For sections with slender legs: 683 M ncrc FS (F10-7) 684 where 0.71E 685 F  (F10-8) cr 2 b  t 686 b = full width of leg in compression, in. (mm) 3 687 Sc = elastic section modulus to the toe in compression relative to the axis of bending, in. 688 (mm3). For bending about one of the geometric axes of an equal-leg angle with no 689 lateral-torsional restraint, Sc shall be 0.80 of the geometric axis section modulus. 690 691 F11. RECTANGULARDRAFT BARS AND ROUNDS 692 693 This section applies to rectangular bars bent about either geometric axis, and rounds. 694 695 The nominal flexural strength, Mn, shall be the lower value obtained according to the limit states of 696 yielding (plastic moment) and lateral-torsional buckling. 697 698 1. Yielding 699

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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Ldb 0.08E 700 For rectangular bars with 2  bent about their major axis, rectangular bars bent about tFy 701 their minor axis and rounds: 702

703 M npyMFZFS 1.6 yx (F11-1) 704 705 2. Lateral-Torsional Buckling 706 Ld 0.08E 707 (a) For rectangular bars with b  bent about their major axis, the limit state of lateral- 2 t Fy 708 torsional buckling does not apply. 709 0.08EELd 1.9 710 (b) For rectangular bars with b bent about their major axis: 2 Fyyt F 711 F Ld y 712 M CM1.52 0.274 b M (F11-2) nb2 y p t E 713 Ld 1.9E 714 (c) For rectangular bars with b  bent about their major axis: 2 t Fy 715

716 M ncrxp FS M (F11-3) 717 where

1.9ECb 718 Fcr  (F11-4) Ldb t2 719 Lb = length between points that are either braced against lateral displacement of the 720 compression region, or between points braced to prevent twist of the cross 721 section, in. (mm) 722 d = depth of rectangular bar, in. (mm) 723 t = width of rectangular bar parallel to axis of bending, in. (mm) 724 725 (d) For rounds and rectangular bars bent about their minor axis, the limit state of lateral-torsional 726 buckling need not be considered. 727 728 729 F12. UNSYMMETRICAL SHAPES 730 731 This section applies toDRAFT all unsymmetrical shapes, except single angles. 732 733 The nominal flexural strength, Mn, shall be the lowest value obtained according to the limit states of 734 yielding (yield moment), lateral-torsional buckling, and local buckling where 735 736 Mnnmin FS (F12-1) 737 where 3 3 738 Smin = minimum elastic section modulus relative to the axis of bending, in. (mm ) 739 740 User Note: The design provisions within this section can be overly conservative for certain shapes, 741 unbraced lengths, and moment diagrams. To improve economy, the provisions of Appendix 1 are

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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742 recommended as an alternative for determining the nominal flexural strength of members of 743 unsymmetrical shape. 744 745 1. Yielding 746

747 FFny (F12-2) 748 749 2. Lateral-Torsional Buckling 750

751 Fncry FF (F12-3) 752 where 753 Fcr = lateral-torsional buckling stress for the section as determined by analysis, ksi (MPa) 754 755 User Note: In the case of Z-shaped members, it is recommended that Fcr be taken as 0.5Fcr of a 756 channel with the same flange and web properties. 757 758 3. Local Buckling 759 760 Fncry FF (F12-4) 761 where 762 Fcr = local buckling stress for the section as determined by analysis, ksi (MPa) 763 764 F13. PROPORTIONS OF BEAMS AND GIRDERS 765 766 1. Strength Reductions for Members with Holes in the Tension Flange 767 768 This section applies to rolled or built-up shapes and cover-plated beams with holes, proportioned on 769 the basis of flexural strength of the gross section. 770 In addition to the limit states specified in other sections of this Chapter, the nominal flexural 771 strength, Mn, shall be limited according to the limit state of tensile rupture of the tension flange.

772 (a) When FuAfn  YtFyAfg, the limit state of tensile rupture does not apply. 773 774 (b) When FuAfn < YtFyAfg, the nominal flexural strength, Mn, at the location of the holes in the tension 775 flange shall not be taken greater than 776 FAufn 777 M nx S (F13-1) Afg 778 where 779 780 Afg = gross area of tension flange, calculated in accordance with the provisions of Section 781 B4.3a, in.2DRAFT (mm2) 782 Afn = net area of tension flange, calculated in accordance with the provisions of Section B4.3b, 783 in.2 (mm2) 3 3 784 Sx = minimum elastic section modulus taken about the x-axis, in (mm ) 785 Yt = 1.0 for Fy/Fu  0.8 786 = 1.1 otherwise 787 788 2. Proportioning Limits for I-Shaped Members 789 790 Singly symmetric I-shaped members shall satisfy the following limit: 791

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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I 792 0.1yc 0.9 (F13-2) I y 793 794 I-shaped members with slender webs shall also satisfy the following limits: 795 a 796 (a) When  1.5 h 797 hE 798   12.0 (F13-3) tF wymax 799 a 800 (b) When  1.5 h 801 hE0.40 802   (F13-4) tF wymax 803 804 where 805 a = clear distance between transverse stiffeners, in. (mm) 806 807 In unstiffened girders h/tw shall not exceed 260. The ratio of the web area to the compression flange 808 area shall not exceed 10. 809 810 3. Cover Plates 811 812 For members with cover plates, the following apply: 813 814 (a) Flanges of welded beams or girders are permitted to be varied in thickness or width by splicing 815 a series of plates or by the use of cover plates. 816 817 (b) High-strength bolts or welds connecting flange to web, or cover plate to flange, shall be 818 proportioned to resist the total horizontal shear resulting from the bending forces on the girder. 819 The longitudinal distribution of these bolts or intermittent welds shall be in proportion to the 820 intensity of the shear. 821 822 (c) However, the longitudinal spacing shall not exceed the maximum specified for compression or 823 tension members in Section E6 or D4, respectively. Bolts or welds connecting flange to web 824 shall also be proportioned to transmit to the web any loads applied directly to the flange, unless 825 provision is made to transmit such loads by direct bearing. 826 827 (d) Partial-length coverDRAFT plates shall be extended beyond the theoretical cutoff point and the 828 extended portion shall be attached to the beam or girder by high-strength bolts in a slip-critical 829 connection or fillet welds. The attachment shall, at the applicable strength given in Sections 830 J2.2, J3.8 or B3.11, develop the cover plate’s portion of the flexural strength in the beam or 831 girder at the theoretical cutoff point. 832 833 (e) For welded cover plates, the welds connecting the cover plate termination to the beam or girder 834 shall be continuous welds along both edges of the cover plate in the length a , defined in the 835 following, and shall develop the cover plate’s portion of the available strength of the beam or 836 girder at the distance a from the end of the cover plate. 837

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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838 (1) When there is a continuous weld equal to or larger than three-fourths of the plate thickness 839 across the end of the plate 840 841 a = w (F13-5) 842 843 where 844 w = width of cover plate, in. (mm) 845 846 (2) When there is a continuous weld smaller than three-fourths of the plate thickness across the 847 end of the plate 848 849 a = 1.5w (F13-6) 850 851 (3) When there is no weld across the end of the plate 852 853 a = 2w (F13-7) 854 855 4. Built-Up Beams 856 857 Where two or more beams or channels are used side-by-side to form a flexural member, they shall be 858 connected together in compliance with Section E6.2. When concentrated loads are carried from one 859 beam to another or distributed between the beams, diaphragms having sufficient stiffness to distribute 860 the load shall be welded or bolted between the beams. 861 862 5. Unbraced Length for Moment Redistribution 863 864 For moment redistribution in indeterminate beams according to Section B3.3, the laterally unbraced 865 length, Lb, of the compression flange adjacent to the redistributed end moment locations shall not 866 exceed Lm determined as follows. 867 868 (a) For doubly symmetric and singly symmetric I-shaped beams with the compression flange 869 equal to or larger than the tension flange loaded in the plane of the web: 870 871 M E 872 L 0.12 0.076 1 r (F13-8) my MF2 y 873 874 (b) For solid rectangular bars and symmetric box beams bent about their major axis: 875 M EE  876 L 0.17 0.10 1 rr0.10 (F13-9) my y MF2 yy  F 877 DRAFT 878 879 where 880 Fy = specified minimum yield stress of the compression flange, ksi (MPa) 881 M1= smaller moment at end of unbraced length, kip-in. (N-mm) 882 M2= larger moment at end of unbraced length, kip-in. (N-mm) 883 ry = radius of gyration about y-axis, in. (mm) 884 (M1 /M2) is positive when moments cause reverse curvature and negative for single curvature 885 886 There is no limit on Lb for members with round or square cross sections or for any beam bent about 887 its minor axis.

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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1 CHAPTER G

2 DESIGN OF MEMBERS FOR SHEAR 3 4 5 This chapter addresses webs of singly or doubly symmetric members subject to shear in the plane of the 6 web, single angles and HSS sections, and shear in the weak direction of singly or doubly symmetric shapes. 7 8 The chapter is organized as follows: 9 G1. General Provisions 10 G2. Members with Unstiffened or Stiffened Webs when Tension Field Action is not Considered 11 G3. Tension Field Action 12 G4. Single Angles and Tees 13 G5. Rectangular HSS and Box-Shaped Members 14 G6. Round HSS 15 G7. Weak Axis Shear in Doubly Symmetric and Singly Symmetric Shapes 16 G8. Beams and Girders with Web Openings 17

18 User Note: For cases not included in this chapter, the following sections apply: 19  H3.3 Unsymmetric sections 20  J4.2 Shear strength of connecting elements 21  J10.6 Web panel zone shear 22 23 G1. GENERAL PROVISIONS 24 25

26 The design shear strength, vVn, and the allowable shear strength, Vn/v, shall be determined as 27 follows: 28 29 (a) For all provisions in this chapter except Section G2.1(a): 30 DRAFT 31

32 v = 0.90 (LRFD) v = 1.67 (ASD) 33 34 (b) The nominal shear strength, Vn, shall be determined according to Sections G2 through G7. 35 36 37 G2. MEMBERS WITH UNSTIFFENED OR STIFFENED WEBS WHEN TENSION 38 FIELD ACTION IS NOT CONSIDERED 39 40 1. Shear Strength 41 42 This section applies to webs of doubly symmetric shapes, singly symmetric I-shapes and channels 43 subject to shear in the plane of the web. It applies to unstiffened webs, to webs with ah 3.0 , 44 and to end panels of members with interior web panels having ah 3.0 . 45 46 The nominal shear strength, Vn, is 47 Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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48 Vn = 0.6FyAwCvPB (G2-1) 49

50 (a) For webs of rolled I-shaped members with htwy 2.24 EF :

51 v = 1.00 (LRFD) v= 1.50 (ASD) 52 and 53 CvPB = 1.0 (G2-2) 54 55 User Note: All current ASTM A6 W, S and HP shapes except W44x230, W40x149, W36x135, 56 W33x118, W30x90, W24x55, W16x26 and W12x14 meet the criteria stated in Section G2.1(a) 57 for Fy = 50 ksi (345 MPa). 58 59 (b) For webs of all other doubly symmetric shapes and singly symmetric I-shapes,and channels, 60 except round HSS, 61 62 (1) The web shear post buckling strength coefficient, CvPB, is determined as follows: 63

64 (i) When h/twvy 110 . k E/F 65 66 CvPB = 1.0 (G2-3) 67

68 (ii) When htwvy110 . kE/F 69

1.10kEvy / F 70 CvPB = (G2-4) ht/ w 71 where 2 2 72 Aw = area of web, the overall depth times the web thickness, dtw, in. (mm ) 73 h = for rolled shapes, the clear distance between flanges less the fillet or corner radii, in. 74 (mm) 75 = for built-up welded sections, the clear distance between flanges, in. (mm) 76 = for built-up bolted sections, the distance between fastener lines, in. (mm) 77 tw = thickness of web, in. (mm) 78 79 (2) The web plate shear buckling coefficient, kv, is determined as follows:

80 (i)DRAFT For webs without transverse stiffeners and with h/tw  260: 81 82 kv =5.34 83 84 85 86 (ii) For webs with transverse stiffeners: 5 87 k= 5  (G2-5) v 2 ah/ 88 = 5.34 when a / h > 3.0 89 where 90 a = clear distance between transverse stiffeners, in. (mm) 91 92 User Note: For all ASTM A6 W, S, M and HP shapes except M12.5x12.4, M12.5x11.6, M12x11.8, M12x10.8, M12x10, M10x8 M10x7.5 93 and , when Fy  50 ksi (345 MPa), CvPB = 1.0. 94 95 User Note: Members without transverse stiffeners with h/tw > 150 and transversely stiffened 2 96 members with a/h > [260/(h/tw)] may require special considerations to control distortion during Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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97 fabrication and under load. In particular, members with highly slender webs are more apt to be 98 limited by web local yielding, web local crippling, and/or the web compression buckling provisions 99 of Sections J10.2, J10.3 and J10.5. 100 101 2. Transverse Stiffeners 102 103 For transverse stiffeners, the following shall apply. 104

105 (a) Transverse stiffeners are not required where ht/2.46/wy EF, or where the available shear

106 strength provided in accordance with Section G2.1 for kv = 5.34 is greater than the required 107 shear strength. 108 109 (b) The moment of inertia, Ist, of transverse stiffeners used to develop the available web shear 110 strength, as provided in Section G2.1, about an axis in the web center for stiffener pairs or about 111 the face in contact with the web plate for single stiffeners, shall meet the following requirement: 112 3 113 Ist ≥ btw j (G2-6) 114 115 where 25. 116 j.205 (G2-7) a/h 2 117 118 and b is the smaller of the dimensions a and h 119 120 (c) Transverse stiffeners are permitted to be stopped short of the tension flange, provided bearing is 121 not needed to transmit a concentrated load or reaction. The weld by which transverse stiffeners 122 are attached to the web shall be terminated not less than four times nor more than six times the 123 web thickness from the near toe to the web-to-flange weld. When single stiffeners are used, 124 they shall be attached to the compression flange, if it consists of a rectangular plate, to resist any 125 uplift tendency due to torsion in the flange. 126 (d) Bolts connecting stiffeners to the girder web shall be spaced not more than 12 in. (305 mm) on 127 center. If intermittent fillet welds are used, the clear distance between welds shall not be more 128 than 16 times the web thickness nor more than 10 in. (250 mm). 129 DRAFT 130 G3. TENSION FIELD ACTION 131 132 133 1. Shear Strength 134 135 This section applies to interior web panels of doubly symmetric shapes and singly symmetric I- 136 shapes and channels subject to shear in the plane of the web, when the web plate is supported on all 137 four sides by flanges or stiffeners and ah 3.0. 138 139 140 The nominal shear strength, Vn, is determined as follows: 141

142 (a) When h/twvy110 . k E/F

143 VFAnyw 0.6 (G3-1) 144 145 146 Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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147 (b) When ht/1.10/wvy kEF

148 (1) When 22AAwfcft A .5, hbfc  6.0 and hbft  6.0  1 CvB 149 VFACnywvB0.6 (G3-2) 2 1.15 1 ah / 150 151 (2) Otherwise 152   1 CvB 153 VFACnywvB0.6  (G3-3) 2 1.15ah 1 a / h  154 where 155 156 The web shear buckling coefficient, CvB, is determined as follows: 157

158 (i) When h/twvy 110 . k E/F 159 160 CvB = 1.0 (G3-4) 161

162 (ii) When 110.kE/Fh/t.kE/Fvy w137 vy 163

1.10kEvy / F 164 CvB = (G3-5) ht/ w 165

166 (iii) When h/twvy 137 . k E/F 167 1.51kE 168 C = v (G3-6) vB 2 ht/ wy F 169 170 kv is DRAFT as defined in Section G2.1 2 2 171 Afc = area of compression flange, in. (mm ) 2 2 172 Aft = area of tension flange, in. (mm ) 173 bfc = width of compression flange, in. (mm) 174 bft = width of tension flange, in. (mm) 175 176 User Note: Members that do not meet the requirements of Section G3.1(b)(1) may predict less 177 strength using tension field action than when using the post buckling strength as provided by Section 178 G2.1. 179 180 2. Transverse Stiffeners 181 182 Transverse stiffeners subject to tension field action shall meet the requirements of Section G2.2 and 183 the following limitations: E 184 (a) bt st  0.56 (G3-7) Fyst

185 (b) IIststststw121 I  I  (G3-8) 186 Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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187 where

188 bt st = width-to-thickness ratio of the stiffener

189 Fyst = specified minimum yield stress of the stiffener material, ksi (MPa) 190 Ist = moment of inertia of the transverse stiffeners about an axis in the web center for 191 stiffener pairs, or about the face in contact with the web plate for single stiffeners, 192 in.4 (mm4) 193 Ist1 = minimum moment of inertia of the transverse stiffeners required for development of 194 the web shear resistance without tension field action in Section G2.2, in.4 (mm4) 195 Ist2 = minimum moment of inertia of the transverse stiffeners required for development of 4 4 196 the full tension field resistance of the stiffened web panels, Vr = Vc2, in. (mm ) 41.3 1.5 h st Fyw  197 =  (G3-9) 40 E

198 Vr =larger of the required shear strengths in the adjacent panels, kips (N) 199 Vc1 = available shear strength without tension field action calculated with Vn as defined in 200 Section G2.1, kips (N) 201 Vc2 = available shear strength with tension field action calculated with Vn as defined in 202 Section G3.2, kips (N)

203 st = the larger of FywF yst and 1.0

VVrc 1 204 w = maximum shear ratio  0 within the web panels on each side of the VVcc21

205 transverse stiffener; in cases where Vc2 is less than Vc1, w shall be taken equal to zero. 206 207 Fyw = specified minimum yield stress of the web material, ksi (MPa) 208 209 User Note: Ist may conservatively be taken as Ist2. Equation G3-9 provides the minimum stiffener 210 moment of inertia required to attain full tension field action. If less post buckling shear strength is 211 required, Equation G3-8 provides a linear interpolation between the minimum moment of inertia 212 required to develop web shear buckling and that required to develop full tension field action. 213 214 G4. SINGLE ANGLES AND TEES 215 216 The nominal shear strength, Vn, of a single angle leg or a tee stem is 217 218 DRAFT 219 VFbtCnyv 0.6 B (G4-1) 220 where 221 b = width of the leg resisting the shear force or depth of the tee stem, in. (mm) 222 t = thickness of angle leg or of tee stem, in. (mm) 223 CvB = web shear buckling strength coefficient as defined in Section G3.1 with h/tw =b/t and 224 kv =1.2 225 226 G5. RECTANGULAR HSS AND BOX SECTIONS 227 228 The nominal shear strength, Vn, of rectangular HSS and box sections is 229 230

231 VFACnywv 0.6 B (G5-1) 232 where 2 2 233 Aw = 2ht, in. (mm )

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234 h = width resisting the shear force, taken as the clear distance between the flanges less the 235 inside corner radius on each side for HSS or the clear distance between flanges for box 236 sections, in. (mm) 237 t = design wall thickness as defined in Section B4.2, in. (mm) 238 CvB = web shear buckling strength coefficient as defined in Section G3.1 with h/tw =h/t and kv 239 =5 240 241 242 If the corner radius is not known, h shall be taken as the corresponding outside dimension minus 3 243 times the thickness. 244 245 G6. ROUND HSS 246 247 The nominal shear strength, Vn, of round HSS, according to the limit states of shear yielding and 248 shear buckling, shall be determined as: 249 250 Vn = FcrAg/2 (G6-1) 251 252 where 253 254 Fcr shall be the larger of 255 160.E 256 Fcr  5 (G6-2a) 4 Lv D  Dt 257 258 and 0.78E 259 Fcr  3 (G6-2b) D 2  t 260 261 but shall not exceed 0.6Fy 262 2 2 263 Ag = gross cross-sectional area of member, in. (mm ) 264 D =DRAFT outside diameter, in. (mm) 265 Lv = distance from maximum to zero shear force, in. (mm) 266 t = design wall thickness, in. (mm) 267 268 User Note: The shear buckling equations, Equations G6-2a and G6-2b, will control for D/t over 269 100, high-strength steels, and long lengths. For standard sections, shear yielding will usually 270 control and Fcr = 0.6Fy. 271 272 G7. WEAK AXIS SHEAR IN DOUBLY SYMMETRIC AND SINGLY SYMMETRIC 273 SHAPES 274 275 For doubly and singly symmetric shapes loaded in the weak axis without torsion, the nominal shear 276 strength, Vn, for each shear resisting element is 277 278

279 VFbtCnyffv 0.6 B (G7-1) 280 281

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282 where 283 CvB = web shear buckling strength coefficient as defined in Section G3.1 with 284 h/tw =bf/2tf for I-shaped members and tees or h/tw =bf/tf for channels and kv 1.2 285 286

287 User Note: For all ASTM A6 W, S, M and HP shapes, when Fy  50 ksi (345 MPa), CvB = 1.0. 288 289 G8. BEAMS AND GIRDERS WITH WEB OPENINGS 290 291 The effect of all web openings on the shear strength of steel and composite beams shall be 292 determined. Reinforcement shall be provided when the required strength exceeds the available 293 strength of the member at the opening.

DRAFT

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1 CHAPTER H 2

3 DESIGN OF MEMBERS FOR COMBINED FORCES AND TORSION 4 5 6 This chapter addresses members subject to axial force and flexure about one or both axes, with or without 7 torsion, and members subject to torsion only. 8 The chapter is organized as follows: 9 H1. Doubly and Singly Symmetric Members Subject to Flexure and Axial Force 10 H2. Unsymmetric and Other Members Subject to Flexure and Axial Force 11 H3. Members Subject to Torsion and Combined Torsion, Flexure, Shear and/or Axial Force 12 H4. Rupture of Flanges with Holes and Subjected to Tension 13 User Note: For composite members, see Chapter I. 14 15 16 H1. DOUBLY AND SINGLY SYMMETRIC MEMBERS SUBJECT TO FLEXURE AND 17 AXIAL FORCE 18 19 1. Doubly and Singly Symmetric Members Subject to Flexure and Compression 20 21 The interaction of flexure and compression in doubly symmetric members and singly symmetric 22 members constrained to bend about a geometric axis (x and/or y) shall be limited by Equations H1- 23 1a and H1-1b. 24 User Note: Section H2 is permitted to be used in lieu of the provisions of this section. P 25 (a) WhenDRAFT r  0.2 Pc 26 P 8 M M 27 r rx + ry 1.0 (H1-1a) PMM9  ccxcy 28 P 29 (b) When r  0.2 Pc 30 P M M 31 r rx + ry 1.0 (H1-1b)  2PMMccxcy 32 where 33 Pr = required axial strength, determined in accordance with Chapter C, using LRFD or 34 ASD load combinations, kips (N) 35 Pc = available axial strength, kips (N) 36 Mr = required flexural strength, determined in accordance with Chapter C, using LRFD or 37 ASD load combinations, kip-in. (N-mm) 38 Mc = available flexural strength, kip-in. (N-mm) 39 x = subscript relating symbol to major axis bending 40 y = subscript relating symbol to minor axis bending 41 42 For design according to Section B3.1 (LRFD): Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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43 44 Pr = required axial strength, determined in accordance with Chapter C, using LRFD load 45 combinations, kips (N)

46 Pc = cPn = design axial strength, determined in accordance with Chapter E, kips (N) 47 Mr = required flexural strength, determined in accordance with Chapter C, using LRFD 48 load combinations, kip-in. (N-mm)

49 Mc = bMn = design flexural strength determined in accordance with Chapter F, kip-in. 50 (N-mm) 51 c = resistance factor for compression = 0.90 52 b = resistance factor for flexure = 0.90 53 54 For design according to Section B3.2 (ASD): 55 56 Pr = required axial strength, determined in accordance with Chapter C, using ASD load 57 combinations, kips (N)

58 Pc = Pn /c = allowable axial strength, determined in accordance with Chapter E, kips 59 (N) 60 Mr = required flexural strength, determined in accordance with Chapter C, using ASD 61 load combinations, kip-in. (N-mm)

62 Mc = Mn/b = allowable flexural strength determined in accordance with Chapter F, kip- 63 in. (N-mm)

64 c = safety factor for compression = 1.67 65 b = safety factor for flexure = 1.67 66 67 2. Doubly and Singly Symmetric Members Subject to Flexure and Tension 68 69 The interaction of flexure and tension in doubly symmetric members and singly symmetric members 70 constrained to bend about a geometric axis (x and/or y) shall be limited by Equations H1-1a and H1- 71 1b, 72 where 73 DRAFT 74 For design according to Section B3.1 (LRFD): 75 76 Pr = required axial strength, determined in accordance with Chapter C, using LRFD load 77 combinations, kips (N)

78 Pc = tPn = design axial strength, determined in accordance with Section D2, kips (N) 79 Mr = required flexural strength, determined in accordance with Chapter C, using LRFD 80 load combinations, kip-in. (N-mm)

81 Mc = bMn = design flexural strength determined in accordance with Chapter F, kip-in. 82 (N-mm) 83 t = resistance factor for tension (see Section D2) 84 b = resistance factor for flexure = 0.90 85 86 For design according to Section B3.2 (ASD): 87 88 Pr = required axial strength, determined in accordance with Chapter C, using ASD load 89 combinations, kips (N)

90 Pc = Pn / t = allowable axial strength, determined in accordance with Section D2, 91 kips (N) 92 Mr = required flexural strength, determined in accordance with Chapter C, using ASD 93 load combinations, kip-in. (N-mm)

94 Mc = Mn/b = allowable flexural strength determined in accordance with Chapter F, kip- 95 in. (N-mm)

96 t = safety factor for tension (see Section D2)

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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97 b = safety factor for flexure = 1.67 98 99

Pr 100 For doubly symmetric members, Cb in Chapter F is permitted to be multiplied by 1 for Pey 101 axial tension that acts concurrently with flexure 102 103 where  2 EI P  y 104 ey 2 (H1-2) Lb 105 and 106  = 1.0 (LRFD)  = 1.6 (ASD) 107 108 109 3. Doubly Symmetric Rolled Compact Members Subject to Single Axis Flexure and Compression 110 111 For doubly symmetric rolled compact members, with the effective length for torsional buckling less 112 than or equal to the effective length for y-axis flexural buckling, LLcz c y , subjected to flexure and 113 compression with moments primarily about their major axis, it is permissible to address the two 114 independent limit states, in-plane instability and out-of-plane buckling or lateral-torsional buckling, 115 separately in lieu of the combined approach provided in Section H1.1, 116 117 where 118 Lcz = effective length for buckling about the longitudinal axis, in. (mm) 119 Lcy = effective length for buckling about the y-axis, in. (mm) 120

121 For members with MMry cy  0.05 , the provisions of Section H1.1 shall be followed.

122 (a) ForDRAFT the limit state of in-plane instability, Equations H1-1 shall be used with Pc taken as the 123 available compressive strength in the plane of bending and Mcx taken as the available flexural 124 strength based on the limit state of yielding. 125 126 (b) For the limit state of out-of-plane buckling and lateral-torsional buckling: 2 PPM 127 rr1.5 0.5 rx 1.0 (H1-2)  PPCMcy cy b cx 128 where

129 Pcy = available compressive strength out of the plane of bending, kips (N) 130 Cb = lateral-torsional buckling modification factor determined from Section F1 131 Mcx = available lateral-torsional strength for major axis flexure determined in 132 accordance with Chapter F using Cb = 1.0, kip-in. (N-mm) 133

134 User Note: In Equation H1-2, CbMcx may be larger than bMpx in LRFD or Mpx/b in ASD. The 135 yielding resistance of the beam-column is captured by Equations H1-1. 136 137 H2. UNSYMMETRIC AND OTHER MEMBERS SUBJECT TO FLEXURE AND 138 AXIAL FORCE 139

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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140 This section addresses the interaction of flexure and axial stress for shapes not covered in Section 141 H1. It is permitted to use the provisions of this Section for any shape in lieu of the provisions of 142 Section H1. ff f 143 ra rbw rbz 1.0 (H2-1) FFca cbw F cbz 144 145 where 146 fra = required axial stress at the point of consideration, determined in accordance with 147 Chapter C, using LRFD or ASD load combinations, ksi (MPa) 148 Fca = available axial stress at the point of consideration, ksi (MPa) 149 frbw, frbz = required flexural stress at the point of consideration, determined in accordance with 150 Chapter C, using LRFD or ASD load combinations, ksi (MPa) 151 Fcbw ,Fcbz = available flexural stress at the point of consideration, ksi (MPa) 152 w = subscript relating symbol to major principal axis bending 153 z = subscript relating symbol to minor principal axis bending 154 155 User Note: The subscripts w and z represent the x and y subscripts for doubly symmetric sections. 156 157 For design according to Section B3.1 (LRFD): 158 159 fra = required axial stress at the point of consideration, determined in accordance 160 with Chapter C, using LRFD load combinations, ksi (MPa)

161 Fca = cFcr = design axial stress, determined in accordance with Chapter E for 162 compression or Section D2 for tension, ksi (MPa) 163 frbw, frbz = required flexural stress at the point of consideration, determined in 164 accordance with Chapter C, using LRFD load combinations, ksi (MPa)

bnM 165 Fcbw, Fcbz = = design flexural stress determined in accordance with Chapter F, S 166 ksi (MPa). Use the section modulus for the specific location in the cross 167 DRAFTsection and consider the sign of the stress. 168 c = resistance factor for compression = 0.90 169 t = resistance factor for tension (Section D2) 170 b = resistance factor for flexure = 0.90 171 172 173 For design according to Section B3.2 (ASD): 174 175 fra = required axial stress at the point of consideration, determined in 176 accordance with Chapter C, using ASD load combinations, ksi (MPa) 177 Fca = allowable axial stress determined in accordance with Chapter E for 178 compression, or Section D2 for tension, ksi (MPa) 179 frbw, frbz = required flexural stress at the point of consideration, determined in 180 accordance with Chapter C, using ASD load combinations, ksi (MPa)

M n 181 Fcbw, Fcbz = = allowable flexural stress determined in accordance with Chapter bS 182 F, ksi (MPa). Use the section modulus for the specific location in the 183 cross section and consider the sign of the stress.

184 c = safety factor for compression = 1.67 185 t = safety factor for tension (see Section D2) 186 b = safety factor for flexure = 1.67 187 188

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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189 Equation H2-1 shall be evaluated using the principal bending axes by considering the sense of the 190 flexural stresses at the critical points of the cross section. The flexural terms are either added to or 191 subtracted from the axial term as applicable. When the axial force is compression, second order 192 effects shall be included according to the provisions of Chapter C. 193 194 A more detailed analysis of the interaction of flexure and tension is permitted in lieu of Equation H2- 195 1. 196 197 H3. MEMBERS SUBJECT TO TORSION AND COMBINED TORSION, FLEXURE, 198 SHEAR AND/OR AXIAL FORCE 199 200 1. Round and Rectangular HSS Subject to Torsion 201

202 The design torsional strength, TTn, and the allowable torsional strength, Tn/T, for round and 203 rectangular HSS according to the limit states of torsional yielding and torsional buckling shall 204 be determined as follows: 205

206 Tn = FcrC (H3-1) 207

208 T = 0.90 (LRFD) T = 1.67 (ASD) 209 210 211 where 212 C is the HSS torsional constant 213 214 The critical stress, Fcr, shall be determined as follows: 215 216 (a) For round HSS, Fcr shall be the larger of 217 218 DRAFT 1.23EE0.6 219 (1) and (H3-2a) L/D(( D/t))5/4 D/t 3/2 220 221 and 222 0.60E 223 (2) F  (H3-2b) cr 3 D 2  t 224 225 but shall not exceed 0.6Fy, 226 227 where 228 L = length of the member, in. (mm) 229 D = outside diameter, in. (mm) 230 231 (b) For rectangular HSS 232

233 (1) When h / t  245./EFy

234 Fcr = 0.6Fy (H3-3) 235

236 (2) When 245./EFyy ht /./307 EF Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

H-6

0.6Fyy 2.45EF /  237 Fcr  (H3-4) h  t 238

239 (3) When 307./EFy  ht /260 0.4582 E 240 F  (H3-5) cr 2 h  t 241 242 where 243 h = flat width of longer side as defined in Section B4.1b(d), in. (mm) 244 t = design wall thickness defined in Section B4.2, in. (mm) 245 246 User Note: The torsional constant, C, may be conservatively taken as: Dtt2 247 For round HSS: C  2 248 For rectangular HSS: CBtHtt2( )(  ) 4.5(4 ) t3 249 250 2. HSS Subject to Combined Torsion, Shear, Flexure and Axial Force 251 252 When the required torsional strength, Tr, is less than or equal to 20% of the available torsional 253 strength, Tc, the interaction of torsion, shear, flexure and/or axial force for HSS may be determined 254 by Section H1 and the torsional effects may be neglected. When Tr exceeds 20% of Tc, the 255 interaction of torsion, shear, flexure and/or axial force shall be limited, at the point of consideration, 256 by

2 PMrr VT rr 257 1.0 (H3-6) DRAFTPMcc VT cc 258 259 where 260 261 For design according to Section B3.1 (LRFD): 262 263 Pr = required axial strength, determined in accordance with Chapter C, using LRFD load 264 combinations, kips (N)

265 Pc = Pn = design tensile or compressive strength in accordance with Chapter D or E, kips 266 (N) 267 Mr = required flexural strength, determined in accordance with Chapter C, using LRFD load 268 combinations, kip-in. (N-mm)

269 Mc = bMn = design flexural strength in accordance with Chapter F, kip-in. (N-mm) 270 Vr = required shear strength, determined in accordance with Chapter C, using LRFD load 271 combinations, kips (N)

272 Vc = vVn = design shear strength in accordance with Chapter G, kips (N) 273 Tr = required torsional strength, determined in accordance with Chapter C, using LRFD load 274 combinations, kip-in. (N-mm)

275 Tc = TTn = design torsional strength in accordance with Section H3.1, kip-in. (N-mm) 276 277 For design according to Section B3.2 (ASD): 278 279 Pr = required axial strength, determined in accordance with Chapter C, using ASD load 280 combinations, kips (N) Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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281 Pc = Pn / = allowable tensile or compressive strength in accordance with Chapter D or E, 282 kips (N) 283 Mr = required flexural strength, determined in accordance with Chapter C, using ASD load 284 combinations, kip-in. (N-mm)

285 Mc = Mn /b = allowable flexural strength in accordance with Chapter F, kip-in. (N-mm) 286 Vr = required shear strength, determined in accordance with Chapter C, using ASD load 287 combinations, kips (N)

288 Vc = Vn /v = allowable shear strength in accordance with Chapter G, kips (N) 289 Tr = required torsional strength, determined in accordance with Chapter C, using ASD load 290 combinations, kip-in. (N-mm)

291 Tc = Tn /T = allowable torsional strength in accordance with Section H3.1, kip-in. (N-mm) 292 293 3. Non-HSS Members Subject to Torsion and Combined Stress 294 295 The available torsional strength for non-HSS members shall be the lowest value obtained according 296 to the limit states of yielding under normal stress, shear yielding under shear stress, or buckling, 297 determined as follows: 298

299 T = 0.90 (LRFD) T= 1.67 (ASD) 300 301 (a) For the limit state of yielding under normal stress 302 303 Fn = Fy (H3-7) 304 305 306 (b) For the limit state of shear yielding under shear stress 307 308 Fn = 0.6Fy (H3-8) 309 310 311 (c) ForDRAFT the limit state of buckling 312 313 Fn = Fcr (H3-9) 314 315 where 316 Fcr = buckling stress for the section as determined by analysis, ksi (MPa) 317 318 Constrained local yielding is permitted adjacent to areas that remain elastic. 319 320 H4. RUPTURE OF FLANGES WITH HOLES AND SUBJECTED TO TENSION 321 322 At locations of bolt holes in flanges subject to tension under combined axial force and major axis 323 flexure, flange tensile rupture strength shall be limited by Equation H4-1. Each flange subject to 324 tension due to axial force and flexure shall be checked separately. 325 PM 326 rrx1.0 (H4-1) PMccx 327 328 where 329 330 Pr = required axial strength of the member at the location of the bolt holes, determined in 331 accordance with Chapter C,, positive in tension, negative in compression, kips (N) 332 Pc = available axial strength for the limit state of tensile rupture of the net section at the location 333 of bolt holes, kips (N)

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334 Mrx = required flexural strength at the location of the bolt holes, determined in accordance with 335 Chapter C, positive for tension in the flange under consideration, negative for compression, 336 kip-in. (N-mm) 337 Mcx = available flexural strength about x-axis for the limit state of tensile rupture of the flange, 338 determined according to Section F13.1. When the limit state of tensile rupture in flexure 339 does not apply, use the plastic bending moment, Mp, determined with bolt holes not taken 340 into consideration, kip-in. (N-mm) 341 342 For design according to Section B3.1 (LRFD): 343 344 Pr = required axial strength, determined in accordance with Chapter C, using LRFD 345 load combinations, kips (N) 346 Pc = tPn = design axial strength for the limit state of tensile rupture, determined in 347 accordance with Section D2(b), kips (N) 348 Mrx = required flexural strength, determined in accordance with Chapter C, using LRFD 349 load combinations, kip-in. (N-mm) 350 Mcx = bMn = design flexural strength determined in accordance with Section F13.1 or 351 the plastic bending moment, Mp, determined with bolt holes not taken into 352 consideration, as applicable, kip-in. (N-mm) 353 t = resistance factor for tensile rupture = 0.75 354 b = resistance factor for flexure = 0.90 355 356 For design according to Section B3.2 (ASD): 357 358 Pr = required axial strength, determined in accordance with Chapter C, using ASD load 359 combinations, kips (N)

360 Pc = Pn / t = allowable axial strength for the limit state of tensile rupture, determined 361 in accordance with Section D2(b), kips (N) 362 Mrx = required flexural strength, determined in accordance with Chapter C, using ASD 363 load combinations, kip-in. (N-mm)

364 Mcx = Mn/b = allowable flexural strength determined in accordance with Section F13.1, 365 DRAFTor the plastic bending moment, Mp, determined with bolt holes not taken into 366 consideration, as applicable, kip-in. (N-mm)

367 t = safety factor for tensile rupture = 2.00 368 b = safety factor for flexure = 1.67

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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1 CHAPTER I

2 DESIGN OF COMPOSITE MEMBERS 3 4 5 This chapter addresses composite members composed of rolled or built-up structural 6 steel shapes or HSS and structural concrete acting together, and steel beams 7 supporting a reinforced concrete slab so interconnected that the beams and the slab 8 act together to resist bending. Simple and continuous composite beams with steel 9 headed stud anchors, encased, and filled beams, constructed with or without 10 temporary shores, are included. 11 12 The chapter is organized as follows: 13 14 I1. General Provisions 15 I2. Axial Force 16 I3. Flexure 17 I4. Shear 18 I5. Combined Axial Force and Flexure 19 I6. Load Transfer 20 I7. Composite Diaphragms and Collector Beams 21 I8. Steel Anchors 22 I9. Special Cases 23 24 I1. GENERAL PROVISIONS 25 26 In determining load effects in members and connections of a structure that 27 includes composite members, consideration shall be given to the effective 28 sections at the time each increment of load is applied. 29 DRAFT 30 1. Concrete and Steel Reinforcement 31 32 The design, detailing and material properties related to the concrete and 33 reinforcing steel portions of composite construction shall comply with the 34 reinforced concrete and reinforcing bar design specifications stipulated by the 35 applicable building code. Additionally, the provisions in the Building Code 36 Requirements for Structural Concrete and Commentary (ACI 318) and the 37 Metric Building Code Requirements for Structural Concrete and Commentary 38 (ACI 318M), subsequently referred to in Chapter I collectively as ACI 318, 39 shall apply with the following exceptions and limitations: 40 41 (a) ACI 318 Sections 7.8.2 and 10.13, and Chapter 21 shall be excluded in 42 their entirety. 43 (b) Concrete and steel reinforcement material limitations shall be as specified 44 in Section I1.3. 45 (c) Transverse reinforcement limitations shall be as specified in Section 46 I2.1a(b) and I2.2a(c), in addition to those specified in ACI 318. 47 Minimum longitudinal reinforcement limitations shall be as specified in 48 Section I2.1a(c) and I2.2a(c). Concrete and steel reinforcement components 49 designed in accordance with ACI 318 shall be based on a level of loading 50 corresponding to LRFD load combinations.

