Getting the most out of wood: “The Wood Products Council” is a Registered Provider with The American Institute of Architects Continuing Education Systems Tension-face reinforcing (AIA/CES). Credit(s) earned on completion of this program will be reported to AIA/CES for AIA members. Certificates of Completion for Edwin Nagy, PhD, PE both AIA members and non-AIA members are available upon request. edwin.nagy@maine .edu This program is registered with AIA/CES for continuing professional Kleinschmidt Associates, Pittsfield, ME and education. As such, it does not include content that may be deemed University of Maine Orono, ME or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product.
Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.
Nagy March 2011 1 Nagy March 2011 2
Acknowledgments Learning Objectives (UMaine/AEWC) At the end of this program, participants will be able to: Shane Bourgault Keith Martin
1. To identify how fiber reinforced polymers (FRP) are used to strengthen wood Eric Cassidy Paul Melrose products. JhClJosh Clapp BbO'NilBob O'Neil 2. To apply the technologies of FRP glue laminated timbers and FRP panels in building design. Habib Dagher Larry Parent 3. To evaluate the implications of the AASHTO design specifications for FRP Bill Davids Nick Parlin glulam use in Timber Bridges by understanding the technical background. Tony Dumais Will Syron 4. To discover why FRP reinforced panels can cost effectively meet the Unified Facilities Criteria 4-010-01: DoD Minimum Antiterrorism Standards and how this technology can be used in disaster resilient design. Bob Lindyberg Dan Thomas
Roberto Lopez-Anido Many, many undergraduates Nagy March 2011 3 Nagy March 2011 4 Acknowledgments Wood Mechanical Properties (Funding) Relatively brittle in tension, very ductile in compression • ERDC - U. S. Army Corps of Engineers
•FHWA tension ss • USDA-WUR ee str •NIST •NSF strain • APA-The Engineered Wood Association
compression Skip Wood Mech Intro
Nagy March 2011 5 Nagy March 2011 6
Wood Mechanical Properties Wood Mechanical Properties • Clear, straight-grained wood is strongest in tension • Elastic and strength properties are highly variable CoV for E averages 22% for clear wood • Clear, straight-grained structural lumber does not exist CoV of MOR averages 16% for clear wood • Failure usually occurs in tension or shear near a defect • 5% Lower Tolerance Limit (LTL) is determined • Sloping grain also significantly reduces strength from cumulative distribution function (CDF) (Grain angle of 10o can cut strength by 20% or more) 1 yy Probabilit 5% LTL 0.05 Typical bending failure at knot Strength Property Nagy March 2011 7 Nagy March 2011 8 Two Ways to Higher Strength Redistribution of Defects A. Increase tensile cappyyacity by removing/moving/bandaging defects B. Reduce variability to increase 5% value B 2) Wood A. Increase in mean ity A stthtrength B. Increase in 5th Improved 1)
Wood robabil pp(g)ercentile (design) PP strength 1) http://www.gogreendesign.biz/images/PiSL_Coffee_2.jpg 3) 2) http://www.sbebuilders.com/images/glulam.jpg 3) http://img.ecplaza.com/my/sara888/3.jpg BkiStthBreaking Strength Nagy March 2011 9 Nagy March 2011 10
Reinforcing Defects Three Improved Wood Technologies
• FRP-Reinforced Glulam Beams • Coated Lumber for Blast-resistant Structures Knot • FRP-Reinforced OSB for Shear Walls
Reinforcing (Steel, wood, FRP...)
Nagy March 2011 11 Nagy March 2011 12 Glulam Beams - Overview FRP-Reinforced Glulam Compression Selective stacking: •May have high-grade lamination on top •Lower-gradlde lam ina tions in core •Higher-grade lamination on bottom Tension Glulam manufacturers standardize layups • Low grades stronger in compression •Depp,pends on manufacturer, species • FRP tension reinforcement can mitigate tension failure •Design strengths and E are established for Can we build beams with low-quality, cheap laminations and a small amount of FRP each lay-up that are stronger than beams with expensive high -grade tension laminations?