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51 User Note: It is the intent of the Specification that the concrete and 52 reinforcing steel portions of composite concrete members be detailed utilizing 53 the noncomposite provisions of ACI 318 as modified by the Specification. All 54 requirements specific to composite members are covered in the Specification. 55 Note that the design basis for ACI 318 is strength design. Designers using 56 ASD for steel must be conscious of the different load factors. 57 58 2. Nominal Strength of Composite Sections 59 60 The nominal strength of composite sections shall be determined in accordance 61 with either the plastic stress distribution method, the strain compatibility 62 method, the elastic stress distribution method, or the effective stress-strain 63 method as defined in this section. 64 65 The tensile strength of the concrete shall be neglected in the determination of 66 the nominal strength of composite members. 67 68 Local buckling effects shall be evaluated for filled composite members as 69 defined in Section I1.4. Local buckling effects need not be evaluated for 70 encased composite members. 71 72 2a. Plastic Stress Distribution Method 73 74 For the plastic stress distribution method, the nominal strength shall be 75 computed assuming that steel components have reached a stress of Fy in either 76 tension or compression and concrete components in compression due to axial 77 force and/or flexure have reached a stress of 0.85 fc . For round HSS filled 78 with concrete, a stress of 0.95 fc is permitted to be used for concrete 79 components in compression due to axial force and/or flexure to account for 80 the effects of concreteDRAFT confinement. 81 82 2b. Strain Compatibility Method 83 84 For the strain compatibility method, a linear distribution of strains across the 85 section shall be assumed, with the maximum concrete compressive strain 86 equal to 0.003 in./in. (mm/mm). The stress-strain relationships for steel and 87 concrete shall be obtained from tests or from published results. 88 89 User Note: The strain compatibility method should be used to determine 90 nominal strength for irregular sections and for cases where the steel does not 91 exhibit elasto-plastic behavior. General guidelines for the strain compatibility 92 method for encased members subjected to axial load, flexure or both are given 93 in AISC Design Guide 6 and ACI 318. 94 95 2c. Elastic Stress Distribution Method 96 97 For the elastic stress distribution method, the nominal strength shall be 98 determined from the superposition of elastic stresses for the limit state of 99 yielding or concrete crushing. 100 101 2d. Effective Stress-Strain Method 102 103 For the effective stress-strain method, the nominal strength shall be computed 104 assuming strain compatibility, and effective stress-strain relationships for

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105 steel and concrete components accounting for the effects of local buckling, 106 yielding, interaction and concrete confinement. 107 108 3. Material Limitations 109 110 For concrete, structural steel, and steel reinforcing bars in composite systems: 111 (a) For the determination of the available strength, concrete shall have a 112 compressive strength, fc , of not less than 3 ksi (21 MPa) nor more than 113 10 ksi (70 MPa) for normal weight concrete and not less than 3 ksi (21 114 MPa) nor more than 6 ksi (42 MPa) for lightweight concrete. 115 User Note: Higher strength concrete material properties may be used 116 for stiffness calculations but may not be relied upon for strength calcula- 117 tions unless justified by testing or analysis. 118 (b) The specified minimum yield stress of structural steel used in calculating 119 the strength of composite members shall not exceed 75 ksi (525 MPa). 120 c) The specified minimum yield stress of reinforcing bars used in calculating 121 the strength of composite members shall not exceed 80 ksi (550 MPa). 122 4. Classification of Filled Composite Sections for Local Buckling 123 124 For compression, filled composite sections are classified as compact, 125 noncompact or slender. For a section to qualify as compact, the maximum 126 width-to-thickness ratio of its compression steel elements shall not exceed the 127 limiting width-to-thickness ratio, λp, from Table I1.1a. If the maximum width- 128 to-thickness ratio of one or more steel compression elements exceeds λp, but 129 does not exceed λr from Table I1.1a, the filled composite section is 130 noncompact. If the maximum width-to-thickness ratio of any compression 131 steel element exceeds λr, the section is slender. The maximum permitted 132 width-to-thickness ratio shall be as specified in the table. 133 DRAFT 134 For flexure, filled composite sections are classified as compact, noncompact 135 or slender. For a section to qualify as compact, the maximum width-to- 136 thickness ratio of its compression steel elements shall not exceed the limiting 137 width-to-thickness ratio, λp, from Table I1.1b. If the maximum width-to- 138 thickness ratio of one or more steel compression elements exceeds λp, but 139 does not exceed λr from Table I1.1b, the section is noncompact. If the width- 140 to-thickness ratio of any steel element exceeds λr, the section is slender. The 141 maximum permitted width-to-thickness ratio shall be as specified in the table. 142 143 Refer to Table B4.1a and Table B4.1b for definitions of width (b and D) and 144 thickness (t) for rectangular and round HSS sections and boxes of uniform 145 thickness. 146 147 User Note: All current ASTM A500 Grade B square HSS sections are 148 compact according to the limits of Table I1.1a and Table I1.1b, except 149 HSS778, HSS881/8, HSS998 and HSS1212x, which are 150 noncompact for both axial compression and flexure. 151 152 All current ASTM A500 Grade B round HSS sections are compact according 153 to the limits of Table I1.1a and Table I1.1b for both axial compression and 154 flexure with the exception of HSS16.00.25, which is noncompact for 155 flexure. 156 157

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TABLE I1.1a Limiting Width-to-Thickness Ratios for Compression Steel Elements in Composite Members Subject to Axial Compression For Use with Section I2.2

Width-to- p r Description of Thickness Compact/ Noncompact/ Maximum Element Ratio Noncompact Slender Permitted Walls of Rectangular E E E HSS and Boxes b/t 2.26 3.00 5.00 of Uniform Fy Fy Fy Thickness 015. E 019. E 031. E Round HSS D/t Fy Fy Fy 158 TABLE I1.1b Limiting Width-to-Thickness Ratios for Compression Steel Elements in Composite Members Subject to Flexure For Use with Section I3.4 Width-to- p r Description of Thickness Compact/ Noncompact/ Maximum Element Ratio Noncompact Slender Permitted Flanges of Rectangular E E E HSS and Boxes of b/t 2.26 3.00 5.00 Uniform Fy Fy Fy Thickness Webs of Rectangular E E E HSS and Boxes h/t 3.00 5.70 5.70 of Uniform Fy Fy Fy Thickness DRAFT Round HSS 009. E 031. E 031. E D/t Fy Fy Fy 159 160 5. Stiffness for Calculation of Required Strengths 161 162 The provisions of Chapter C shall apply for calculation of stiffness of encased 163 composite members and filled composite members for use in calculation of 164 required strengths, with the following exceptions: 165 166 Stiffness of encased composite members and filled composite members for use 167 in calculation of required strengths with the direct analysis method shall be as 168 follows: 169 170 (1) The nominal flexural stiffness of members subject to net compression 171 shall be taken as the effective stiffness of the composite section, EIeff, as 172 defined in Section I2. 173 174 (2) The nominal axial stiffness of members subject to net compression shall 175 be taken as the summation of the elastic axial stiffnesses of each compo- 176 nent. 177

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178 (3) Stiffness of members subject to net tension shall be taken as the stiffness 179 of the bare steel members in accordance with Chapter C. 180 181 (4) A factor of 0.80 shall be applied to the stiffnesses of all composite 182 members that are considered to contribute to the stability of the structure. 183 An additional factor, τb = 0.8, shall be applied to the flexural stiffnesses of 184 all composite members whose flexural stiffnesses are considered to 185 contribute to the stability of the structure. 186 187 User Note: Taken together, the stiffness reduction factors require the use 188 of 0.64EIeff for the flexural stiffness and 0.8 times the nominal axial 189 stiffness of encased composite members and filled composite members 190 subject to net compression in the analysis. 191 192 The stiffness values given in this section are not intended for the calcula- 193 tion of deflections. Stiffness values appropriate for the calculation of 194 deflections are discussed in the Commentary. 195 196 I2. AXIAL FORCE 197 198 This section applies to two types of composite members subject to axial force: 199 encased composite members and filled composite members. 200 201 1. Encased Composite Members 202 203 1a. Limitations 204 205 For encased composite members, the following limitations shall be met: 206 207 (a) The cross-sectional area of the steel core shall comprise at least 1% of 208 the totalDRAFT composite cross section. 209 (b) Concrete encasement of the steel core shall be reinforced with 210 continuous longitudinal bars and lateral ties or spirals. 211 Where lateral ties are used, a minimum of either a No. 3 (10 mm) bar 212 spaced at a maximum of 12 in. (305 mm) on center, or a No. 4 (13 213 mm) bar or larger spaced at a maximum of 16 in. (406 mm) on center 214 shall be used. Deformed wire or welded wire reinforcement of equiva- 215 lent area are permitted. 216 Maximum spacing of lateral ties shall not exceed 0.5 times the least 217 column dimension. 218 (c) The minimum reinforcement ratio for continuous longitudinal

219 reinforcing, sr, shall be 0.004, where sr is given by:

Asr 220 sr (I2-1) Ag 221 where 2 2 222 Ag = gross area of composite member, in. (mm ) 2 2 223 Asr = area of continuous reinforcing bars, in. (mm ) 224 225 User Note: Refer to Sections 7.10 and 10.9.3 of ACI 318 for additional tie 226 and spiral reinforcing provisions. 227 228 1b. Compressive Strength

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229

230 The design compressive strength, cPn, and allowable compressive strength, 231 Pn/c, of doubly symmetric axially loaded encased composite members shall 232 be determined for the limit state of flexural buckling based on member 233 slenderness as follows: 234  235 c = 0.75 (LRFD) c =2.00 (ASD) 236 P 237 (a) When no  2.25 Pe 238 Pno Pe (I2-2) 239 PPnno 0.658       240 P 241 (b) When no  2.25 Pe 242 (I2-3) 243    Pn= 0.877Pe 244 245 where 246 PFAFAfA 0.85  (I2-4) no y s ysr sr c c 247 Pe = elastic critical buckling load determined in accordance with 248 Chapter C or Appendix 7, kips (N) 2 2 249 =  (EIeff) / (Lc) (I2-5) 2 2 250 Ac = area of concrete, in. (mm ) 2 2 251 As = area of the steel section, in. (mm ) 252 Ec = modulus of elasticity of concrete 253 = wf1.5  , ksi ( 0.043wf1.5  , MPa) DRAFTcc cc 2 2 254 EIeff = effective stiffness of composite section, kip-in. (N-mm ) 255 = EsIs +EsIsr +C1EcIc (I2-6) C  coefficient for calculation of effective rigidity of an 256 1 encased composite compression member 257 258 = 0.25 + 3 ≤0.7 259 E s = modulus of elasticity of steel 260 = 29,000 ksi (200 000 MPa) 261 Fy = specified minimum yield stress of steel section, ksi (MPa) 262 Fysr = specified minimum yield stress of reinforcing bars, ksi (MPa) 263 Ic = moment of inertia of the concrete section about the elastic 264 neutral axis of the composite section, in.4 (mm4) 265 Is = moment of inertia of steel shape about the elastic neutral axis of 266 the composite section, in.4 (mm4) 267 Isr = moment of inertia of reinforcing bars about the elastic neutral 268 axis of the composite section, in.4 (mm4) 269 K = effective length factor 270 L = laterally unbraced length of the member, in. (mm)

271 Lc = KL = effective length of the member, in. (mm) 272

273 fc = specified compressive strength of concrete, ksi (MPa)

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3 274 wc = weight of concrete per unit volume, (90 ≤ wc ≤ 155 lb/ft or 1500 3 275 ≤ wc ≤ 2500 kg/m ) 276 277 The available compressive strength need not be less than that specified for 278 the bare steel member as required by Chapter E. 279 280 1c. Tensile Strength 281 282 The available tensile strength of axially loaded encased composite members 283 shall be determined for the limit state of yielding as: 284

285 PnFA y s F ysr A sr (I2-8) 286

287 t = 0.90 (LRFD) t = 1.67 (ASD) 288 289 1d. Load Transfer 290 291 Load transfer requirements for encased composite members shall be 292 determined in accordance with Section I6. 293 294 1e. Detailing Requirements 295 296 For encased composite members, the following detailing requirements shall 297 be met: 298 299 (a) Clear spacing between the steel core and longitudinal reinforcing shall be 300 a minimum of 1.5 reinforcing bar diameters, but not less than 1.5 in. (38 301 mm). 302 303 (b) If the composite cross section is built up from two or more encased steel 304 shapes, theDRAFT shapes shall be interconnected with lacing, tie plates or 305 comparable components to prevent buckling of individual shapes due to 306 loads applied prior to hardening of the concrete. 307 308 2. Filled Composite Members 309 310 2a. Limitations 311 312 For filled composite members, the following limitations shall be met: 313 314 (a) The cross-sectional area of the steel section shall comprise at least 1% 315 of the total composite cross section. 316 (b) Filled composite members shall be classified for local buckling 317 according to Section I1.4. 318 (c) Minimum longitudinal reinforcement is not required. If longitudinal 319 reinforcement is provided, internal transverse reinforcement is not 320 required for strength calculations. 321 322 2b. Compressive Strength 323 324 The available compressive strength of axially loaded doubly symmetric filled 325 composite members shall be determined for the limit state of flexural buckling 326 in accordance with Section I2.1b with the following modifications: 327

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328 (a) For compact sections 329 330 Pno = Pp (I2-9a) 331 332 where

Es 333 PFACfAApysccsr2   (I2-9b) Ec

334 C2 = 0.85 for rectangular sections and 0.95 for round sections 335 336 (b) For noncompact sections 337 PPpy 2 338 PPno p2   p (I2-9c) rp 339 340 where 341 λ, λp and λr are slenderness ratios determined from Table I1.1a 342 343 Pp is determined from Equation I2-9b 344

Es 345 PFAyys0.7 fAA ccsr  (I2-9d) Ec 346 347 (c) For slender sections

Es 348 PFAno cr s0.7 fAA c c  sr (I2-9e) Ec 349 350 where 351 (1) DRAFT For rectangular filled sections 9E 352 F  s (I2-10) cr 2 b  t 353 354 (2) For round filled sections 0.72F F  y 355 cr 0.2 (I2-11) D Fy  tEs 356 357 The effective stiffness of the composite section, EIeff, for all sections shall be: 358 359 EIeff = EsIs + EsIsr +C3EcIc (I2-12) 360 361 where 362 C3 = coefficient for calculation of effective rigidity of filled composite 363 compression member 364 = (I2-13) 365 =0.45+3 ≤0.9 366 The available compressive strength need not be less than specified for the 367 bare steel member as required by Chapter E. 368 369 2c. Tensile Strength

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370 371 The available tensile strength of axially loaded filled composite members 372 shall be determined for the limit state of yielding as: 373

374 PAFAFnsysrysr (I2-14) 375 376 t = 0.90 (LRFD) t = 1.67 (ASD) 377 378 2d. Load Transfer 379 380 Load transfer requirements for filled composite members shall be deter- 381 mined in accordance with Section I6. 382 383 I3. FLEXURE 384 385 This section applies to three types of composite members subject to flexure: 386 composite beams with steel anchors consisting of steel headed stud anchors 387 or steel channel anchors, concrete encased members, and concrete filled 388 members. 389 390 1. General 391 392 1a. Effective Width 393 394 The effective width of the concrete slab shall be the sum of the effective 395 widths for each side of the beam centerline, each of which shall not exceed: 396 397 (a) one-eighth of the beam span, center-to-center of supports; 398 (b)one-half the distance to the centerline of the adjacent beam; or 399 (c) the distance to the edge of the slab. 400 DRAFT 401 1b. Strength During Construction 402 403 When temporary shores are not used during construction, the steel section 404 alone shall have sufficient strength to support all loads applied prior to the 405 concrete attaining 75% of its specified strength fc. The available flexural 406 strength of the steel section shall be determined in accordance with Chapter 407 F. 408 409 2. Composite Beams With Steel Headed Stud or Steel Channel Anchors 410 411 2a. Positive Flexural Strength 412

413 The design positive flexural strength, bMn, and allowable positive flexural 414 strength, Mn/b, shall be determined for the limit state of yielding as 415 follows: 416

417 b = 0.90 (LRFD) b = 1.67 (ASD) 418

419 (a) When h / tw 3.76E / Fy 420 421 Mn shall be determined from the plastic stress distribution on the com- 422 posite section for the limit state of yielding (plastic moment). 423

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424 User Note: All current ASTM A6 W, S and HP shapes satisfy the

425 limit given in Section I3.2a(a) for Fy  50 ksi (345 MPa). 426

427 (b) When h / tw > 3.76E / Fy 428 429 Mn shall be determined from the superposition of elastic stresses, con- 430 sidering the effects of shoring, for the limit state of yielding (yield 431 moment). 432 433 2b. Negative Flexural Strength 434 435 The available negative flexural strength shall be determined for the steel 436 section alone, in accordance with the requirements of Chapter F. 437 438 Alternatively, the available negative flexural strength shall be determined 439 from the plastic stress distribution on the composite section, for the limit 440 state of yielding (plastic moment), with 441

442 b = 0.90 (LRFD) b = 1.67 (ASD) 443 444 provided that the following limitations are met: 445 446 (a) The steel beam is compact and is adequately braced in accordance 447 with Chapter F. 448 449 (b) Steel headed stud or steel channel anchors connect the slab to the steel 450 beam in the negative moment region. 451 452 (c) The slab reinforcement parallel to the steel beam, within the effective 453 width of the slab, is developed. 454 DRAFT 455 2c. Composite Beams With Formed Steel Deck 456 457 1. General 458 459 The available flexural strength of composite construction consisting of 460 concrete slabs on formed steel deck connected to steel beams shall be 461 determined by the applicable portions of Sections I3.2a and I3.2b, with 462 the following requirements: 463 464 (a) The nominal rib height shall not be greater than 3 in. (75 mm). 465 The average width of concrete rib or haunch, wr, shall be not less 466 than 2 in. (50 mm), but shall not be taken in calculations as more 467 than the minimum clear width near the top of the steel deck. 468 469 (b) The concrete slab shall be connected to the steel beam with steel 470 headed stud anchors welded either through the deck or directly to 471 the steel cross section. Steel headed stud anchors, after installa- 472 tion, shall extend not less than 1½ in. (38 mm) above the top of 473 the steel deck and there shall be at least ½ in. (13 mm) of speci- 474 fied concrete cover above the top of the steel headed stud anchors. 475 476 (c) The slab thickness above the steel deck shall be not less than 2 in. 477 (50 mm). 478

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479 (d) Steel deck shall be anchored to all supporting members at a spac- 480 ing not to exceed 18 in. (460 mm). Such anchorage shall be pro- 481 vided by steel headed stud anchors, a combination of steel headed 482 stud anchors and arc spot (puddle) welds, or other devices speci- 483 fied by the contract documents. 484 485 2. Deck Ribs Oriented Perpendicular to Steel Beam 486 487 Concrete below the top of the steel deck shall be neglected in deter- 488 mining composite section properties and in calculating Ac for deck ribs 489 oriented perpendicular to the steel beams. 490 491 3. Deck Ribs Oriented Parallel to Steel Beam 492 493 Concrete below the top of the steel deck is permitted to be included in 494 determining composite section properties and in calculating Ac. 495 496 Formed steel deck ribs over supporting beams are permitted to be split 497 longitudinally and separated to form a concrete haunch. 498 499 When the nominal depth of steel deck is 1½ in. (38 mm) or greater, the 500 average width, wr, of the supported haunch or rib shall be not less than 501 2 in. (50 mm) for the first steel headed stud anchor in the transverse 502 row plus four stud diameters for each additional steel headed stud an- 503 chor. 504 505 2d. Load Transfer Between Steel Beam and Concrete Slab 506 507 1. Load Transfer for Positive Flexural Strength 508 509 The entire horizontal shear at the interface between the steel beam and 510 the concreteDRAFT slab shall be assumed to be transferred by steel headed 511 stud or steel channel anchors, except for concrete-encased beams as 512 defined in Section I3.3. For composite action with concrete subject to 513 flexural compression, the nominal shear force between the steel beam 514 and the concrete slab transferred by steel anchors, V', between the 515 point of maximum positive moment and the point of zero moment 516 shall be determined as the lowest value in accordance with the limit 517 states of concrete crushing, tensile yielding of the steel section, or the 518 shear strength of the steel anchors: 519 520 (a) Concrete crushing 521 522 V ' = 0.85fc'Ac (I3-1a) 523 524 (b) Tensile yielding of the steel section 525 526 V ' = FyAs (I3-1b) 527 528 (c) Shear strength of steel headed stud or steel channel anchors 529 530 V ' = Qn (I3-1c) 531 532 where 2 2 533 Ac = area of concrete slab within effective width, in. (mm ) 2 2 534 As = area of steel cross section, in. (mm )

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535 Qn = sum of nominal shear strengths of steel headed stud or 536 steel channel anchors between the point of maximum pos- 537 itive moment and the point of zero moment, kips (N) 538 539 The effect of ductility (slip capacity) of the shear connection at the 540 interface of the concrete slab and the steel beam shall be considered. 541 542 User Note: One practical method of addressing ductility at the inter- 543 face is to provide at a minimum the equivalent, in terms of anchor 544 strength, of one steel headed stud anchor per foot (approximately three 545 per meter) of beam length. This and other methods for the considera- 546 tion of ductility may be found in the Commentary. 547 548 2. Load Transfer for Negative Flexural Strength 549 550 In continuous composite beams where longitudinal reinforcing steel in the 551 negative moment regions is considered to act compositely with the steel 552 beam, the total horizontal shear between the point of maximum negative 553 moment and the point of zero moment shall be determined as the lower 554 value in accordance with the following limit states: 555 556 (a) For the limit state of tensile yielding of the slab reinforcement 557 558 V ' = FysrAsr (I3-2a) 559 where 560 Asr = area of developed longitudinal reinforcing steel within the 561 effective width of the concrete slab, in.2 (mm2) 562 Fysr = specified minimum yield stress of the reinforcing steel, ksi 563 (MPa)

564 (b) For the limit state of shear strength of steel headed stud or steel channel 565 anchorsDRAFT 566 567 V ' = Qn (I3-2b) 568 569 3. Encased Composite Members 570 571 The available flexural strength of concrete-encased members shall be 572 determined as follows: 573

574 b = 0.90 (LRFD) b = 1.67 (ASD) 575 576 The nominal flexural strength, Mn, shall be determined using one of the 577 following methods: 578 579 (a) The superposition of elastic stresses on the composite section, consider- 580 ing the effects of shoring for the limit state of yielding (yield moment). 581 582 (b) The plastic stress distribution on the steel section alone, for the limit 583 state of yielding (plastic moment) on the steel section. 584 585 (c) The plastic stress distribution on the composite section or the strain- 586 compatibility method, for the limit state of yielding (plastic moment) 587 on the composite section. For concrete-encased members, steel an- 588 chors shall be provided. 589

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590 4. Filled Composite Members 591 592 4a. Limitations 593 594 Filled composite sections shall be classified for local buckling according to 595 Section I1.4. 596 597 4b. Flexural Strength 598 599 The available flexural strength of filled composite members shall be 600 determined as follows: 601

602 b = 0.90 (LRFD) b = 1.67 (ASD) 603 604 The nominal flexural strength, Mn, shall be determined as follows: 605 606 (a) For compact sections 607 608 M np M (I3-3a) 609 610 where 611 Mp = moment corresponding to plastic stress distribution over 612 the composite cross section, kip-in. (N-mm) 613 614 (b) For noncompact sections

p 615 Mn = Mp – [Mp – My] (I3-3b) rp 616 617 where 618 DRAFTλ, λp and λr are slenderness ratios determined from Table I1.1b. 619 620 My = yield moment corresponding to yielding of the tension 621 flange and first yield of the compression flange, kip-in. 622 (N-mm). The capacity at first yield shall be calculated 623 assuming a linear elastic stress distribution with the max- 624 imum concrete compressive stress limited to 0.7 fc and 625 the maximum steel stress limited to Fy. 626 627 (c) For slender sections, Mn, shall be determined as the first yield 628 moment. The compression flange stress shall be limited to the local 629 buckling stress, Fcr, determined using Equation I2-10 or I2-11. The 630 concrete stress distribution shall be linear elastic with the maximum

631 compressive stress limited to 0.70fc. 632 633 I4. SHEAR 634 635 1. Filled and Encased Composite Members 636

637 The design shear strength, vVn, and allowable shear strength, Vn/v, shall 638 be determined based on one of the following: 639 640 (a) The available shear strength of the steel section alone as specified in 641 Chapter G 642

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643 (b) The available shear strength of the reinforced concrete portion 644 (concrete plus steel reinforcement) alone as defined by ACI 318 with 645

646 v = 0.75 (LRFD) v = 2.00 (ASD) 647 648 649 (c) The nominal shear strength of the steel section as defined in Chapter G 650 plus the nominal strength of the reinforcing steel as defined by ACI 651 318 with a combined resistance or safety factor of 652

653 v = 0.75 (LRFD) v = 2.00 (ASD)

654 2. Composite Beams With Formed Steel Deck

655 The available shear strength of composite beams with steel headed stud or 656 steel channel anchors shall be determined based upon the properties of the 657 steel section alone in accordance with Chapter G. 658 659 I5. COMBINED FLEXURE AND AXIAL FORCE 660 661 The interaction between flexure and axial forces in composite members shall 662 account for stability as required by Chapter C. The available compressive 663 strength and the available flexural strength shall be determined as defined in 664 Sections I2 and I3, respectively. To account for the influence of length effects 665 on the axial strength of the member, the nominal axial strength of the member 666 shall be determined in accordance with Section I2. 667 668 For encased composite members, the interaction between axial force and 669 flexure shall be based on the interaction equations of Section H1.1 or one of 670 the methods as defined in Section I1.2. 671 DRAFT 672 For filled composite members with compact sections, the interaction between 673 axial force and flexure shall be based either on the interaction equations of 674 Section H1.1, one of the methods as defined in Section I1.2, or Equations I5- 675 1a and I5-1b. 676 677 For filled composite members with noncompact or slender sections, the 678 interaction between axial forces and flexure shall be based on the interaction 679 equations of Section H1.1, the method defined in Section I.2d, or Equations 680 I5-1a and I5-1b. 681 P r  c P p 682 (a) When c P 1 c  M  r  p r  1.0 P c  M  683 c m  c  (I5-1a) P r  c P p 684 (b) When c

1 cPmr M r 685 1.0 (I5-1b) cPMpc c 686 687 For rectangular filled composite members:

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688 -0.4 689 cp = 0.17 csr (I5-2) 690 691 When csr ≥ 0.5 692 -0.11 693 cm = 1.06 csr ≥ 1.0 (I5-3a) 694 695 When csr < 0.5 696 -0.36 697 cm = 0.90 csr ≤ 1.67 (I5-3b) 698 699 For round HSS filled composite members: 700 -0.4 701 cp = 0.27 csr (I5-4) 702 703 When csr ≥ 0.5 704 -0.08 705 cm = 1.10 csr ≥ 1.0 (I5-5a) 706 707 When csr < 0.5 708 -0.32 709 cm = 0.95 csr ≤ 1.67 (I5-5b) 710 711 where As FAFysryr 712 csr  (I5-6) Afcc 713 714 715 User Note: Methods described in Section I1.2 for determining the available 716 strength of composite beam-columns are discussed in the Commentary. For 717 filled compositeDRAFT members (compact, noncompact or slender), the use of 718 Equation I5-1 provides additional available strength over the interaction 719 equations in Section H1.1. 720 721 I6. LOAD TRANSFER 722 723 1. General Requirements 724 725 When external forces are applied to an axially loaded encased or filled 726 composite member, the introduction of force to the member and the transfer 727 of longitudinal shear within the member shall be assessed in accordance with 728 the requirements for force allocation presented in this section. 729

730 The design strength, Rn, or the allowable strength, Rn/Ω, of the applicable 731 force transfer mechanisms as determined in accordance with Section I6.3 shall

732 equal or exceed the required longitudinal shear force to be transferred, Vr , as 733 determined in accordance with Section I6.2. Force transfer mechanisms shall 734 be located within the load transfer region as determined in accordance with 735 Section I6.4. 736 737 2. Force Allocation 738 739 Force allocation shall be determined based upon the distribution of external 740 force in accordance with the following requirements: 741

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742 User Note: Bearing strength provisions for externally applied forces are

743 provided in Section J8. For filled composite members, the term A21A in 744 Equation J8-2 may be taken equal to 2.0 due to confinement effects. 745 746 2a. External Force Applied to Steel Section 747 748 When the entire external force is applied directly to the steel section, the force

749 required to be transferred to the concrete,Vr , shall be determined as: 750

751 Vr = Pr (1– FyAs / Pno) (I6-1) 752 where 753 Pno = nominal axial compressive strength without consideration of 754 length effects, determined by Equation I2-4 for encased composite 755 members, and Equation I2-9a or Equation I2-9c, as applicable, for 756 compact or noncompact filled composite members, kips (N) 757 Pr = required external force applied to the composite member, kips (N) 758 759 User Note: Equation I6-1 does not apply to slender filled composite 760 members for which the external force is applied directly to the concrete fill in 761 accordance with Section I6.2b, or concurrently to the steel and concrete in 762 accordance with Section I6.2c. 763 764 2b. External Force Applied to Concrete 765 766 When the entire external force is applied directly to the concrete encasement

767 or concrete fill, the force required to be transferred to the steel, Vr , shall be 768 determined as: 769 770 (a) For encased or filled composite members that are compact or noncompact 771 DRAFT 772 VPFAPrrysno   /  (I6-2a) 773 774 (b) For slender filled composite members 775

776 Vr = Pr (AsFcr /Pno) (I6-2b) 777 778 where 779 Pno = nominal axial compressive strength without consideration of 780 length effects, determined by Equation I2-4 for encased compo- 781 site members, and Equation I2-9a for filled composite mem- 782 bers, kips (N) 783 Pr = required external force applied to the composite member, kips 784 (N) 785 Fcr = critical buckling stress for steel elements of filled composite 786 members determined using Equation I2-10 or I2-11, as applica- 787 ble 788 789 2c. External Force Applied Concurrently to Steel and Concrete 790 791 When the external force is applied concurrently to the steel section and 792 concrete encasement or concrete fill, Vr shall be determined as the force 793 required to establish equilibrium of the cross section. 794

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795 User Note: The Commentary provides an acceptable method of determining 796 the longitudinal shear force required for equilibrium of the cross section. 797 798 3. Force Transfer Mechanisms 799 800 The nominal strength, Rn, of the force transfer mechanisms of direct bond 801 interaction, shear connection and direct bearing shall be determined in 802 accordance with this section. Use of the force transfer mechanism providing 803 the largest nominal strength is permitted. Force transfer mechanisms shall not 804 be superimposed. 805 806 The force transfer mechanism of direct bond interaction shall not be used for 807 encased composite members. 808 809 3a. Direct Bearing 810 811 Where force is transferred in an encased or filled composite member by direct 812 bearing from internal bearing mechanisms, the available bearing strength of 813 the concrete for the limit state of concrete crushing shall be determined as: 814

815 Rn = 17. f cA1 (I6-3) 816

817 B =0.65 (LRFD)B = 2.31 (ASD) 818 819 where 2 2 820 A1 = loaded area of concrete, in. (mm ) 821 822 User Note: An example of force transfer via an internal bearing mechanism is 823 the use of internal steel plates within a filled composite member. 824 825 3b. Shear Connection 826 DRAFT 827 Where force is transferred in an encased or filled composite member by shear 828 connection, the available shear strength of steel headed stud or steel channel 829 anchors shall be determined as: 830 831 Rc = ΣQcv (I6-4) 832 833 where

834 Qcv = sum of available shear strengths, Qnv or Qnv  as applicable, of 835 steel headed stud or steel channel anchors, determined in ac- 836 cordance with Section I8.3a or Section I8.3d, respectively, 837 placed within the load introduction length as defined in Section 838 I6.4, kips (N) 839 840 3c. Direct Bond Interaction 841 842 Where force is transferred in a filled composite member by direct bond 843 interaction, the available bond strength between the steel and concrete shall be 844 determined as follows: 845 846  = 0.50 (LRFD)  = 3.00 (ASD) 847

848 Rn = pbininLF (I6-5)

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849 850 851 852 where 853 854 H = maximum transverse dimension of rectangular steel member, in. 855 (mm) 856 D = outside diameter of round HSS, in. (mm) 857 Fin = nominal bond stress 858 =12tH22 0.1, ksi ( 2100 tH 0.7, MPa) for rectangular cross 859 sections 860 = 30tD22 0.2, ksi (5300 tD 1.4, MPa) for circular cross sections

861 Lin = load introduction length, determined in accordance with Section 862 I6.4, in. (mm) 863 Rn = nominal bond strength, kips (N) 864 pb = perimeter of the steel-concrete bond interface within the composite 865 cross section, in. (mm) 866 t = design wall thickness of HSS member as defined in Section B4.2, 867 in. (mm) 868 869 4. Detailing Requirements 870 871 4a. Encased Composite Members 872 873 Force transfer mechanisms shall be distributed within the load introduction 874 length, which shall not exceed a distance of two times the minimum 875 transverse dimension of the encased composite member above and below the 876 load transfer region. Anchors utilized to transfer longitudinal shear shall be 877 placed on at least two faces of the steel shape in a generally symmetric 878 configuration about the steel shape axes. 879 DRAFT 880 Steel anchor spacing, both within and outside of the load introduction length, 881 shall conform to Section I8.3e. 882 883 4b. Filled Composite Members 884 885 Force transfer mechanisms shall be distributed within the load introduction 886 length, which shall not exceed a distance of two times the minimum 887 transverse dimension of a rectangular steel member or two times the diameter 888 of a round steel member both above and below the load transfer region. For 889 the specific case of load applied to the concrete of a filled composite member 890 containing no internal reinforcement, the load introduction length shall 891 extend beyond the load transfer region in only the direction of the applied 892 force. Steel anchor spacing within the load introduction length shall conform 893 to Section I8.3e. 894 895 I7. COMPOSITE DIAPHRAGMS AND COLLECTOR BEAMS 896 897 Composite slab diaphragms and collector beams shall be designed and 898 detailed to transfer loads between the diaphragm, the diaphragm’s boundary 899 members and collector elements, and elements of the lateral force resisting 900 system. 901 902 User Note: Design guidelines for composite diaphragms and collector beams 903 can be found in the Commentary.

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904 905 I8. STEEL ANCHORS 906 907 1. General 908

909 The diameter of a steel headed stud anchor, dsa, shall be ¾ in. (19 mm) or 910 less. Additionally, dsa, shall not be greater than 2.5 times the thickness of the 911 base metal to which it is welded, unless it is welded to a flange directly over a 912 web. 913 914 Section I8.2 applies to a composite flexural member where steel anchors are 915 embedded in a solid concrete slab or in a slab cast on formed steel deck. 916 Section I8.3 applies to all other cases. 917 918 2. Steel Anchors in Composite Beams 919 920 The length of steel headed stud anchors shall not be less than four stud 921 diameters from the base of the steel headed stud anchor to the top of the stud 922 head after installation. 923 924 2a. Strength of Steel Headed Stud Anchors 925 926 The nominal shear strength of one steel headed stud anchor embedded in a 927 solid concrete slab or in a composite slab with decking shall be determined as:  928 QAfERRAFnsaccgpsau0.5 (I8-1) 929 930 where 2 2 931 Asa = cross-sectional area of steel headed stud anchor, in. (mm ) 932 Ec = modulus of elasticity of concrete 933 = w1.5 f  , ksi ( 0.043w1.5 f  , MPa) ccDRAFTcc 934 Fu = specified minimum tensile strength of a steel headed stud 935 anchor, ksi (MPa) 936 Rg = 1.0 for: 937 (a) one steel headed stud anchor welded in a steel deck rib with 938 the deck oriented perpendicular to the steel shape; 939 (b) any number of steel headed stud anchors welded in a row di- 940 rectly to the steel shape; 941 (c) any number of steel headed stud anchors welded in a row 942 through steel deck with the deck oriented parallel to the steel 943 shape and the ratio of the average rib width to rib depth  1.5 944 = 0.85 for: 945 (a) two steel headed stud anchors welded in a steel deck rib with 946 the deck oriented perpendicular to the steel shape; 947 (b) one steel headed stud anchor welded through steel deck with 948 the deck oriented parallel to the steel shape and the ratio of 949 the average rib width to rib depth < 1.5 950 = 0.7 for three or more steel headed stud anchors welded in a steel 951 deck rib with the deck oriented perpendicular to the steel shape 952 Rp = 0.75 for: 953 (a) steel headed stud anchors welded directly to the steel shape; 954 (b) steel headed stud anchors welded in a composite slab with

955 the deck oriented perpendicular to the beam and emid-ht  2 956 in. (50 mm);

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957 (c) steel headed stud anchors welded through steel deck, or steel 958 sheet used as girder filler material, and embedded in a com- 959 posite slab with the deck oriented parallel to the beam 960 = 0.6 for steel headed stud anchors welded in a composite slab 961 with deck oriented perpendicular to the beam and emid-ht < 2 in. 962 (50 mm) 963 emid-ht = distance from the edge of steel headed stud anchor shank to the 964 steel deck web, measured at mid-height of the deck rib, and in 965 the load bearing direction of the steel headed stud anchor (in 966 other words, in the direction of maximum moment for a simply 967 supported beam), in. (mm) 968 969 User Note: The table below presents values for Rg and Rp for 970 several cases. Capacities for steel headed stud anchors can be 971 found in the Manual. 972 Condition Rg No decking 1.0 0.75 Decking oriented parallel to the steel shape

wr 1.5 1.0 0.75 hr 0.85** 0.75 wr 1.5 hr Decking oriented perpendicular to the steel shape Number of steel headed stud anchors occupying the same decking rib 1 1.0 0.6+ DRAFT+ 2 0.85 0.6 3 or more 0.7 0.6+ hr = nominal rib height, in. (mm) wr = average width of concrete rib or haunch (as defined in Section I3.2c), in. (mm)

** for a single steel headed stud anchor

+ this value may be increased to 0.75 when emid-ht ≥ 2 in. (51 mm)

973 974 2b. Strength of Steel Channel Anchors 975 976 The nominal shear strength of one hot-rolled channel anchor embedded in a 977 solid concrete slab shall be determined as:

978 QttlfEnfwacc0.3( 0.5 )  (I8-2) 979 where 980 la = length of channel anchor, in. (mm) 981 tf = thickness of flange of channel anchor, in. (mm) 982 tw = thickness of channel anchor web, in. (mm) 983 984 The strength of the channel anchor shall be developed by welding the channel 985 to the beam flange for a force equal to Qn, considering eccentricity on the 986 anchor.

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987 988 2c. Required Number of Steel Anchors 989 990 The number of anchors required between the section of maximum bending 991 moment, positive or negative, and the adjacent section of zero moment shall 992 be equal to the horizontal shear as determined in Sections I3.2d.1 and I3.2d.2 993 divided by the nominal shear strength of one steel anchor as determined from 994 Section I8.2a or Section I8.2b. The number of steel anchors required between 995 any concentrated load and the nearest point of zero moment shall be sufficient 996 to develop the maximum moment required at the concentrated load point. 997 998 2d. Detailing Requirements 999 1000 Steel anchors in composite beams shall meet the following requirements: 1001 1002 (a) Steel anchors required on each side of the point of maximum bending 1003 moment, positive or negative, shall be distributed uniformly between that 1004 point and the adjacent points of zero moment, unless specified otherwise on 1005 the contract documents. 1006 1007 (b) Steel anchors shall have at least 1 in. (25 mm) of lateral concrete cover in 1008 the direction perpendicular to the shear force, except for anchors installed in the 1009 ribs of formed steel decks. 1010 1011 (c) The minimum distance from the center of an anchor to a free edge in the direction of 1012 the shear force shall be 8 in. (203 mm) if normal weight concrete is used and 10 in. (250 1013 mm) if lightweight concrete is used. The provisions of ACI 318 Appendix D are 1014 permitted to be used in lieu of these values. 1015 1016 (d) Minimum center-to-center spacing of steel headed stud anchors shall be 1017 four diameters in any direction. For composite beams that do not contain 1018 anchors locatedDRAFT within formed steel deck oriented perpendicular to the beam 1019 span, an additional minimum spacing limit of six diameters along the 1020 longitudinal axis of the beam shall apply. 1021 1022 (e) The maximum center-to-center spacing of steel anchors shall not exceed 1023 eight times the total slab thickness or 36 in. (900 mm). 1024 1025 3. Steel Anchors in Composite Components 1026 1027 This section shall apply to the design of cast-in-place steel headed stud 1028 anchors and steel channel anchors in composite components. 1029 1030 The provisions of the applicable building code or ACI 318 Appendix D are 1031 permitted to be used in lieu of the provisions in this section. 1032 1033 User Note: The steel headed stud anchor strength provisions in this section 1034 are applicable to anchors located primarily in the load transfer (connection) 1035 region of composite columns and beam-columns, concrete-encased and filled 1036 composite beams, composite coupling beams, and composite walls, where the 1037 steel and concrete are working compositely within a member. They are not 1038 intended for hybrid construction where the steel and concrete are not working 1039 compositely, such as with embed plates. 1040

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1041 Section I8.2 specifies the strength of steel anchors embedded in a solid 1042 concrete slab or in a concrete slab with formed steel deck in a composite 1043 beam. 1044 1045 Limit states for the steel shank of the anchor and for concrete breakout in 1046 shear are covered directly in this Section. Additionally, the spacing and 1047 dimensional limitations provided in these provisions preclude the limit states 1048 of concrete pryout for anchors loaded in shear and concrete breakout for 1049 anchors loaded in tension as defined by ACI 318 Appendix D. 1050 1051 For normal weight concrete: Steel headed stud anchors subjected to shear only 1052 shall not be less than five stud diameters in length from the base of the steel 1053 headed stud to the top of the stud head after installation. Steel headed stud 1054 anchors subjected to tension or interaction of shear and tension shall not be 1055 less than eight stud diameters in length from the base of the stud to the top of 1056 the stud head after installation. 1057 1058 For lightweight concrete: Steel headed stud anchors subjected to shear only 1059 shall not be less than seven stud diameters in length from the base of the steel 1060 headed stud to the top of the stud head after installation. Steel headed stud 1061 anchors subjected to tension shall not be less than ten stud diameters in length 1062 from the base of the stud to the top of the stud head after installation. The 1063 nominal strength of steel headed stud anchors subjected to interaction of shear 1064 and tension for lightweight concrete shall be determined as stipulated by the 1065 applicable building code or ACI 318 Appendix D. 1066 1067 Steel headed stud anchors subjected to tension or interaction of shear and 1068 tension shall have a diameter of the head greater than or equal to 1.6 times the 1069 diameter of the shank. 1070 1071 User Note: The following table presents values of minimum steel headed 1072 stud anchor h/dDRAFT ratios for each condition covered in the Specification: 1073 Loading Normal Weight Lightweight Condition Concrete Concrete Shear h/dsa ≥ 5 h/dsa ≥ 7 Tension h/dsa ≥ 8 h/dsa ≥ 10 * Shear and h/dsa ≥ 8 N/A Tension h/dsa = ratio of steel headed stud anchor shank length to the top of the stud head, to shank diameter

* Refer to ACI 318 Appendix D for the calculation of interaction effects of anchors embedded in lightweight concrete. 1074 1075 1076 3a. Shear Strength of Steel Headed Stud Anchors in Composite Components 1077 1078 Where concrete breakout strength in shear is not an applicable limit state, the

1079 design shear strength, vQnv, and allowable shear strength, Qnv/v, of one steel 1080 headed stud anchor shall be determined as: 1081 

1082 QFAnv u sa (I8-3) 1083  1084 v = 0.65 (LRFD) v = 2.31 (ASD)

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1085 1086 where 1087 Qnv = nominal shear strength of steel headed stud anchor, kips (N) 2 2 1088 Asa = cross-sectional area of steel headed stud anchor, in. (mm ) 1089 Fu = specified minimum tensile strength of a steel headed stud anchor, 1090 ksi (MPa) 1091 1092 Where concrete breakout strength in shear is an applicable limit state, the 1093 available shear strength of one steel headed stud anchor shall be determined 1094 by one of the following: 1095 1096 (a) Where anchor reinforcement is developed in accordance with Chapter 12 1097 of ACI 318 on both sides of the concrete breakout surface for the steel 1098 headed stud anchor, the minimum of the steel nominal shear strength 1099 from Equation I8-3 and the nominal strength of the anchor reinforce- 1100 ment shall be used for the nominal shear strength, Qnv, of the steel 1101 headed stud anchor. 1102 (b) As stipulated by the applicable building code or ACI 318 Appendix D. 1103 1104 User Note: If concrete breakout strength in shear is an applicable limit state 1105 (for example, where the breakout prism is not restrained by an adjacent steel 1106 plate, flange or web), appropriate anchor reinforcement is required for the 1107 provisions of this Section to be used. Alternatively, the provisions of the 1108 applicable building code or ACI 318 Appendix D may be used. 1109 1110 3b. Tensile Strength of Steel Headed Stud Anchors in Composite 1111 Components 1112 1113 Where the distance from the center of an anchor to a free edge of concrete in 1114 the direction perpendicular to the height of the steel headed stud anchor is 1115 greater than or equal to 1.5 times the height of the steel headed stud anchor 1116 measured to theDRAFT top of the stud head, and where the center-to-center spacing 1117 of steel headed stud anchors is greater than or equal to three times the height 1118 of the steel headed stud anchor measured to the top of the stud head, the 1119 available tensile strength of one steel headed stud anchor shall be determined 1120 as: 1121  QFA 1122 nt u sa (I8-4) 1123  1124 t = 0.75 (LRFD) t = 2.00 (ASD) 1125 1126 where 1127 Qnt = nominal tensile strength of steel headed stud anchor, kips (N) 1128 1129 Where the distance from the center of an anchor to a free edge of concrete in 1130 the direction perpendicular to the height of the steel headed stud anchor is less 1131 than 1.5 times the height of the steel headed stud anchor measured to the top 1132 of the stud head, or where the center-to-center spacing of steel headed stud 1133 anchors is less than three times the height of the steel headed stud anchor 1134 measured to the top of the stud head, the nominal tensile strength of one steel 1135 headed stud anchor shall be determined by one of the following: 1136 1137 (a) Where anchor reinforcement is developed in accordance with Chapter 12 1138 of ACI 318 on both sides of the concrete breakout surface for the steel 1139 headed stud anchor, the minimum of the steel nominal tensile strength

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1140 from Equation I8-4 and the nominal strength of the anchor reinforcement 1141 shall be used for the nominal tensile strength, Qnt, of the steel headed stud 1142 anchor. 1143 (b) As stipulated by the applicable building code or ACI 318 Appendix D. 1144 1145 User Note: Supplemental confining reinforcement is recommended around 1146 the anchors for steel headed stud anchors subjected to tension or interaction of 1147 shear and tension to avoid edge effects or effects from closely spaced anchors. 1148 See the Commentary and ACI 318 Section D5.2.9 for guidelines. 1149 1150 3c. Strength of Steel Headed Stud Anchors for Interaction of Shear and 1151 Tension in Composite Components 1152 1153 Where concrete breakout strength in shear is not a governing limit state, and 1154 where the distance from the center of an anchor to a free edge of concrete in 1155 the direction perpendicular to the height of the steel headed stud anchor is 1156 greater than or equal to 1.5 times the height of the steel headed stud anchor 1157 measured to the top of the stud head, and where the center-to-center spacing 1158 of steel headed stud anchors is greater than or equal to three times the height 1159 of the steel headed stud anchor measured to the top of the stud head, the 1160 nominal strength for interaction of shear and tension of one steel headed stud 1161 anchor shall be determined as: 1162 5/3 5/3 QQrt rv 1163   1.0 (I8-5) QQ ct cv 1164 where 1165 Qct = available tensile strength, kips (N) 1166 Qrt = required tensile strength, kips (N) 1167 Qcv = available shear strength, kips (N) 1168 Qrv = required shear strength, kips (N) 1169 DRAFT 1170 For design in accordance with Section B3.3 (LRFD): 1171 1172 Qrt = required tensile strength using LRFD load combinations, 1173 kips (N)

1174 Qct = tQnt = design tensile strength, determined in accordance 1175 with Section I8.3b, kips (N) 1176 Qrv = required shear strength using LRFD load combinations, 1177 kips (N)

1178 Qcv = vQnv = design shear strength, determined in accordance 1179 with Section I8.3a, kips (N)

1180 t = resistance factor for tension = 0.75

1181 v = resistance factor for shear = 0.65 1182 1183 For design in accordance with Section B3.4 (ASD): 1184 1185 Qrt = required tensile strength using ASD load combinations, 1186 kips (N)

1187 Qct = Qnt/t = allowable tensile strength, determined in accord- 1188 ance with Section I8.3b, kips (N) 1189 Qrv = required shear strength using ASD load combinations, kips 1190 (N)

1191 Qcv = Qnv/v = allowable shear strength, determined in accord- 1192 ance with Section I8.3a, kips (N)

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1193 t = safety factor for tension = 2.00 1194 v = safety factor for shear = 2.31 1195 1196 Where concrete breakout strength in shear is a governing limit state, or where 1197 the distance from the center of an anchor to a free edge of concrete in the 1198 direction perpendicular to the height of the steel headed stud anchor is less 1199 than 1.5 times the height of the steel headed stud anchor measured to the top 1200 of the stud head, or where the center-to-center spacing of steel headed stud 1201 anchors is less than three times the height of the steel headed stud anchor 1202 measured to the top of the stud head, the nominal strength for interaction of 1203 shear and tension of one steel headed stud anchor shall be determined by one 1204 of the following: 1205 1206 (a) Where anchor reinforcement is developed in accordance with Chapter 12 1207 of ACI 318 on both sides of the concrete breakout surface for the steel 1208 headed stud anchor, the minimum of the steel nominal shear strength 1209 from Equation I8-3 and the nominal strength of the anchor reinforcement 1210 shall be used for the nominal shear strength, Qnv, of the steel headed stud 1211 anchor, and the minimum of the steel nominal tensile strength from 1212 Equation I8-4 and the nominal strength of the anchor reinforcement shall 1213 be used for the nominal tensile strength, Qnt, of the steel headed stud 1214 anchor for use in Equation I8-5. 1215 (b) As stipulated by the applicable building code or ACI 318 Appendix D. 1216 1217 3d. Shear Strength of Steel Channel Anchors in Composite Components 1218 1219 The available shear strength of steel channel anchors shall be based on the 1220 provisions of Section I8.2b with the resistance factor and safety factor as 1221 specified below. 1222

1223 v = 0.75 (LRFD) v = 2.00 (ASD) 1224 DRAFT 1225 3e. Detailing Requirements in Composite Components 1226 1227 Steel anchors in composite components shall meet the following require- 1228 ments: 1229 1230 (a) Minimum concrete cover to steel anchors shall be in accordance with ACI 1231 318 provisions for concrete protection of headed shear stud reinforcement. 1232 1233 (b) Minimum center-to-center spacing of steel headed stud anchors shall be 1234 four diameters in any direction. 1235 1236 (c) The maximum center-to-center spacing of steel headed stud anchors shall 1237 not exceed 32 times the shank diameter. 1238 1239 (d) The maximum center-to-center spacing of steel channel anchors shall be 1240 24 in. (600 mm). 1241 1242 User Note: Detailing requirements provided in this section are absolute 1243 limits. See Sections I8.3a, I8.3b and I8.3c for additional limitations required 1244 to preclude edge and group effect considerations. 1245 1246

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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1 2

3 CHAPTER J

4 DESIGN OF CONNECTIONS 5 6 7 8 This chapter addresses connecting elements, connectors and the affected elements 9 of connected members not subject to fatigue loads. 10 11 The chapter is organized as follows: 12 13 J1. General Provisions 14 J2. Welds 15 J3. Bolts and Threaded Parts 16 J4. Affected Elements of Members and Connecting Elements 17 J5. Fillers 18 J6. Splices 19 J7. Bearing Strength 20 J8. Column Bases and Bearing on Concrete 21 J9. Anchor Rods and Embedments 22 J10. Flanges and Webs with Concentrated Forces 23 24 User Note: For cases not included in this chapter, the following sections apply: 25  Chapter K Design of HSS and Box Member Connections 26  Appendix 3 Design for Fatigue 27 DRAFT

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-2

28 29 J1. GENERAL PROVISIONS 30 31 1. Design Basis 32

33 The design strength, Rn, and the allowable strength Rn/, of connections 34 shall be determined in accordance with the provisions of this chapter and the 35 provisions of Chapter B. 36 37 The required strength of the connections shall be determined by structural 38 analysis for the specified design loads, consistent with the type of construc- 39 tion specified, or shall be a proportion of the required strength of the 40 connected members when so specified herein. 41 42 Where the gravity axes of intersecting axially loaded members do not 43 intersect at one point, the effects of eccentricity shall be considered. 44 45 2. Simple Connections 46 47 Simple connections of beams, girders and trusses shall be designed as flexible 48 and are permitted to be proportioned for the reaction shears only, except as 49 otherwise indicated in the design documents. Flexible beam connections shall 50 accommodate end rotations of simple beams. Some inelastic but self-limiting 51 deformation in the connection is permitted to accommodate the end rotation 52 of a simple beam. 53 54 3. Moment Connections 55 56 End connections of restrained beams, girders and trusses shall be designed for 57 the combined effect of forces resulting from moment and shear induced by the 58 rigidity of the connections. Response criteria for moment connections are 59 provided in Section B3.4b. 60 61 User Note: See Chapter C and Appendix 7 for analysis requirements to 62 establish the required strength for the design of connections. 63 64 4. Compression Members with Bearing Joints 65 66 Compression members relying on bearing for load transfer shall meet the 67 following requirements: 68 69 (a) For columnsDRAFT bearing on bearing plates or finished to bear at splices, there 70 shall be sufficient connectors to hold all parts in place. 71 72 (b) For compression members other than columns finished to bear, the splice 73 material and its connectors shall be arranged to hold all parts in line and 74 their required strength shall be the lesser of: 75 76 (1) An axial tensile force of 50% of the required compressive strength 77 of the member; or 78 (2) The moment and shear resulting from a transverse load equal to 2% 79 of the required compressive strength of the member. The trans- 80 verse load shall be applied at the location of the splice exclusive of 81 other loads that act on the member. The member shall be taken as 82 pinned for the determination of the shears and moments at the 83 splice.

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84 85 User Note: All compression joints should also be proportioned to resist any 86 tension developed by the load combinations stipulated in Section B2. 87 88 5. Splices in Heavy Sections 89 90 When tensile forces due to applied tension or flexure are to be transmitted 91 through splices in heavy sections, as defined in Sections A3.1c and A3.1d, by 92 complete-joint-penetration groove (CJP) welds, the following provisions 93 apply: (1) material notch-toughness requirements as given in Sections A3.1c 94 and A3.1d; (2) weld access hole details as given in Section J1.6; (3) filler 95 metal requirements as given in Section J2.6; and (4) thermal cut surface 96 preparation and inspection requirements as given in Section M2.2. The 97 foregoing provision is not applicable to splices of elements of built-up shapes 98 that are welded prior to assembling the shape. 99 100 User Note: CJP groove welded splices of heavy sections can exhibit 101 detrimental effects of weld shrinkage. Members that are sized for compression 102 that are also subject to tensile forces may be less susceptible to damage from 103 shrinkage if they are spliced using partial-joint-penetration (PJP) groove welds 104 on the flanges and fillet-welded web plates, or using bolts for some or all of 105 the splice. 106 107 6. Weld Access Holes 108 109 Weld access holes shall meet the following requirements: 110 111 (a) All weld access holes required to facilitate welding operations shall be 112 detailed to provide room for weld backing as needed. 113 114 (b) The access hole shall have a length from the toe of the weld preparation 115 not less than 1½ times the thickness of the material in which the hole is made, 116 nor less than 1½ in. (38 mm). 117 118 (c) The access hole shall have a height not less than the thickness of the 119 material with the access hole, nor less than 3/4 in. (19 mm), nor does it need to 120 exceed 2 in. (50 mm). 121 122 (d) For sections that are rolled or welded prior to cutting, the edge of the web 123 shall be sloped or curved from the surface of the flange to the reentrant surface 124 of the access hole. 125 DRAFT 126 (e) In hot-rolled shapes, and built-up shapes with CJP groove welds that join 127 the web-to-flange, weld access holes shall be free of notches and sharp 128 reentrant corners. 129 130 (f) No arc of the weld access hole shall have a radius less than a in. (10 mm). 131 132 (g) In built-up shapes with fillet or partial-joint-penetration groove welds that 133 join the web-to-flange, weld access holes shall be free of notches and sharp 134 reentrant corners. 135 136 (h) The access hole is permitted to terminate perpendicular to the flange, 137 providing the weld is terminated at least a distance equal to the weld size away 138 from the access hole. 139

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-4

140 (i) For heavy sections as defined in Sections A3.1c and A3.1d, the thermally 141 cut surfaces of weld access holes shall be ground to bright metal. 142 143 (j) If the curved transition portion of weld access holes is formed by predrilled 144 or sawed holes, that portion of the access hole need not be ground. 145 146 (k) Weld access holes in other shapes need not be ground nor inspected by dye 147 penetrant or magnetic particle methods. 148 149 7. Placement of Welds and Bolts 150 151 Groups of welds or bolts at the ends of any member which transmit axial force 152 into that member shall be sized so that the center of gravity of the group 153 coincides with the center of gravity of the member, unless provision is made 154 for the eccentricity. The foregoing provision is not applicable to end 155 connections of single angle, double angle and similar members. 156 157 8. Bolts in Combination with Welds 158 159 High strength bolts in connections originally designed as bearing connections 160 or connections designed as slip-critical connections containing either standard 161 or oversized holes are permitted to share the load with longitudinal welds on a 162 common faying surface according to all the requirements of this section. The 163 available strength Rn and Rn/Ω of the combined joint shall be based on the 164 combined strength of (1) the nominal slip resistance Rn for bolts as defined in 165 Equation J3-4 according to the requirements of a slip-critical connection and 166 (2) the nominal weld strength Rn as defined in Section J2.4. All of the 167 following additional requirements shall apply: 168 169 (a)  = 0.75 (LRFD) Ω = 2.00 (ASD) for the combined joint 170 171 (b) The high strength bolts shall be tightened according to the requirements of 172 Section J3.1. 173 174 (c) The longitudinal welds and the high strength bolts shall each have a 175 minimum strength of no less than 33% of the required strength of the 176 connection. 177 178 (d) The nominal weld size shall be constant and shall extend the full length of 179 the bolted connection. 180 181 In joints withDRAFT combined bolts and longitudinal welds, the strength of the 182 connection need not be taken as less than either the strength of the bolts alone 183 or the strength of the welds alone. 184 185 Bolts in bearing-type connections, where the bolts are in a snug-tight 186 condition, shall not be considered as sharing the load in combination with 187 welds. 188 189 In making welded alterations to structures, existing rivets and high - strength 190 bolts tightened to the requirements for slip critical connections are permitted 191 to be utilized for carrying loads present at the time of alteration and the 192 welding need only provide the additional required strength. The weld design 193 strength shall provide the additional required strength but not less than 25% of 194 the required strength of the connection. 195

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196 User Note: The provisions of this section are generally recommended for 197 alteration in building designs or for field corrections. Use of the combined 198 strength of bolts and welds on a common faying surface is not recommended 199 for new design. 200 201 9. High-Strength Bolts in Combination with Rivets 202 203 In both new work and alterations, in connections designed as slip-critical 204 connections in accordance with the provisions of Section J3, high-strength 205 bolts are permitted to be considered as sharing the load with existing rivets. 206 207 J2. WELDS 208 209 All provisions of AWS D1.1 apply under this Specification, with the 210 exception that the provisions of the listed AISC Specification Sections apply 211 under this Specification in lieu of the cited AWS provisions as follows: 212 213 (a) Section J1.6 in lieu of AWS D1.1 Section 5.17.1 214 (b) Section J2.2a in lieu of AWS D1.1 Section 2.4.2.10 215 (c) Table J2.2 in lieu of AWS D1.1 Table 2.1 216 (d) Table J2.5 in lieu of AWS D1.1 Table 2.3 217 (e) Appendix 3, Table A-3.1 in lieu of AWS D1.1 Table 2.5 218 (f) Section B3.11 and Appendix 3 in lieu of AWS D1.1 Section 2, Part C 219 (g) Section M2.2 in lieu of AWS D1.1 Sections 5.15.4.3 and 5.15.4.4 220 221 1. Groove Welds 222 223 1a. Effective Area 224 225 The effective area of groove welds shall be taken as the length of the weld 226 times the effective throat. 227 228 The effective throat of a complete-joint-penetration (CJP) groove weld shall 229 be the thickness of the thinner part joined. 230 231 When filled flush to the surface, the effective weld throat for a partial-joint- 232 penetration (PJP) groove weld shall be as shown in Table J2.1 and the 233 effective weld throat for a flare groove weld shall be as shown in Table J2.2. 234 The effective throat of a partial-joint-penetration (PJP) groove weld or flare 235 groove weld filled less than flush shall be as shown in Table J2.1 or Table 236 J2.2, less the greatest perpendicular dimension measured from a line flush to 237 the base metal surface to the weld surface. 238 DRAFT 239 240 User Note: The effective throat of a partial-joint-penetration groove weld is 241 dependent on the process used and the weld position. The design drawings 242 should either indicate the effective throat required or the weld strength 243 required, and the fabricator should detail the joint based on the weld process 244 and position to be used to weld the joint. 245 246 Larger effective throats than those in Table J2.2 are permitted for a given 247 welding procedure specification (WPS), provided the fabricator establishes by 248 qualification the consistent production of such larger effective throat. 249 Qualification shall consist of sectioning the weld normal to its axis, at mid- 250 length, and terminal ends. Such sectioning shall be made on a number of

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-6

251 combinations of material sizes representative of the range to be used in the 252 fabrication. 253 254 1b. Limitations 255 256 The minimum effective throat of a partial-joint-penetration groove weld shall 257 not be less than the size required to transmit calculated forces nor the size 258 shown in Table J2.3. Minimum weld size is determined by the thinner of the 259 two parts joined. 260 261 TABLE J2.1 262 Effective Throat of 263 Partial-Joint-Penetration Groove Welds Welding Position F (flat), H (horizontal), Groove Type V (vertical), (AWS D1.1, Effective Welding Process OH (overhead) Figure 3.3) Throat Shielded metal arc J or U groove (SMAW) All Gas metal arc (GMAW) 60 V Flux cored arc (FCAW) depth of J or U groove groove Submerged arc (SAW) F 60 bevel or V Gas metal arc (GMAW) depth of F, H 45 bevel Flux cored arc (FCAW) groove Shielded metal arc depth of All (SMAW) groove 45 bevel Gas metal arc (GMAW) minus 1/8 in. V, OH Flux cored arc (FCAW) (3 mm) 264 265 266 TABLE J2.2 267 Effective Throats of 268 Flare Groove Welds 269 Welding Process Flare Bevel Groove[a] Flare V-Groove GMAW and FCAW-G 5/8 R 3/4 R SMAW and FCAW-S 5/16 R 5/8 R SAW 5/16 R 1/2 R [a] DRAFT For flare bevel groove with R < 3/8 in. (10 mm), use only reinforcing fillet weld on filled flush joint. General note: R = radius of joint surface (is permitted to be assumed equal to 2t for HSS) 270 271 TABLE J2.3 272 Minimum Effective Throat of 273 Partial-Joint-Penetration Groove Welds 274 Material Thickness of Minimum Effective Thinner Part Joined, in. (mm) Throat,[a] in. (mm) To ¼ (6) inclusive 8 (3) Over ¼ (6) to ½ (13) 3/16 (5)

Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-7

Over ½ (13) to ¾ (19) ¼ (6) Over ¾ (19) to 1½ (38) 5/16 (8) Over 1½ (38) to 2¼ (57) 3/8 (10) Over 2¼ (57) to 6 (150) ½ (13) Over 6 (150) 5/8 (16) [a] See Table J2.1.

275 276 2. Fillet Welds 277 278 2a. Effective Area

279 The effective area of a fillet weld shall be the effective length multiplied by 280 the effective throat. The effective throat of a fillet weld shall be the shortest 281 distance from the root to the face of the diagrammatic weld. An increase in 282 effective throat is permitted if consistent penetration beyond the root of the 283 diagrammatic weld is demonstrated by tests using the production process and 284 procedure variables. 285 286 For fillet welds in holes and slots, the effective length shall be the length of 287 the centerline of the weld along the center of the plane through the throat. In 288 the case of overlapping fillets, the effective area shall not exceed the nominal 289 cross-sectional area of the hole or slot, in the plane of the faying surface. 290 291 2b. Limitations 292 293 Fillet welds shall meet the following limitations: 294 295 (a) The minimum size of fillet welds shall be not less than the size required to 296 transmit calculated forces, nor the size as shown in Table J2.4. These 297 provisions do not apply to fillet weld reinforcements of partial- or complete- 298 joint-penetration groove welds. 299 300 TABLE J2.4 301 Minimum Size of Fillet Welds 302 Material Thickness of Minimum Size of Thinner Part Joined, in. (mm) Fillet Weld,[a] in. (mm) To ¼ (6) inclusive 1/8 (3) Over ¼ (6) to ½ (13) 3/16 (5) Over ½ (13) to ¾ (19) ¼ (6) Over ¾ (19) 5/16 (8) [a] Leg dimension of filletDRAFT welds. Single pass welds must be used. Note: See Section J2.2b for maximum size of fillet welds. 303 304 (b) The maximum size of fillet welds of connected parts shall be: 305 306 (1) Along edges of material less than ¼-in. (6 mm) thick; not greater 307 than the thickness of the material. 308 309 (2) Along edges of material ¼ in. (6 mm) or more in thickness; not 310 greater than the thickness of the material minus z in. (2 mm), unless the 311 weld is especially designated on the drawings to be built out to obtain 312 full-throat thickness. In the as-welded condition, the distance between 313 the edge of the base metal and the toe of the weld is permitted to be less 314 than z in. (2 mm) provided the weld size is clearly verifiable.

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-8

315 316 (c) The minimum length of fillet welds designed on the basis of strength shall be not 317 less than four times the nominal weld size, or else the effective size of the 318 weld shall not be taken to exceed one-quarter of its length. For the effect 319 of longitudinal fillet weld length in end connections upon the effective 320 area of the connected member, see Section D3. 321 322 (d) The effective length of fillet welds shall be determined as follows: 323 324 (1) For end-loaded fillet welds with a length up to 100 times the weld 325 size, it is permitted to take the effective length equal to the actual length. 326 327 (2) When the length of the end-loaded fillet weld exceeds 100 times the 328 weld size, the effective length shall be determined by multiplying the actual 329 length by the reduction factor, , determined as: 330 331  = 1.2 – 0.002(l/w)  1.0 (J2-1) 332 333 where 334 l = actual length of end-loaded weld, in. (mm) 335 w = size of weld leg, in. (mm) 336 337 (3) When the length of the weld exceeds 300 times the leg size, w, the 338 effective length shall be taken as 180w. 339 340 (e) Intermittent fillet welds are permitted to be used to transfer calculated 341 stress across a joint or faying surfaces and to join components of built-up 342 members. The length of any segment of intermittent fillet welding shall be not 343 less than four times the weld size, with a minimum of 1½ in. (38 mm). 344 345 (f) In lap joints, the minimum amount of lap shall be five times the thickness 346 of the thinner part joined, but not less than 1 in. (25 mm). Lap joints joining 347 plates or bars subjected to axial stress that utilize transverse fillet welds only 348 shall be fillet welded along the end of both lapped parts, except where the 349 deflection of the lapped parts is sufficiently restrained to prevent opening of 350 the joint under maximum loading. 351 352 (g) Fillet weld terminations shall be detailed in a manner that does not result 353 in a notch in the base metal subject to applied tension loads. Components 354 shall not be connected by welds where the weld would prevent the 355 deformation required to provide assumed design conditions. 356 DRAFT 357 User Note: Fillet weld terminations should be detailed in a manner that does 358 not result in a notch in the base metal transverse to applied tension loads. An 359 accepted practice to avoid notches in base metal is to stop fillet welds short of 360 the edge of the base metal by a length approximately equal to the size of the 361 weld. In most welds the effect of stopping short can be neglected in strength 362 calculations. 363 364 Two common details where welds are terminated to permit relative 365 deformation between the connected parts: 366 367  Welds on the outstanding legs of beam clip angle connections are 368 returned on the top of the outstanding leg and stopped no more than 4 369 times the weld size and not greater than half the leg width from the outer 370 toe of the angle.

Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-9

371  Fillet welds connecting transverse stiffeners to webs of girders that are ¾ 372 in. thick or less are stopped 4 to 6 times the web thickness from the web 373 toe of the flange-to web fillet weld, except where the end of the stiffener 374 is welded to the flange. 375 376 Details of fillet weld terminations may be shown on shop standard details. 377 378 379 (h) Fillet welds in holes or slots are permitted to be used to transmit shear and 380 resist loads perpendicular to the faying surface in lap joints or to prevent the 381 buckling or separation of lapped parts and to join components of built-up 382 members. Such fillet welds are permitted to overlap, subject to the provisions 383 of Section J2. Fillet welds in holes or slots are not to be considered plug or 384 slot welds. 385 386 3. Plug and Slot Welds 387 388 3a. Effective Area 389 390 The effective shearing area of plug and slot welds shall be taken as the 391 nominal cross-sectional area of the hole or slot in the plane of the faying surface. 392 393 3b. Limitations 394 395 Plug or slot welds are permitted to be used to transmit shear in lap joints or to 396 prevent buckling or separation of lapped parts and to join component parts of 397 built-up members, subject to the following limitations: 398 399 (a)The diameter of the holes for a plug weld shall not be less than the 400 thickness of the part containing it plus c in. (8 mm), rounded to the next 401 larger odd z in. (even mm), nor greater than the minimum diameter plus 8 402 in. (3 mm) or 2¼ times the thickness of the weld. 403 404 (b) The minimum center-to-center spacing of plug welds shall be four times 405 the diameter of the hole. 406 407 (c) The length of slot for a slot weld shall not exceed 10 times the thickness of 408 the weld. 409 410 (d) The width of the slot shall be not less than the thickness of the part 411 containing it plus c in. (8 mm) rounded to the next larger odd z in. (even 412 mm), nor shall it be larger than 2¼ times the thickness of the weld. 413 DRAFT 414 (e) The ends of the slot shall be semicircular or shall have the corners rounded 415 to a radius of not less than the thickness of the part containing it, except those 416 ends which extend to the edge of the part. 417 418 (f) The minimum spacing of lines of slot welds in a direction transverse to 419 their length shall be four times the width of the slot. 420 421 (g) The minimum center-to-center spacing in a longitudinal direction on any 422 line shall be two times the length of the slot. 423 424 (h) The thickness of plug or slot welds in material s in. (16 mm) or less in 425 thickness shall be equal to the thickness of the material. In material over s in.

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-10

426 (16 mm) thick, the thickness of the weld shall be at least one-half the 427 thickness of the material but not less than s in. (16 mm). 428 429 4. Strength 430 431 (a) The design strength, Rn and the allowable strength, Rn/, of welded 432 joints shall be the lower value of the base material strength determined 433 according to the limit states of tensile rupture and shear rupture and the 434 weld metal strength determined according to the limit state of rupture as 435 follows: 436 437 For the base metal 438 Rn = FnBM ABM (J2-2) 439 440 For the weld metal 441 Rn = FnwAwe (J2-3) 442 443 444 where 445 FnBM = nominal stress of the base metal, ksi (MPa) 446 F nw = nominal stress of the weld metal, ksi (MPa) 2 2 447 ABM = cross-sectional area of the base metal, in. (mm ) 2 2 448 Awe = effective area of the weld, in. (mm ) 449

450 The values of , , FnBM and Fnw and limitations thereon are given in 451 Table J2.5. 452 453 DRAFT

Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-11

454 TABLE J2.5

455 Available Strength of Welded Joints, ksi (MPa) Effective Nominal Area Required Filler Load Type and Direction Pertinent Stress  and  (ABM or Metal Strength Relative to Weld Axis Metal (FnBM or Fnw) [a][b] Awe) Level ksi (MPa) in.2 (mm2) COMPLETE-JOINT-PENETRATION GROOVE WELDS Matching filler metal shall Strength of the joint is controlled be used. For T and corner joints with backing left in Tension by the base metal place, notch tough filler Normal to weld axis metal is required. See Section J2.6. Filler metal with a strength Strength of the joint is controlled level equal to or one by the base metal Compression strength level less than

Normal to weld axis matching filler metal is permitted. Tension or compression in parts Filler metal with a strength level equal to or less than Tension or compression joined parallel to a weld is permitted to be neglected in design of welds matching filler metal is Parallel to weld axis joining the parts. permitted. Strength of the joint is controlled Matching filler metal shall by the base metal Shear be used. [c]

PARTIAL-JOINT-PENETRATION GROOVE WELDS INCLUDING FLARE V-GROOVE AND FLARE BEVEL GROOVE WELDS  =0.75 Base F See J4 =2.00 u Tension  = 0.80 Normal to weld axis See Weld 0.60 F = 1.88 EXX J2.1a

Compression Compressive stress is permitted to be neglected Column to base plate and in design of welds joining the parts. column splices designed per Section J1.4(1) Filler metal with a strength level Base  = 0.90 See equal to or less Fy Compression DRAFT = 1.67 J4 than matching Connections of members filler metal is designed to bear other permitted. than columns as  = 0.80 See described in Section Weld 0.60 FEXX J1.4(2) = 1.88 J2.1a

 = 0.90 Base See = 1.67 Fy Compression J4

Connections not finished-  = 0.80 to-bear See Weld = 1.88 0.90 FEXX  J2.1a

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-12

Tension or compression in parts joined parallel to Filler metal with Tension or compression a weld is permitted to be neglected in design of a strength level Parallel to weld axis welds joining the parts. equal to or less Base Governed by J4 than matching  = 0.75 See filler metal is Shear Weld 0.60 FEXX = 2.00 J2.1a permitted. FILLET WELDS INCLUDING FILLETS IN HOLES AND SLOTS AND SKEWED T-JOINTS Base Governed by J4 Filler metal with  = 0.75 [d] See Shear Weld 0.60 FEXX a strength level = 2.00 J2.2a equal to or less Tension or compression in parts joined parallel to than matching Tension or compression a weld is permitted to be neglected in design of filler metal is Parallel to weld axis welds joining the parts. permitted. PLUG AND SLOT WELDS Filler metal with Base Governed by J4 a strength level Shear equal to or less Parallel to faying surface  = 0.75 than matching Weld 0.60FEXX J2.3a on the effective area = 2.00 filler metal is permitted [a] For matching weld metal see AWS D1.1, Section 3.3. [b] Filler metal with a strength level one strength level greater than matching is permitted. [c] Filler metals with a strength level less than matching are permitted to be used for groove welds between the webs and flanges of built-up sections transferring shear loads, or in applications where high restraint is a concern. In these applications, the weld joint shall be detailed and the weld shall be designed using the thickness of the material as the effective throat, where  = 0.80,  = 1.88 and 0.60FEXX is the nominal strength. [d] Alternatively, the provisions of Section J2.4(a) are permitted provided the deformation compatibility of the various weld elements is considered. Sections J2.4(b) and (c) are special applications of Section J2.4(a) that provide for deformation compatibility.

456 457 (b) For fillet welds, the available strength is permitted to be determined 458 accounting for a directional strength increase of (1.0 + 0.50 sin1.5) if 459 strain compatibility of the various weld elements is considered, 460 461 where 462 = 0.75 (LRFD);  = 2.00 (ASD) 463  = angle between the line of action of the required force and the weld 464 longitudinal axis, degrees 465 466 (1) For a linear weld group with a uniform leg size, loaded through the 467 centerDRAFT of gravity 468 Rn = Fnw Awe (J2-4) 469 where 1.5 470 FFnw 0.60EXX  1.0 0.50 sin (J2-5) 471 and 472 FEXX = filler metal classification strength, ksi (MPa) 473   474 475 User Note: A linear weld group is one in which all elements are in a

476 line or are parallel. 477 478 479

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480 (2) For fillet weld groups concentrically loaded and consisting of 481 elements with a uniform leg size that are oriented both longitudinally 482 and transversely to the direction of applied load, the combined strength, 483 Rn, of the fillet weld group shall be determined as the greater of 484 485 (i) Rn = Rnwl + Rnwt (J2-10a) 486 487 or 488 489 (ii) Rn = 0.85 Rnwl + 1.5 Rnwt (J2-10b) 490 491 492 where 493 Rnwl = total nominal strength of longitudinally loaded fillet welds, as 494 determined in accordance with Table J2.5, kips (N) 495 Rnwt = total nominal strength of transversely loaded fillet welds, as 496 determined in accordance with Table J2.5 without the alter- 497 nate in Section J2.4(a), kips (N) 498 499 User Note: The instantaneous center method is a valid way to calculate the 500 strength of weld groups consisting of weld elements in various directions 501 based on strain compatibility. 502 503 5. Combination of Welds 504 505 If two or more of the general types of welds (groove, fillet, plug, slot) are 506 combined in a single joint, the strength of each shall be separately computed 507 with reference to the axis of the group in order to determine the strength of 508 the combination. 509 510 6. Filler Metal Requirements 511 512 The choice of filler metal for use with complete-joint-penetration groove 513 welds subject to tension normal to the effective area shall comply with the 514 requirements for matching filler metals given in AWS D1.1. 515 516 User Note: The following User Note Table summarizes the AWS D1.1 517 provisions for matching filler metals. Other restrictions exist. For a complete 518 list of base metals and prequalified matching filler metals see AWS D1.1, 519 Table 3.1. 520 DRAFTBase Metal Matching Filler Metal A36 ≤ ¾ in. thick 60 & 70 ksi filler metal A36> ¾ A572 (Gr. 50 SMAW: E7015, E7016, in. thick & 55) E7018, E7028 A588* A913 (Gr. Other processes: 70 A1011 50) ksi filler metal A992 A1018 A913 (Gr. 80 ksi filler metal 60 & 65)

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-14

521 * For corrosion resistance and color similar to the base 522 metal, see AWS D1.1, Clause 3.7.3 523 524 Notes: 525 Filler metals shall meet the requirements of AWS 526 A5.1, A5.5, A5.17, A5.18, A5.20, A5.23, A5.28 or A5.29. 527 In joints with base metals of different strengths, use 528 either a filler metal that matches the higher strength 529 base metal or a filler metal that matches the lower 530 strength and produces a low hydrogen deposit. 531 Filler metal with a specified minimum Charpy V-notch toughness of 20 ft-lb 532 (27 J) at 40 F (4 C) or lower shall be used in the following joints: 533 534 (a) Complete-joint-penetration groove welded T- and corner joints with 535 steel backing left in place, subject to tension normal to the effective 536 area, unless the joints are designed using the nominal strength and 537 resistance factor or safety factor as applicable for a partial-joint- 538 penetration groove weld 539 (b) Complete-joint-penetration groove welded splices subject to tension 540 normal to the effective area in heavy sections as defined in Sections 541 A3.1c and A3.1d 542 543 The manufacturer’s Certificate of Conformance shall be sufficient evidence of 544 compliance. 545 546 7. Mixed Weld Metal 547 548 When Charpy V-notch toughness is specified, the process consumables for all 549 weld metal, tack welds, root pass and subsequent passes deposited in a joint 550 shall be compatible to ensure notch-tough composite weld metal. 551 552 J3. BOLTS AND THREADED PARTS 553 554 ASTM A307 bolts are permitted except where pretensioning is specified. 555 1. High-Strength Bolts 556 557 Use of high-strength bolts shall conform to the provisions of the Specification 558 for Structural Joints Using High-Strength Bolts, hereafter referred to as the 559 RCSC Specification, as approved by the Research Council on Structural 560 Connections, except as otherwise provided in this Specification. High- 561 strength bolts in this Specification are grouped according to material strength 562 as follows: DRAFT 563 564 Group AASTM F3125 Grades A325, A325M, F1852, A354 Grade BC, 565 and A449 566 Group BASTM F3125 Grades A490, A490M, F2280, and A354 Grade 567 BD 568 Group C – ASTM F3043 and F3111 569 570 Use of Group C high strength bolt/nut/washer assemblies shall conform to 571 the applicable provisions of their ASTM standard. ASTM F3043 and F3111 572 Grade 1 assemblies may be installed only to the snug-tight condition. ASTM 573 F3043 and F3111 Grade 2 assemblies may be used in snug-tight, preten- 574 sioned and slip-critical connections, using procedures provided in the 575 applicable ASTM standard.

Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-15

576 577 User Note: The use of Group C assemblies is limited to specific building 578 locations and noncorrosive environmental conditions by the applicable 579 ASTM standard. 580 581 When assembled, all joint surfaces, including those adjacent to the washers, 582 shall be free of scale, except tight mill scale. 583 584 (a) Bolts are permitted to be installed to the snug-tight condition when used 585 in: 586 587 (1) Bearing-type connections except as stipulated in Section E6 588 589 (2) Tension or combined shear and tension applications, for Group A 590 bolts only, where loosening or fatigue due to vibration or load fluc- 591 tuations are not design considerations 592 593 (b) Bolts in the following connections shall be pretensioned: 594 595 (1) As required by the RCSC Specification 596 (2) Connections subjected to vibratory loads where bolt loosening is a 597 consideration 598 (3) End connections of built-up members composed of two shapes 599 either interconnected by bolts, or with at least one open side inter- 600 connected by perforated cover plates or lacing with tie plates, as 601 required in Section E6.1 602 603 (c) The following connections shall be designed as slip critical: 604 605 (1) As required by the RCSC Specification 606 (2) The extended portion of bolted, partial-length cover plates , as 607 required in Section F13.3 608 (3) Bolted connections with undeveloped fills, as required in Section 609 J5.2(d). 610 611 The snug-tight condition is defined in the RCSC Specification. Bolts to be 612 tightened to a condition other than snug tight shall be clearly identified on the 613 design drawings. 614 615 User Note: There are no specific minimum or maximum tension require- 616 ments for snug-tight bolts. Fully pretensioned bolts such as ASTM F3125 617 Grade F1852 or F2280 are permitted unless specifically prohibited on design 618 drawings. DRAFT 619 620 When bolt requirements cannot be provided within the RCSC Specification 621 limitations because of requirements for lengths exceeding 12 diameters or 622 diameters exceeding 1½ in. (38 mm), bolts or threaded rods conforming to 623 Group A or Group B materials are permitted to be used in accordance with the 624 provisions for threaded parts in Table J3.2. 625 When ASTM A354 Gr. BC, A354 Gr. BD, or A449 bolts and threaded rods 626 are used in slip-critical connections, the bolt geometry including the thread 627 pitch, thread length, head and nut(s) shall be equal to or (if larger in diameter) 628 proportional to that required by the RCSC Specification. Installation shall 629 comply with all applicable requirements of the RCSC Specification with

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-16

630 modifications as required for the increased diameter and/or length to provide 631 the design pretension. 632 2. Size and Use of Holes 633 634 The following requirements apply for bolted connections: 635 636 (a) The maximum sizes of holes for bolts are given in Table J3.3 or Table 637 J3.3M, except that larger holes, required for tolerance on location of anchor 638 rods in concrete foundations, are permitted in column base details. 639 640 (b) Standard holes or short-slotted holes transverse to the direction of the load 641 shall be provided in accordance with the provisions of this specification, 642 unless oversized holes, short-slotted holes parallel to the load, or long-slotted 643 holes are approved by the engineer of record. 644 645 (c) Finger shims up to ¼ in. (6 mm) are permitted in slip-critical connections 646 designed on the basis of standard holes without reducing the nominal shear 647 strength of the fastener to that specified for slotted holes. 648 649 TABLE J3.1 650 Minimum Bolt Pretension, kips*

651 Group A * Group C, Grade 2 ** Group B * Bolt Size, in. (e.g., A325 (e.g. F3043 Grade 2 (e.g., A490 Bolts) Bolts) bolts) ½ 12 15 5/8 19 24 ¾ 28 35 7/8 39 49 1 51 64 90 1 1/8 56 64 80 113 1 ¼ 71 81 102 143 1 3/8 85 97 121 1 ½ 103 118 148 ** Equal to 0.70 * Equal to 0.70 times the minimum tensile strength of bolts, rounded times the off to nearest kip, as specified in ASTM specifications for A325 and minimum tensile A490 bolts with UNC threads. strength of bolts, rounded off to nearest kip, for DRAFTASTM F3043 Grade 2 and F3111 Grade 2. 652 653 654 655 656 657 TABLE J3.1M 658 Minimum Bolt Pretension, kN* Group A ( e.g., A325M Group B ( e.g., A490M Bolt Size, mm Bolts) Bolts)

Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-17

M16 91 114 M20 142 179 M22 176 221 M24 205 257 M27 267 334 M30 326 408 M36 475 595

*Equal to 0.70 times the minimum tensile strength of bolts, rounded off to nearest kN, as specified in ASTM specifications for A325M and A490M bolts with UNC threads. 659 660 (d) Oversized holes are permitted in any or all plies of slip-critical 661 connections, but they shall not be used in bearing-type connections. 662 663 (e) Short-slotted holes are permitted in any or all plies of slip-critical or 664 bearing-type connections. The slots are permitted without regard to direction 665 of loading in slip-critical connections, but the length shall be normal to the 666 direction of the load in bearing-type connections. 667 668 (f) Long-slotted holes are permitted in only one of the connected parts of 669 either a slip-critical or bearing-type connection at an individual faying 670 surface. Long-slotted holes are permitted without regard to direction of 671 loading in slip-critical connections, but shall be normal to the direction of 672 load in bearing-type connections. 673 674 (h) Washers shall be provided in accordance with the RCSC Specification 675 Section 6, except for Group C assemblies, where washers shall be provided in 676 accordance with the applicable ASTM standard. 677 678 User Note: When Group C heavy hex fastener assemblies are used, a single 679 washer is used under both the bolt head and nut. When Group C twist-off bolt 680 assemblies are used, a single washer is used under the nut. Washers are of the 681 type specified in the ASTM standard for the assembly. 682 683 3. Minimum Spacing 684 685 The distance between centers of standard, oversized or slotted holes shall not 686 be less than 2⅔ times the nominal diameter, d, of the fastener. However, the 687 clear distance between bolt holes or slots shall not be less than d. 688 689 User Note: A distance between centers of standard, oversize or slotted holes 690 of 3d is preferred.DRAFT 691 692 User Note: ASTM F1554 anchor rods may be furnished in accordance with 693 product specifications with a body diameter less than the nominal diameter. 694 Load effects such as bending and elongation should be calculated based on 695 minimum diameters permitted by the product specification. See ASTM F1554 696 and the table, “Applicable ASTM Specifications for Various Types of 697 Structural Fasteners,” in Part 2 of the AISC Steel Construction Manual.