Nagy March 2011 13 Nagy March 2011 14
FRP-Glulam Strength and Ductility 100kN 3% GRP MOR=65.3MPa Tension 1% GRP knot finger joint MOR=49.9MPa ad oo L
Ft > Fc
ad CONTROL oo 130mm x 305mm x 6 .4m span L MOR=27.7MPa Fc > Ft 0 Mid-Span Displacement Deflection 0 250mm Nagy March 2011 15 Nagy March 2011 16 FtiFatigue T esti ng Specimen in Test Setup
Specimen FRP Reinf. No. of Number Type Configuration Replicates S1-S3 GC Full length 3 S4-S6 GC 3 S7-S9 GC 3 S13-S15 GC 3 S19-S21 CP Full length 3 S25-27 CP 3
Nagy March 2011 17 Nagy March 2011 18
Tension Failure Compression Failure Exhibited by 12 of 18 specimens tested • Exhibited by 2 specimens at < 2x106 cycles • Governed post -fatigue strength for specimen S21
Specimen S5 Specimen S21 (at 1 . 2x106 cycles) (post-fatigue failure)
Nagy March 2011 19 Nagy March 2011 20 Shear Failure Typical Failure Mode for S4-S6 Exhibited by 2 of 18 specimens tested
Fracture initiated at FRP termination
Nagy March 2011 21 Nagy March 2011 22
Summary of Results Residual Strength After Fatigue (2e6 cycles) Specimen FRP Reinf. Mean MOR/Fb Number Type Configuration MOR • Mean MOR = 53.4MPa (COV = 0.109) S1-S3 GC Full length 59. 5 343.4 • Using ASTM D2915 to compute Fb with a population of 19 S4-S6 GC — — and a 75% confidence interval: S7-S9 GC 49.1 2.8 Fb =(534= (53.4 – 1. 964*0.109*52 . 5)/2. 1 = 20. 1 MPa S13-S15 GC 48.8 2.8 • Expected Fb = 17.5 MPa S19-S21 CP Full length 48.9 2.8 • No apparent bending strength reduction due to fatigue S25-27 CP 55.3 3.2
Nagy March 2011 23 Nagy March 2011 24 Conclusions Wood-FRP Bond Integgyrity • Untreated full length reinforced glulams do Hygrothermal Effects not appear to be prone to fatigue failures – Must be aware of potential for compression and shear failures (effect of higher reinforcement # 1 Durability Issue ratios) – Significant delaminations between wood and FRP can be tolerated in higggh shear regions Expansion
• FRP termination restraints are necessary for Skip Hygrothermal and partia l leng th re in force d glllulam Creep Details – Requires periodic bolt re-tensioning, likely not cost-effective High interfacial stresses Nagy March 2011 25 Nagy March 2011 FRP 26
Wood-FRP Bond Integrity Matrix of Hygrothermal Tests Hygrothermal Effects • In-service weather conditions used to generate EMC for an average annualll cycle • EMCs used with 1D Fickian Diffusion Model to generate moisture profile for annual high and low conditions Specimen FRP Reinf. No. of • FEA predicts hygrothermal tensile and shear stresses NbNumber Type CfitiConfiguration RlitReplicates 16 16 S10-S12 GC Full length 3 nt (%) t (%) ee nn 15 15 54 mm S16-S18 GC 3 Stress 14 14 concentration S22-S24 CP Full length 3 oisture Cont isture Conte 13 13 oo MM M 0 50 100 150 200 250 300 0 20 40 60 80 100 120 Cross Section Width (mm) Number of Days MC Change Monthly Moisture Wood-FRP Interface at Surface Profiles Stresses
Nagy March 2011 27 Nagy March 2011 28 Creep Testing Results with Moisture Cycling • One spp()ecimen (S10) was Six Douglas-fir beams were loaded for nearly two years failed prematurely due to 130 mm handling errors 6400 mm 2 unreinforced • The other 8 specimens 2ith11%GFRP2 with 1.1% GFRP survived 2x106 load cycles 2 with 3.3% GFRP with no ill effects 05 mm • The average fail ure loa d o f 33 Concrete weights 121 kN compares well with GFRP reinforcing the control specimens • Compared to the control • Sheltered environment, some environmental control specimens, similar failure • Displacement, temperature and humidity were monitored modes were observed • Moisture content was determined by weighing blocks
Nagy March 2011 29 Nagy March 2011 30
Creep Testing – 10 yrs later Experimental Results
Sep 97 Mar 98 Sep 98 Mar 99 50 14 1.1% GFRP 40 13 t (%) (%) nn 30 12 0% GFRP e Creep e Conte vv 20 33%GFRP3.3% GFRP 11
Relati 10 10 Moistur Moisture Content 0 9 0 200 400 600 Time (days)