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-18

TABLE J3.2 Nominal Strength of Fasteners and Threaded Parts, ksi (MPa) Nominal Shear Strength Nominal Tensile in Bearing-Type Strength, Connections, [a] [b] Description of Fasteners Fnt, ksi (MPa) Fnv, ksi (MPa) A307 bolts 45 (310)[c] 27 (188)[c] [d]

Group A (e.g., A325) 90 (620) 54 (372) bolts, when threads are not excluded from shear planes

Group A (e.g., A325) bolts, when threads are 90 (620) 68 (457) excluded from shear planes

Group B (e.g., A490) 113 (780) 68 (457) bolts, when threads are not excluded from shear planes Group B (e.g., A490) 113 (780) 84 (579) bolts, when threads are excluded from shear planes Group C (e.g., F3043) bolt assemblies, when 150 (1035) 90 (620) threads and transition area of shank are not excluded from the shear plane Group C (e.g., F3043) bolt assemblies, when 150 (1035) 113 (779) threads and transition area of shank are excluded from the shear plane

Threaded parts meeting 0.75 Fu 0.450 Fu the requirements of Section A3.4, when threads are not excluded from shear planes DRAFT

Threaded parts meeting 0.75 Fu 0. 563 Fu the requirements of Section A3.4, when threads are excluded from shear planes

Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-19

[a] For high-strength bolts subject to tensile fatigue loading, see Appendix 3.

[b] For end loaded connections with a fastener pattern length greater than 38 in. (965 mm), Fnv shall be reduced to 83.3% of the tabulated values. Fastener pattern length is the maximum distance parallel to the line of force between the centerline of the bolts connecting two parts with one faying surface.

[c] For A307 bolts the tabulated values shall be reduced by 1% for each z in. (2 mm) over 5 diameters of length in the grip.

[d] Threads permitted in shear planes.

698 699 4. Minimum Edge Distance 700 701 The distance from the center of a standard hole to an edge of a connected part 702 in any direction shall not be less than either the applicable value from Table J3.4 703 or Table J3.4M, or as required in Section J3.10. The distance from the center of 704 an oversized or slotted hole to an edge of a connected part shall be not less 705 than that required for a standard hole to an edge of a connected part plus the 706 applicable increment, C2, from Table J3.5 or Table J3.5M. 707 708 User Note: The edge distances in Tables J3.4 and J3.4M are minimum edge 709 distances based on standard fabrication practices and workmanship 710 tolerances. The appropriate provisions of Sections J3.10 and J4 must be 711 satisfied. 712 713 5. Maximum Spacing and Edge Distance 714 715 The maximum distance from the center of any bolt to the nearest edge of parts 716 in contact shall be 12 times the thickness of the connected part under 717 consideration, but shall not exceed 6 in. (150 mm). The longitudinal spacing 718 of fasteners between elements consisting of a plate and a shape or two plates 719 in continuous contact shall be as follows: 720 721 (a) For painted members or unpainted members not subject to corrosion, the 722 spacing shall not exceed 24 times the thickness of the thinner part or 12 723 in. (305 mm). 724 725 (b) For unpainted members of weathering steel subject to atmospheric 726 corrosion, the spacing shall not exceed 14 times the thickness of the 727 thinner part or 7 in. (180 mm). 728 DRAFT 729 User Note: Dimensions in (a) and (b) do not apply to elements consisting of 730 two shapes in continuous contact. 731 732 TABLE J3.3 733 Nominal Hole Dimensions, in. Hole Dimensions Bolt Standard Oversize Short-Slot Long-Slot Diameter (Dia.) (Dia.) (Width x Length) (Width x Length) ½ 9/16 5/8 9/16 x 11/16 9/16 x 1¼ 5/8 11/16 13/16 11/16 x 7/8 11/16 x 1 9/16 ¾ 13/16 15/16 13/16 x 1 13/16 x 1 7/8 7/8 15/16 1 1/16 15/16 x 1 1/8 15/16 x 2 3/16 1 1 1/8 1¼ 1 1/8 x 1 5/16 1 1/8 x 2½ 1 1/8 d + 1/8 d + 5/16 (d + 1/8) x (d + 3/8) (d + 1/8) x (2.5 x d)

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-20

734 735 736 TABLE J3.3M 737 Nominal Hole Dimensions, mm Hole Dimensions Bolt Standard Oversize Short-Slot Long-Slot Diameter (Dia.) (Dia.) (Width x (Width x Length) Length) M16 18 20 18 x 22 18 x 40 M20 22 24 22 x 26 22 x 50 M22 24 28 24 x 30 24 x 55 M24 27[a] 30 27 x 32 27 x 60 M27 30 35 30 x 37 30 x 67 M30 33 38 33 x 40 33 x 75 M36 d + 3 d + 8 (d + 3) x (d + 10) (d + 3) x 2.5d

[a] Clearance provided allows the use of a 1-in.-diameter bolt. 738 739 TABLE J3.4 [a] 740 Minimum Edge Distance from [b] 741 Center of Standard Hole to Edge of Connected Part, 742 in.

Bolt Diameter, Minimum Edge Distance, in. in.

½ ¾ 5/8 7/8 ¾ 1 7/8 11/8 1 1 ¼ 11/8 1 ½ 1 ¼ 1 5/8 Over 1¼ 1¼ x d [a] If necessary, lesser edge distances are permitted provided the applicable provisions from Sections J3.10 and J4 are satisfied, but edge distances less than one bolt diameter are not permitted without approval from the engineer of record. [b] For oversized or slotted holes, see Table J3.5.

743 DRAFT

Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-21

744 745 746 747 748 749 750 TABLE J3.4M [a] 751 Minimum Edge Distance from [b] 752 Center of Standard Hole to Edge of Connected Part, 753 mm

Bolt Diameter, Minimum Edge Distance, mm mm

16 22 20 26 22 28 24 30 27 34 30 38 36 46 Over 36 1.25d [a] If necessary, lesser edge distances are permitted provided the applicable provisions from Sections J3.10 and J4 are satisfied, but edge distances less than one bolt diameter are not permitted without approval from the engineer of record. [b] For oversized or slotted holes, see Table J3.5M.

754 755 6. Tensile and Shear Strength of Bolts and Threaded Parts 756 757 The design tensile or shear strength, Rn, and the allowable tensile or shear 758 strength, Rn/, of a snug-tightened or pretensioned high-strength bolt or 759 threaded part shall be determined according to the limit states of tension 760 rupture and shear rupture as: 761 762 Rn = Fn Ab (J3-1) 763 764  = 0.75 (LRFD)  = 2.00 (ASD) 765 766 where DRAFT 2 2 767 Ab = nominal unthreaded body area of bolt or threaded part, in. (mm ) 768 Fn = nominal tensile stress, Fnt, or shear stress, Fnv, from Table J3.2, ksi 769 (MPa) 770 771 The required tensile strength shall include any tension resulting from prying 772 action produced by deformation of the connected parts. 773 774 User Note: The force that can be resisted by a snug-tightened or preten- 775 sioned high-strength bolt or threaded part may be limited by the bearing 776 strength at the bolt hole per Section J3.10. The effective strength of an 777 individual fastener may be taken as the lesser of the fastener shear strength 778 per Section J3.6 or the bearing strength at the bolt hole per Section J3.10. The

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-22

779 strength of the bolt group is taken as the sum of the effective strengths of the 780 individual fasteners. 781 782 7. Combined Tension and Shear in Bearing-Type Connections 783 784 The available tensile strength of a bolt subjected to combined tension and 785 shear shall be determined according to the limit states of tension and shear 786 rupture as: 787 Rn = Fnt Ab (J3-2) 788 789  = 0.75 (LRFD)  = 2.00 (ASD) 790 791 where

792 Fnt = nominal tensile stress modified to include the effects of shear 793 stress, ksi (MPa)

Fnt Fnt 1.3FfF nt rv  nt (LRFD) (J3-3a) Fnv

Fnt Fnt 1.3FfF nt rv  nt (ASD) (J3-3b) Fnv

794 Fnt = nominal tensile stress from Table J3.2, ksi (MPa) 795 Fnv = nominal shear stress from Table J3.2, ksi (MPa) 796 frv = required shear stress using LRFD or ASD load combinations, ksi 797 (MPa) 798 799 The available shear stress of the fastener shall equal or exceed the required 800 shear stress, frv. 801 User Note: Note that when the required stress, f, in either shear or tension, is less than or equal to 30% of the corresponding available stress, the effects of combined stress need not be investigated. Also note that Equations J3-3a and J3-3b can be rewritten so as to find a nominal shear stress, Fnv, as a function of the required tensile stress, ft. 802 803 TABLE J3.5 804 Values of Edge Distance Increment C2, in. Slotted Holes Nominal Long Axis Perpendicular to Long Axis Diameter of Oversized Edge Parallel to Fastener, in. Holes Short Slots Long Slots[a] Edge  7/8 DRAFT1/16 1/8 1 1/8 1/8 3/4d 0 1 1/8 1/8 3/16 [a] When length of slot is less than maximum allowable (see Table J3.3), C2 is permitted to be reduced by one-half the difference between the maximum and actual slot lengths. 805 806

Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-23

807 808 809 TABLE J3.5M 810 Values of Edge Distance Increment C2, mm Nominal Slotted Holes Diameter of Long Axis Perpendicular to Long Axis Fastener, Oversized Edge Parallel to Mm Holes Short Slots Long Slots [a] Edge  22 2 3 24 3 3 0.75d 0  27 3 5 [a] When length of slot is less than maximum allowable (see Table J3.3M), C2 is permitted to be reduced by one-half the difference between the maximum and actual slot lengths. 811 812 8. High-Strength Bolts in Slip-Critical Connections 813 814 Slip-critical connections shall be designed to prevent slip and for the limit 815 states of bearing-type connections. When slip-critical bolts pass through 816 fillers, all surfaces subject to slip shall be prepared to achieve design slip 817 resistance. 818 819 The single bolt available slip resistance for the limit state of slip shall be 820 determined as follows: 821 822 Rn = μDu hfTbns (J3-4) 823 824 (a) For standard size and short-slotted holes perpendicular to the direction of 825 the load 826 827  = 1.00 (LRFD) Ω = 1.50 (ASD) 828 829 (b) For oversized and short-slotted holes parallel to the direction of the load 830 831  = 0.85 (LRFD) Ω = 1.76 (ASD) 832 833 (c) For long-slotted holes 834 835  = 0.70 (LRFD) Ω = 2.14 (ASD) 836 837 DRAFT 838 where 839 840 μ = mean slip coefficient for Class A or B surfaces, as applicable, and 841 determined as follows, or as established by tests: 842 843 (1) For Class A surfaces (unpainted clean mill scale steel surfaces or 844 surfaces with Class A coatings on blast-cleaned steel or hot- 845 dipped galvanized and roughened surfaces) 846 847  = 0.30 848 849 (2) For Class B surfaces (unpainted blast-cleaned steel surfaces or 850 surfaces with Class B coatings on blast-cleaned steel)

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-24

851 852  = 0.50 853 854 Du = 1.13, a multiplier that reflects the ratio of the mean installed bolt 855 pretension to the specified minimum bolt pretension. The use of 856 other values are permitted if approved by the engineer of record. 857 858 Tb = minimum fastener tension given in Table J3.1, kips, or Table J3.1M, 859 kN 860 861 hf = factor for fillers, determined as follows: 862 863 864 865 866 867 (1) For one filler between connected parts 868 hf = 1.0 869 870 (2) For two or more fillers between connected parts 871 hf = 0.85 872 873 (3) For joints using either Class B surfaces or Class A surfaces 874 with turn-of-nut tightening 875 hf = 1.0 876 877 ns = number of slip planes required to permit the connection to slip 878 879 9. Combined Tension and Shear in Slip-Critical Connections 880 881 When a slip-critical connection is subjected to an applied tension that reduces 882 the net clamping force, the available slip resistance per bolt, from Section 883 J3.8, shall be multiplied by the factor, ksc, as follows: 884

Tu 885 ksc = 10  (LRFD) (J3-5a) DTnubb

1.5Ta 886 ksc = 10  (ASD) (J3-5b) DTnubb 887 888 where 889 Ta = requiredDRAFT tension force using ASD load combinations, kips (kN) 890 Tu = required tension force using LRFD load combinations, kips (kN) 891 nb = number of bolts carrying the applied tension 892 893 10. Bearing and Tearout Strength at Bolt Holes 894

895 The available strength, Rn and Rn/, at bolt holes shall be determined for the 896 limit states of bearing and tearout, as follows: 897 898  = 0.75 (LRFD)  = 2.00 (ASD) 899 900 The nominal strength of the connected material, Rn, is determined as follows: 901

Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-25

902 (a) For a bolt in a connection with standard, oversized and short-slotted 903 holes, independent of the direction of loading, or a long-slotted hole 904 with the slot parallel to the direction of the bearing force 905 906 (1)Bearing 907 908 (i) When deformation at the bolt hole at service load is a design 909 consideration 910 (J3-6a) 911 Rn = 2.4dtFu 912 913 (ii) When deformation at the bolt hole at service load is not a de- 914 sign consideration 915 916 (J3-6b) 917 Rn = 3.0dtFu 918 919 (2) Tearout 920 921 (i) When deformation at the bolt hole at service load is a design 922 consideration 923 924 Rn = 1.2lctFu (J3-6c) 925 926 (ii) When deformation at the bolt hole at service load is not a de- 927 sign consideration 928 929 Rn = 1.5lctFu (J3-6d) 930 931 (b) For a bolt in a connection with long-slotted holes with the slot 932 perpendicular to the direction of force 933 934 (1) Bearing 935 (J3-6e) 936 Rn = 2.0dtFu 937 938 (2) Tearout 939 940 Rn = 1.0lctFu (J3-6f) 941 942 (c) For connections made using bolts that pass completely through an 943 unstiffened box member or HSS, see Section J7 and Equation J7-1 944 DRAFT 945 where 946 Fu = specified minimum tensile strength of the connected material, ksi 947 (MPa) 948 d = nominal bolt diameter, in. (mm) 949 lc = clear distance, in the direction of the force, between the edge of the 950 hole and the edge of the adjacent hole or edge of the material, in. 951 (mm) 952 t = thickness of connected material, in. (mm) 953 954 Bearing strength shall be checked for both bearing-type and slip-critical 955 connections. The use of oversized holes and short- and long-slotted holes 956 parallel to the line of force is restricted to slip-critical connections per Section 957 J3.2.

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-26

958 959 11. Special Fasteners 960 961 The nominal strength of special fasteners other than the bolts presented in 962 Table J3.2 shall be verified by tests. 963 964 12. Wall Strength at Tension Fasteners 965 966 When bolts or other fasteners in tension are attached to an unstiffened box or 967 HSS wall, the strength of the wall shall be determined by rational analysis. 968 969 J4. AFFECTED ELEMENTS OF MEMBERS AND CONNECTING 970 ELEMENTS 971 972 This section applies to elements of members at connections and connecting 973 elements, such as plates, gussets, angles and brackets. 974 975 1. Strength of Elements in Tension 976

977 The design strength, Rn, and the allowable strength, Rn /, of affected and 978 connecting elements loaded in tension shall be the lower value obtained 979 according to the limit states of tensile yielding and tensile rupture. 980 981 (a) For tensile yielding of connecting elements 982 Rn = FyAg (J4-1) 983 984  = 0.90 (LRFD)  = 1.67 (ASD) 985 986 (b) For tensile rupture of connecting elements 987 Rn = FuAe (J4-2) 988 989  = 0.75 (LRFD)  = 2.00 (ASD) 990 991 where 2 2 992 Ae = effective net area as defined in Section D3, in. (mm 993 994 User Note: The effective net area of the connection plate may be limited due 995 to stress distribution as calculated by methods such as the Whitmore section. 996 997 2. Strength of Elements in Shear 998 999 The available DRAFTshear strength of affected and connecting elements in shear 1000 shall be the lower value obtained according to the limit states of shear 1001 yielding and shear rupture: 1002 1003 (a) For shear yielding of the element: 1004 Rn = 0.60FyAgv (J4-3) 1005 1006 = 1.00 (LRFD)  = 1.50 (ASD) 1007 1008 where 2 2 1009 Agv = gross area subject to shear, in. (mm ) 1010 1011 (b) For shear rupture of the element: 1012 Rn = 0.60Fu Anv (J4-4) 1013

Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-27

1014 = 0.75 (LRFD)  = 2.00 (ASD) 1015 1016 where 2 2 1017 Anv = net area subject to shear, in. (mm ) 1018 1019 3. Block Shear Strength 1020 1021 The available strength for the limit state of block shear rupture along a shear 1022 failure path or paths and a perpendicular tension failure path shall be 1023 determined as 1024

1025 Rn = 0.60FuAnv +Ubs Fu Ant  0.60FyAgv + UbsFuAnt (J4-5) 1026 1027  = 0.75 (LRFD)  = 2.00 (ASD) 1028 1029 where 2 2 1030 Ant = net area subject to tension, in. (mm ) 1031 1032 Where the tension stress is uniform, Ubs = 1; where the tension stress is 1033 nonuniform, Ubs = 0.5. 1034 1035 User Note: Typical cases where Ubs should be taken equal to 0.5 are 1036 illustrated in the Commentary. 1037 1038 4. Strength of Elements in Compression 1039 1040 The available strength of connecting elements in compression for the limit 1041 states of yielding and buckling shall be determined as follows: 1042 1043 (a) When Lc/r ≤ 25 1044 1045 Pn = FyAg (J4-6) 1046 1047  = 0.90 (LRFD)  = 1.67 (ASD) 1048 1049 (b) When Lc/r >25, the provisions of Chapter E apply. 1050 1051 where 1052 K = effective length factor 1053 L = laterally unbraced length of the member, in. (mm) 1054 Lc = KL = effective length, in. (mm) 1055 DRAFT 1056 User Note: The effective length factors used in compu- 1057 ting compressive strengths of connecting elements are specific to the end 1058 restraint provided and may not necessarily be taken as unity when the direct 1059 analysis method is employed. 1060 1061 5. Strength of Elements in Flexure 1062 1063 The available flexural strength of affected elements shall be the lower value 1064 obtained according to the limit states of flexural yielding, local buckling, 1065 flexural lateral-torsional buckling and flexural rupture. 1066 1067 J5. FILLERS 1068

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-28

1069 1. Fillers in Welded Connections 1070 1071 Whenever it is necessary to use fillers in joints required to transfer applied 1072 force, the fillers and the connecting welds shall conform to the requirements 1073 of Section J5.1a or Section J5.1b, as applicable. 1074 1075 1a. Thin Fillers 1076 1077 Fillers less than ¼ in. (6 mm) thick shall not be used to transfer stress. When 1078 the thickness of the fillers is less than ¼ in. (6 mm), or when the thickness of 1079 the filler is ¼ in. (6 mm) or greater but not sufficient to transfer the applied 1080 force between the connected parts, the filler shall be kept flush with the edge 1081 of the outside connected part, and the size of the weld shall be increased over 1082 the required size by an amount equal to the thickness of the filler. 1083 1084 1b. Thick Fillers 1085 1086 When the thickness of the fillers is sufficient to transfer the applied force 1087 between the connected parts, the filler shall extend beyond the edges of the 1088 outside connected base metal. The welds joining the outside connected base 1089 metal to the filler shall be sufficient to transmit the force to the filler and the 1090 area subjected to the applied force in the filler shall be sufficient to prevent 1091 overstressing the filler. The welds joining the filler to the inside connected 1092 base metal shall be sufficient to transmit the applied force. 1093 1094 2. Fillers in Bolted Bearing Type Connections 1095 1096 When a bolt that carries load passes through fillers that are equal to or less 1097 than ¼ in. (6 mm) thick, the shear strength shall be used without reduction. 1098 When a bolt that carries load passes through fillers that are greater than ¼ in. 1099 (6 mm) thick, one of the following requirements shall apply: 1100 1101 (a) The shear strength of the bolts shall be multiplied by the factor 1102 1103 1  0.4(t - 0.25) 1104 1105 (S.I.: 1  0.0154(t - 6)) 1106 1107 but not less than 0.85, where t is the total thickness of the fillers; 1108 1109 (b) The fillers shall be welded or extended beyond the joint and bolted to 1110 uniformlyDRAFT distribute the total force in the connected element over the 1111 combined cross section of the connected element and the fillers; 1112 1113 (c) The size of the joint shall be increased to accommodate a number of bolts 1114 that is equivalent to the total number required in (b); or 1115 1116 1117 User Note: See Section J3.8 for a provision to resist slip. 1118 1119 J6. SPLICES 1120 1121 Groove-welded splices in plate girders and beams shall develop the nominal 1122 strength of the smaller spliced section. Other types of splices in cross sections 1123 of plate girders and beams shall develop the strength required by the forces at 1124 the point of the splice.

Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-29

1125 1126 J7. BEARING STRENGTH 1127

1128 The design bearing strength, Rn, and the allowable bearing strength, Rn / , 1129 of surfaces in contact shall be determined for the limit state of bearing (local 1130 compressive yielding) as follows: 1131 1132  = 0.75 (LRFD)  = 2.00 (ASD) 1133 1134 The nominal bearing strength, Rn, shall be determined as follows: 1135 1136 (a) For finished surfaces, pins in reamed, drilled, or bored holes, and ends of 1137 fitted bearing stiffeners 1138 1139 Rn = 1.8Fy Apb (J7-1) 1140 1141 where 1142 2 2 1143 Apb = projected area in bearing, in. (mm ) 1144 Fy = specified minimum yield stress, ksi (MPa) 1145 1146 (b) For expansion rollers and rockers 1147 1148 (1) When d  25 in. (635 mm) 1149 1150 Rn = 1.2(Fy – 13)lbd / 20 (J7-2) 1151 1152 (S.I.: Rn = 1.2(Fy –90)lbd / 20) (J7-2M) 1153 1154 (2) When d >25 in. (635 mm)

1155 R.(F)ld/nyb6 0 13 20 (J7-3) 1156 1157 (S.I.:RFldnyb30.2( 90) / 20 ) (J7-3M) 1158 1159 where 1160 d = diameter, in. (mm) 1161 lb = length of bearing, in. (mm) 1162 1163 J8. COLUMN BASES AND BEARING ON CONCRETE 1164 1165 Provisions shallDRAFT be made to transfer the column loads and moments to the 1166 footings and foundations. 1167

1168 In the absence of code regulations, the design bearing strength, cPp, and the 1169 allowable bearing strength, Pp/c, for the limit state of concrete crushing are 1170 permitted to be taken as follows: 1171

1172 c = 0.65 (LRFD) c = 2.31 (ASD) 1173 1174 The nominal bearing strength, Pp, is determined as follows: 1175 1176 (a) On the full area of a concrete support: 1177

1178 Pp = 0.85fcA1 (J8-1)

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-30

1179 1180 (b) On less than the full area of a concrete support: 1181  1182 PfAAApc 085./121 1.7 fcA1 (J8-2) 1183 1184 where 2 2 1185 A1 = area of steel concentrically bearing on a concrete support, in. (mm ) 1186 A2 = maximum area of the portion of the supporting surface that is 1187 geometrically similar to and concentric with the loaded area, in.2 1188 (mm2)

1189 fc = specified compressive strength of concrete, ksi (MPa) 1190 1191 1192 J9. ANCHOR RODS AND EMBEDMENTS 1193 1194 Anchor rods shall be designed to provide the required resistance to loads 1195 on the completed structure at the base of columns including the net tensile 1196 components of any bending moment resulting from load combinations 1197 stipulated in Section B2. The anchor rods shall be designed in accordance 1198 with the requirements for threaded parts in Table J3.2. 1199 1200 Design of column bases and anchor rods for the transfer of forces to the 1201 concrete foundation including bearing against the concrete elements shall 1202 satisfy the requirements of ACI 318 or ACI 349. 1203 1204 User Note: When columns are required to resist a horizontal force at the 1205 base plate, bearing against the concrete elements should be considered. 1206 1207 When anchor rods are used to resist horizontal forces, hole size, anchor 1208 rod setting tolerance, and the horizontal movement of the column shall be 1209 considered in the design. 1210 1211 Larger oversized holes and slotted holes are permitted in base plates when 1212 adequate bearing is provided for the nut by using ASTM F844 washers or 1213 plate washers to bridge the hole. 1214 1215 User Note: The permitted hole sizes, corresponding washer dimensions 1216 and nuts are given in the AISC Steel Construction Manual and ASTM 1217 F1554. 1218 1219 User Note: DRAFTSee ACI 318 for embedment design and for shear friction 1220 design. See OSHA for special erection requirements for anchor rods. 1221 1222 J10. FLANGES AND WEBS WITH CONCENTRATED FORCES 1223 1224 This section applies to single- and double-concentrated forces applied normal 1225 to the flange(s) of wide flange sections and similar built-up shapes. A single- 1226 concentrated force is either tensile or compressive. Double-concentrated 1227 forces are one tensile and one compressive and form a couple on the same 1228 side of the loaded member. 1229 1230 When the required strength exceeds the available strength as determined for 1231 the limit states listed in this section, stiffeners and/or doublers shall be 1232 provided and shall be sized for the difference between the required strength 1233 and the available strength for the applicable limit state. Stiffeners shall also

Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-31

1234 meet the design requirements in Section J10.8. Doublers shall also meet the 1235 design requirement in Section J10.9. 1236 1237 User Note: See Appendix 6.3 for requirements for the ends of cantilever 1238 members. 1239 1240 Stiffeners are required at unframed ends of beams in accordance with the 1241 requirements of Section J10.7. 1242 1243 User Note: Sections J10.2, J10.3 and J10.5 can be applied to HSS and box 1244 sections, with the following modifications: 1245 1246 (a) The thickness of the wall can be substituted for tw and tf 1247 1248 (b) d and h can be taken equal to H3t, where H is the dimension of the wall 1249 normal to the bearing length 1250 1251 (c) k can be taken as the outside corner radius of the HSS > 1.5t. 1252 1253 The nominal strength from Sections J10.2, J10.3 and J10.5 is the strength for 1254 each sidewall. 1255 1256 1257 1. Flange Local Bending 1258 1259 This section applies to tensile single-concentrated forces and the tensile 1260 component of double-concentrated forces. 1261

1262 The design strength, Rn, and the allowable strength, Rn/for the limit state 1263 of flange local bending shall be determined as: 1264 2 1265 Rn = 6.25Fyf tf (J10-1) 1266 1267  = 0.90 (LRFD)  = 1.67 (ASD) 1268 1269 where 1270 Fyf = specified minimum yield stress of the flange, ksi (MPa) 1271 tf = thickness of the loaded flange, in. (mm) 1272 1273 If the length of loading across the member flange is less than 0.15bf, where bf 1274 is the member flange width, Equation J10-1 need not be checked. 1275 DRAFT 1276 When the concentrated force to be resisted is applied at a distance from the 1277 member end that is less than 10tf, Rn shall be reduced by 50%. 1278 1279 When required, a pair of transverse stiffeners shall be provided. 1280 1281 2. Web Local Yielding 1282 1283 This section applies to single-concentrated forces and both components of 1284 double-concentrated forces. 1285 1286 The available strength for the limit state of web local yielding shall be 1287 determined as follows: 1288 1289  = 1.00 (LRFD)  = 1.50 (ASD)

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-32

1290 1291 The nominal strength, Rn, shall be determined as follows: 1292 1293 (a) When the concentrated force to be resisted is applied at a distance from the 1294 member end that is greater than the depth of the member, d, 1295 1296 Rn = Fyw tw (5k + lb) (J10-2) 1297 1298 (b) When the concentrated force to be resisted is applied at a distance from 1299 the member end that is less than or equal to the depth of the member, d, 1300 1301 Rn = Fyw tw (2.5k + lb) (J10-3) 1302 1303 where 1304 Fyw = specified minimum yield stress of the web material, ksi 1305 (MPa) 1306 k = distance from outer face of the flange to the web toe of the 1307 fillet, in. (mm) 1308 lb = length of bearing (not less than k for end beam reactions), in. 1309 (mm) 1310 tw = thickness of web, in. (mm) 1311 1312 When required, a pair of transverse stiffeners or a doubler plate shall be 1313 provided. 1314 1315 3. Web Crippling 1316 1317 This section applies to compressive single-concentrated forces or the 1318 compressive component of double-concentrated forces. 1319 1320 The available strength for the limit state of web local crippling shall be 1321 determined as follows: 1322  1323  = 0.75 (LRFD)  = 2.00 (ASD) 1324 1325 The nominal strength, Rn, shall be determined as follows: 1326 1327 (a) When the concentrated compressive force to be resisted is applied at a 1328 distance from the member end that is greater than or equal to d / 2: 1.5 lt EFyw t f 1329 Rt 0.802  1 3 bw Q (J10-4) nw f dtfw t DRAFT 1330 (b) When the concentrated compressive force to be resisted is applied at a 1331 distance from the member end that is less than d / 2: 1332

1333 (1) For lb / d  0.2 1.5 lt EFyw t f 1334 Rt 0.402  1 3 bw Q (J10-5a) nw f dtfw t  1335 1336 (2) For lb / d > 0.2 1.5 4lt EFyw t f 1337 Rt 0.402  1bw 0.2  Q (J10-5b) nw f dtfw t 

Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-33

1338 where 1339 d = full nominal depth of the section, in. (mm) 1340 Qf = 1.0 for wide flanges and for HSS (connecting surface) in tension 1341 = as given in Table K3.2 for all other HSS conditions 1342 1343 When required, a transverse stiffener, a pair of transverse stiffeners, or a 1344 doubler plate extending at least three quarters of the depth of the web shall be 1345 provided. 1346 1347 4. Web Sidesway Buckling 1348 1349 This section applies only to compressive single-concentrated forces applied to 1350 members where relative lateral movement between the loaded compression 1351 flange and the tension flange is not restrained at the point of application of the 1352 concentrated force. 1353 1354 The available strength of the web for the limit state of sidesway buckling shall 1355 be determined as follows: 1356 1357  = 0.85 (LRFD)  = 1.76 (ASD) 1358 1359 The nominal strength, Rn, shall be determined as follows: 1360 1361 (a) If the compression flange is restrained against rotation 1362

1363 (1) When (h / tw) / (Lb / bf)  2.3 1364 3 3 Ctrwf t h/t 1365 R.104w (J10-6) n 2  h L/bbf  1366 1367 (2) When (h / tw) / (Lb / bf) > 2.3, the limit state of web sidesway buckling 1368 does not apply. 1369 1370 When the required strength of the web exceeds the available strength, local 1371 lateral bracing shall be provided at the tension flange or either a pair of 1372 transverse stiffeners or a doubler plate shall be provided. 1373 1374 (b) If the compression flange is not restrained against rotation 1375

1376 (1) When (h / tw) / (Lb / bf)  1.7 1377 DRAFT 3 3 Ctrwf t h/t 1378 R. 04w (J10-7) n 2  h L/bbf 

1379 2i) When (h / tw) / (Lb / bf) > 1.7, the limit state of web sidesway buck- 1380 ling does not apply. 1381 1382 When the required strength of the web exceeds the available strength, local 1383 lateral bracing shall be provided at both flanges at the point of application of 1384 the concentrated forces. 1385 1386 In Equations J10-6 and J10-7, the following definitions apply: 1387

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-34

6 1388 Cr = 960,000 ksi (6.62x10 MPa) when Mu < My (LRFD) or 1.5Ma < My 1389 (ASD) at the location of the force 6 1390 = 480,000 ksi (3.31x10 MPa) when Mu  My (LRFD) or 1.5Ma  My 1391 (ASD) at the location of the force 1392 Lb = largest laterally unbraced length along either flange at the point of load, in. 1393 (mm) 1394 Ma = required flexural strength using ASD load combinations, kip-in. (N- 1395 mm) 1396 Mu = required flexural strength using LRFD load combinations, kip-in. 1397 (N-mm) 1398 bf = width of flange, in. (mm) 1399 h = clear distance between flanges less the fillet or corner radius for rolled 1400 shapes; distance between adjacent lines of fasteners or the clear dis- 1401 tance between flanges when welds are used for built-up shapes, in. 1402 (mm) 1403 1404 User Note: For determination of adequate restraint, refer to Appendix 6. 1405 1406 5. Web Compression Buckling 1407 1408 This section applies to a pair of compressive single-concentrated forces or the 1409 compressive components in a pair of double-concentrated forces, applied at 1410 both flanges of a member at the same location. 1411 1412 The available strength for the limit state of web local buckling shall be 1413 determined as 3 24tEFwyw 1414 R  Qf (J10-8) n h 1415 1416  = 0.90 (LRFD)  = 1.67 (ASD) 1417 where 1418 Qf = 1.0 for wide flanges and for HSS (connecting surface) in tension. 1419 = as given in Table K3.2 for all other HSS conditions 1420 When the pair of concentrated compressive forces to be resisted is applied at a 1421 distance from the member end that is less than d / 2, Rn shall be reduced by 1422 50%. 1423 1424 When required, a single transverse stiffener, a pair of transverse stiffeners, or 1425 a doubler plate extending the full depth of the web shall be provided. 1426 1427 6. Web Panel Zone Shear 1428 DRAFT 1429 This section applies to double-concentrated forces applied to one or both 1430 flanges of a member at the same location. 1431 1432 The available strength of the web panel zone for the limit state of shear 1433 yielding shall be determined as follows: 1434 1435  = 0.90 (LRFD)  = 1.67 (ASD) 1436 1437 The nominal strength, Rn, shall be determined as follows: 1438 1439 (a) When the effect of inelastic panel-zone deformation on frame stability is 1440 not accounted for in the analysis: 1441

Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-35

1442 (1) For αPr  0.4 Py 1443 1444 Rn = 0.60Fy dc tw (J10-9) 1445 1446 (2) For αPr > 0.4 Py 1447

Pr 1448 RFdtnycw0.60 1.4 (J10-10) Py 1449 1450 (b) When frame stability, including inelastic panel-zone deformation, is 1451 accounted for in the analysis: 1452 1453 (1) For αPr  0.75 Py 1454 2 3btcf cf 1455 RFdt0.60 1 (J10-11) nycw ddtbcw 1456 1457 1458 (2) For αPr > 0.75 Py 1459 3bt2 1.2P 1460 RFdt0.60 1cf cf  1.9 r (J10-12) nycw ddtbcw P y 1461 1462 In Equations J10-9 through J10-12, the following definitions apply: 1463 2 2 1464 Ag = gross cross-sectional area of member, in. (mm ) 1465 Fy = specified minimum yield stress of the column web, ksi (MPa) 1466 Pr = required axial strength using LRFD or ASD load combinations, kips 1467 (N) 1468 Py = Fy Ag, axial yield strength of the column, kips (N) 1469 bcf = width of column flange, in. (mm) 1470 db = depth of beam, in. (mm) 1471 dc = depth of column, in. (mm) 1472 tcf = thickness of column flange, in. (mm) 1473 tw = thickness of column web, in. (mm) 1474 α = 1.00 (LRFD); = 1.60 (ASD) 1475 1476 When required,DRAFT doubler plate(s) or a pair of diagonal stiffeners shall be 1477 provided within the boundaries of the rigid connection whose webs lie in a 1478 common plane. 1479 1480 See Section J10.9 for doubler plate design requirements. 1481 1482 7. Unframed Ends of Beams and Girders 1483 1484 At unframed ends of beams and girders not otherwise restrained against 1485 rotation about their longitudinal axes, a pair of transverse stiffeners, extending 1486 the full depth of the web, shall be provided. 1487 1488 8. Additional Stiffener Requirements for Concentrated Forces 1489

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-36

1490 Stiffeners required to resist tensile concentrated forces shall be designed in 1491 accordance with the requirements of Section J4.1 and welded to the loaded 1492 flange and the web. The welds to the flange shall be sized for the difference 1493 between the required strength and available strength. The stiffener to web 1494 welds shall be sized to transfer to the web the algebraic difference in tensile 1495 force at the ends of the stiffener. 1496 1497 Stiffeners required to resist compressive concentrated forces shall be designed 1498 in accordance with the requirements in Section J4.4 and shall either bear on or 1499 be welded to the loaded flange and welded to the web. The welds to the 1500 flange shall be sized for the difference between the required strength and the 1501 applicable limit state strength. The weld to the web shall be sized to transfer 1502 to the web the algebraic difference in compression force at the ends of the 1503 stiffener. For fitted bearing stiffeners, see Section J7. 1504 1505 Transverse full depth bearing stiffeners for compressive forces applied to a 1506 beam or plate girder flange(s) shall be designed as axially compressed 1507 members (columns) in accordance with the requirements of Section E6.2 and 1508 Section J4.4. The member properties shall be determined using an effective 1509 length of 0.75h and a cross section composed of two stiffeners, and a strip of 1510 the web having a width of 25tw at interior stiffeners and 12tw at the ends of 1511 members. The weld connecting full depth bearing stiffeners to the web shall 1512 be sized to transmit the difference in compressive force at each of the 1513 stiffeners to the web. 1514 1515 Transverse and diagonal stiffeners shall comply with the following additional 1516 requirements: 1517 1518 (a) The width of each stiffener plus one-half the thickness of the column 1519 web shall not be less than one-third of the flange or moment connection 1520 plate width delivering the concentrated force. 1521 (b) The thickness of a stiffener shall not be less than one-half the thickness 1522 of the flange or moment connection plate delivering the concentrated 1523 load, nor less than the width divided by 16. 1524 (c) Transverse stiffeners shall extend a minimum of one-half the depth of 1525 the member except as required in Section J10.5 and Section J10.7. 1526 1527 9. Additional Doubler Plate Requirements for Concentrated Forces 1528 1529 Doubler plates required for compression strength shall be designed in 1530 accordance with the requirements of Chapter E. 1531 1532 Doubler platesDRAFT required for tensile strength shall be designed in accordance 1533 with the requirements of Chapter D. 1534 1535 Doubler plates required for shear strength (see Section J10.6) shall be 1536 designed in accordance with the provisions of Chapter G. 1537 1538 Doubler plates shall comply with the following additional requirements: 1539 1540 (a) The thickness and extent of the doubler plate shall provide the additional 1541 material necessary to equal or exceed the strength requirements.

1542 (b) The doubler plate shall be welded to develop the proportion of the total 1543 force transmitted to the doubler plate. 1544

Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION J-37

1545 10. Transverse Forces on Plate Elements 1546 1547 When a force is applied transverse to the plane of a plate element, the nominal 1548 strength shall consider the limit states of shear and flexure in accordance with 1549 Sections J4.2 and J4.5. 1550 1551 User Note: The flexural strength can be checked based on yield-line theory 1552 and the shear strength can be determined based on a punching shear model. 1553 See AISC Steel Construction Manual Part 9 for further discussion. 1554 1555

DRAFT

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION K-1

1 CHAPTER K

2 DESIGN OF HSS CONNECTIONS 3 4 This chapter addresses connections to HSS members and box sections of uniform 5 wall thickness, where seam welds between box-section elements are complete-joint- 6 penetration groove welds in the connection region. 7 8 For the purposes of this Specification, the centerlines of branch members and chord 9 members shall lie in a common plane. Rectangular HSS connections are further 10 limited to have all members oriented with walls parallel to the plane. 11 12 The tables in this chapter are often accompanied by limits of applicability. Joints 13 complying with the limits of applicability listed can be designed considering only 14 those limit states provided for each joint configuration. Joints not complying with 15 the limits of applicability listed are not prohibited and must be designed by rational 16 analysis. 17 18 User Note: Connection strength is often governed by the size of HSS members, 19 especially the wall thickness of truss chords, and this must be considered in the 20 initial design. To ensure economical and dependable connections can be designed, 21 the connections should be considered in the design of the members. Angles between 22 the chord and the branch(es) of less than 30 can make welding and inspection 23 difficult and should be avoided. Sections K2, K3 and K4 represent design 24 procedures for specific configurations of HSS connections. The limits of 25 applicability provided reflect limitations on tests conducted to date, measures to 26 eliminate undesirable limit states, and other considerations. See Chapter J for 27 additional requirements for bolting to HSS. See Section J3.10(c) for through-bolts. 28 29 The chapter is organized as follows: 30 31 K1. General HSS Connection Parameters 32 K2. Concentrated Forces on HSS 33 K3. HSS-to-HSS Truss Connections 34 K4. HSS-to-HSSDRAFT Moment Connections 35 K5. Welds of Plates and Branches to Rectangular HSS 36 37 38 K1. GENERAL HSS CONNECTION PARAMETERS 39 40 This section provides parameters to be used in the design of plate-to-HSS and 41 HSS-to-HSS connections. 42 43 1. Definitions of Parameters 44 2 2 45 Ag = gross cross-sectional area of member, in. (mm ) 46 B = overall width of rectangular HSS main member, measured 90 to the 47 plane of the connection, in. (mm) 48 Bb = overall width of rectangular HSS branch member or plate, measured 49 90 to the plane of the connection, in. (mm) 50 D = outside diameter of round HSS main member, in. (mm) 51 Db = outside diameter of round HSS branch member, in. (mm) 52 Fc = available stress in main member, ksi (MPa)

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

53 = Fy for LRFD; 0.60Fy for ASD 54 Fy = specified minimum yield stress of HSS main member material, ksi 55 (MPa) 56 Fyb = specified minimum yield stress of HSS branch member or plate 57 material, ksi (MPa) 58 Fu = specified minimum tensile strength of HSS member material, ksi 59 (MPa) 60 H = overall height of rectangular HSS main member, measured in the plane 61 of the connection, in. (mm) 62 Hb = overall height of rectangular HSS branch member, measured in the 63 plane of the connection, in. (mm) 64 lend = distance from the near side of the connecting branch or plate to end of 65 chord, in. (mm) 66 t = design wall thickness of HSS main member, in. (mm) 67 tb = design wall thickness of HSS branch member or thickness of plate, in. 68 (mm) 69 70 2. Rectangular HSS 71 72 2a. Effective Width for Connections to Rectangular HSS 73 74 The effective width of elements (plates or rectangular HSS branches) 75 perpendicular to the longitudinal axis of a rectangular HSS member that 76 delivers a force component transverse to the face of the member shall be 77 taken as: 78 79 When 1.0 > Bb/B > 0.85 80

10t Fty 81 BBB (K1-1) ebb BFtyb b

82 When Bb/B ≤ 0.85

83 BBeb (K1-2) 84 85 K2. CONCENTRATED FORCES ON HSS 86 87 The design strength,DRAFT Rn, and the allowable strength, Rn/, of connections 88 shall be determined in accordance with the provisions of this chapter and the 89 provisions of Section B3.6. 90 91 1. Definitions of Parameters 92 93 lb = bearing length of the load, measured parallel to the axis of the HSS 94 member (or measured across the width of the HSS in the case of load- 95 ed cap plates), in. (mm) 96 97 2. Round HSS 98 99 The available strength of connections with concentrated loads and within 100 the limits in Table K2.1A shall be taken as shown in Table K2.1. 101

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102 TABLE K2.1. Available Strengths of Plate-to-Round HSS Connections Connection Type Connection Available Strength Plate Bending Transverse Plate T- and Cross-Connections Limit state: HSS local yielding

Plate Axial Load In-Plane Out-of-Plane

 55. RFtsin 2 Q M  0.5BR nyB f(K2-1) __ nbn 1081 . b D

0.90 (LRFD) 1. 67 (ASD)

Longitudinal Plate T-, Y- and Cross- Limit state: HSS plastification Connections

Out-of- Plate Axial Load In-Plane Plane

2 lb RFtQnysin 5.. 5 1  0 25 f (K2-2) MlRnbn0.8 __ D

0.90 (LRFD) 1.67 (ASD)

Longitudinal Plate T-Connections Limit state: HSS punching shear tb

DRAFT

MFtl 5K2-3 nup 

For Rn, see Chapter J.

The required moment, Mr, is the shear force times the eccentricity between the shear force and the HSS wall. For single-plate connections, the eccentricity may be taken as the distance from the HSS wall to the center of Cap Plate Connections gravity of the bolt group.Limit state: local yielding of HSS Axial Load

RFttlFAnybby25 (K2-4) tb

1.00 (LRFD) 1.50 (ASD)

FUNCTIONS

Qf = 1 for HSS (connecting surface) in tension = 1.0 – 0.3U ( 1 + U ) for HSS (connecting surface) in compression (K2-5)

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

PMro ro U , where Pro and Mro are determined on the side of the joint that has FAcg FS c (K2-6) the lower compression stress. Pro and Mro refer to required strengths in the HSS.

Pro = Pu for LRFD; Pa for ASD. Mro = Mu for LRFD; Ma for ASD. 103 104 105 106 TABLE K2.1A Limits of Applicability of Table K2.1

HSS wall slenderness: Dt 50 for T-connections under branch plate axial load or bending Dt 40 for cross-connections under branch plate axial load or bending

Dt 0. 11 EFy under branch plate shear loading

Dt 0. 11 EFy for cap plate connections in compression

Width ratio: 0.. 2BDb 1 0 for transverse branch plate connections

Material strength: Fy  52 ksi (360 MPa)

Ductility: FFyu 0. 8

BDb / End distance: lDend  1. 25 for transverse and longitudinal branch plate connections unde 2 axial load Note 1: ASTM A500 Grade C is acceptable.

107 108 109 3. Rectangular HSS 110 111 The available strength of connections with concentrated loads shall be 112 determined based on the applicable limit states from Chapter J and Table 113 K2.2. 114 115 TABLE K2.2 Available Strengths of Plate-to Rectangular HSS Connections Connection Type Connection Available Strength Transverse PlateDRAFT T- and Cross- Limit state: local yielding of plate, for all  Connections, 10 under Plate Axial Load RFtBFtB (K2-7) nypyBt ppp

095(LRFD).   158(ASD).

116 117 TABLE K2.2A Limits of Applicability of Table K2.2

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION K-5

HSS wall slenderness: Bt or Ht 35 for loaded wall, for transverse branch plate connections Bt or Ht 40 for loaded wall, for longitudinal branch plate and through plate connections

Btt3 or Htt 3 1.40 EF for loaded wall, for branch plate shear loading  y

Width ratio: 0.25BBb 1.0 for transverse branch plate connections Material strength: Fy  52 ksi (360 MPa) Ductility: FFyu 0.8 lB1 for transverse and longitudinal branch plate End distance: end  connections under axial load

Note 1: ASTM A500 Grade C is acceptable. Note 2: When the connection end distance, l , is less than the required end end distance limit, a cap plate is required to be designed at the end of the chord.

118 119 120 K3. HSS-TO-HSS TRUSS CONNECTIONS 121

122 The design strength, Pn, and the allowable strength, Pn/, of connections 123 shall be determined in accordance with the provisions of this chapter and 124 the provisions of Section B3.6. 125 126 HSS-to-HSS truss connections are defined as connections that consist of 127 one or more branch members that are directly welded to a continuous 128 chord that passes through the connection and shall be classified as follows: 129 130 (a) When the punching load, Pr sinθ, in a branch member is equilibrated 131 by beam shear in the chord member, the connection shall be classi- 132 fied as a T-connection when the branch is perpendicular to the chord, 133 and a DRAFTY-connection otherwise. 134 (b) When the punching load, Pr sinθ, in a branch member is essentially 135 equilibrated (within 20%) by loads in other branch member(s) on the 136 same side of the connection, the connection shall be classified as a K- 137 connection. The relevant gap is between the primary branch mem- 138 bers whose loads equilibrate. An N-connection can be considered as 139 a type of K-connection. 140 141 User Note: A K-connection with one branch perpendicular to the 142 chord is often called an N-connection. 143 144 (c) When the punching load, Prsinθ, is transmitted through the chord 145 member and is equilibrated by branch member(s) on the opposite 146 side, the connection shall be classified as a cross-connection. 147 (d) When a connection has more than two primary branch members, or 148 branch members in more than one plane, the connection shall be clas- 149 sified as a general or multiplanar connection. 150 151 When branch members transmit part of their load as K-connections and 152 part of their load as T-, Y- or cross-connections, the adequacy of the

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

153 connections shall be determined by interpolation on the proportion of the 154 available strength of each in total. 155 156 For trusses that are made with HSS that are connected by welding branch 157 members to chord members, eccentricities within the limits of applicability 158 are permitted without consideration of the resulting moments for the design 159 of the connection. 160 161 1. Definitions of Parameters 162

163 Ov = lov/lp  100, % 164 e = eccentricity in a truss connection, positive being away from the 165 branches, in. (mm) 166 g = gap between toes of branch members in a gapped K-connection, 167 neglecting the welds, in. (mm)

168 lb = Hb / sin, in. (mm) 169 170 lov = overlap length measured along the connecting face of the chord 171 beneath the two branches, in. (mm) 172 lp = projected length of the overlapping branch on the chord, in. (mm) 173 β = width ratio; the ratio of branch diameter to chord diameter = Db/D 174 for round HSS; the ratio of overall branch width to chord width = 175 Bb/B for rectangular HSS 176 eff = effective width ratio; the sum of the perimeters of the two branch 177 members in a K-connection divided by eight times the chord width 178 γ = chord slenderness ratio; the ratio of one-half the diameter to the wall 179 thickness = D/2t for round HSS; the ratio of one-half the width to 180 wall thickness = B/2t for rectangular HSS 181 η = load length parameter, applicable only to rectangular HSS; the ratio 182 of the length of contact of the branch with the chord in the plane of 183 the connection to the chord width = lb/B 184  = acute angle between the branch and chord (degrees) 185 ζ = gap ratio; the ratio of the gap between the branches of a gapped K- 186 connection to the width of the chord = g/B for rectangular HSS 187 188 2. Round HSS 189 DRAFT 190 The available strength of HSS-to-HSS truss connections within the limits 191 in Table K3.1A shall be taken as the lowest value of the applicable limit 192 states shown in Table K3.1. 193 194

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION K-7

TABLE K3.1. Available Strengths of Round HSS-to-HSS Truss Connections Connection Type Connection Available Axial Strength Limit state: shear yielding (punching) General Check  For T-, Y-, Cross- and K-Connections with gap, when 1sin PFtDnyb0.6  (K3-1) 2sin 2 DDtb (tens/comp) 2  0.95 (LRFD) 1.58 (ASD) T- and Y-Connections Limit state: chord plastification

PFtsin22 3.1  15.6  0.2 Q nyf (K3-2)

0.90 (LRFD) 1.67 (ASD)

Cross-Connections

Limit state: chord plastification

2 5.7 PFtQnysin  f (K3-3) 10.81 0.90 (LRFD) 1.67 (ASD)

K-Connections with gap or overlap Limit state: chord plastification

D PFtQQsin2 2.0 11.33 b comp nycompression branch  gf(K3-4) D

PPsin  sin  DRAFTnntension branch compression branch (K3-5)

0.90 (LRFD) 1.67 (ASD) . FUNCTIONS

Qf = 1 for chord (connecting surface) in tension = 1.0 – 0.3U ( 1 + U ) for HSS (connecting surface) in compression (K3-6)

PMro ro U , where Pro and Mro are determined on the side of the joint that has the lower FAcg FS c (K3-7) compression stress. Pro and Mro refer to required strengths in the HSS. Pro = Pu for LRFD; Pa for ASD. Mro = Mu for LRFD; Ma for ASD. a  0.0241.2 Q 0.2 1  (K3-8) g 0.5g exp1.33 1 t [a] Note that exp(x) is equal to ex, where e=2.71828 is the base of the natural logarithm.

195

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

196 197 TABLE K3.1A Limits of Applicability of Table K3.1 Joint eccentricity: 0.eD. 55 0 25 for K-connections Chord wall slenderness: Dt 50 for T-, Y- and K-connections Dt 40 for cross-connections Branch wall slenderness: Dtbb 50 for tension branch

Dtbb 0 . 05 EF yb for compression branch Width ratio: 0.DD. 2b 1 0 for T-, Y-, cross- and overlapped K-connections

0.4DDb 1 . 0 for gapped K-connections

Gap: gtbbcomp t tens for gapped K-connections

Overlap: 25%Ov 100% for overlapped K-connections

Branch thickness: ttbboverlapping overlapped for branches in overlapped K-connections

Material strength: FFyyb and  52 ksi (360 MPa)

Ductility: FFyu and F ybub F 0 . 8 End distance:

 lD.end 1 25 for T-, Y-, X-, and K-connections 2 

Note 1: ASTM A500 Grade C is acceptable. 198 199 200 3. Rectangular HSS 201 202 The available strength of HSS-to-HSS truss connections shall be deter- 203 mined based on the applicable limit states from Chapter J. The available 204 strength of HSS-to-HSS truss connections within the limits in Table K3.2A 205 shall be taken as the lowest value of the applicable limit states shown in 206 Table K3.2 and Chapter J. 207 208 209 DRAFT 210 211

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION K-9

TABLE K3.2. Available Strengths of Rectangular HSS-to-HSS Truss Connections

Connection Type Connection Available Axial Strength Gapped K-Connections Limit state: chord wall plastification, for all 

PFt.Qsin20 9 8   .5 nyefff  (K3-9)   090(LRFD).   1. 67 (ASD)

Limit state: shear yielding (punching), when BBtb   2 Do not check for square branches.   PFtBnysin 0.6 2  eop (K3-10)   095(LRFD).   1. 58 (ASD)

TABLE K3.2 (continued) Connection Type Connection Available Axial Strength Gapped K-Connections (continued) Limit state: shear of chord side walls in the gap region

Determine Pnsin in accordance with Section G5. Do not check for square chords. Limit state: local yielding of branch/branches due to uneven load distribution. Do not check for square branches or if Bt 15 PFtHB24B t nybbbb e b  (K3-11)   095(LRFD).   1. 58 (ASD)

Overlapped K-Connections Limit state: local yielding of branch/branches due to uneven load distribution   095(LRFD).   1. 58 (ASD)

when 25%Ov 50% : DRAFTO  v Ptni, Ft ybibi 24H bi bi BeiB ej  (K3-12)  50 

when 50%Ov 80% :   PFtHni,  ybibi24 bi t bi BBei ej  (K3-13)

when 80%Ov 100% : PFtH24t BB  (K3-14) Note that the force arrows shown for overlapped K- n,i ybi bi bi bi bi ej  connections may be reversed; i and j control member identification.

Subscript i refers to the overlapping branch

Subscript j refers to the overlapped branch FA PP ybj bj (K3-13) n,j n,i  FAybi bi FUNCTIONS

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

Qf  1 for chord (connecting surface) in tension U 1.. 3 0 4  1 . 0 for chord (connecting surface) in compression, for T-, Y- and cross-connections (K3-15)  U 1.. 3 0 4  1 . 0 for chord (connecting surface) in compression, for gapped K-connections (K3-16) eff PM U ro ro , FAcg FS c where Pro and Mro are determined on the side of the joint that has the lower (K3-17) compression stress. Pro and Mro refer to required strengths in the HSS. PPro u for LRFD; Pa for ASD. MMro u for LRFD; Ma for ASD. BH  BH  4B (K3-18) eff b b compression branch b b tension branch 5   (K3-19) eop 

TABLE K3.2A Limits of Applicability of Table K3.2 Joint eccentricity: 0.55eH 0.25 for K-connections Chord wall slenderness: Bt and Ht 35 for gapped K-connections and T-, Y- and cross-connections Branch wall slenderness: Bt 30 for overlapped K-connections Ht 35 for overlapped K-connections Btbb and Ht bb 35 for tension branch E  1.25 for compression branch of gapped K-, T-, Y- and F yb Cross-connections

 35 for compression branch of gapped K-, T-, Y- and cross-connections E  1.1 for compression branch of overlapped K-connections F DRAFTyb Width ratio: BBbb and HB 0.25 for T-, Y- cross- and overlapped K-connections Aspect ratio: 0.5HBbb 2.0 and 0.5  HB 2.0 Overlap: 25%Ov 100% for overlapped K-connections Branch width ratio: BBbi bj  0.75 for overlapped K-connections, where subscript i refers to the overlapping branch and subscript j refers to the overlapped branch Branch thickness ratio: ttbi bj  1.0 for overlapped K-connections, where subscript i refers to the overlapping branchand subscript j refers to the overlapped branch Material strength: FFyyb and  52 ksi (360 MPa) Ductility: FFyu and F ybub F 0.8 lB1 for T- and Y-connections End distance: end

Note 1: ASTM A500 Gr C is acceptable.

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION K-11

Additional limits for gapped K-connections BH  Width ratio: bb and 0.1 BB 50

eff 0.35

Gap ratio: gB 0.5 1 eff

Gap: gtbbcompression branch t tension branch

Branch size: smaller BBbb 0.63 larger , if both branches are square Note: Maximum gap size will be controlled by the eH limit. If gap is large, treat as two Y-connections. 212 213 214 215 K4. HSS-TO-HSS MOMENT CONNECTIONS 216 217 The design strength, Mn, and the allowable strength, Mn/, of connections 218 shall be determined in accordance with the provisions of this chapter and 219 the provisions of Section B3.6. 220 221 HSS-to-HSS moment connections are defined as connections that consist 222 of one or two branch members that are directly welded to a continuous 223 chord that passes through the connection, with the branch or branches 224 loaded by bending moments. 225 226 A connection shall be classified as: 227 228 (a) A T-connection when there is one branch and it is perpendicular to the 229 chord and as a Y-connection when there is one branch but not per- 230 pendicular to the chord 231 (b) A cross-connection when there is a branch on each (opposite) side of 232 the chord 233 234 1. Definitions of Parameters 235 3 236 Zb = Plastic section modulus of branch about the axis of bending, in. 237 (mm3) 238 β = widthDRAFT ratio 239 = Db/D for round HSS; ratio of branch diameter to chord diameter 240 = Bb/B for rectangular HSS; ratio of overall branch width to chord 241 width 242 γ = chord slenderness ratio 243 = D/2t for round HSS; ratio of one-half the diameter to the wall 244 thickness 245 = B/2t for rectangular HSS; ratio of one-half the width to the wall 246 thickness 247 η = load length parameter, applicable only to rectangular HSS 248 = lb/B; the ratio of the length of contact of the branch with the chord in 249 the plane of the connection to the chord width, where lb=Hb /sin θ 250 θ = acute angle between the branch and chord (degrees) 251

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

252 2. Round HSS 253 254 The available strength of moment connections within the limits of Table 255 K4.1A shall be taken as the lowest value of the applicable limit states 256 shown in Table K4.1. 257 258 TABLE K4.1 Available Strengths of Round HSS-to-HSS Moment Connections

Connection Type Connection Available Flexural Strength Branch(es) under In-Plane Bending T-, Y- and Cross-Connections Limit state: chord plastification

20.5 MFtDQnybsin5.39   f (K4-1)

0.90 (LRFD) 1. 67 (ASD)

Limit state: shear yielding (punching), when DDtb  2  13sin 2 MFtDnyb 0.6 2 (K4-2) 4sin  0.95 (LRFD) 1.58 (ASD) Branch(es) under Out-of-Plane Bending T-, Y- and Cross-Connections Limit state: chord plastification

2  3.0  M nybsinFt D  Q f (K4-3) 10.81

0.90 (LRFD) 1.67 (ASD) Limit state: shear yielding (punching), when DDt 2  DRAFT b 3sin MFtD 0.6 2 (K4-4) nyb2 4sin  0.95 (LRFD) 1.58 (ASD)

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION K-13

For T-, Y- and Cross-connections, with branch(es) under combined axial load, in-plane bending and out-of-plane bending, or any combination of these load effects: 2  (K4-5) LRFD: PPu n M rip--  M nip  M rop -  M nop - 1.0 2 ASD: PP M M   M M 1.0 (K4-6) a n rip-- nip rop - nop -

Pn = design strength (or Pn / = allowable strength) obtained from Table K2.1

Mn-ip = design strength (or Mn-ip / = allowable strength) for in-plane bending

Mn-op = design strength (or Mn-op / = allowable strength) for out-of-plane bending

Mr-ip = Mu-ip for LRFD; Ma-ip for ASD

Mr-op = Mu-op for LRFD; Ma-op for ASD FUNCTIONS

Q f  1 for chord (connecting surface) in tension 1.0 0.3UU 1  for chord (connecting surface) in compression (K3-6) PM U ro ro , where Pro and Mro are determined on the side of the joint that has the lower FAc g FSc (K3-7) compression stress. Pro and Mro refer to required strengths in the HSS. Pro = Pu for LRFD; Pa for ASD. Mro = Mu for LRFD; Ma for ASD. 259 TABLE K4.1A Limits of Applicability of Table K4.1

Chord wall slenderness: Dt 50 for T- and Y-connections Dt 40 for Cross-connections Branch wall slenderness: Dt 50 bb Dtbb 005. EF yb

Width ratio: 02..DDb 10

Material strength: FFyyb and  52 ksi (360 MPa)

Ductility: FFyu and F ybub F 0. 8 Note: ASTM A500 Gr C is acceptable. 260 261 DRAFT

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

262 3. Rectangular HSS 263 264 The available strength of HSS-to-HSS of moment connections shall be 265 determined based on the applicable limit states from Chapter J. The 266 available strength of HSS-to-HSS moment connections within the limits of 267 Table K4.2A shall be taken as the lowest value of the applicable limit 268 states shown in Table K4.2 and Chapter J. 269

TABLE K4.2 Available Strengths of Rectangular HSS-to-HSS Moment Connections

Connection Type Connection Available Flexural Strength

Branch(es) under Out-of-Plane Bending Limit state: chord wall plastification, when 085. T- and Cross-Connections   05.Hbb 1 2BB 1  MFt2  Q (K4-7) ny 11   f      100(LRFD).   1. 50 (ASD)

Limit state: sidewall local yielding, when 085. * MFtBtHtny  b5    100(LRFD). 1. 50 (ASD) Limit state: local yielding of branch/branches due to uneven load distribution, when 085.  2  Be 2 MFZnybb 05.  1 Bt b (K4-9) B b  b    095(LRFD).   1. 58 (ASD)

Limit state: chord distortional failure, for T-connections and unbalanced cross-connections

MFtHtBHtBH2   (K4-10) nyb    100(LRFD).   1. 50 (ASD) DRAFT

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TABLE K4.2 (continued) For T- and cross-connections, with branch(es) under combined axial load, in-plane bending and out-of-plane bending, or any combination of these load effects:  LRFD: PPun M ripnipropnop--  M  M -  M - 10 . (K4-11) ASD: PP M M M M 10 . an ripnip--   ropnop - -  (K4-12)

Pn = design strength (or Pn / = allowable strength) obtained from Table K3.2,

Mn-ip = design strength (or Mn-ip / = allowable strength) for in-plane bending (above),

Mn-op = design strength (or Mn-op / = allowable strength) for out-of-plane bending (above)

Mr-ip = Mu-ip for LRFD; Ma-ip for ASD

Mr-op = Mu-op for LRFD; Ma-op for ASD FUNCTIONS

Qf  1 for chord (connecting surface) in tension U 1.. 3 0 4  1 . 0 for chord (connecting surface) in compression (K3-14)  PM U ro ro , where Pro and Mro are determined on the side of the joint that has the lower FAc g FSc (K3-16) compression stress. Pro and Mro refer to required strengths in the HSS. Pro = Pu for LRFD; Pa for ASD.

Mro = Mu for LRFD; Ma for ASD.

* FFyy for T-connections and 0. 8Fy for cross-connections

271 TABLE K4.2A Limits of Applicability of Table K4.2

Branch angle: 90 Chord wall slenderness: Bt and Ht 35

Branch wall slenderness: Btbbbb and Ht 35 E 125. DRAFT Fyb

Width ratio: BBb 025.

Aspect ratio: 0.... 5HBbb 2 0 and 0 5  HB 2 0

Material strength: FFyyb and  52 ksi (360 MPa)

Ductility: FFyu and F ybub F 0. 8 Note 1: ASTM A500 Grade C is acceptable.

272 273 274 K5. WELDS OF PLATES AND BRANCHES TO RECTANGULAR HSS 275 276 The design strength, Rn, Mn and Pn, and the allowable strength, Rn/, 277 Mn/ and Pn/, of connections shall be determined in accordance with the 278 provisions of this chapter and the provisions of Section B3.6. 279 280 The available strength of branch connections shall be determined for the 281 limit state of nonuniformity of load transfer along the line of weld, due to

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

282 differences in relative stiffness of HSS walls in HSS-to-HSS connections 283 and between elements in transverse plate-to-HSS connections, as follows: 284 285 Rn or Pn= Fnwtwle (K5-1) 286 287 Mn-ip = FnwSip (K5-2) 288 289 Mn-op = FnwSop (K5-3) 290 291 For interaction, see Equations K4-14 and K4-15. 292 293 (a) For fillet welds 294 295  = 0.75 (LRFD)  = 2.00 (ASD) 296 297 (b) For partial-joint-penetration groove welds 298 299  = 0.80 (LRFD)  = 1.88 (ASD) 300 301 where 302 Fnw = nominal stress of weld metal (Chapter J) with no increase in 303 strength due to directionality of load, ksi (MPa) 304 Sip = effective elastic section modulus of welds for in-plane bending 305 (Table K5.1), in.3 (mm3) 306 Sop = effective elastic section modulus of welds for out-of-plane bend- 307 ing (Table K5.1), in.3 (mm3) 308 le = total effective weld length of groove and fillet welds to rectangu- 309 lar HSS for weld strength calculations, in. (mm) 310 tw = smallest effective weld throat around the perimeter of branch or 311 plate, in. (mm) 312 DRAFT

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION K-17

TABLE K5.1 Effective Weld Properties for Connections to Rectangular HSS

Connection Type Connection Weld Strength Transverse Plate T- and Cross-Connections Effective Weld Properties under Plate Axial Load

lB 2 (K5-4) ee

where le = total effective weld length for welds on both sides of the transverse plate

T-, Y-, and Cross-Connections Effective Weld Properties under Branch Axial Load or Bending 2H lBb 2 (K5-5) eesin

2 tHwb  Hb StBip w e  (K5-6) 3 sin sin

3 HttBB3  bw2 wbe Stop w B b B b (K5-7) sin  3 Bb

 When 0.85 or  50 , Bte 2 shall not exceed 2 DRAFT

Gapped K-Connections Effective Weld Properties under Branch Axial Load  When 50 :

212Ht . lBtbb212. (K5-8) ebbsin

When 60 :

212Ht .  lBtbb12. (K5-9) ebbsin

When 50 60 , linear interpolation shall be used to

determine le

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

TABLE K5.1 (continued) Overlapped K-Connections Overlapping Member Effective Weld Properties under Branch Axial Load (all dimensions are for the overlapping branch, i )

When 25%Ov 50% :

le,i 

 (K5-10) 2OOvvHHbi O v bi 1 BBei ej 50 100 sin 100 sin  i ij

When 50%Ov 80% :

le,i 

 Note that the force arrows shown for overlapped K- OOvvHHbi bi (K5-11) 21 BB connections may be reversed; i and j control  ei ej 100 sini 100 sinij member identification  When 80%Ov 100% :

le,i     (K5-12) OOvvHHbi bi 21 BBbi ej 100 sin 100 sin  i ij

 when BBbi  0.85 or i 50 , Bei 2 shall not exceed Bb/4  and when BBbi bj  0.85 or 180ij   50 , Bej 2 shall

not exceed 2tbj

DRAFT Subscript i refers to the overlapping branch

Subscript j refers to the overlapped branch

Overlapped Member Effective Weld Properties (all dimensions are for the overlapped branch, j )

2Hbj lBej, 2 ej (K5-13) sin j

 When BBbj 0.85 or j 50 , lH.te,j212sin bj bj  j

313 314

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION K-19

315 When an overlapped K-connection has been designed in accordance with Table 316 K3.2 of this chapter, and the branch member component forces normal to the chord 317 are 80% “balanced” (i.e., the branch member forces normal to the chord face differ 318 by no more than 20%), the “hidden” weld under an overlapping branch may be 319 omitted if the remaining welds to the overlapped branch everywhere develop the 320 full capacity of the overlapped branch member walls. 321 322 The weld checks in Table K5.1 are not required if the welds are capable of 323 developing the full strength of the branch member wall along its entire perimeter (or 324 a plate along its entire length). 325 326 User Note: The approach used here to allow down-sizing of welds assumes a 327 constant weld size around the full perimeter of the HSS branch. Special attention is 328 required for equal width (or near-equal width) connections which combine partial- 329 joint-penetration groove welds along the matched edges of the connection, with 330 fillet welds generally across the main member face. 331

DRAFT

Specification for Structural Steel Buildings, public review DRAFT dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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CHAPTER L

DESIGN FOR SERVICEABILITY

This chapter addresses the evaluation of the structure and its components for the serviceability limit states of deflections, drift, vibration, wind-induced motion, thermal distortion, and connection slip. The chapter is organized as follows: L1. General Provisions L2. Deflections L2. Drift L4. Vibration L5. Wind-Induced Motion L6. Thermal Expansion and Contraction L7. Connection Slip

L1. GENERAL PROVISIONS

Serviceability is a state in which the function of a building, its appearance, maintainability, durability, and the comfort of its occupants are preserved under typical usage. Limiting values of structural behavior for serviceability (such as maximum deflections and accelerations) shall be chosen with due regard to the intended function of the structure. Serviceability shall be evaluated using applicable load combinations.

User Note: Serviceability limit states, service loads, and appropriate load combinations for serviceability considerations can be found in ASCE/SEI 7 Appendix C. The performance requirements for serviceability in this chapter are consistent with ASCE/SEI 7 Appendix C. Service loads are those that act on the structure at an arbitrary point in time and are not usually taken as the nominal loads.

Reduced stiffness values used in the direct analysis method, described in Chapter C, are not intended for use with the provisions of this chapter.

L2. DEFLECTIONS

Deflections in structural members and structural systems shall be limited so as not to impair the serviceability of the structure.

L3. DRIFT

Drift shall be limited so as not to impair the serviceability of the structure. DRAFT L4. VIBRATION

The effect of vibration on the comfort of the occupants and the function of the structure shall be considered. The sources of vibration to be considered include occupant loading, vibrating machinery and others identified for the structure.

L5. WIND-INDUCED MOTION

The effect of wind-induced motion of buildings on the comfort of occupants shall be considered.

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

L-2

L6. THERMAL EXPANSION AND CONTRACTION

The effects of thermal expansion and contraction of a building shall be considered.

L7. CONNECTION SLIP

The effects of connection slip shall be included in the design where slip at bolted connections may cause deformations that impair the serviceability of the structure. Where appropriate, the connection shall be designed to preclude slip.

User Note: For the design of slip-critical connections, see Sections J3.8 and J3.9. For more information on connection slip, refer to the RCSC Specification for Structural Joints Using High-Strength Bolts.

DRAFT

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

M-1

2 CHAPTER M

3 FABRICATION AND ERECTION 4 5 6 7 This chapter addresses requirements for shop drawings, fabrication, shop painting 8 and erection. 9 10 The chapter is organized as follows: 11 12 M1. Shop and Erection Drawings 13 M2. Fabrication 14 M3. Shop Painting 15 M4. Erection 16 17 M1. SHOP AND ERECTION DRAWINGS 18 19 Shop and erection drawings are permitted to be prepared in stages. Shop 20 drawings shall be prepared in advance of fabrication and give complete 21 information necessary for the fabrication of the component parts of the 22 structure, DRAFTincluding the location, type and size of welds and bolts. Erection 23 drawings shall be prepared in advance of erection and give information 24 necessary for erection of the structure. Shop and erection drawings shall 25 clearly distinguish between shop and field welds and bolts and shall clearly 26 identify pretensioned and slip-critical high-strength bolted connections. Shop 27 and erection drawings shall be made with due regard to speed and economy in 28 fabrication and erection. 29 30 M2. FABRICATION 31 32 1. Cambering, Curving and Straightening 33 34 Local application of heat or mechanical means is permitted to be used to 35 introduce or correct camber, curvature and straightness. The temperature of 36 heated areas shall not exceed 1,100 °F (593 C) for ASTM A514/A514M and 37 ASTM A852/A852M steel nor 1,200 °F (649 C) for other steels. 38 39 2. Thermal Cutting 40 41 Thermally cut edges shall meet the requirements of AWS D1.1, clauses 42 5.15.1.2, 5.15.4.3 and 5.15.4.4 with the exception that thermally cut free 43 edges that will not be subject to fatigue shall be free of round-bottom gouges 44 greater than x in. (5 mm) deep and sharp V-shaped notches. Gouges deeper 45 than x in. (5 mm) and notches shall be removed by grinding or repaired by 46 welding. 47 48 Reentrant corners shall be formed with a curved transition. The radius need 49 not exceed that required to fit the connection. Discontinuous corners are 50 permitted where the material on both sides of the discontinuous reentrant 51 corner are connected to a mating piece to prevent deformation and associated 52 stress concentration at the corner. 53

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

54 User Note: Reentrant corners with a radius of 1/2 to 3/8 in. (13 to 10 mm) are 55 acceptable for statically loaded work. Where pieces need to fit tightly together, 56 a discontinuous reentrant corner is acceptable if the pieces are connected close 57 to the corner on both sides of the discontinuous corner. Slots in HSS for 58 gussets may be made with semicircular ends or with curved corners. Square 59 ends are acceptable provided the edge of the gusset is welded to the HSS. 60 61 Weld access holes shall meet the geometrical requirements of Section J1.6. 62 Beam copes and weld access holes in shapes that are to be galvanized shall be 63 ground to bright metal. For shapes with a flange thickness not exceeding 2 in. 64 (50 mm), the roughness of thermally cut surfaces of copes shall be no greater 65 than a surface roughness value of 2,000 in. (50 m) as defined in ASME 66 B46.1. For beam copes and weld access holes in which the curved part of the 67 access hole is thermally cut in ASTM A6/A6M hot-rolled shapes with a 68 flange thickness exceeding 2 in. (50 mm) and welded built-up shapes with 69 material thickness greater than 2 in. (50 mm), a preheat temperature of not 70 less than 150 °F (66 C) shall be applied prior to thermal cutting. The 71 thermally cut surface of access holes in ASTM A6/A6M hot-rolled shapes 72 with a flange thickness exceeding 2 in. (50 mm) and built-up shapes with a 73 material thickness greater than 2 in. (50 mm) shall be ground. 74 75 User Note: The AWS Surface Roughness Guide for Oxygen Cutting (AWS 76 C4.1-77) sample 2 may be used as a guide for evaluating the surface 77 roughness of copes in shapes with flanges not exceeding 2 in. (50 mm) thick. 78 79 3. Planing of Edges 80 81 Planing or finishing of sheared or thermally cut edges of plates or shapes is not 82 required unless specifically called for in the construction documents or 83 included in a stipulated edge preparation for welding. 84 85 4. Welded Construction 86 87 The technique of welding, the workmanship, appearance, and quality of 88 welds, and the methods used in correcting nonconforming work shall be in 89 accordance with AWS D1.1 except as modified in Section J2. 90 91 5. Bolted Construction 92 93 Parts of bolted members shall be pinned or bolted and rigidly held together 94 during assembly. Use of a drift pin in bolt holes during assembly shall not 95 distort the metal or enlarge the holes. Poor matching of holes shall be cause 96 for rejection. 97 98 Bolt holes shall comply with the provisions of the RCSC Specification for 99 Structural Joints Using High-Strength Bolts, hereafter referred to as the 100 RCSC Specification, Section 3.3 except that thermally cut holes are permitted 101 with a surface roughness profile not exceeding 1,000 in. (25 m) as defined 102 in ASME B46.1. Gouges shall not exceed a depth of 1/16 in. (2 mm). Water 103 jet cut holes are also permitted. 104 105 User Note: The AWS Surface Roughness Guide for Oxygen Cutting (AWS 106 C4.1-77) sample 3 may be used as a guide for evaluating the surface 107 roughness of thermally cut holes. 108

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109 Fully inserted finger shims, with a total thickness of not more than ¼ in. (6 110 mm) within a joint, are permitted without changing the strength (based upon 111 hole type) for the design of connections. The orientation of such shims is 112 independent of the direction of application of the load. 113 114 The use of high-strength bolts shall conform to the requirements of the RCSC 115 Specification, except as modified in Section J3. 116 117 6. Compression Joints 118 119 Compression joints that depend on contact bearing as part of the splice 120 strength shall have the bearing surfaces of individual fabricated pieces 121 prepared by milling, sawing or other equivalent means. 122 123 7. Dimensional Tolerances 124 125 Dimensional DRAFTtolerances shall be in accordance with Chapter 6 of the AISC 126 Code of Standard Practice for Steel Buildings and Bridges, hereafter referred 127 to as the AISC Code of Standard Practice. 128 129 8. Finish of Column Bases 130 131 Column bases and base plates shall be finished in accordance with the 132 following requirements: 133 134 (a) Steel bearing plates 2 in. (50 mm) or less in thickness are permitted 135 without milling provided a smooth and notch-free contact bearing sur- 136 face is obtained. Steel bearing plates over 2 in. (50 mm) but not over 4 137 in. (100 mm) in thickness are permitted to be straightened by pressing or, 138 if presses are not available, by milling for bearing surfaces, except as 139 stipulated in subparagraphs 2 and 3 of this section, to obtain a smooth and 140 notch-free contact bearing surface. Steel bearing plates over 4 in. (100 141 mm) in thickness shall be milled for bearing surfaces, except as stipulat- 142 ed in subparagraphs 2 and 3 of this section. 143 144 (b) Bottom surfaces of bearing plates and column bases that are grouted to 145 ensure full bearing contact on foundations need not be milled. 146 147 (c) Top surfaces of bearing plates need not be milled when complete-joint- 148 penetration groove welds are provided between the column and the 149 bearing plate. 150 151 9. Holes for Anchor Rods 152 153 Holes for anchor rods are permitted to be thermally cut in accordance with the 154 provisions of Section M2.2. 155 156 10. Drain Holes 157 158 When water can collect inside HSS or box members, either during 159 construction or during service, the member shall be sealed, provided with a 160 drain hole at the base, or otherwise protected from water infiltration. 161 162 11. Requirements for Galvanized Members 163

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

164 Members and parts to be galvanized shall be designed, detailed and 165 fabricated to provide for flow and drainage of pickling fluids and zinc and to 166 prevent pressure buildup in enclosed parts. 167 168 User Note: See The Design of Products to be Hot-Dip Galvanized After 169 Fabrication, American Galvanizer’s Association, and ASTM A123, F2329, 170 A384 and A780 for useful information on design and detailing of galvanized 171 members. See Section M2.2 for requirements for copes of members to be 172 galvanized. 173 174 M3. SHOP PAINTING 175 176 1. General Requirements 177 178 Shop painting and surface preparation shall be in accordance with the 179 provisions in Chapter 6 of the AISC Code of Standard Practice. 180 181 Shop paint is not required unless specified by the contract documents. 182 183 2. Inaccessible Surfaces 184 185 Except for contact surfaces, surfaces inaccessible after shop assembly shall be 186 cleaned and painted prior to assembly, if required by the construction 187 documents. 188 189 3. Contact Surfaces 190 191 Paint is permitted in bearing-type connections. For slip-critical connections, 192 the faying surface requirements shall be in accordance with the RCSC 193 Specification, Section 3.2.2(b). 194 195 4. Finished Surfaces 196 197 Machine-finished surfaces shall be protected against corrosion by a rust 198 inhibitive coating that can be removed prior to erection, or which has 199 characteristics that make removal prior to erection unnecessary. 200 201 5. Surfaces Adjacent to Field Welds 202 203 Unless otherwise specified in the design documents, surfaces within 2 in. (50 204 mm) of any field weld location shall be free of materials that would prevent 205 weld quality from meeting the quality requirements of this specification, or 206 produce unsafe fumes during welding. 207 208 M4. ERECTION 209 210 1. Column Base Setting 211 212 Column bases shall be set level and to correct elevation with full bearing on 213 concrete or masonry as defined in Chapter 7 of the AISC Code of Standard 214 Practice. 215 216 2. Stability and Connections 217

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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218 The frame of structural steel buildings shall be carried up true and plumb 219 within the limits defined in Chapter 7 of the AISC Code of Standard Practice. 220 As erection progresses, the structure shall be secured to support dead, erection 221 and other loads anticipated to occur during the period of erection. Temporary 222 bracing shall be provided, in accordance with the requirements of the AISC 223 Code of Standard Practice, wherever necessary to support the loads to which 224 the structure may be subjected, including equipment and the operation of 225 same. Such bracing shall be left in place as long as required for safety. 226 227 3. Alignment 228 229 No permanent bolting or welding shall be performed until the affected 230 portions of the structure have been aligned as required by the construction 231 documents. 232 233 4. Fit of Column Compression Joints and Base Plates 234 235 Lack of contact bearing not exceeding a gap of 1/16 in. (2 mm), regardless of 236 the type of splice used (partial-joint-penetration groove welded or bolted), is 237 permitted. If the gap exceeds 1/16 in. (2 mm), but is equal to or less than ¼ in. 238 (6 mm), and if an engineering investigation shows that sufficient contact area 239 does not exist, the gap shall be packed out with nontapered steel shims. Shims 240 need not be other than mild steel, regardless of the grade of the main material. 241 242 5. Field Welding 243 244 Surfaces in and adjacent to joints to be field welded shall be prepared as 245 necessary to assure weld quality. This preparation shall include surface 246 preparation necessary to correct for damage or contamination occurring 247 subsequent to fabrication. 248 249 6. Field Painting 250 251 Responsibility for touch-up painting, cleaning and field painting shall be 252 allocated in accordance with accepted local practices, and this allocation shall 253 be set forth explicitly in the contract documents. 254 255

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

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1 2 CHAPTER N 3 4 QUALITY CONTROL AND QUALITY ASSURANCE 5 6 This chapter addresses minimum requirements for quality control, quality assurance 7 and nondestructive testing for structural steel systems and steel elements of 8 composite members for buildings and other structures. 9 10 User Note: This chapter does not address quality control or quality assurance for 11 the following items: 12 (a) Steel (open web) joists and girders 13 (b) Tanks or pressure vessels 14 (c) Cables, cold-formed steel products or gage material 15 (d) Concrete reinforcing bars, concrete materials or placement of concrete for 16 composite members 17 (e) Surface preparations or coatings 18 (f) Steel decking and deck fasteners 19 20 The Chapter is organized as follows: 21 22 N1. General Provisions 23 N2. Fabricator and Erector Quality Control Program 24 N3. Fabricator and Erector Documents 25 N4. Inspection and Nondestructive Testing Personnel 26 N5. Minimum Requirements for Inspection of Structural Steel Buildings 27 N6. Approved Fabricators and Erectors 28 N7. Nonconforming Material and Workmanship 29 30 N1. GENERAL PROVISIONS 31 DRAFT 32 Quality control (QC) as specified in this chapter shall be provided by the 33 fabricator and erector. Quality assurance (QA) as specified in this chapter 34 shall be provided by others when required by the authority having jurisdic- 35 tion (AHJ), applicable building code (ABC), purchaser, owner, or engineer 36 of record (EOR). Nondestructive testing (NDT) shall be performed by the 37 agency or firm responsible for quality assurance, except as permitted in 38 accordance with Section N6. 39 40 User Note: The QA/QC requirements in Chapter N are considered 41 adequate and effective for most steel structures and are strongly encour- 42 aged without modification. When the ABC and AHJ requires the use of a 43 quality assurance plan, this chapter outlines the minimum requirements 44 deemed effective to provide satisfactory results in steel building construc- 45 tion. There may be cases where supplemental inspections are advisable. 46 Additionally, where the contractor’s quality control program has demon- 47 strated the capability to perform some tasks this plan has assigned to 48 quality assurance, modification of the plan could be considered. 49 50 User Note: The producers of materials manufactured in accordance with 51 standard specifications referenced in Section A3 in this Specification, and 52 steel deck manufacturers, are not considered to be fabricators or erectors. 53 54 N2. FABRICATOR AND ERECTOR QUALITY CONTROL PROGRAM 55

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56 The fabricator and erector shall establish, maintain and implement quality 57 control procedures to ensure that their work is performed in accordance 58 with this Specification and the construction documents. 59 60 1. Material Identification 61 62 Material identification procedures shall comply with the requirements of 63 Section 6.1 of the AISC Code of Standard Practice, and shall be monitored 64 by the fabricator’s quality control inspector (QCI). 65 66 2. Fabricator Quality Control Procedures 67 68 The fabricator’s quality control procedures shall address inspection of the 69 following as a minimum, as applicable: 70 71 (a) Shop welding, high-strength bolting, and details in accordance with 72 Section N5 73 (b) Shop cut and finished surfaces in accordance with Section M2 74 (c) Shop heating for straightening, cambering and curving in accordance 75 with Section M2.1 76 (d) Tolerances for shop fabrication in accordance with Section 6.4 of the 77 AISC Code of Standard Practice 78 79 3. Erector Quality Control Procedures 80 81 The erector’s quality control procedures shall address inspection of the 82 following as a minimum, as applicable: 83 84 (a) Field welding, high-strength bolting, and details in accordance with 85 Section N5 86 (b) Steel deck in accordance with SDI Standard for Quality Control and 87 QualityDRAFT Assurance for Installation of Steel Deck 88 (c) Headed steel stud anchor placement and attachment in accordance 89 with Section N5.4 90 (d) Field cut surfaces in accordance with Section M2.2 91 (e) Field heating for straightening in accordance with Section M2.1 92 (f) Tolerances for field erection in accordance with Section 7.13 of the 93 Code of Standard Practice 94 95 N3. FABRICATOR AND ERECTOR DOCUMENTS 96 97 1. Submittals for Steel Construction 98 99 The fabricator or erector shall submit the following documents for review 100 by the engineer of record (EOR) or the EOR’s designee, in accordance 101 with Section 4 or A4.4 of the Code of Standard Practice, prior to fabrica- 102 tion or erection, as applicable: 103 104 (a) Shop drawings, unless shop drawings have been furnished by others 105 (b) Erection drawings, unless erection drawings have been furnished by 106 others 107 108 2. Available Documents for Steel Construction 109 110 The following documents shall be available in electronic or printed form 111 for review by the EOR or the EOR’s designee prior to fabrication or

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION N-3

112 erection, as applicable, unless otherwise required in the construction 113 documents to be submitted: 114 115 (a) For main structural steel elements, copies of material test reports 116 in accordance with Section A3.1. 117 (b) For steel castings and forgings, copies of material test reports in 118 accordance with Section A3.2. 119 (c) For fasteners, copies of manufacturer’s certifications in accord- 120 ance with Section A3.3. 121 (d) For anchor rods and threaded rods, copies of material test reports 122 in accordance with Section A3.4. 123 (e) For welding consumables, copies of manufacturer’s certifications 124 in accordance with Section A3.5. 125 (f) For headed stud anchors, copies of manufacturer’s certifications 126 in accordance with Section A3.6. 127 (g) Manufacturer’s product data sheets or catalog data for welding 128 filler metals and fluxes to be used. The data sheets shall describe 129 the product, limitations of use, recommended or typical welding 130 parameters, and storage and exposure requirements, including 131 baking, if applicable. 132 (h) Welding procedure specifications (WPSs). 133 (i) Procedure qualification records (PQRs) for WPSs that are not 134 prequalified in accordance with AWS D1.1/D1.1M or AWS 135 D1.3/D1.3M, as applicable. 136 (j) Welding personnel performance qualification records (WPQR) 137 and continuity records. 138 (k) Fabricator’s or erector’s, as applicable, written quality control 139 manual that shall include, as a minimum: 140 (1) Material control procedures 141 (2) Inspection procedures 142 (3) Nonconformance procedures 143 (l) Fabricator’sDRAFT or erector’s, as applicable, QC inspector qualifications. 144 (m) Fabricator NDT personnel qualifications, if NDT is performed by 145 fabricator. 146 147 N4. INSPECTION AND NONDESTRUCTIVE TESTING PERSONNEL 148 149 1. Quality Control Inspector Qualifications 150 151 QC welding inspection personnel shall be qualified to the satisfaction of 152 the fabricator’s or erector’s QC program, as applicable, and in accordance 153 with either of the following: 154 155 (a) Associate welding inspectors (AWI) or higher as defined in AWS 156 B5.1, Standard for the Qualification of Welding Inspectors, or 157 (b) Qualified under the provisions of AWS D1.1/D1.1M subclause 158 6.1.4 159 160 QC bolting inspection personnel shall be qualified on the basis of docu- 161 mented training and experience in structural bolting inspection. 162 163 2. Quality Assurance Inspector Qualifications 164 165 QA welding inspectors shall be qualified to the satisfaction of the QA 166 agency’s written practice, and in accordance with either of the following: 167

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168 (a) Welding inspectors (WIs) or senior welding inspectors (SWIs), as 169 defined in AWS B5.1, Standard for the Qualification of Welding 170 Inspectors, except AWIs are permitted to be used under the direct 171 supervision of WIs, who are on the premises and available when 172 weld inspection is being conducted, or 173 (b) Qualified under the provisions of AWS D1.1/D1.1M subclause 174 6.1.4 175 176 QA bolting inspection personnel shall be qualified on the basis of docu- 177 mented training and experience in structural bolting inspection. 178 179 3. NDT Personnel Qualifications 180 181 Nondestructive testing personnel, for NDT other than visual, shall be 182 qualified in accordance with their employer’s written practice, which shall 183 meet or exceed the criteria of AWS D1.1/D1.1M Structural Welding Code 184 —Steel clause 6.14.6, and: 185 186 (a) American Society for Nondestructive Testing (ASNT) SNT-TC- 187 1A, Recommended Practice for the Qualification and Certifica- 188 tion of Nondestructive Testing Personnel, or 189 (b) ASNT CP-189, Standard for the Qualification and Certification 190 of Nondestructive Testing Personnel. 191 192 N5. MINIMUM REQUIREMENTS FOR INSPECTION OF 193 STRUCTURAL STEEL BUILDINGS 194 195 1. Quality Control 196 197 QC inspection tasks shall be performed by the fabricator’s or erector’s 198 QCI, as applicable, in accordance with Sections N5.4, N5.6 and N5.7.. 199 DRAFT 200 Tasks in Tables N5.4-1 through N5.4-3 and Tables N5.6-1 through N5.6-3 201 listed for QC are those inspections performed by the QCI to ensure that the 202 work is performed in accordance with the construction documents. 203 204 For QC inspection, the applicable construction documents are the shop 205 drawings and the erection drawings, and the applicable referenced 206 specifications, codes and standards. 207 208 User Note: The QCI need not refer to the design drawings and project 209 specifications. The Code of Standard Practice, Section 4.2(a), requires the 210 transfer of information from the contract documents (design drawings and 211 project specification) into accurate and complete shop and erection 212 drawings, allowing QC inspection to be based upon shop and erection 213 drawings alone. 214 215 2. Quality Assurance 216 217 218 The QAI shall review the material test reports and certifications as listed in 219 Section N3.2 for compliance with the construction documents. 220 221 QA inspection tasks shall be performed by the QAI, in accordance with 222 Sections N5.4, N5.6 and N5.7. 223

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION N-5

224 Tasks in Tables N5.4-1 through N5.4-3 and N5.6-1 through N5.6-3 listed 225 for QA are those inspections performed by the QAI to ensure that the work 226 is performed in accordance with the construction documents. 227 228 Concurrent with the submittal of such reports to the AHJ, EOR or owner, 229 the QA agency shall submit to the fabricator and erector: 230 231 (a) Inspection reports 232 (b) Nondestructive testing reports 233 234 3. Coordinated Inspection 235 236 When a task is noted to be performed by both QC and QA, it is permitted 237 to coordinate the inspection function between the QCI and QAI so that the 238 inspection functions are performed by only one party. When QA relies 239 upon inspection functions performed by QC, the approval of the engineer 240 of record and the authority having jurisdiction is required. 241 242 4. Inspection of Welding 243 244 Observation of welding operations and visual inspection of in-process and 245 completed welds shall be the primary method to confirm that the materials, 246 procedures and workmanship are in conformance with the construction 247 documents. For structural steel, all provisions of AWS D1.1/D1.1M 248 Structural Welding Code—Steel for statically loaded structures shall apply. 249 250 User Note: Section J2 of this Specification contains exceptions to AWS 251 D1.1/D1.1M. 252 253 As a minimum, welding inspection tasks shall be in accordance with 254 Tables N5.4-1, N5.4-2 and N5.4-3. In these tables, the inspection tasks are 255 as follows: DRAFT 256 257 O – Observe these items on a random basis. Operations need not be 258 delayed pending these inspections. 259 P – Perform these tasks for each welded joint or member. 260

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TABLE N5.4-1

Inspection Tasks Prior to Welding

Inspection Tasks Prior to Welding QC QA Welder qualification records and continuity records P O Welding procedure specifications (WPSs) available P P Manufacturer certifications for welding consumables available P P Material identification (type/grade) O O Welder identification system1 O O Fit-up of groove welds (including joint geometry)  Joint preparations  Dimensions (alignment, root opening, root face, bevel)  Cleanliness (condition of steel surfaces) O O  Tacking (tack weld quality and location)  Backing type and fit (if applicable)

Fit-up of CJP groove welds of HSS T, Y and K joints without backing (including joint geometry)  Joint preparations  Dimensions (alignment, root opening, root face, bevel) P O  Cleanliness (condition of steel surfaces)  Tacking (tack weld quality and location)

Configuration and finish of access holes O O Fit-up of fillet welds  Dimensions (alignment, gaps at root) O O  Cleanliness (condition of steel surfaces)  Tacking (tack weld quality and location) Check welding equipment O  1 DRAFT The fabricator or erector, as applicable, shall maintain a system by which a welder who has welded a joint or member can be identified. Stamps, if used, shall be the low-stress type.

261

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TABLE N5.4-2

Inspection Tasks During Welding

Inspection Tasks During Welding QC QA Control and handling of welding consumables  Packaging O O  Exposure control O O No welding over cracked tack welds Environmental conditions  Wind speed within limits O O  Precipitation and temperature WPS followed  Settings on welding equipment  Travel speed  Selected welding materials O O  Shielding gas type/flow rate  Preheat applied  Interpass temperature maintained (min./max.)  Proper position (F, V, H, OH) Welding techniques  Interpass and final cleaning O O  Each pass within profile limitations  Each pass meets quality requirements Placement and installationDRAFT of steel headed stud anchors P P 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278

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TABLE N5.4-3

Inspection Tasks After Welding

Inspection Tasks After Welding QC QA Welds cleaned O O Size, length and location of welds P P Welds meet visual acceptance criteria  Crack prohibition  Weld/base-metal fusion  Crater cross section P P  Weld profiles  Weld size  Undercut  Porosity Arc strikes P P k-area1 P P Weld access holes in rolled heavy shapes and built-up heavy shapes2 P P Backing removed and weld tabs removed (if required) P P Repair activities P P Document acceptance or rejection of welded joint or member P P No prohibited welds have been added without the approval of the engineer of O O record 1 When welding of doubler plates, continuity plates or stiffeners has been performed in the k-area, visually inspect the web k-area for cracks within 3 in. (75 mm) of the weld. 2 After rolled heavy shapes (see A3.1c) and built-up heavy shapes (see A3.1d) are welded, visually inspect the weld access hole for cracks 279 280 DRAFT 281 5. Nondestructive Testing of Welded Joints 282 283 5a. Procedures 284 285 Ultrasonic testing (UT), magnetic particle testing (MT), penetrant testing 286 (PT) and radiographic testing (RT), where required, shall be performed by 287 QA in accordance with AWS D1.1/D1.1M. Acceptance criteria shall be in 288 accordance with AWS D1.1/D1.1M for statically loaded structures, unless 289 otherwise designated in the design drawings or project specifications. 290 291 5b. CJP Groove Weld NDT 292 293 For structures in risk category III or IV, UT shall be performed by QA on 294 all CJP groove welds subject to transversely applied tension loading in 295 butt, T- and corner joints, in materials c in. (8 mm) thick or greater. For 296 structures in risk category II, UT shall be performed by QA on 10% of CJP 297 groove welds in butt, T- and corner joints subject to transversely applied 298 tension loading, in materials c in. (8 mm) thick or greater. 299 300 User Note: For structures in risk category I, NDT of CJP groove welds is 301 not required. For all structures in all risk categories, NDT of CJP groove 302 welds in materials less than c in. (8 mm) thick is not required. 303 304

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305 5c. Welded Joints Subjected to Fatigue 306 307 When required by Appendix 3, Table A-3.1, welded joints requiring weld 308 soundness to be established by radiographic or ultrasonic inspection shall 309 be tested by QA as prescribed. Reduction in the rate of UT is prohibited. 310 311 5d. Reduction of Rate of Ultrasonic Testing 312 313 The rate of UT is permitted to be reduced if approved by the EOR and the 314 AHJ. Where the initial rate for UT is 100%, the NDT rate for an individual 315 welder or welding operator is permitted to be reduced to 25%, provided the 316 reject rate, the number of welds containing unacceptable defects divided by 317 the number of welds completed, is demonstrated to be 5% or less of the 318 welds tested for the welder or welding operator. A sampling of at least 40 319 completed welds for a job shall be made for such reduction evaluation. For 320 evaluating the reject rate of continuous welds over 3 ft (1 m) in length 321 where the effective throat is 1 in. (25 mm) or less, each 12 in. (300 mm) 322 increment or fraction thereof shall be considered as one weld. For 323 evaluating the reject rate on continuous welds over 3 ft (1 m) in length 324 where the effective throat is greater than 1 in. (25 mm), each 6 in. (150 325 mm) of length or fraction thereof shall be considered one weld. 326 327 5e. Increase in Rate of Ultrasonic Testing 328 329 For structures in Risk Category II, where the initial rate for UT is 10%, the 330 NDT rate for an individual welder or welding operator shall be increased to 331 100% should the reject rate, the number of welds containing unacceptable 332 defects divided by the number of welds completed, exceeds 5% of the 333 welds tested for the welder or welding operator. A sampling of at least 20 334 completed welds for a job shall be made prior to implementing such an 335 increase. When the reject rate for the welder or welding operator, after a 336 sampling ofDRAFT at least 40 completed welds, has fallen to 5% or less, the rate 337 of UT shall be returned to 10%. For evaluating the reject rate of continuous 338 welds over 3 ft (1 m) in length where the effective throat is 1 in. (25 mm) 339 or less, each 12-in. (300 mm) increment or fraction thereof shall be 340 considered as one weld. For evaluating the reject rate on continuous welds 341 over 3 ft (1 m) in length where the effective throat is greater than 1 in. (25 342 mm), each 6 in. (150 mm) of length or fraction thereof shall be considered 343 one weld. 344 345 5f. Documentation 346 347 All NDT performed shall be documented. For shop fabrication, the NDT 348 report shall identify the tested weld by piece mark and location in the 349 piece. For field work, the NDT report shall identify the tested weld by 350 location in the structure, piece mark, and location in the piece. 351 352 When a weld is rejected on the basis of NDT, the NDT record shall 353 indicate the location of the defect and the basis of rejection. 354 355 6. Inspection of High-Strength Bolting 356 357 Observation of bolting operations shall be the primary method used to 358 confirm that the materials, procedures and workmanship incorporated in 359 construction are in conformance with the construction documents and the 360 provisions of the RCSC Specification.

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361 362 (a) For snug-tight joints, pre-installation verification testing as specified 363 in Table N5.6-1 and monitoring of the installation procedures as 364 specified in Table N5.6-2 are not applicable. The QCI and QAI need 365 not be present during the installation of fasteners in snug-tight 366 joints. 367 368 (b) For pretensioned joints and slip-critical joints, when the installer is 369 using the turn-of-nut method with matchmarking techniques, the di- 370 rect-tension-indicator method, or the twist-off-type tension control 371 bolt method, monitoring of bolt pretensioning procedures shall be as 372 specified in Table N5.6-2. The QCI and QAI need not be present 373 during the installation of fasteners when these methods are used by 374 the installer. 375 376 (c) For pretensioned joints and slip-critical joints, when the installer is 377 using the calibrated wrench method or the turn-of-nut method with- 378 out matchmarking, monitoring of bolt pretensioning procedures 379 shall be as specified in Table N5.6-2. The QCI and QAI shall be 380 engaged in their assigned inspection duties during installation of fas- 381 teners when these methods are used by the installer. 382 383 As a minimum, bolting inspection tasks shall be in accordance with Tables 384 N5.6-1, N5.6-2 and N5.6-3. In these tables, the inspection tasks are as 385 follows: 386 387 O  Observe these items on a random basis. Operations need not be 388 delayed pending these inspections. 389 P  Perform these tasks for each bolted connection. 390 DRAFT

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TABLE N5.6-1

Inspection Tasks Prior to Bolting

Inspection Tasks Prior to Bolting QC QA

Manufacturer’s certifications available for fastener materials O P Fasteners marked in accordance with ASTM requirements O O Proper fasteners selected for the joint detail (grade, type, bolt length if threads are O O to be excluded from shear plane) Proper bolting procedure selected for joint detail O O

Connecting elements, including the appropriate faying surface condition and hole O O preparation, if specified, meet applicable requirements

Pre-installation verification testing by installation personnel observed and P O documented for fastener assemblies and methods used

Proper storage provided for bolts, nuts, washers and other fastener components O O

391 TABLE N5.6-2

Inspection Tasks During Bolting

Inspection Tasks During Bolting QC QA Fastener assemblies, of suitable condition, placed in all holes and washers (if DRAFTO O required) are positioned as required

Joint brought to the snug-tight condition prior to the pretensioning operation O O

Fastener component not turned by the wrench prevented from rotating O O

Fasteners are pretensioned in accordance with the RCSC Specification, O O progressing systematically from the most rigid point toward the free edges 392 393 TABLE N5.6-3

Inspection Tasks After Bolting

Inspection Tasks After Bolting QC QA Document acceptance or rejection of bolted connections P P 394 395

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396 7. Inspection of Galvanized Structural Steel Main Members 397 398 Exposed cut surfaces of galvanized structural steel main members and 399 exposed corners of rectangular HSS shall be visually inspected for cracks 400 subsequent to galvanizing. Cracks shall be repaired or the member shall be 401 rejected. 402 403 User Note: It is normal practice for fabricated steel that requires hot dip 404 galvanizing to be delivered to the galvanizer, and then shipped to the 405 jobsite. As a result, inspection on site is common. 406 407 8. Other Inspection Tasks 408 409 The fabricator’s QCI shall inspect the fabricated steel to verify compliance 410 with the details shown on the shop drawings, such as proper application of 411 shop joint details at each connection. The erector’s QCI shall inspect the 412 erected steel frame to verify compliance with the field installed details 413 shown on the erection drawings, such as braces, stiffeners, member 414 locations and proper application of field joint details at each connection. 415 416 The QAI shall be on the premises for inspection during the placement of 417 anchor rods and other embedments supporting structural steel for compli- 418 ance with the construction documents. As a minimum, the diameter, grade, 419 type and length of the anchor rod or embedded item, and the extent or 420 depth of embedment into the concrete, shall be verified prior to placement 421 of concrete. 422 423 The QAI shall inspect the fabricated steel or erected steel frame, as 424 appropriate, to verify compliance with the details shown on the construc- 425 tion documents, such as braces, stiffeners, member locations and proper 426 application of joint details at each connection. 427 DRAFT 428 The acceptance or rejection of joint details and proper application of joint 429 details shall be documented. 430 431 N6. APPROVED FABRICATORS AND ERECTORS 432 433 QA inspections, except NDT, may be waived when the work is performed 434 in a fabricating shop or by an erector approved by the AHJ to perform the 435 work without QA. NDT of welds completed in an approved fabricator’s 436 shop may be performed by that fabricator when approved by the AHJ. 437 When the fabricator performs the NDT, the QA agency shall review the 438 fabricator’s NDT reports. 439 440 At completion of fabrication, the approved fabricator shall submit a 441 certificate of compliance to the AHJ stating that the materials supplied and 442 work performed by the fabricator are in accordance with the construction 443 documents. At completion of erection, the approved erector shall submit a 444 certificate of compliance to the AHJ stating that the materials supplied and 445 work performed by the erector are in accordance with the construction 446 documents. 447 448 N7. NONCONFORMING MATERIAL AND WORKMANSHIP 449 450 Identification and rejection of material or workmanship that is not in 451 conformance with the construction documents is permitted at any time

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452 during the progress of the work. However, this provision shall not relieve 453 the owner or the inspector of the obligation for timely, in-sequence 454 inspections. Nonconforming material and workmanship shall be brought to 455 the immediate attention of the fabricator or erector, as applicable. 456 457 Nonconforming material or workmanship shall be brought into conform- 458 ance, or made suitable for its intended purpose as determined by the 459 engineer of record. 460 461 Concurrent with the submittal of such reports to the AHJ, EOR or owner, 462 the QA agency shall submit to the fabricator and erector: 463 464 (a) Nonconformance reports 465 (b) Reports of repair, replacement or acceptance of nonconforming items

DRAFT

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP 1-1

1 2 APPENDIX 1 3 4 EXTENSIONS TO THE DIRECT ANALYSIS METHOD 5 6 This appendix extends the direct analysis method of design for stability, as defined 7 in Chapter C, by providing opportunities for using more advanced methods of 8 structural analysis to directly model member imperfections and/or the redistribution 9 of member and connection forces and moments as a result of localized yielding. 10 Design by the methods of Appendix 1 shall be conducted in accordance with 11 Section B3.1, using load and resistance factor design (LRFD). 12 13 The appendix is organized as follows: 14 15 1.1 Design by Direct Modeling of Member Imperfections 16 1.2 Design by Direct Modeling of Inelasticity 17 18 19 1.1 DESIGN BY DIRECT MODELING OF MEMBER IMPERFECTIONS 20 21 1. General Stability Requirements 22 23 Design by a second-order elastic analysis that includes the direct modeling of 24 member imperfections is permitted for all structures subject to the limitations 25 defined in this section. All requirements of Chapter C apply, with additional 26 requirements and exceptions as noted below. All load-dependent effects 27 shall be calculated at a level of loading corresponding to LRFD load 28 combinations. 29 30 The influenceDRAFT of torsion shall be considered, including its impact on member 31 deformations and second-order effects. 32 33 The provisions of this method apply only to doubly symmetric members, 34 including I-shaped, HSS and box-shaped members, unless evidence is 35 provided that the method is applicable to other member types. 36 37 2. Calculation of Required Strengths 38 39 For design using a second-order elastic analysis that includes the direct 40 modeling of member imperfections, the required strengths of components of 41 the structure shall be determined from an analysis conforming to Section C2, 42 with additional requirements and exceptions as noted below. 43 44 2a. General Analysis Requirements 45 46 The analysis of the structure shall also conform to the following require- 47 ments: 48 49 (a) Torsional member deformations shall be considered in the analysis. 50 51 (b) The analysis shall ensure that equilibrium and compatibility are 52 satisfied for the structure in its deformed shape, including all flexural, 53 shear, axial, and torsional deformations, and all other component and 54 connection deformations that contribute to the displacements of the

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

55 structure. The analysis shall consider P-Δ, P-δ, and all twisting effects 56 as applicable to the structure. The use of the approximate methods 57 appearing in Appendix 8 is not permitted. 58 59 User Note: A rigorous second-order analysis of the structure is an 60 important requirement for this method of design. Many analysis rou- 61 tines common in design offices are based on a more traditional sec- 62 ond-order analysis approach that includes only P-Δ and P-δ effects 63 without consideration of additional second-order effects related to 64 member twist, which can be significant for some members with un- 65 braced lengths near or exceeding Lr. A rigorous second-order analysis 66 as defined herein also includes the beneficial effects of additional 67 member torsional strength due to warping restraint, which can be con- 68 servatively neglected. Refer to the Commentary for additional infor- 69 mation and guidance. 70 71 (c) In all cases, the analysis shall directly model the effects of initial 72 imperfections due to both points of intersection of members displaced 73 from their nominal locations, and initial out-of-straightness or offsets 74 of members along their length. The magnitude of the initial displace- 75 ments shall be the maximum amount considered in the design; the 76 pattern of initial displacements shall be such that it provides the great- 77 est destabilizing effect. The use of notional loads to represent either 78 type of imperfection is not permitted. 79 80 User Note: Initial displacements similar in configuration to both dis- 81 placements due to loading and anticipated buckling modes should be 82 considered in the modeling of imperfections. The magnitude of the 83 initial points of intersection of members displaced from their nominal 84 locations should be based on permissible construction tolerances, as 85 specified in the AISC Code of Standard Practice for Steel Buildings 86 and BridgesDRAFT or other governing requirements, or on actual imperfec- 87 tions if known. When these displacements are due to erection toler- 88 ances, 1/500 is often considered, based on the tolerance of the out-of- 89 plumbness ratio specified in the Code of Standard Practice. For out- 90 of-straightness of members, a 1/1000 out-of-straightness ratio is often 91 considered. Refer to the Commentary for additional guidance. 92 93 2b. Adjustments to Stiffness 94 95 The analysis of the structure to determine the required strengths of 96 components shall use reduced stiffnesses as defined in Section C2.3. Such 97 stiffness reduction, including factors of 0.8 and τb, shall be applied to all 98 stiffnesses that are considered to contribute to the stability of the structure. 99 The use of notional loads to represent τb is not permitted. 100 101 User Note: Stiffness reduction should be applied to all member properties 102 including torsional properties (GJ and ECw) affecting twist of the member 103 cross section. One practical method of including stiffness reduction is to 104 reduce E and G by 0.8τb, leaving all member cross-section properties at their 105 nominal value. 106 107 Applying this stiffness reduction to some members and not others can, in 108 some cases, result in artificial distortion of the structure under load and 109 thereby lead to an unintended redistribution of forces. This can be avoided

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APP 1-3

110 by applying the reduction to all members, including those that do not 111 contribute to the stability of the structure. 112 113 3. Calculation of Available Strengths 114 115 For design using a second-order elastic analysis that includes the direct 116 modeling of member imperfections, the available strengths of members and 117 connections shall be calculated in accordance with the provisions of Chapters 118 D, E, F, G, H, I, J and K, as applicable, except as defined below, with no 119 further consideration of overall structure stability. 120 121 The nominal compressive strength of members, Pn, may be taken as the 122 cross-section compressive strength, FyAg or as FyAe, for members with 123 slender elements, with Ae as defined in Section E7. 124 125 1.2 DESIGN BY DIRECT MODELING OF INELASTICITY 126 127 User Note: Design by the provisions of this section is independent of the 128 requirements of Section 1.1. 129 130 1. GENERAL REQUIREMENTS 131 132 The design strength of the structural system and its members and connections 133 shall equal or exceed the required strength as determined by the inelastic 134 analysis. The provisions of Section 1.2 do not apply to seismic design. 135 136 The inelastic analysis shall take into account: (a) flexural, shear, , axial and 137 torsional member deformations, and all other component and connection 138 deformations that contribute to the displacements of the structure; (b) second- 139 order effects (including P-, , P-, and twisting effects); (c) geometric 140 imperfections; (d) stiffness reductions due to inelasticity, including partial 141 yielding of theDRAFT cross section which may be accentuated by the presence of 142 residual stresses; and (e) uncertainty in system, member, and connection 143 strength and stiffness. 144 145 Strength limit states detected by an inelastic analysis that incorporates all of 146 the above requirements are not subject to the corresponding provisions of the 147 Specification when a comparable or higher level of reliability is provided by 148 the analysis. Strength limit states not detected by the inelastic analysis shall 149 be evaluated using the corresponding provisions of Chapters D, E, F, G, H, I, 150 J and K. 151 152 Connections shall meet the requirements of Section B3.4. 153 154 Members and connections subject to inelastic deformations shall be shown to 155 have ductility consistent with the intended behavior of the structural system. 156 Force redistribution due to rupture of a member or connection is not 157 permitted. 158 159 Any method that uses inelastic analysis to proportion members and 160 connections to satisfy these general requirements is permitted. A design 161 method based on inelastic analysis that meets the preceding strength 162 requirements, the ductility requirements of Section 1.2.2, and the analysis 163 requirements of Section 1.2.3 satisfies these general requirements.

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

164 2. DUCTILITY REQUIREMENTS 165 Members and connections with elements subject to yielding shall be 166 proportioned such that all inelastic deformation demands are less than or 167 equal to their inelastic deformation capacities. In lieu of explicitly ensuring 168 that the inelastic deformation demands are less than or equal to their inelastic 169 deformation capacities, the following requirements shall be satisfied for steel 170 members subject to plastic hinging.

171 2a. Material 172 173 The specified minimum yield stress, Fy, of members subject to plastic 174 hinging shall not exceed 65 ksi (450 MPa).

175 2b. Cross Section 176 177 The cross section of members at plastic hinge locations shall be doubly 178 symmetric with width-to-thickness ratios of their compression elements not

179 exceeding pd, where pd is equal to p from Table B4.1b, except as modified 180 below: 181 182 (a) For the width-to-thickness ratio, h/tw, of webs of I-shaped sections, 183 rectangular HSS, and box-shaped sections subject to combined flexure 184 and compression 185

186 (1) When Pu/cPy  0.125

EP2.75 u 187 pd 3.76 1  (A-1-1) FPycy 188

189 (2) When Pu/cPy > 0.125 DRAFTEP E u 190 pd 1.12 2.33   1.49 (A-1-2) Fycyy PF 191 where 192 h = as defined in Section B4.1, in. (mm) 193 tw = web thickness, in. (mm) 194 Pu = required axial strength in compression, kips (N) 195 Py = FyAg = axial yield strength, kips (N) 196 c = resistance factor for compression = 0.90 197 198 (b) For the width-to-thickness ratio, b/t, of flanges of rectangular HSS and 199 box-shaped sections, and for flange cover plates, and diaphragm plates 200 between lines of fasteners or welds 201

202 pd = 0.94 EF/ y (A-1-3) 203 where 204 b = as defined in Section B4.1, in. (mm) 205 t = as defined in Section B4.1, in. (mm) 206 207 (c) For the diameter-to-thickness ratio, D/t, of circular HSS in flexure 208 209 pd = 0.045E/Fy (A-1-4) 210 211 where

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APP 1-5

212 D = outside diameter of round HSS, in. (mm)

213 2c. Unbraced Length 214 215 In prismatic member segments that contain plastic hinges, the laterally 216 unbraced length, Lb, shall not exceed Lpd, determined as follows. For 217 members subject to flexure only, or to flexure and axial tension, Lb shall be 218 taken as the length between points braced against lateral displacement of the 219 compression flange, or between points braced to prevent twist of the cross 220 section. For members subject to flexure and axial compression, Lb shall be 221 taken as the length between points braced against both lateral displacement in 222 the minor axis direction and twist of the cross section. 223 224 (a) For I-shaped members bent about their major axis: 225 226 M1 E (A-1-5) Lpdy0.12 0.076 r MF2 y 227 228 where 229 ry = radius of gyration about minor axis, in. (mm) 230 231 (1) When the magnitude of the bending moment at any location within 232 the unbraced length exceeds M2 233

234 MM12 / 1 (A-1-6a) 235 236 Otherwise: 237 238 (2) When Mmid < (M1 + M2) / 2 239 DRAFT  240 M11 M (A-1-6b) 241 242 (3) When Mmid > (M1 + M2) / 2 243  244 M12 2–MMMmid 2 (A-1-6c) 245 246 where 247 M1 = smaller moment at end of unbraced length, kip-in. (N-mm) 248 M2 = larger moment at end of unbraced length, kip-in. (N-mm). M2 249 shall be taken as positive in all cases. 250 Mmid = moment at middle of unbraced length, kip-in. (N-mm)  251 M 1 = effective moment at end of unbraced length opposite from

252 M2, kip-in. (N-mm) 253 254 The moments M1 and Mmid are individually taken as positive when 255 they cause compression in the same flange as the moment M2 and 256 negative otherwise. 257 258 (2) For solid rectangular bars and for rectangular HSS and box-shaped 259 members bent about their major axis 260

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

 M  E E 261 L  0.17  0.10 1  r  0.10 r (A-1-7) pd  M  F y F y  2  y y 262 263 For all types of members subject to axial compression and containing plastic 264 hinges, the laterally unbraced lengths about the cross section major and

265 minor axes shall not exceed 4.71rEFx y and 4.71rEFyy, respectively. 266 267 There is no Lpd limit for member segments containing plastic hinges in the 268 following cases: 269 270 (a) Members with circular or square cross sections subject only to flexure or 271 to combined flexure and tension 272 (b) Members subject only to flexure about their minor axis or combined 273 tension and flexure about their minor axis 274 (c) Members subject only to tension

275 2d. Axial Force 276 To assure ductility in compression members with plastic hinges, the 277 design strength in compression shall not exceed 0.75FyAg. 278 3. ANALYSIS REQUIREMENTS 279 280 The structural analysis shall satisfy the general requirements of Section 12..1. 281 These requirements are permitted to be satisfied by a second-order inelastic 282 analysis meeting the requirements of this Section. 283 284 Exception: 285 For continuous beams not subject to axial compression, a first-order inelastic 286 or plastic analysis is permitted and the requirements of Sections 1.2.3b and 287 1.2.3c are waived. 288 DRAFT 289 User Note: Refer to the Commentary for guidance in conducting a 290 traditional plastic analysis and design in conformance with these provisions.

291 3a. Material Properties and Yield Criteria 292 293 The specified minimum yield stress, Fy, and the stiffness of all steel members 294 and connections shall be reduced by a factor of 0.90 for the analysis, except 295 as stipulated in Section 1.2.3c. 296 297 The influence of axial force, major axis bending moment, and minor axis 298 bending moment shall be included in the calculation of the inelastic response. 299 300 The plastic strength of the member cross section shall be represented in the 301 analysis either by an elastic-perfectly-plastic yield criterion expressed in 302 terms of the axial force, major axis bending moment, and minor axis bending 303 moment, or by explicit modeling of the material stress-strain response as 304 elastic-perfectly-plastic.

305 3b. Geometric Imperfections 306 307 In all cases, the analysis shall directly model the effects of initial imperfec- 308 tions due to both points of intersection of members displaced from their 309 nominal locations, and initial out-of-straightness or offsets of members along

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP 1-7

310 their length. The magnitude of the initial displacements shall be the 311 maximum amount considered in the design; the pattern of initial displace- 312 ments shall be such that it provides the greatest destabilizing effect.

313 3c. Residual Stress and Partial Yielding Effects 314 315 The analysis shall include the influence of residual stresses and partial 316 yielding. This shall be done by explicitly modeling these effects in the 317 analysis or by reducing the stiffness of all structural components as specified 318 in Section C2.3. 319 320 If the provisions of Section C2.3 are used, then: 321 322 (a) The 0.9 stiffness reduction factor specified in Section 1.2.3a shall be 323 replaced by the reduction of the elastic modulus, E, by 0.8 as specified in 324 Section C2.3, and 325 326 (b) The elastic-perfectly-plastic yield criterion, expressed in terms of the 327 axial force, major axis bending moment, and minor axis bending mo- 328 ment, shall satisfy the cross section strength limit defined by Equations 329 H1-1a and H1-1b using Pc = 0.9Py, Mcx = 0.9Mpx and Mcy = 0.9Mpy. DRAFT

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP1-1

1 APPENDIX 2 2

3 DESIGN FOR PONDING 4 5 6 This appendix provides methods for determining whether a roof system has 7 adequate strength and stiffness to resist ponding. These methods are valid for flat 8 roofs with rectangular bays where the beams are uniformly spaced and the girders 9 are considered to be uniformly loaded. 10 11 The appendix is organized as follows: 12 13 2.1. Simplified Design for Ponding 14 2.2. Improved Design for Ponding 15 16 The members of a roof system shall be considered to have adequate strength and 17 stiffness against ponding by satisfying the requirements of Appendix 2, Sections 2.1 18 or 2.2. 19 20 21 2.1. SIMPLIFIED DESIGN FOR PONDING 22 23 The roof system shall be considered stable for ponding and no further 24 investigation is needed if both of the following two conditions are met: 25

26 Cp + 0.9Cs  0.25 (A-2-1) 27 4 -6 28 DRAFT Id  25(S )10 (A-2-2) 29 4 30 (S.I.: Id  3 940 S ) (A-2-2M) 31 where 4 32LLsp 32 Cp  7 (A-2-3) 10 I p 33 4 504LLsp 34 Cp  (S.I.) (A-2-3M) I p 4 32SLs 35 Cs  7 (A-2-4) 10 Is 36 4 504SLs 37 Cs  (S.I.) (A-2-4M) Is 38 39 Id = moment of inertia of the steel deck supported on secondary 40 members, in.4 per ft (mm4 per m) 4 4 41 Ip = moment of inertia of primary members, in. (mm ) 4 4 42 Is = moment of inertia of secondary members, in. (mm ) 43 Lp = length of primary members, ft (m) 44 Ls = length of secondary members, ft (m) 45 S = spacing of secondary members, ft (m)

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

46 47 For trusses and steel joists, the calculation of the moments of inertia, Ip and 48 Is, shall include the effects of web member strain when used in the above 49 equation. 50 51 User Note: When the moment of inertia is calculated using only the truss 52 or joist chord areas, the reduction in the moment of inertia due to web 53 member strain can typically be taken as 15%. 54 55 A steel deck shall be considered a secondary member when it is directly 56 supported by the primary members. 57 58 2.2. IMPROVED DESIGN FOR PONDING 59 60 It shall be permitted to use the provisions in this section when a more 61 accurate evaluation of framing stiffness is needed than that given by 62 Equations A-2-1 and A-2-2. 63 64 Define the stress indexes 65

0.8Ffyo U p   for the primary member (A-2-5) fo p 66 0.8Ffyo U s   for the secondary member  A-2-6 fo s 67 68 where 69 fo = stress due to impounded water due to either nominal rain or snow 70 loads (exclusive of the ponding contribution), and other loads acting 71 concurrently as specified in Section B2, ksi (MPa) 72 DRAFT 73 For roof framing consisting of primary and secondary members, evaluate 74 the combined stiffness as follows. Enter Figure A-2.1 at the level of the 75 computed stress index, Up, determined for the primary beam; move 76 horizontally to the computed Cs value of the secondary beams and then 77 downward to the abscissa scale. The combined stiffness of the primary and 78 secondary framing is sufficient to prevent ponding if the flexibility 79 coefficient read from this latter scale is more than the value of Cp comput- 80 ed for the given primary member; if not, a stiffer primary or secondary 81 beam, or combination of both, is required. 82 83 A similar procedure must be followed using Figure A-2.2. 84 85 For roof framing consisting of a series of equally spaced wall bearing 86 beams, evaluate the stiffness as follows. The beams are considered as 87 secondary members supported on an infinitely stiff primary member. For 88 this case, enter Figure A-2.2 with the computed stress index, Us. The 89 limiting value of Cs is determined by the intercept of a horizontal line 90 representing the Us value and the curve for Cp = 0. 91 92 93 94

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP1-3

DRAFT 95 96 97 Fig. A-2.1. Limiting flexibility coefficient for the primary systems. 98 99 100 Evaluate the stability against ponding of a roof consisting of a metal roof 101 deck of relatively slender depth-to-span ratio, spanning between beams 102 supported directly on columns, as follows. Use Figure A-2.1 or A-2.2, 103 using as Cs the flexibility coefficient for a one-foot (one-meter) width of 104 the roof deck (S = 1.0). 105

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

106 DRAFT 107 Fig.A-2.2. Limiting flexibility coefficient for the secondary systems.

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP3-1

APPENDIX 3

FATIGUE

This appendix applies to members and connections subject to high cycle loading within the elastic range of stresses of frequency and magnitude sufficient to initiate cracking and progressive failure.

User Note: See AISC Seismic Provisions for Structural Steel Buildings for structures subject to seismic loads.

The appendix is organized as follows:

3.1. General Provisions 3.2. Calculation of Maximum Stresses and Allowable Stress Ranges 3.3. Plain Material and Welded Joints 3.4. Bolts and Threaded Parts 3.5. Fabrication and Erection Requirements for Fatigue 3.6. Nondestructive Examination Requirements for Fatigue

3.1. GENERAL PROVISIONS

The fatigue resistance of members consisting of shapes or plate shall be determined when the number of cycles of application of live load exceeds 20,000. No evaluation of fatigue resistance of members consisting of HSS in building-type structures subject to code mandated wind loads is required. When the applied cyclic stress range is less than the threshold allowable stress range, FTH, no further evaluation of fatigue resistance is required. See Table A-3.1. The engineerDRAFT of record shall provide either complete details including weld sizes or shall specify the planned cycle life and the maximum range of moments, shears and reactions for the connections. The provisions of this Appendix shall apply to stresses calculated on the basis of the applied cyclic load spectrum. The maximum permitted stress due to peak cyclic loads shall be 0.66Fy. In the case of a stress reversal, the stress range shall be computed as the numerical sum of maximum repeated tensile and compressive stresses or the numerical sum of maximum shearing stresses of opposite direction at the point of probable crack initiation. The cyclic load resistance determined by the provisions of this Appendix is applicable to structures with suitable corrosion protection or subject only to mildly corrosive atmospheres, such as normal atmospheric conditions.

The cyclic load resistance determined by the provisions of this Appendix is applicable only to structures subject to temperatures not exceeding 300 F (150 C).

3.2. CALCULATION OF MAXIMUM STRESSES AND STRESS RANGES

Calculated stresses shall be based upon elastic analysis. Stresses shall not be amplified by stress concentration factors for geometrical discontinuities.

For bolts and threaded rods subject to axial tension, the calculated stresses shall include the effects of prying action, if any. In the case of axial stress combined with bending, the maximum stresses, of each kind, shall be those determined for concurrent arrangements of the applied load. Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP3-2

For members having symmetric cross sections, the fasteners and welds shall be arranged symmetrically about the axis of the member, or the total stresses including those due to eccentricity shall be included in the calculation of the stress range.

For axially loaded angle members where the center of gravity of the connecting welds lies between the line of the center of gravity of the angle cross section and the center of the connected leg, the effects of eccentricity shall be ignored. If the center of gravity of the connecting welds lies outside this zone, the total stresses, including those due to joint eccentricity, shall be included in the calculation of stress range.

3.3. PLAIN MATERIAL AND WELDED JOINTS

In plain material and welded joints the range of stress due to the applied cyclic loads shall not exceed the allowable stress range computed as follows.

(a) For stress categories A, B, B, C, D, E and E the allowable stress range, FSR, shall be determined by Equation A-3-1 or A-3-1M, as follows:

0.333 C f FSR1,000 F TH (A-3-1) nSR 0.333 C f FSR6,900 F TH (S.I.) (A-3-1M) nSR where Cf = constant from Table A-3.1 for the fatigue category FSR = allowable stress range, ksi (MPa) FTH = threshold allowable stress range, maximum stress range for indefinite design life from Table A-3.1, ksi (MPa) nSR = number of stress range fluctuations in design life DRAFT (b) For stress category F, the allowable stress range, FSR, shall be determined by Equation A-3-2 or A-3- 2M as follows:

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP3-3

0.167 1.5 FSR 100 8 ksi (A-3-2) nSR

0.167 1.5 FSR 690 55 MPa  S.I. (A-3-2M) nSR

(c) For tension-loaded plate elements connected at their end by cruciform, T or corner details with partial- joint-penetration (PJP) groove welds transverse to the direction of stress, with or without reinforcing or contouring fillet welds or if joined with only fillet welds, the allowable stress range on the cross section of the tension-loaded plate element shall be determined as the lesser of the following:

(1) Based upon crack initiation from the toe of the weld on the tension loaded plate element (i.e., when RPJP = 1.0), the allowable stress range, FSR, shall be determined by Equation A-3-1 or A-3-1M for stress category C.

(2) Based upon crack initiation from the root of the weld, the allowable stress range, FSR, on the tension loaded plate element using transverse PJP groove welds, with or without reinforcing or contouring fillet welds, the allowable stress range on the cross section at the root of the weld shall be determined by Equation A-3-3 or A-3-3M, for stress category C as follows:

0.333 4.4 FRSR  1, 000 PJP  (A-3-3) nSR 0.333 4.4 FRSR  6900PJP  S.I. (A-3-3M) nSR where RPJP, the reduction factor for reinforced or nonreinforced transverse PJP groove welds, is determined as follows: DRAFT 2aw  0.65 0.59 0.72  ttpp R  1.0 (A-3-4) PJP 0.167 t p

2aw  1.12 1.01 1.24  ttpp  RPJP 1.0 (S.I.) (A-3-4M) t0.167 p

2a = length of the nonwelded root face in the direction of the thickness of the tension- loaded plate, in. (mm) w = leg size of the reinforcing or contouring fillet, if any, in the direction of the thickness of the tension-loaded plate, in. (mm) tp = thickness of tension loaded plate, in. (mm)

If RPJP = 1.0, the stress range will be limited by the weld toe and category C will control.

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP3-4

(3) Based upon crack initiation from the roots of a pair of transverse fillet welds on opposite sides of the tension loaded plate element, the allowable stress range, FSR, on the cross section at the root of the welds shall be determined by Equation A-3-5 or A-3-5M, for stress category C as follows:

0.333 4.4 FRSR  1,000 FIL  (A-3-5) nSR

0.333 4.4 FRSR  6900FIL  S.I. (A-3-5M) n SR where RFIL is the reduction factor for joints using a pair of transverse fillet welds only.

0.06 0.72wt / p R 1.0 (A-3-6) FIL 0.167 t p

0.103 1.24wt / p R 1.0 S.I. (A-3-6M) FIL 0.167  t p

If RFIL = 1.0, the stress range will be limited by the weld toe and category C will control.

User Note: Stress categories C and C are cases where the fatigue crack initiates in the root of the weld. These cases do not have a fatigue threshold and cannot be designed for an infinite life. Infinite life can be approximated by use of a very high cycle life such as 2 x 108. Alternatively, if the size of the weld is increased such that RFIL or RPJP is equal to 1.0, then the base metal controls, resulting in stress category C where there is a fatigue threshold and the crack initiates at the toe of the weld.

3.4. BOLTS AND THREADED PARTS

In bolts and threadedDRAFT parts, the range of stress of the applied cyclic load shall not exceed the allowable stress range computed as follows.

(a) For mechanically fastened connections loaded in shear, the maximum range of stress in the connected material of the applied cyclic load shall not exceed the allowable stress range computed using Equation A-3-1 where Cf and FTH are taken from Section 2 of Table A-3.1.

(b) For high-strength bolts, common bolts, threaded anchor rods and hanger rods with cut, ground or rolled threads, the maximum range of tensile stress on the net tensile area from applied axial load and moment plus load due to prying action shall not exceed the allowable stress range computed using Equation A-3-1, where Cf and FTH are taken from Case 8.5 (stress category G). The net area in tension, At, is given by Equation A-3-7 or A-3-7M.

 0. 9743 2 AdF I (A-3-7) tb4 H n K

 2 Adtb0.9382 p S.I. (A-3-7M) 4

where

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP3-5

db = the nominal diameter (body or shank diameter), in. (mm) n = threads per in. p = pitch, (mm per thread)

For joints in which the material within the grip is not limited to steel or joints which are not tensioned to the requirements of Table J3.1 or J3.1M, all axial load and moment applied to the joint plus effects of any prying action shall be assumed to be carried exclusively by the bolts or rods.

For joints in which the material within the grip is limited to steel and which are pretensioned to the requirements of Table J3.1 or J3.1M, an analysis of the relative stiffness of the connected parts and bolts is permitted to be used to determine the tensile stress range in the pretensioned bolts due to the total applied cyclic load and moment plus effects of any prying action. Alternatively, the stress range in the bolts shall be assumed to be equal to the stress on the net tensile area due to 20% of the absolute value of the applied cyclic axial load and moment from dead, live and other loads.

3.5. FABRICATION AND ERECTION REQUIREMENTS FOR FATIGUE

Longitudinal steel backing, if used, shall be continuous. If splicing of steel backing is required for long joints, the splice shall be made with a complete joint penetration groove weld, ground flush to permit a tight fit. If fillet welds are used to attach left-in-place longitudinal backing, they shall be continuous.

In transverse complete-joint-penetration T- and corner-joints, a reinforcing fillet weld, not less than ¼ in. (6 mm) in size shall be added at reentrant corners.

The surface roughness of thermally cut edges subject to cyclic stress ranges, that include tension, shall not exceed 1,000 in. (25 m), where ASME B46.1 is the reference standard.

User Note: AWS C4.1 Sample 3 may be used to evaluate compliance with this requirement.

Reentrant corners at cuts, copes and weld access holes shall form a radius not less than the prescribed radius in Table A-3.1DRAFT by predrilling or subpunching and reaming a hole, or by thermal cutting to form the radius of the cut.

For transverse butt joints in regions of tensile stress, weld tabs shall be used to provide for cascading the weld termination outside the finished joint. End dams shall not be used. Weld tabs shall be removed and the end of the weld finished flush with the edge of the member.

Fillet welds subject to cyclic loading normal to the outstanding legs of angles or on the outer edges of end plates shall have end returns around the corner for a distance not less than two times the weld size; the end return distance shall not exceed four times the weld size.

3.6. NONDESTRUCTIVE EXAMINATION REQUIREMENTS FOR FATIGUE

In the case of complete-joint-penetration groove welds, the maximum allowable stress range calculated by Equation A-3-1 applies only to welds that have been ultrasonically or radiographically tested and meet the acceptance requirements of Sections 6.12.2 or 6.13.2 of AWS D1.1/D1.1M.

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP3-6

TABLE A-3.1 Fatigue Design Parameters

Description Stress Constant Threshold Potential Crack Category Cf FTH Initiation Point ksi (MPa)

SECTION 1 – PLAIN MATERIAL AWAY FROM ANY WELDING

1.1 Base metal, except noncoated weathering steel, with as-rolled or Away from all cleaned surfaces. Flame-cut edges A 25 24 welds or structural with surface roughness value of 1,000 (165) connections in. (25 m) or less, but without reentrant corners. 1.2 Noncoated weathering steel base metal with as-rolled or cleaned Away from all surfaces. Flame-cut edges with surface B 12 16 welds or structural roughness value of 1,000 in. (25 m) (110) connections or less, but without reentrant corners. 1.3 Member with reentrant corners at copes, cuts, block-outs or other At any external geometrical discontinuities, except weld edge or at hole access holes. perimeter R ≥ 1 in. (25 mm) with radius formed by predrilling, subpunching and reaming or C 4.4 10 thermally cut and ground to a bright (69) metal surface

R ≥ 3/8 in. (10 mm) and the radius need not be ground to a bright metal surface E’ 0.39 2.6 (18)

1.4 Rolled cross sections with weld access holes made to requirements of At reentrant cor- Section J1.6. ner of weld Access hole R ≥ 1 in. (25 mm) with access hole radius formed by DRAFTpredrilling, C 4.4 10 subpunching and reaming or thermally (69) cut and ground to a bright metal surface

Access hole R ≥ 3/8 in. (10 mm) and the E’ radius need not be ground to a bright 0.39 2.6 (18) metal surface 1.5 Members with drilled or reamed In net section holes. originating at 10 side of the hole C 4.4 (69) Holes containing pretensioned bolts

Open holes without bolts D 2.2 7 (48) SECTION 2 – CONNECTED MATERIAL IN MECHANICALLY FASTENED JOINTS

2.1 Gross area of base metal in lap joints connected by high-strength bolts B 12 16 Through gross in joints satisfying all requirements for (110) section near hole slip-critical connections. 2.2 Base metal at net section of high- strength bolted joints, designed on the In net section basis of bearing resistance, but B 12 16 originating at side fabricated and installed to all (110) of hole requirements for slip-critical connections. 2.3 Base metal at the net section of riveted joints. C 4.4 10 In net section (69) originating at side of hole Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP3-7

2.4 Base metal at net section of eyebar E 1.1 4.5 In net section head or pin plate. (31) originating at side of hole

TABLE A-3.1 (cont’d)

Fatigue Design Parameters

DRAFT

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP3-8

DRAFT

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP3-9

TABLE A-3.1 (Cont’d)

Fatigue Design Parameters

Description Stress Constant Threshold Potential Crack Category Cf, FTH Initiation Point ksi (MPa) SECTION 3 – WELDED JOINTS JOINING COMPONENTS OF BUILT-UP MEMBERS

3.1 Base metal and weld metal in From surface or members without attachments built up internal of plates or shapes connected by B 12 16 discontinuities in continuous longitudinal complete-joint- weld (110) penetration groove welds, back gouged and welded from second side, or by continuous fillet welds.

3.2 Base metal and weld metal in From surface or members without attachments built up internal of plates or shapes, connected by discontinuities in 6.1 12 continuous longitudinal complete-joint- B weld penetration groove welds with left-in- (83) place continuous steel backing, or by continuous partial-joint -penetration groove welds.

3.3 Base metal at the ends of From the weld longitudinal welds that terminate at weld termination into access holes in connected built-up the web or flange

members, as well as weld toes of fillet welds that wrap around ends of weld access holes. 7 Access hole R ≥ 1 in. (25mm) with D 2.2 (48) radius formed by predrilling, subpunching and reaming or thermally cut and ground to bright metal surface

Access hole R ≥ 3/8 in. (10DRAFT mm) and the 2.6 (18) radius need not be ground to a bright E’ 0.39 metal surface

3.4 Base metal at ends of longitudinal E 1.1 4.5 In connected intermittent fillet weld segments. (31) material at start and stop locations of any weld

3.5 Base metal at ends of partial length In flange at toe of welded coverplates narrower than the end weld (if flange having square or tapered ends, present) or in

with or without welds across the ends. flange at termination of longitudinal weld

Flange thickness  0.8 in. (20 mm) E 1.1 4.5 (31)

Flange thickness > 0.8 in. (20 mm) E 0.39 2.6 (18) 3.6 Base metal at ends of partial length In flange at toe of welded coverplates or other end weld or in attachments wider than the flange with flange at welds across the ends. termination of

longitudinal weld Flange thickness  0.8 in. (20 mm) E 1.1 4.5 or in edge of (31) flange

Flange thickness > 0.8 in. (20 mm) E 0.39 2.6 (18)

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP3-10

3.7 Base metal at ends of partial length In edge of flange welded coverplates wider than the at end of flange without welds across the ends. coverplate weld

Flange thickness  0.8 in. (20 mm) E 0.39 2.6 (18) Flange thickness > 0.8 in. (20 mm) is None not permitted

SECTION 4 – LONGITUDINAL FILLET WELDED END CONNECTIONS

4.1 Base metal at junction of axially Initiating from end loaded members with longitudinally of any weld welded end connections. Welds are on termination

each side of the axis of the member to extending into the balance weld stresses. base metal

t  0.5 in. (12 mm) E 1.1 4.5 (31)

t > 0.5 in. (12 mm) E 0.39 2.6 (18) DRAFT

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP3-11

DRAFT

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP3-12

DRAFT

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP3-13

TABLE A-3.1 (Cont’d)

Fatigue Design Parameters

Description Stress Constant Threshold Potential Crack Category Cf FTH Initiation Point ksi (MPa) SECTION 5 – WELDED JOINTS TRANSVERSE TO DIRECTION OF STRESS 5.1 Weld metal and base metal in or adjacent to complete-joint-penetration From internal groove welded splices in plate, rolled discontinuities in shapes or built-up cross sections with B 12 16 weld metal or no change in cross section with welds along the fusion ground essentially parallel to the (110) boundary direction of stress and inspected in accordance with Section 3.6. 5.2 Weld metal and base metal in or adjacent to complete-joint-penetration From internal groove welded splices with welds discontinuities in ground essentially parallel to the metal or along the direction of stress at transitions in fusion boundary or thickness or width made on a slope no at start of greater than 1:2½ and inspected in transition when Fy accordance with Section 3.6.  90 ksi (620 MPa)

Fy < 90 ksi (620 MPa) B 12 16

(110)

Fy  90 ksi (620 MPa) B 6.1 12 (83) 5.3 Base metal and weld metal in or adjacent to complete-joint- penetration From internal groove welded splices with welds discontinuities in ground essentially parallel to the weld metal or direction of stress at transitions in width along the fusion made on a radius of not less than 24 in. B 12 16 boundary (600 mm) with the point ofDRAFT tangency at (110) the end of the groove weld and inspected in accordance with Section 3.6. 5.4 Weld metal and base metal in or adjacent to complete-joint- penetration From weld groove welds in T or corner joints or extending into splices, without transitions in thickness base metal or into C 4.4 10 or with transition in thickness having weld metal slopes no greater than 1:2½, when weld (69) reinforcement is not removed and inspected in accordance with Section 3.6. 5.5 Base metal and weld metal in or From the toe of the adjacent to transverse CJP groove groove weld or the welded butt splices with backing left in toe of the weld place. attaching backing

when applicable Tack welds inside groove D 2.2 7 (48)

Tack welds outside the groove and not 1.1 closer than ½ in. (12 mm) to the edge of E 4.5 (31) base metal.

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP3-14

5.6 Base metal and weld metal at transverse end connections of tension- loaded plate elements using partial- joint- penetration groove welds in butt. T

or corner joints, with reinforcing or

contouring fillets, FSR shall be the smaller of the toe crack or root crack allowable stress range. Initiating from weld Crack initiating from weld toe: C 4.4 10 toe extending into (69) base metal

Initiating at weld

See Eqn. root extending into Crack initiating from weld root: C A-3-3 or None and through weld A-3-3M

DRAFT

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP3-15

TABLE A-3.1 (Cont’d)

Fatigue Design Parameters

DRAFT

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP3-16

DRAFT

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP3-17

TABLE A-3.1 (Cont’d) Fatigue Design Parameters

Description Stress Constant Threshold Potential Crack Category Cf FTH Initiation Point ksi (MPa) SECTION 5 – WELDED JOINTS TRANSVERSE TO DIRECTION OF STRESS (cont’d)

5.7 Base metal and weld metal at transverse end connections of tension- loaded plate elements using a pair of fillet welds on opposite sides of the plate. FSR shall be the smaller of the toe crack or root crack allowable stress range. Initiating from weld Crack initiating from weld toe: C 4.4 10 toe extending into (69) base metal

See Eqn.

A-3-5 or

Crack initiating from weld root: A-3-5M C'' None Initiating at weld

root extending into and through weld

5.8 Base metal of tension loaded plate C 4.4 10 From geometrical elements and on built-up shapes and (69) discontinuity at toe rolled beam webs or flanges at toe of of fillet extending transverse fillet welds DRAFTadjacent to into base metal welded transverse stiffeners.

SECTION 6 – BASE METAL AT WELDED TRANSVERSE MEMBER CONNECTIONS

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP3-18

6.1 Base metal of equal or unequal Near point of thickness at details attached by tangency of radius complete-joint-penetration groove welds at edge of member subject to longitudinal loading only when the detail embodies a transition radius, R, with the weld termination ground smooth and inspected in accordance with Section 3.6. 12 16 R  24 in. (600 mm) B (110)

C 4.4 10 6 in. ≤ R < 24 in. (150 mm ≤ R < 600 mm) (69)

D 2.2 7 2 in. ≤ R < 6 in. (48)

(50 mm ≤ R < 150 mm)

E 1.1 4.5 R < 2 in. (50 mm) (31)

DRAFT

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP3-19

TABLE A-3.1 (Cont’d) Fatigue Design Parameters

DRAFT

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP3-20

TABLE A-3.1 (Cont’d)

Fatigue Design Parameters Description Stress Constant Threshold Potential Crack Category Cf FTH Initiation Point ksi (MPa)

SECTION 6 – BASE METAL AT WELDED TRANSVERSE MEMBER CONNECTIONS (cont’d)

6.2 Base metal at details of equal thickness attached by complete-joint- penetration groove welds, subject to transverse loading with or without longitudinal loading, when the detail embodies a transition radius, R, with the weld termination ground smooth and inspected in accordance with Section 3.6.

------

(a) When weld reinforcement is Near points of removed: tangency of radius or in the weld or at R  24 in. (600 mm) 12 16 fusion boundary or B (110) member or attachment 6 in. ≤ R < 24 in. C 10 4.4 (150 mm ≤ R < 600 mm) (69)

2 in. ≤ R < 6 in. D 2.2 7 (50 mm ≤ R < 150 mm) (48)

R < 2 in. (50 mm) E 1.1 4.5

(31)

(b) When weld reinforcement is not At toe of the weld removed: DRAFT either along edge of member or the R  6 in. (150 mm) 10 C 4.4 attachment (69)

2 in. ≤ R < 6 in. D 7 2.2 (50 mm ≤ R < 150 mm) (48)

R < 2 in. (50 mm) E 1.1 4.5 (31)

6.3 Base metal at details of unequal thickness attached by complete-joint- penetration groove welds, subject to transverse loading with or without longitudinal loading, when the detail embodies a transition radius, R, with the weld termination ground smooth and in accordance with Section 3.6: ------

(a) When weld reinforcement is removed:

R > 2 in. (50 mm) D 2.2 7 (48) At toe of weld along edge of thinner material R  2 in. (50 mm) 4.5 E 1.1 In weld termination (b) When reinforcement is not removed: (31) in small radius Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP3-21

Any radius 4.5 At toe of weld (31) along edge of thinner material E 1.1

TABLE A-3.1 (Cont’d) Fatigue Design Parameters

DRAFT

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP3-22

TABLE A-3.1 (Cont’d) Fatigue Design Parameters

Description Stress Constant Threshold Potential Crack Category Cf FTH Initiation Point ksi (MPa) SECTION 6 – BASE METAL AT WELDED TRANSVERSE MEMBER CONNECTIONS (cont’d) 6.4 Base metal of equal or unequal Initiating in base thickness, subject to longitudinal stress metal at the weld at transverse members, with or without termination or at transverse stress, attached by fillet or the toe of the weld partial-joint-penetration groove welds extending into the parallel to direction of stress when the base metal detail embodies a transition radius, R, with weld termination ground smooth: D 2.2 7 R > 2 in. (50 mm) (48)

E 1.1 R  2 in. (50 mm) 4.5 (31)

SECTION 7 – BASE METAL AT SHORT ATTACHMENTS1 7.1 Base metal subject to longitudinal Initiating in base loading at details with welds parallel or metal at the weld transverse to the direction of stress with termination or at or without transverse load on the detail, the toe of the weld where the detail embodies no transition extending into the radius and with detail length, a, in base metal direction of stress and thickness of the attachment, b:

a < 2 in. (50 mm) for any thickness, b C 4.4 10 (69) DRAFT

2 in. (50 mm)  a  lesser of 12 b D 2.2 7 or 4 in. (100 mm) (48)

a > lesser of 12b or 4 in. (100 mm) E 1.1 4.5 when b  0.8 in. (20 mm) (31)

0.39 a > 4 in. (100 mm) E when b > 0.8 in. (20 mm) 2.6 (18)

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP3-23

7.2 Base metal subject to longitudinal Initiating in base stress at details attached by fillet or metal at the weld partial-joint-penetration groove welds, termination, with or without transverse load on extending into the detail, when the detail embodies a base metal transition radius, R, with weld termination ground smooth:

R > 2 in. (50 mm) D 2.2 7 (48)

1.1 E 4.5 R  2 in. (50 mm) (31)

1 “Attachment” as used herein is defined as any steel detail welded to a member, which causes a deviation in the stress flow in the member and thus reduces the fatigue resistance. The reduction is due to the presence of the attachment, not due to the loading on the attachment.

DRAFT

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP3-24

TABLE A-3.1 (Cont’d) Fatigue Design Parameters

DRAFT

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP3-25

TABLE A-3.1 (Cont’d) Fatigue Design Parameters

Description Stress Constant Threshold Potential Crack Category Cf FTH Initiation Point ksi (MPa)

SECTION 8 - MISCELLANEOUS

8.1 Base metal at steel headed stud C 4.4 10 At toe of weld in anchors attached by fillet weld or (69) base metal automatic stud welding.

8.2 Shear on throat of any fillet weld, F See Eqn. See Eqn. Initiating at the continuous or intermittent, longitudinal A-3-2 or A-3-2 or root of the fillet or transverse. weld, extending A-3-2M A-3-2M into the weld

8.3 Base metal at plug or slot welds. E 1.1 4.5 Initiating in the (31) base metal at the end of the plug or slot weld, extending into the base metal

8.4 Shear on plug or slot welds. F See Eqn. See Eqn. Initiating in the A-3-2 or A-3-2 or weld at the faying surface, extending A-3-2M A-3-2M into the weld

8.5 High-strength bolts, commonDRAFT bolts, G 0.39 7 Initiating at the threaded anchor rods, and hanger rods, (48) root of the threads, whether pretensioned in accordance extending into the with Table J3.1 or J3.1M or snug fastener tightened with cut, ground or rolled threads. Stress range on tensile stress area due to applied cyclic load plus prying action when applicable.

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP3-26

TABLE A-3.1 (Cont’d) Fatigue Design Parameters

DRAFT

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

1 APPENDIX 4 2

3 STRUCTURAL DESIGN FOR FIRE CONDITIONS 4 5 6 This appendix provides criteria for the design and evaluation of structural steel 7 components, systems and frames for fire conditions. These criteria provide for the 8 determination of the heat input, thermal expansion and degradation in mechanical 9 properties of materials at elevated temperatures that cause progressive decrease in 10 strength and stiffness of structural components and systems at elevated 11 temperatures. 12 13 The appendix is organized as follows: 14 15 4.1. General Provisions 16 4.2. Structural Design for Fire Conditions by Analysis 17 4.3. Design by Qualification Testing

18 4.1. GENERAL PROVISIONS 19 20 The methods contained in this appendix provide regulatory evidence of 21 compliance in accordance with the design applications outlined in this 22 section. 23 24 1. Performance Objective 25 26 Structural components, members and building frame systems shall be 27 designed so as to maintain their load-bearing function during the design- 28 basis fire and to satisfy other performance requirements specified for the 29 building occupancy.DRAFT 30 31 Deformation criteria shall be applied where the means of providing 32 structural fire resistance, or the design criteria for fire barriers, requires 33 evaluation of the deformation of the load-carrying structure. 34 35 Within the compartment of fire origin, forces and deformations from the 36 design-basis fire shall not cause a breach of horizontal or vertical com- 37 partmentation. 38 39 2. Design by Engineering Analysis 40 41 The analysis methods in Section 4.2 are permitted to be used to document 42 the anticipated performance of steel framing when subjected to design- 43 basis fire scenarios. Methods in Section 4.2 provide evidence of compli- 44 ance with performance objectives established in Section 4.1.1. 45 46 The analysis methods in Section 4.2 are permitted to be used to demon- 47 strate an equivalency for an alternative material or method, as permitted by 48 the applicable building code. 49 50 Structural design for fire conditions using Appendix 4.2 shall be performed 51 using the load and resistance factor design method in accordance with the 52 provisions of Section B3.3 (LRFD).

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP4-2

53 54 3. Design by Qualification Testing 55 56 The qualification testing methods in Section 4.3 are permitted to be used to 57 document the fire resistance of steel framing subject to the standardized 58 fire testing protocols required by the applicable building code. 59 4. Load Combinations and Required Strength 60 61 In the absence of applicable building code provisions for design under fire 62 exposures, the required strength of the structure and its elements shall be 63 determined from the gravity load combination as follows: 64 65 [0.9 or 1.2] D + T + 0.5L + 0.2S (A-4-1) 66 67 where 68 D = nominal dead load 69 L = nominal occupancy live load 70 S = nominal snow load 71 T = nominal forces and deformations due to the design-basis fire de- 72 fined in Section 4.2.1. 73 74 User Note: ASCE/SEI 7 Section 2.5 contains this load combination for 75 extraordinary events, which includes fire. 76 77 A notional load, Ni = 0.002Yi, as defined in Section C2.2, where Ni = 78 notional load applied at framing level i and Yi = gravity load from combi- 79 nation A-4-1 acting on framing level i, shall be applied in combination 80 with the loads stipulated in Equation A-4-1. Unless otherwise stipulated 81 by the applicable building code, D, L and S shall be the nominal loads 82 specified in ASCE/SEI 7.

83 4.2. STRUCTURALDRAFT DESIGN FOR FIRE CONDITIONS BY ANALYSIS 84 85 It is permitted to design structural members, components and building 86 frames for elevated temperatures in accordance with the requirements of 87 this section. 88 89 1. Design-Basis Fire 90 91 A design-basis fire shall be identified to describe the heating conditions for 92 the structure. These heating conditions shall relate to the fuel commodities 93 and compartment characteristics present in the assumed fire area. The total 94 fuel load shall be determined for the occupancy of the space. Heating 95 conditions shall be specified either in terms of a heat flux or temperature of 96 the upper gas layer created by the fire. The variation of the heating 97 conditions with time shall be determined for the duration of the fire. 98 99 The analysis methods in Section 4.2 shall be used in accordance with the 100 provisions for alternative materials, designs and methods as permitted by 101 the applicable building code. Where the analysis methods in Section 4.2 102 are used to demonstrate equivalency to hourly ratings based on qualifica- 103 tion testing in Section 4.3, the design-basis fire shall be permitted to be 104 determined in accordance with ASTM E119. 105 1a. Localized Fire 106 Specification for Structural Steel Buildings, public review draft dated March 2, 2015

AMERICAN INSTITUTE OF STEEL CONSTRUCTION

107 Where the heat release rate from the fire is insufficient to cause flashover, 108 a localized fire exposure shall be assumed. In such cases, the fuel compo- 109 sition, arrangement of the fuel array and floor area occupied by the fuel 110 shall be used to determine the radiant heat flux from the flame and smoke 111 plume to the structure. 112 113 1b. Post-Flashover Compartment Fires 114 115 Where the heat release rate from the fire is sufficient to cause flashover, a 116 post-flashover compartment fire shall be assumed. The determination of 117 the temperature versus time profile resulting from the fire shall include fuel 118 load, ventilation characteristics of the space (natural and mechanical), 119 compartment dimensions and thermal characteristics of the compartment 120 boundary. 121 122 The fire duration in a particular area shall be determined from the total 123 combustible mass, or fuel load in the space. In the case of either a 124 localized fire or a post-flashover compartment fire, the fire duration shall 125 be determined as the total combustible mass divided by the mass loss rate. 126 127 1c. Exterior Fires 128 129 The exposure effects of the exterior structure to flames projecting from 130 windows or other wall openings as a result of a post-flashover compart- 131 ment fire shall be addressed along with the radiation from the interior fire 132 through the opening. The shape and length of the flame projection shall be 133 used along with the distance between the flame and the exterior steelwork 134 to determine the heat flux to the steel. The method identified in Section 135 4.2.1b shall be used for describing the characteristics of the interior 136 compartment fire. 137 138 1d. Active FireDRAFT Protection Systems 139 140 The effects of active fire protection systems shall be addressed when 141 describing the design-basis fire. 142 143 Where automatic smoke and heat vents are installed in nonsprinklered 144 spaces, the resulting smoke temperature shall be determined from calcula- 145 tion. 146 147 2. Temperatures in Structural Systems under Fire Conditions 148 149 Temperatures within structural members, components and frames due to 150 the heating conditions posed by the design-basis fire shall be determined 151 by a heat transfer analysis. 152 153 3. Material Strengths at Elevated Temperatures 154 155 Material properties at elevated temperatures shall be determined from 156 test data. In the absence of such data, it is permitted to use the material 157 properties stipulated in this section. These relationships do not apply for 158 steels with yield strengths in excess of 65 ksi (448 MPa) or concretes 159 with specified compression strength in excess of 8,000 psi (55 MPa). 160 161 3a. Thermal Elongation

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP4-4

162 163 The coefficients of expansion shall be taken as follows: 164 (a) For structural and reinforcing steels: For calculations at tempera- 165 tures above 150 F (65 C), the coefficient of thermal expansion 166 shall be 7.8  10-6/F (1.4  10-5/oC). 167 168 (b) For normal weight concrete: For calculations at temperatures above 169 150 F (65 C), the coefficient of thermal expansion shall be 1.0  170 10-5/F (1.8  10-5/oC). 171 172 (c) For lightweight concrete: For calculations at temperatures above 173 150 F (65 C), the coefficient of thermal expansion shall be 4.4  174 10-6/F (7.9  10-6/oC). 175 176 3b. Mechanical Properties at Elevated Temperatures 177 178 The deterioration in strength and stiffness of structural members, com- 179 ponents and systems shall be taken into account in the structural analysis 180 of the frame. The values Fy(T), Fp(T), Fu(T), E(T), G(T), Fnt(T), Fnv(T), 181 fc(T), Ec(T) and cu(T) at elevated temperature to be used in structural 182 analysis, expressed as the ratio with respect to the property at ambient, 183 assumed to be 68 F (20 C), shall be defined as in Tables A-4.2.1, A- 184 4.2.2 and A-4.2.3. Fp(T) is the proportional limit at elevated tempera- 185 tures, which is calculated as a ratio to yield strength as specified in Table 186 A-4.2.1. It is permitted to interpolate between these values. 187

188 For lightweight concrete, values of cu shall be obtained from tests. TABLE A-4.2.1 PropertiesDRAFT of Steel at Elevated Temperatures

Steel Temperature, kE = E(T)/E k = F (T)/F k = F (T)/F k = F (T)/F ºF (ºC) = G(T)/G p p y y y y u u y 68 (20) 1.00 1.00 1.00 1.00 200 (93) 1.00 1.00 1.00 1.00 400(204) 0.90 0.80 1.00 1.00 600 (316) 0.78 0.58 1.00 1.00 750 (399) 0.70 0.42 1.00 1.00 800 (427) 0.67 0.40 0.94 0.94 1000 (538) 0.49 0.29 0.66 0.66 1200 (649) 0.22 0.13 0.35 0.35 1400 (760) 0.11 0.06 0.16 0.16 1600 (871) 0.07 0.04 0.07 0.07 1800 (982) 0.05 0.03 0.04 0.04 2000 (1093) 0.02 0.01 0.02 0.02 2200 (1204) 0.00 0.00 0.00 0.00 189 190 191 192 193

Specification for Structural Steel Buildings, public review draft dated March 2, 2015

AMERICAN INSTITUTE OF STEEL CONSTRUCTION

TABLE A-4.2.2 Properties of Concrete at Elevated Temperatures

Concrete k c = fc(T) / fc εcu(T), % Temperature

Normal weight Lightweight Normal weight ºF (ºC) concrete concrete Ec(T) / Ec concrete 68 (20) 1.00 1.00 1.00 0.25 200 (93) 0.95 1.00 0.93 0.34 400( 204) 0.90 1.00 0.75 0.46 550 (288) 0.86 1.00 0.61 0.58 600 (316) 0.83 0.98 0.57 0.62 800 (427) 0.71 0.85 0.38 0.80 1000 (538) 0.54 0.71 0.20 1.06 1200 (649) 0.38 0.58 0.092 1.32 1400 (760) 0.21 0.45 0.073 1.43 1600 (871) 0.10 0.31 0.055 1.49 1800(982) 0.05 0.18 0.036 1.50 2000 (1093) 0.01 0.05 0.018 1.50 2200 (1204) 0.00 0.00 0.000 0.00 194 195 TABLE A-4.2.3 Properties of Group A and Group B High Strength Bolts At Elevated Temperatures Bolt Temperature °F (°C) Fnt (T)/Fnt or Fnv(T)/Fnv 68 (20) 1.00 200 (93) 0.97 300 DRAFT(149) 0.95 400 (204) 0.93 600 (316) 0.88 800 (427) 0.71 900 (482) 0.59 1000 (538) 0.42 1200 (649) 0.16 1400 (760) 0.08 1600 (871) 0.04 1800 (982) 0.01 2000 (1093) 0 196 197 198 199 4. Structural Design Requirements 200 201 4a. General Structural Integrity 202 203 The structural frame and foundation shall be capable of providing the 204 strength and deformation capacity to withstand, as a system, the structural 205 actions developed during the fire within the prescribed limits of defor- 206 mation. The structural system shall be designed to sustain local damage 207 with the structural system as a whole remaining stable.

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP4-6

208 209 Continuous load paths shall be provided to transfer all forces from the 210 exposed region to the final point of resistance. 211 212 4b. Strength Requirements and Deformation Limits 213 214 Conformance of the structural system to these requirements shall be 215 demonstrated by constructing a mathematical model of the structure based 216 on principles of structural mechanics and evaluating this model for the 217 internal forces and deformations in the members of the structure developed 218 by the temperatures from the design-basis fire. 219 220 Individual members shall have the design strength necessary to resist the 221 shears, axial forces and moments determined in accordance with these 222 provisions. 223 224 Connections shall develop the strength of the connected members or the 225 forces. Where the means of providing fire resistance requires the evalua- 226 tion of deformation criteria, the deformation of the structural system, or 227 members thereof, under the design-basis fire shall not exceed the pre- 228 scribed limits. 229 230 It shall be permitted to include membrane action of composite floor slabs 231 for fire resistance if the design provides for the effects of increased 232 connection tensile forces and redistributed gravity load demands on the 233 adjacent framing supports. 234 235 4c. Methods of Analysis 236 237 1. Advanced Methods of Analysis 238 239 The methodsDRAFT of analysis in this section are permitted for the design of all 240 steel building structures for fire conditions. The design-basis fire exposure 241 shall be that determined in Section 4.2.1. The analysis shall include both a 242 thermal response and the mechanical response to the design-basis fire. 243 244 The thermal response shall produce a temperature field in each structural 245 element as a result of the design-basis fire and shall incorporate 246 temperature-dependent thermal properties of the structural elements and 247 fire-resistive materials, as per Section 4.2.2. 248 249 The mechanical response results in forces and deformations in the 250 structural system subjected to the thermal response calculated from the 251 design-basis fire. The mechanical response shall take into account 252 explicitly the deterioration in strength and stiffness with increasing 253 temperature, the effects of thermal expansions, and large deformations. 254 Boundary conditions and connection fixity must represent the proposed 255 structural design. Material properties shall be defined as per Section 4.2.3. 256 257 The resulting analysis shall address all relevant limit states, such as 258 excessive deflections, connection ruptures, and overall or local buckling. 259 260 2. Simple Methods of Analysis 261

Specification for Structural Steel Buildings, public review draft dated March 2, 2015

AMERICAN INSTITUTE OF STEEL CONSTRUCTION

262 The methods of analysis in this section are permitted to be used for the 263 evaluation of the performance of individual members at elevated tempera- 264 tures during exposure to fire. 265 266 The support and restraint conditions (forces, moments and boundary 267 conditions) applicable at normal temperatures are permitted to be assumed 268 to remain unchanged throughout the fire exposure. 269 270 For steel temperatures less than or equal to 400 °F (204 °C), the member 271 and connection design strengths shall be determined without consideration 272 of temperature effects. 273 274 User Note: At temperatures below 400 oF (204 °C), the degradation in 275 steel properties need not be considered in calculating member strengths for 276 the simple method of analysis; however, forces and deformations induced 277 by elevated temperatures must be considered. 278 279 (a) Tension Members 280 It is permitted to model the thermal response of a tension element 281 using a one-dimensional heat transfer equation with heat input as de- 282 termined by the design-basis fire defined in Section 4.2.1. 283 284 The design strength of a tension member shall be determined using the 285 provisions of Chapter D, with steel properties as stipulated in Section 286 4.2.3 and assuming a uniform temperature over the cross section using 287 the temperature equal to the maximum steel temperature. 288 289 (b) Compression Members 290 It is permitted to model the thermal response of a compression element 291 using a one-dimensional heat transfer equation with heat input as de- 292 termined by the design-basis fire defined in Section 4.2.1. 293 DRAFT 294 The design strength of a compression member shall be determined 295 using the provisions of Chapter E with steel properties as stipulated in 296 Section 4.2.3 and Equation A-4-2 used in lieu of Equations E3-2 and 297 E3-3 to calculate the nominal compressive strength for flexural buck- 298 ling: 299

éùFTy () êúFTe () 300 Fcr()TF= êú 0.42 y ()T (A-4-2) ëûêú 301 302 where Fy(T) is the yield stress at elevated temperature and Fe(T) is the 303 critical elastic buckling stress calculated from Equation E3-4 with the 304 elastic modulus E(T) at elevated temperature. Fy(T) and E(T) are ob- 305 tained using coefficients from Table A-4.2.1. 306 307 User Note: The design strength of gravity columns may improve due 308 to the rotational restraints from cooler columns in the stories above 309 and below. The increase in design strength can be accounted by re- 310 ducing the column slenderness (KL/r) used to calculate Fe(T) in Equa- 311 tion A-4-2. One rational method for accounting for the beneficial in- 312 fluence of rotational restraints is discussed in the Commentary. 313

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP4-8

314 User Note: This section is limited to compression members subjected 315 to uniform heating, which is the governing case for most fire condi- 316 tions. A rational method for accounting for the effects of non-uniform 317 heating and resulting thermal gradients on the design strength of com- 318 pression members is referenced in the Commentary. 319 320 (c) Flexural Members 321 It is permitted to model the thermal response of flexural elements us- 322 ing a one-dimensional heat transfer equation to calculate bottom 323 flange temperature and to assume that this bottom flange temperature 324 is constant over the depth of the member. 325 326 The design strength of a flexural member shall be determined using 327 the provisions of Chapter F with steel properties as stipulated in Sec- 328 tion 4.2.3 and Equations A-4-3 through A-4-10 used in lieu of Equa- 329 tions F2-2 through F2-6 to calculate the nominal flexural strength for 330 lateral-torsional buckling of laterally unbraced doubly symmetric 331 members:

332 (1) When Lb ≤ Lr(T) 333

éùæöL cx 334 MT()=+-- CMTêú ()éù MT () MT ()1ç b ÷ (A-4-3) nbrpêúëûêú rèøç LT()÷ ëûr

335 (2) When Lb > Lr(T) 336 M ()TFTS= () (A-4-4) ncrx 337 338 where

2 DRAFTCETp2 () Jc æöL 339 FT( )=+bb 1 0.078 ç ÷ (A-4-5) cr 2 ç ÷ æöL Shxoèø r ts ç b ÷ ç ÷ èørts

2 2 E() T Jcæö Jc é FT()ù 340 LT( )=++ 1.95 r ç ÷ 6.76 ê L ú (A-4-6) rts ç ÷ ê ú FLxoxo() T Shèø Shë ET ()û

341 M ()TSFT= () (A-4-7) rxL

342 FL ()TFk=-yp() 0.3 k y (A-4-8)

343 M pxy()TZFT= () (A-4-9)

T o 344 cx =+£0.53 3.0 where T is in F (A-4-10) 450

T o 345 cx =+0.6 £ 3.0 where T is in C (A-4-10M) 250 346 347 The material properties at elevated temperatures, E(T) and Fy(T), and 348 the kp and ky coefficients are calculated in accordance with Table A- 349 4.2.1, and other terms are as defined in Chapter F. 350 Specification for Structural Steel Buildings, public review draft dated March 2, 2015

AMERICAN INSTITUTE OF STEEL CONSTRUCTION

351 (d) Composite Floor Members 352 353 It is permitted to model the thermal response of flexural elements sup- 354 porting a concrete slab using a one-dimensional heat transfer equation 355 to calculate bottom flange temperature. That temperature shall be tak- 356 en as constant between the bottom flange and mid-depth of the web 357 and shall decrease linearly by no more than 25% from the mid-depth 358 of the web to the top flange of the beam. 359 360 The design strength of a composite flexural member shall be deter- 361 mined using the provisions of Chapter I, with reduced yield stresses in 362 the steel consistent with the temperature variation described under 363 thermal response. 364 365 4d. Design Strength 366 367 The design strength shall be determined as in Section B3.3. The nominal 368 strength, Rn, shall be calculated using material properties, as provided in 369 Section 4.2.3, at the temperature developed by the design-basis fire, and as 370 stipulated in this appendix.

371 4.3. DESIGN BY QUALIFICATION TESTING 372 373 1. Qualification Standards 374 375 Structural members and components in steel buildings shall be qualified 376 for the rating period in conformance with ASTM E119. Demonstration of 377 compliance with these requirements using the procedures specified for 378 steel construction in Section 5 of SEI/ASCE/SFPE Standard 29-05, 379 Standard Calculation Methods for Structural Fire Protection, is permitted. 380 381 2. RestrainedDRAFT Construction 382 383 For floor and roof assemblies and individual beams in buildings, a 384 restrained condition exists when the surrounding or supporting structure is 385 capable of resisting forces and accommodating deformations caused by 386 thermal expansion throughout the range of anticipated elevated tempera- 387 tures. 388 389 Steel beams, girders and frames supporting concrete slabs that are welded 390 or bolted to integral framing members shall be considered restrained 391 construction. 392 393 3. Unrestrained Construction 394 395 Steel beams, girders and frames that do not support a concrete slab shall be 396 considered unrestrained unless the members are bolted or welded to 397 surrounding construction that has been specifically designed and detailed 398 to resist effects of elevated temperatures. 399 400 A steel member bearing on a wall in a single span or at the end span of 401 multiple spans shall be considered unrestrained unless the wall has been 402 designed and detailed to resist effects of thermal expansion.

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

1 APPENDIX 5

2 EVALUATION OF EXISTING STRUCTURES 3 4 5 This appendix applies to the evaluation of the strength and stiffness under static 6 loads of existing structures by structural analysis, by load tests or by a combination 7 of structural analysis and load tests when specified by the engineer of record or in 8 the contract documents. For such evaluation, the steel grades are not limited to 9 those listed in Section A3.1. This appendix does not address load testing for the 10 effects of occupancy caused loads (vibration), moving loads (vibration and fatigue), 11 wind or seismic loads. Section 5.4 is only applicable to static vertical gravity 12 loads applied to existing roofs or floors. 13 14 The Appendix is organized as follows: 15 16 5.1. General Provisions 17 5.2. Material Properties 18 5.3. Evaluation by Structural Analysis 19 5.4. Evaluation by Load Tests 20 5.5. Evaluation Report 21 22 5.1. GENERAL PROVISIONS 23 24 These provisions shall be applicable when the evaluation of an existing 25 steel structure is specified for (a) verification of a specific set of design 26 loadings or (b) determination of the available strength of a load resisting 27 member or system. The evaluation shall be performed by structural 28 analysis (SectionDRAFT 5.3), by load tests (Section 5.4), or by a combination of 29 structural analysis and load tests, when specified in the contract documents 30 by the engineer of record. Where load tests are used, the engineer of 31 record shall first analyze the structure, prepare a testing plan, and develop a 32 written procedure for the test. The plan shall consider catastrophic collapse 33 and/or excessive levels of permanent deformation, as defined by the 34 engineer of record, and shall include procedures to preclude either 35 occurrence during testing.. 36 37 5.2. MATERIAL PROPERTIES 38 39 1. Determination of Required Tests 40 41 The engineer of record shall determine the specific tests that are required 42 from Sections 5.2.2 through 5.2.6 and specify the locations where they are 43 required. Where available, the use of applicable project records is 44 permitted to reduce or eliminate the need for testing. 45 46 2. Tensile Properties 47 48 Tensile properties of members shall be considered in evaluation by 49 structural analysis (Section 5.3) or load tests (Section 5.4). Such properties 50 shall include the yield stress, tensile strength and percent elongation. 51 Where available, certified material test reports or certified reports of tests 52 made by the fabricator or a testing laboratory in accordance with ASTM

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

53 A6/A6M or A568/A568M, as applicable, is permitted for this purpose. 54 Otherwise, tensile tests shall be conducted in accordance with ASTM 55 A370 from samples taken from components of the structure. 56 57 3. Chemical Composition 58 59 Where welding is anticipated for repair or modification of existing 60 structures, the chemical composition of the steel shall be determined for 61 use in preparing a welding procedure specification (WPS). Where 62 available, results from certified material test reports or certified reports of 63 tests made by the fabricator or a testing laboratory in accordance with 64 ASTM procedures is permitted for this purpose. Otherwise, analyses shall 65 be conducted in accordance with ASTM A751 from the samples used to 66 determine tensile properties, or from samples taken from the same 67 locations. 68 69 4. Base Metal Notch Toughness 70 71 Where welded tension splices in heavy shapes and plates as defined in 72 Section A3.1d are critical to the performance of the structure, the Charpy 73 V-notch toughness shall be determined in accordance with the provisions 74 of Section A3.1d. If the notch toughness so determined does not meet the 75 provisions of Section A3.1d, the engineer of record shall determine if 76 remedial actions are required. 77 78 5. Weld Metal 79 80 Where structural performance is dependent on existing welded connec- 81 tions, representative samples of weld metal shall be obtained. Chemical 82 analysis and mechanical tests shall be made to characterize the weld metal. 83 A determination shall be made of the magnitude and consequences of 84 imperfections.DRAFT If the requirements of AWS D1.1 are not met, the engineer 85 of record shall determine if remedial actions are required. 86 87 6. Bolts and Rivets 88 89 Representative samples of bolts shall be inspected to determine markings 90 and classifications. Where bolts cannot be properly identified, representa- 91 tive samples shall be taken and tested to determine tensile strength in 92 accordance with ASTM F606/F606M and the bolt classified accordingly. 93 Alternatively, the assumption that the bolts are ASTM A307 is permitted. 94 Rivets shall be assumed to be ASTM A502, Grade 1, unless a higher grade 95 is established through documentation or testing. 96 97 5.3. EVALUATION BY STRUCTURAL ANALYSIS 98 99 1. Dimensional Data 100 101 All dimensions used in the evaluation, such as spans, column heights, 102 member spacings, bracing locations, cross-section dimensions, thicknesses, 103 and connection details, shall be determined from a field survey. Alterna- 104 tively, when available, it is permitted to determine such dimensions from 105 applicable project design or shop drawings with field verification of critical 106 values. 107

108 2. Strength Evaluation 109 110 Forces (load effects) in members and connections shall be determined by 111 structural analysis applicable to the type of structure evaluated. The load 112 effects shall be determined for the loads and factored load combinations 113 stipulated in Section B2. 114 115 The available strength of members and connections shall be determined 116 from applicable provisions of Chapters B through K and Appendix 1 of 117 this Specification. 118 119 3. Serviceability Evaluation 120 121 Where required, the deformations at service loads shall be calculated and 122 reported. 123 124 5.4. EVALUATION BY LOAD TESTS 125 126 1. Determination of Load Rating by Testing 127 128 To determine the load rating of an existing floor or roof structure by 129 testing, a test load shall be applied incrementally in accordance with the 130 engineer of record's plan. The structure shall be visually inspected for 131 signs of distress or imminent failure at each load level. Appropriate 132 measures shall be taken if these or any other unusual conditions are 133 encountered. 134 135 The tested strength of the structure shall be taken as the maximum applied 136 test load plus the in-situ dead load. The live load rating of a floor structure 137 shall be determined by setting the tested strength equal to 1.2D + 1.6L, 138 where D is the nominal dead load and L is the nominal live load rating for 139 the structure.DRAFT The nominal live load rating of the floor structure shall not 140 exceed that which can be calculated using applicable provisions of the 141 specification unless approved by the authority having jurisdiction. For roof 142 structures, Lr, S or R, shall be substituted for L, 143 where 144 Lr = nominal roof live load 145 S = nominal snow load 146 R = nominal load due to rainwater or snow, exclusive of the ponding 147 contribution 148 149 More severe load combinations shall be used where required by applicable 150 building codes. 151 152 Periodic unloading shall be considered once the service load level is 153 attained and after the onset of inelastic structural behavior is identified to 154 document the amount of permanent set and the magnitude of the inelastic 155 deformations. Deformations of the structure, such as member deflections, 156 shall be monitored at critical locations during the test, referenced to the 157 initial position before loading. It shall be demonstrated, while maintaining 158 maximum test load for one hour, that the deformation of the structure does 159 not increase by more than 10% above that at the beginning of the holding 160 period. The structure shall then be unloaded and the unloaded deformation 161 recorded. It is permissible to repeat the sequence if necessary to demon- 162 strate compliance. 163

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

164 Deformations of the structure shall also be recorded 24 hours after the test 165 loading is removed to determine the amount of permanent set. Because the 166 amount of acceptable permanent deformation depends on the specific 167 structure, no limit is specified for permanent deformation at maximum 168 loading. Where it is not feasible to load test the entire structure, a segment 169 or zone, of not less than one complete bay representative of the most 170 critical conditions, shall be selected. 171 172 2. Serviceability Evaluation 173 174 When load tests are prescribed, the structure shall be loaded incrementally 175 to the service load level. The service test load shall be held for a period of 176 one hour, and deformations shall be recorded at the beginning and at the 177 end of the one-hour holding period. 178 179 5.5. EVALUATION REPORT 180 181 After the evaluation of an existing structure has been completed, the 182 engineer of record shall prepare a report documenting the evaluation. The 183 report shall indicate whether the evaluation was performed by structural 184 analysis, by load testing, or by a combination of structural analysis and 185 load testing. Furthermore, when testing is performed, the report shall 186 include the loads and load combination used, the load-deformation and 187 time-deformation relationships observed, and deformations after unload- 188 ing. All relevant information obtained from design drawings, material test 189 reports, and auxiliary material testing shall also be reported. Finally, the 190 report shall indicate whether the structure, including all members and 191 connections,DRAFT is adequate to withstand the load effects.

APP6-1

1 2

3 APPENDIX 6

4 MEMBER STABILITY BRACING 5 6 7 This appendix addresses the minimum strength and stiffness necessary to provide a 8 braced point in a column, beam or beam-column. The appendix is organized as 9 follows: 10 11 6.1. General Provisions 12 6.2. Column Bracing 13 6.3. Beam Bracing 14 6.4. Beam-Column Bracing 15 16 User Note: The stability requirements for braced-frame systems are provided in 17 Chapter C. The provisions in this appendix apply to bracing that is not included in 18 the analysis model of the overall structure, but is provided to stabilize individual 19 columns, beams and beam-columns. 20 21 6.1. GENERAL PROVISIONS 22 23 Columns, beams and beam-columns with end and intermediate braced points 24 designed to meet the requirements in Sections 6.2, 6.3 and 6.4, as applicable, 25 are permitted to be designed based on effective lengths, Lc and Lb, taken 26 equal to distance between the braced points. For members subjected to axial 27 compression, Lbr/ryf shall not be greater than 200 for all of the member’s 28 flanges 29 DRAFT 30 where 31 L br = flange unbraced length, in. (mm) 32 ryf = radius of gyration of the flange about its principal axis parallel to 33 the plane of the web, in. (mm) 34 35 Bracing systems shall have the strength and stiffness specified in Sections 36 6.2, 6.3, and 6.4, as applicable. Where such a system braces more than one 37 member, the strength and stiffness of the bracing shall be based on the sum of 38 the required strengths of all members being braced. The evaluation of the 39 stiffness furnished by the bracing shall include the effects of connections and 40 anchoring details. 41 42 User Note: The Commentary to these Sections provides enhancements 43 which, in certain cases, may give somewhat smaller stiffness and/or strength 44 requirements. 45 46 A panel brace (formerly referred to as a relative brace) controls the angular 47 deviation of a segment of the braced member between braced points (that is, 48 the lateral displacement of one end of the segment relative to the other). A 49 point brace (formerly referred to as a nodal brace) controls the movement at 50 the braced point without direct interaction with adjacent braced points. A 51 continuous bracing system consists of bracing that is attached along the entire 52 member length. 53

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP6-2

54 The available strength and stiffness of the bracing members and connections 55 shall equal or exceed the required strength and stiffness, respectively, unless 56 analysis indicates that smaller values are justified. 57 58 In lieu of the requirements of this appendix, 59 1. The required brace strength and stiffness can be obtained using a second- 60 order analysis that satisfies the provisions of Appendix 1, Sections 1.1 or 61 1.2 and includes brace points displaced from their nominal locations in a 62 pattern that provides for the greatest demand on the bracing. 63 64 2. The required bracing stiffness can be obtained as 2/ (LRFD) or 2Ω 65 (ASD) times the ideal bracing stiffness determined from a buckling 66 analysis. The required brace strength can be determined using the 67 provisions of these Sections. 68 69 User Note: The Commentary to Section 6.1 explains how the required 70 bracing stiffness can be determined using a buckling analysis. 71 72 73 6.2. COLUMN BRACING 74 75 It is permitted to brace an individual column at end and intermediate points 76 along its length using either panel or point lateral bracing. 77 78 1. Panel Lateral Bracing 79 80 The panel bracing system shall have the strength and stiffness specified in this 81 section. The connection of the column to the bracing system shall have the 82 strength specified in Section 6.2.2 for a point brace at that location. 83 84 User Note: For smaller values of the connection stiffness the panel 85 DRAFT bracing system and its connection to the column function as a panel and 86 point bracing system arranged in series, including significant interaction 87 effects. Such cases may be evaluated using the general provisions of 88 Section 6.1. 89 90 91 In the direction perpendicular to the longitudinal axis of the column, the 92 required shear strength of the bracing system is 93 94 Vbr = 0.005Pr (A-6-1) 95 96 and, the required shear stiffness of the bracing system is 97

2 Pr Pr 98 βbr   (LRFD) βbr 2  (ASD) (A-6-2)  Lbr Lbr 99 100 where 101  = 0.75 (LRFD);  = 2.00 (ASD) 102 Lbr = unbraced length within the panel under consideration, in. (mm) 103 Pr = required axial strength of the column within the panel under consid- 104 eration using LRFD or ASD load combinations, kips (N) 105 106 2. Point Lateral Bracing 107

Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP6-3

108 In the direction perpendicular to the longitudinal axis of the column, the 109 required strength of end and intermediate point braces is 110 111 Pbr = 0.01Pr (A-6-3) 112 113 and, the required stiffness of the brace is 114

8 Pr Pr 115 br  (LRFD) br 8  (ASD) (A-6-4)  Lbr Lbr 116 117 where 118  = 0.75 (LRFD);  = 2.00 (ASD) 119 Lbr = unbraced length adjacent to the point brace, in. (mm) 120 Pr = largest of the required axial strengths of the column within the 121 unbraced lengths adjacent to the point brace using LRFD or ASD 122 load combinations, kips (N) 123 124 When the unbraced lengths adjacent to a point brace have different Pr/Lbr 125 values, the larger value shall be used to determine the required brace stiffness. 126 127 For intermediate point bracing of an individual column, Lbr in Equation A-6-4 128 need not be taken less than the maximum effective length, Lc, permitted for 129 the column based upon the required axial strength, Pr. 130 131 6.3. BEAM BRACING 132 133 Beams shall be restrained against rotation about their longitudinal axis at 134 points of support. When a braced point is assumed in the design between 135 points of support, lateral bracing, torsional bracing, or a combination of the 136 two shall be provided to prevent the relative displacement of the top and 137 bottom flangesDRAFT (i.e., to prevent twist). In members subject to double curvature 138 bending, the inflection point shall not be considered a braced point unless 139 bracing is provided at that location. 140 141 The requirements of this section shall apply to bracing of doubly- and singly- 142 symmetric I-section members and trusses subjected to flexure within a plane 143 of symmetry and zero net axial force. 144 145 1. Lateral Bracing 146 147 Lateral bracing shall be attached at or near the beam compression flange or 148 truss compression chord, except as follows: 149 150 (a) At the free end of a cantilevered beam or truss, lateral bracing shall be 151 attached at or near the top (tension) flange or chord. 152 (b) For braced beams and trusses subject to double curvature bending, bracing 153 shall be attached at or near both flanges (or chords) at the braced point 154 nearest the inflection point. 155 156 User Note: Bracing of both flanges usually is achieved by a combination of 157 lateral and torsional bracing. 158 159 160 (c ) When used in combination with torsional bracing. 161

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP6-4

162 It is permitted to use either panel or point bracing to provide lateral bracing 163 for beams. 164 165 1a. Panel Bracing 166 167 The panel bracing system shall have the strength and stiffness specified in this 168 section. The connection of the bracing system to the member shall have the 169 strength specified in Section 6.3.1b for a point brace at that location. 170 171 User Note: For smaller values of the connection stiffness the panel bracing 172 system and its connection to the beam function as a panel and point bracing 173 system arranged in series, including significant interaction effects. Such 174 cases may be evaluated using the general provisions of Section 6.1. 175 176 The required shear strength of the bracing system is 177 MCrd 178 Vbr  0.01 (A-6-5) ho 179 180 and, the required shear stiffness of the bracing system is 181

1 4MCrd 4MCrd 182 βbr   (LRFD) βbr  (ASD) (A-6-6)  Lhbr o Lhbr o 183 184 where 185  = 0.75 (LRFD);  = 2.00 (ASD) 186 Cd = 1.0 except in the following case; 187 = 2.0 for the brace closest to the inflection point in a beam subject to 188 double curvature bending 189 Lbr = unbraced length within the panel under consideration, in. (mm) 190 Mr = requiredDRAFT flexural strength of the beam within the panel under

191 consideration using LRFD or ASD load combinations, kip-in. (N- 192 mm) 193 ho = distance between flange centroids, in. (mm) 194 195 1b. Point Bracing 196 197 In the direction perpendicular to the longitudinal axis of the beam, the 198 required strength of end and intermediate point braces is 199

M rdC 200 P.br  002 (A-6-7) ho 201 202 and, the required stiffness of the brace is 203

1 10MCrd 10MCrd 204 br (LRFD) br (ASD) (A-6-8)  Lhbr o Lhbr o 205 206 where 207  = 0.75 (LRFD); = 2.00 (ASD) 208 Lbr = unbraced length adjacent to the point brace, in. (mm)

Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP6-5

209 Mr = largest of the required flexural strengths of the beam within the 210 unbraced lengths adjacent to the point brace using LRFD or ASD 211 load combinations, kip-in. (N-mm) 212 213 When the unbraced lengths adjacent to a point brace have different Mr/Lbr 214 values, the larger value shall be used to determine the required brace 215 stiffness. 216 217 For intermediate point bracing of an individual beam, Lbr in Equation A-6-8 218 need not be taken less than the maximum effective length, Lb, permitted for 219 the beam based upon the required flexural strength, Mr. 220 221 2. Torsional Bracing 222 223 It is permitted to attach torsional bracing at any cross-section location, and it 224 need not be attached near the compression flange. 225 226 User Note: Torsional bracing can be provided with a moment-connected 227 beam, cross-frame, or other diaphragm element. 228 229 2a. Point Bracing 230 231 About the longitudinal axis of the beam, the required flexural strength of the 232 brace is 233

234 M br  002.Mr (A-6-9) 235 236 and, the required flexural stiffness of the brace is 237

T 238 br  (A-6-10) T DRAFT1 sec 239 240 where 2 2 12.4LMr 2.4LMr 241 T  (LRFD) T  (ASD) (A-6-11)  nEIyeff C b nEI yeff Cb 242 33 3.3Ehttb 1.5 ow sts 243 sec   (A-6-12) ho 12 12 244 245 where 246  = 0.75 (LRFD);  = 3.00 (ASD) 247 248 User Note: 1.52 /  = 3.00 in Equation A-6-11 because the moment 249 term is squared. Equation A-6-11 is based on the assumption that the point 250 braces are equally spaced, approximately, along the span length of the beam. 251 Cases involving unequally-spaced torsional bracing may be evaluated using 252 the general provisions of Section 6.1. 253 254 βsec can be taken equal to infinity, and βbr = βT, when a cross-frame is 255 attached near both flanges or a diaphragm is used that is approximately the 256 same depth as the beam being braced.

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP6-6

257 258 E = modulus of elasticity of steel = 29,000 ksi (200 000 MPa) 4 4 259 Iyeff = effective out-of-plane moment of inertia, in. (mm ) 260 = Iyc + (t/c)Iyt 4 261 Iyc = moment of inertia of the compression flange about the y-axis , in. 262 (mm4) 4 263 Iyt = moment of inertia of the tension flange about the y-axis , in. 264 (mm4) 265 L = length of span, in. (mm) 266 Mr = largest of the required flexural strengths of the beam within the 267 unbraced lengths adjacent to the point brace, using LRFD or ASD 268 load combinations, kip-in. (N-mm) M 269 r = maximum value of the required flexural strength of the beam Cb 270 divided by the moment gradient factor, within the unbraced 271 lengths adjacent to the point brace, using LRFD or ASD load 272 combinations, kip-in. (N-mm) 273 bs = stiffener width for one-sided stiffeners, in. (mm) 274 = twice the individual stiffener width for pairs of stiffeners, in. 275 (mm) 276 c = distance from the neutral axis to the extreme compressive fibers, 277 in. (mm) 278 n = number of braced points within the span 279 t = distance from the neutral axis to the extreme tensile fibers, in. 280 (mm) 281 tw = thickness of beam web, in. (mm) 282 tst = thickness of web stiffener, in. (mm) 283 T = overall brace system required stiffness, kip-in./rad (N-mm/rad) 284 sec = web distortional stiffness, including the effect of web transverse 285 stiffeners, if any, kip-in./rad (N-mm/rad) 286 DRAFT 287 User Note: If sec < T, Equation A-6-10 is negative, which indicates 288 that torsional beam bracing will not be effective due to inadequate web 289 distortional stiffness. 290 291 User Note: For doubly symmetric members, c = t and Iyeff = out-of- 4 4 292 plane moment of inertia, Iy, in. (mm ). 293 294 When required, a web stiffener shall extend the full depth of the braced 295 member and shall be attached to the flange if the torsional brace is also 296 attached to the flange. Alternatively, it shall be permissible to stop the 297 stiffener short by a distance equal to 4tw from any beam flange that is not 298 directly attached to the torsional brace. 299 300 2b. Continuous Bracing 301 302 For continuous torsional bracing, Equations A-6-9 and A-6-10 shall be used 303 with the following modifications: 304 305 (a) The brace strength requirement per unit length along the beam shall be 306 taken as Equation A-6-9 divided by the maximum unbraced length 307 permitted for the beam based upon the required flexural strength, Mr. 308 The required flexural strength, Mr, shall be taken as the maximum value 309 throughout the beam span.

Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP6-7

310 (b) The brace stiffness requirement per unit length shall be given by 311 Equations A-6-10 and A-6-11 with L/n = 1.0 312 (c) The web distortional stiffness shall be taken as: 313 3 3.3Etw 314 sec (A-6-13) 12ho 315 316 3. Combined Lateral and Torsional Bracing 317 318 For beams having point torsional bracing combined with panel or point 319 lateral bracing on the flange subjected to flexural compression, the required 320 torsional and lateral brace stiffnesses can be reduced relative to the base 321 values specified in Sections 6.3.1 and 6.3.2, but shall satisfy 322  323 Tbr Lbr 1.0 (A-6-14) Tbro Lbro 324 325 where 326 βTbro = base required torsional brace stiffness given by Equation A-6- 327 10, kip-in./rad (N-mm/rad) 328 βLbro = base required lateral brace stiffness given by Equation A-6-6 329 for panel bracing or Equation A-6-8 for point bracing, kip/in. 330 (N/mm) 331 βTbr = required torsional brace stiffness, kip-in./rad (N-mm/rad) 332 βLbr = required lateral brace stiffness, kip/in. (N/mm) 333 334 For beams having point torsional bracing combined with panel or point 335 lateral bracing on the flange subjected to flexural tension, Eq. A-6-14 shall 336 apply and, in addition, the required torsional brace stiffness shall be greater 2 337 than or equal to the smaller of βPbroho or βTbro 338 DRAFT 339 where 340 βPbro = base required point lateral brace stiffness given by Eq. A-6-8, 341 calculated using the unbraced length between the torsional 342 brace points, kip/in. (N/mm) 343 ho = distance between the flange centroids, in. (mm) 344 345 The provisions of Sections 6.3.1 and 6.3.2 shall apply for the lateral and the 346 torsional brace strength requirements. 347 348 6.4. BEAM-COLUMN BRACING

349 The requirements of this section shall apply to doubly and singly symmetric I- 350 shaped members subjected to combined axial compression and flexure in a 351 plane of symmetry. 352 353 For beam-columns braced by a combination of lateral and torsional bracing, 354 the following shall apply: 355 356 (a) The required lateral bracing stiffness shall be determined using Equation 357 A-6-2 for panel lateral bracing or Equation A-6-4 for point lateral bracing, 358 based on the required member axial force, Pr. In Equation A-6-4, Lbr 359 shall be taken as the actual unbraced length; the provision in Section 6.2.2

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP6-8

360 that L need not be taken less than the maximum permitted effective length 361 based on Pr shall not be applied. 362 363 (b) The required torsional bracing stiffness shall be determined using 364 Equation A-6-10 with an equivalent moment equal to Mr/Cb + Prho/2, 365 where Pr is the axial force in the member being braced and ho is the 366 distance between the flange centroids. 367 368 (c) The required lateral brace strength shall be determined using Equation A- 369 6-1 for panel lateral bracing or Equation A-6-3 for point lateral bracing, 370 based on the required member axial forces, Pr. 371 372 (d) The required torsional brace strength shall be determined using Equation 373 A-6-9 with an equivalent moment equal to Mr + Prho/2, where Pr is the 374 axial force in the member being braced. 375 376 For beam-columns braced by a single lateral bracing system attached at or 377 near a flange subjected to flexural compression throughout the member length, 378 the following shall apply: 379 380 (a) For panel bracing, when the opposite flange is subjected to a net tension 381 force due to the axial and moment loading throughout the member length, 382 the required bracing stiffness shall be taken as the sum of the values 383 determined using Equation A-6-2 with an equivalent axial force equal to 384 Pr/2 and Equation A-6-6 with the required moment Mr. The required 385 bracing strength shall be taken as the sum of the values determined using 386 Equation A-6-1 with an equivalent axial force equal to Pr/2 and Equation 387 A-6-5 with the required moment Mr. 388 (b) For panel bracing, when the opposite flange is subjected to a net 389 compression force due to the axial and moment loading at any position 390 within the member length, the required bracing stiffness shall be taken as 391 the sum ofDRAFT the values determined using Equation A-6-2 with an equiva- 392 lent axial force equal to 2Pr and Equation A-6-6 with the required mo- 393 ment Mr. The required bracing strength shall be taken as the sum of the 394 values determined using Equation A-6-1 with an equivalent axial force 395 equal to 2Pr and Equation A-6-5 with the required moment Mr. 396 (c) For point bracing, when the opposite flange is subjected to a net tension 397 force due to the axial and moment loading throughout the member length, 398 the required bracing stiffness shall be taken as the sum of the values 399 determined using Equation A-6-4 with an equivalent axial force equal to 400 Pr/2 and Equation A-6-8 with the required moment Mr. In Equations A-6- 401 4 and A-6-8, Lbr shall be taken as the actual unbraced length; the provi- 402 sions in Sections 6.2.2 and 6.3.1b that Lbr need not be taken less than the 403 maximum permitted effective length based on Pr and Mr shall not be 404 applied. The required bracing strength shall be taken as the sum of the 405 values determined using Equation A-6-3 with an equivalent axial force 406 equal to Pr/2 and Equation A-6-7 with the required moment Mr. 407 (d) For point bracing, when the opposite flange is subjected to a net 408 compression force due to the axial and moment loading at any position 409 within the member length, the required bracing stiffness shall be taken as 410 the sum of the values determined using Equation A-6-4 with an equiva- 411 lent axial force equal to 2Pr and Equation A-6-8 with the required mo- 412 ment, Mr. In Equations A-6-4 and A-6-8, Lbr shall be taken as the actual 413 unbraced length; the provisions in Sections 6.2.2 and 6.3.1b that Lbr need 414 not be taken less than the maximum permitted effective length based on 415 Pr and Mr shall not be applied. The required bracing strength shall be

Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP6-9

416 taken as the sum of the values determined using Equation A-6-3 with an 417 equivalent axial force equal to 2Pr and Equation A-6-7 with the required 418 moment Mr. 419 420 User Note: Bracing requirements for other more general bracing configurations may be determined using a buckling analysis or a 421 second-order load-deflection analys is as discussed in Section 6.1.

DRAFT

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP7-1

1 2

3 APPENDIX 7

4 ALTERNATIVE METHODS OF DESIGN FOR 5 STABILITY 6 7 8 This appendix presents alternatives to the direct analysis method of design for 9 stability defined in Chapter C. The two alternative methods covered are the 10 effective length method and the first-order analysis method. 11 12 The appendix is organized as follows: 13 14 7.1. General Stability Requirements 15 7.2. Effective Length Method 16 7.3. First-Order Analysis Method 17 18 7.1. GENERAL STABILITY REQUIREMENTS 19 20 The general requirements of Section C1 shall apply. As an alternative to the 21 direct analysis method (defined in Sections C1 and C2), it is permissible to 22 design structures for stability in accordance with either the effective length 23 method, specified in Section 7.2, or the first-order analysis method, specified 24 in Section 7.3, subject to the limitations indicated in those sections. 25 26 7.2. EFFECTIVE LENGTH METHOD 27 28 1. Limitations DRAFT 29 30 The use of the effective length method shall be limited to the following 31 conditions: 32 33 (a) The structure supports gravity loads primarily through nominally vertical 34 columns, walls or frames. 35 36 (b) The ratio of maximum second-order drift to maximum first-order drift 37 (both determined for LRFD load combinations or 1.6 times ASD load 38 combinations, with stiffness not adjusted as specified in Section C2.3) in 39 all stories is equal to or less than 1.5. 40 41 User Note: The ratio of second-order drift to first-order drift in a story 42 may be taken as the B2 multiplier, calculated as specified in Appendix 8. 43 44 2. Required Strengths 45 46 The required strengths of components shall be determined from an elastic 47 analysis conforming to the requirements of Section C2.1, except that the 48 stiffness reduction indicated in Section C2.1(2) shall not be applied; the 49 nominal stiffnesses of all structural steel components shall be used. Notional 50 loads shall be applied in the analysis in accordance with Section C2.2b. 51

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP7-2

52 User Note: Since the condition specified in Section C2.2b(d) will be 53 satisfied in all cases where the effective length method is applicable, the 54 notional load need only be applied in gravity-only load cases. 55 56 3. Available Strengths 57 58 The available strengths of members and connections shall be calculated in 59 accordance with the provisions of Chapters D, E, F, G, H, I, J and K, as 60 applicable. 61 62 For flexural buckling, the effective length, Lc, of members subject to 63 compression shall be taken as KL, where K is as specified in (a) or (b), in the 64 following, as applicable, and L is the laterally unbraced length of the 65 member. 66 67 (a) In braced frame systems, shear wall systems, and other structural 68 systems where lateral stability and resistance to lateral loads does not 69 rely on the flexural stiffness of columns, the effective length factor, K, of 70 members subject to compression shall be taken as unity unless a smaller 71 value is justified by rational analysis. 72 73 (b) In moment frame systems and other structural systems in which the 74 flexural stiffnesses of columns are considered to contribute to lateral 75 stability and resistance to lateral loads, the effective length factor, K, or 76 elastic critical buckling stress, Fe, of those columns whose flexural 77 stiffnesses are considered to contribute to lateral stability and resistance 78 to lateral loads shall be determined from a sidesway buckling analysis of 79 the structure; K shall be taken as 1.0 for columns whose flexural stiff- 80 nesses are not considered to contribute to lateral stability and resistance 81 to lateral loads. 82 83 Exception:DRAFT It is permitted to use K=1.0 in the design of all columns if 84 the ratio of maximum second-order drift to maximum first-order drift 85 (both determined for LRFD load combinations or 1.6 times ASD load 86 combinations) in all stories is equal to or less than 1.1. 87 88 User Note: Methods of calculating the effective length factor, K, are 89 discussed in the Commentary. 90 91 Bracing intended to define the unbraced lengths of members shall have 92 sufficient stiffness and strength to control member movement at the braced 93 points. 94 95 User Note: Methods of satisfying the bracing requirement are provided in 96 Appendix 6. The requirements of Appendix 6 are not applicable to bracing 97 that is included in the analysis of the overall structure as part of the overall 98 force-resisting system. 99 100 7.3. FIRST-ORDER ANALYSIS METHOD 101 102 1. Limitations 103 104 The use of the first-order analysis method shall be limited to the following 105 conditions: 106

Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP7-3

107 (a) The structure supports gravity loads primarily through nominally vertical 108 columns, walls or frames. 109 110 (b) The ratio of maximum second-order drift to maximum first-order drift 111 (both determined for LRFD load combinations or 1.6 times ASD load 112 combinations, with stiffness not adjusted as specified in Section C2.3) in 113 all stories is equal to or less than 1.5. 114 115 User Note: The ratio of second-order drift to first-order drift in a story 116 may be taken as the B2 multiplier, calculated as specified in Appendix 8. 117 118 (c) The required axial compressive strengths of all members whose flexural 119 stiffnesses are considered to contribute to the lateral stability of the 120 structure satisfy the limitation: 121

122 Pr ≤ 0.5Pns (A-7-1) 123 124 where 125  = 1.0 (LRFD); = 1.6 (ASD) 126 Pr = required axial compressive strength under LRFD or ASD load 127 combinations, kips (N) 128 Pns = cross-section compressive strength; for nonslender-element 129 sections Pns = FyAg, and for slender-element sections Pns = 130 FyAe, where Ae is as defined in Section E7, kips (N) 131 132 2. Required Strengths 133 134 The required strengths of components shall be determined from a first-order 135 analysis, with additional requirements (a) and (b) below. The analysis shall 136 consider flexural, shear and axial member deformations, and all other 137 deformations that contribute to displacements of the structure. 138 DRAFT 139 (a) All load combinations shall include an additional lateral load, Ni, applied 140 in combination with other loads at each level of the structure: 141

142 Ni = 2.1(/L)Yi ≥ 0.0042Yi (A-7-2) 143 144 where 145  = 1.00 (LRFD); = 1.60 (ASD) 146 Yi = gravity load applied at level i from the LRFD load combina- 147 tion or ASD load combination, as applicable, kips (N)

148 /L= maximum ratio of to L for all stories in the structure 149  = first-order interstory drift due to the LRFD or ASD load 150 combination, as applicable, in. (mm). Where  varies over

151 the plan area of the structure,  shall be the average drift 152 weighted in proportion to vertical load or, alternatively, the 153 maximum drift. 154 L = height of story, in. (mm) 155 156 The additional lateral load at any level, Ni, shall be distributed over that 157 level in the same manner as the gravity load at the level. The additional 158 lateral loads shall be applied in the direction that provides the greatest 159 destabilizing effect. 160

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP7-4

161 User Note: For most building structures, the requirement regarding the 162 direction of Ni may be satisfied as follows: For load combinations that 163 do not include lateral loading, consider two alternative orthogonal 164 directions for the additional lateral load, in a positive and a negative 165 sense in each of the two directions, same direction at all levels; for load 166 combinations that include lateral loading, apply all the additional lateral 167 loads in the direction of the resultant of all lateral loads in the combina- 168 tion. 169 170 (b) The nonsway amplification of beam-column moments shall be included 171 by applying the B1 amplifier of Appendix 8 to the total member mo- 172 ments. 173 174 User Note: Since there is no second-order analysis involved in the first- 175 order analysis method for design by ASD, it is not necessary to amplify ASD 176 load combinations by 1.6 before performing the analysis, as required in the 177 direct analysis method and the effective length method. 178 179 3. Available Strengths 180 181 The available strengths of members and connections shall be calculated in 182 accordance with the provisions of Chapters D, E, F, G, H, I, J and K, as 183 applicable. 184 185 The effective length for flexural buckling of all members shall be taken as 186 the unbraced length unless a smaller value is justified by rational analysis. 187 188 Bracing intended to define the unbraced lengths of members shall have 189 sufficient stiffness and strength to control member movement at the braced 190 points. 191 192 User Note: MethodsDRAFT of satisfying this requirement are provided in Appendix 193 6. The requirements of Appendix 6 are not applicable to bracing that is 194 included in the analysis of the overall structure as part of the overall force- 195 resisting system.

196

Specification for Structural Steel Buildings, draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP8-1

1 2

3 APPENDIX 8

4 APPROXIMATE SECOND-ORDER ANALYSIS 5 6 7 This appendix provides a procedure to account for second-order effects in structures 8 by amplifying the required strengths indicated by a first-order analysis. 9 10 The appendix is organized as follows: 11 12 8.1. Limitations 13 8.2. Calculation Procedure 14 15 8.1. LIMITATIONS 16 17 The use of this procedure is limited to structures that support gravity loads 18 primarily through nominally vertical columns, walls or frames, except that it 19 is permissible to use the procedure specified for determining P-δ effects for 20 any individual compression member. 21 22 8.2. CALCULATION PROCEDURE 23 24 The required second-order flexural strength, Mr, and axial strength, Pr, of all 25 members shall be determined as: 26 27 Mr = B1Mnt + B2Mlt (A-8-1) 28 29 Pr = Pnt + B2Plt (A-8-2) 30 31 where 32 33 B1 = multiplier to account for P-δ effects, determined for each member 34 subject to compression and flexure, and each direction of bending 35 of the member in accordance with Section 8.2.1. B1 shall be taken 36 as 1.0 for members not subject to compression. 37 B2 = multiplier to account for P-Δ effects, determined for each story of 38 the structure and each direction of lateral translation of the story 39 in accordance with Section 8.2.2. 40 Mlt = first-order moment using LRFD or ASD load combinations, due 41 to lateral translation of the structure only, kip-in. (N-mm) 42 Mnt = first-order moment using LRFD or ASD load combinations, with 43 the structure restrained against lateral translation, kip-in. (N-mm) 44 Mr = required second-order flexural strength using LRFD or ASD load 45 combinations, kip-in. (N-mm) 46 Plt = first-order axial force using LRFD or ASD load combinations, 47 due to lateral translation of the structure only, kips (N) 48 Pnt = first-order axial force using LRFD or ASD load combinations, 49 with the structure restrained against lateral translation, kips (N) 50 Pr = required second-order axial strength using LRFD or ASD load 51 combinations, kips (N) 52

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP8-2

53 User Note: Equations A-8-1 and A-8-2 are applicable to all members in all 54 structures. Note, however, that B1 values other than unity apply only to 55 moments in beam-columns; B2 applies to moments and axial forces in 56 components of the lateral force resisting system (including columns, beams, 57 bracing members and shear walls). See Commentary for more on the 58 application of Equations A-8-1and A-8-2. 59 60 1. Multiplier B1 for P-δ Effects 61 62 The B1 multiplier for each member subject to compression and each direction 63 of bending of the member is calculated as: 64 Cm 65 B1 = 1 (A-8-3) 1  P/P er 1 66 where 67  = 1.00 (LRFD);  = 1.60 (ASD) 68 Cm = coefficient assuming no lateral translation of the frame deter- 69 mined as follows: 70 71 (a) For beam-columns not subject to transverse loading between 72 supports in the plane of bending 73

74 Cm = 0.6  0.4(M1 / M2) (A-8-4) 75 76 where M1 and M2, calculated from a first-order analysis, are 77 the smaller and larger moments, respectively, at the ends of 78 that portion of the member unbraced in the plane of bending 79 under consideration. M1/M2 is positive when the member is 80 bent in reverse curvature, negative when bent in single curva- 81 ture. 82 83 (b) For beam-columns subject to transverse loading between 84 supports, the value of Cm shall be determined either by analy- 85 sis or conservatively taken as 1.0 for all cases. 86 87 Pe1 = elastic critical buckling strength of the member in the plane of 88 bending, calculated based on the assumption of no lateral transla- 89 tion at the member ends, kips (N) 90 91 2EI * 92 Pe1 = 2 (A-8-5) Lc1 93 where

94 EI* = flexural rigidity required to be used in the analysis (=0.8bEI 95 when used in the direct analysis method where b is as de- 96 fined in Chapter C; =EI for the effective length and first- 97 order analysis methods) 98 E = modulus of elasticity of steel = 29,000 ksi (200 000 MPa) 99 I = moment of inertia in the plane of bending, in.4 (mm4) 100 Lc1 = effective length in the plane of bending, calculated based on 101 the assumption of no lateral translation at the member ends, 102 set equal to the laterally unbraced length of the member un- 103 less analysis justifies a smaller value, in. (mm)

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION

APP8-3

104 105 It is permitted to use the first-order estimate of Pr (i.e., Pr = Pnt + Plt) in 106 Equation A-8-3. 107 108 2. Multiplier B2 for P-Δ Effects 109 110 The B2 multiplier for each story and each direction of lateral translation is 111 calculated as: 112 1 113 B 1 (A-8-6) 2 P 1 story Pestory 114 where 115  = 1.00 (LRFD);  = 1.60 (ASD) 116 Pstory = total vertical load supported by the story using LRFD or ASD 117 load combinations, as applicable, including loads in columns 118 that are not part of the lateral force resisting system, kips (N) 119 Pe story = elastic critical buckling strength for the story in the direction 120 of translation being considered, kips (N), determined by side- 121 sway buckling analysis or as: 122

H L 123  PRestory  M (A-8-7) H 124 where

125  RM = 1 – 0.15 (Pmf /Pstory) (A-8-8) 126 L = height of story, in. (mm) 127 Pmf = total vertical load in columns in the story that are part of 128 moment frames, if any, in the direction of translation being 129 considered (= 0 for braced frame systems), kips (N) 130 H = first-order interstory drift, in the direction of translation being 131 considered, due to lateral forces, in. (mm), computed using 132 the stiffness required to be used in the analysis (stiffness re- 133 duced as provided in Section C2.3 when the direct analysis 134 method is used). Where H varies over the plan area of the 135 structure, it shall be the average drift weighted in proportion 136 to vertical load or, alternatively, the maximum drift. 137 H = total story shear, in the direction of translation being consid-

138 ered, produced by the lateral forces used to compute H, kips 139 (N) 140 141 User Note: H and ΔH in Equation A-8-7 may be based on any lat- 142 eral loading that provides a representative value of story lateral 143 stiffness, H /ΔH. 144 145

Specification for Structural Steel Buildings, public review draft dated March 2, 2015 AMERICAN INSTITUTE OF STEEL CONSTRUCTION