Nagy March 2011 31 Nagy March 2011 32 Predictions for Reinforced Beams ReLam: Reinforced Laminated Beam Model 1.1% Reinforcing 3.3% Reinforcing 40 40 %) (( 30 • In-grade/available data 30 Model results Model Lumber 20 • Single section Fb= ? Creep 20 results Lams ee Experimental Experimental • Moment-Curvature 10 results 10 E = ? results • Monte Carlo simulation Relativ 0 0 0 200 400 600 0 200 400 600 Time (days) Time (days) Skip ReLam Details FRP
Nagy March 2011 33 Nagy March 2011 34
ReLam – Step 1: ReLam – Step 2: GtStiPtiGenerate Section Properties Perform M-Φ Analysis c fyield
Lamstock N.A. C
- tress
UTS,,, UCS, E ss strain (mean, COV, PDF) T - 3x3 correlation matrix (y) (y)
FRP Gives NA location
UTS, E (mean, COV, PDF) Gives M corresponding to Φ
Nagy March 2011 35 Nagy March 2011 36 Putting It All Together Putti ng It All T ogeth er • Result is the CDF of beam MOR and MOE
• Allowable Bending Stress Fb=5%LTLMOR/21= 5%LTL MOR/2.1 1. A cross-section is generated from statistical lamstock data 1.00 2. M-Φ analysis is repeated for increasing curvatures to failure tion 0.80 (Momen t capacit y and M-Φ reltilations hip are save d) uu
• Steps 1-2 are repeated (Monte-Carlo simulation) 0.60 5% LTL MOR Distrib • Statistical characteristics of the strength and the load- 0.40 displacement response of a beam can be generated ulative 0200.20 mm Cu 0.00 34 62 MOR (MPa)
Nagy March 2011 37 Nagy March 2011 38
1.00
Validation of ReLAM 0.80 0.60 th VlVolume EfftEffect
5 b 279 Beam Tests 0.40
0.20
0.00 5000 6000 7000 8000 9000 • Decrease strength (maximum stress) with size • Increased probability of defects th Test Series Sample size Difference 5 Fb
646.4m 90 1%1 % 11.0m 66 4 % 15.2m 48 7 % Tension 2.9m- 19.5m 75 5 % What will FRP do to the volume factor?
Nagy March 2011 39 Nagy March 2011 40 ReLam Predictions: C for DF 1.2 v AASHTO D es ign Proce dures for 2% Tension-Reinforced Glulam Beams 1 1% 0.8 0% v
C 0.6 0.1 CV = (1291.5/V)
040.4 130mm x 305mm x 6.4m span 0.2 273mm x 1370mm x 30.5m 0 V = b x d x l
Nagy March 2011 41 Nagy March 2011 42
Recent Additions to AASHTO Design Example • LRFD Bridge Design Specifications: Section 8,
Various Articles 5-1/8” thick glulam deck with 3 ” asphalt surface
Figure 1: • Modification to adjustment factors Bridge elevation view – 8.4.4.5 Volume factor – 8.4.4.2 Format conversion factor L = 56 ft L = 56 ft – 8.4.4.3 Wet service factor Figure 2: Girder • 8.4.1.3 Tension-Reinforced Glulams defined Bridge plan view Spacing = 4.5 ft (Typ.)
Deck – Type of reinforcement (FRP, steel, etc.) Width = 22 ft
– Design values determined via ASTM D7199 Deck Overhang = (ReLam meets the requirements therein) 2 ft (Typ.)
Nagy March 2011 43 Nagy March 2011 44 Maximum Moment Summary Moment and Load Factors The live load moment 32 kip 32 kip Moment Calculations Max Live Moment = per AASHTO LRFD 8 kip 0.64 kip/ft max(0.54*978.88,0.4 *978.88) BidBridge Des ign Dis tr ibu tion fac tor Specifications (2007). Live load moment Max Moment = Live Moment + Dead Moment Design truck combined Dead load moment 59.92 kip 47.92 kip Wood Factors =632.4kip*ft with the design lane load. Girder Distribution Factors (()Table 4.6.2.2.2) CV per ReLam, others = 1.0 Live load DF for interior girders is s/10 Live load DF for exterior girders per the lever rule: LRFD Load Factors where s is the girder spacing. Assume a hinge at each interior girder and Multiple presence factor, m = 1.2 is summing moments about the hinge to calculate the multipliedbytheDFperTable36112multiplied by the DF per Table 3.6.1.1.2-1 exterior girder reaction. Conversion from ASD to LRFD per AASHTO Section 8.4.4.2)
Time effect factor, Cλ = 0.8 (Service Strength State I) Reduction factor, ɸ = 0.85 (flexure) Nagy March 2011 45 Nagy March 2011 46
Design Example Results
Unreinforced (0%) 1% GFRP 2% GFRP 3% GFRP
6756.75" x52x 52-1/2" DF 6756.75" x45x 45" DF with 6756.75" x43x 43-1/2" DF with 6.75" x 0.525" 6.75" x 0.9" GFRP with 6.75" x 1.3" 6.75" x 66" DF GFRP on tension on tension face GFRP on tension face face
Nagy March 2011 47 Nagy March 2011 48 Background Background
Traditional SEAhut
Traditonal SEAhut after blast
Nagy March 2011 49 Nagy March 2011 50
Background
Nagy March 2011 51 Nagy March 2011 52 Quasi-Static Bendinggg Testing of Wall segments in frames Reinforced Plywood Coupons
ASTM 1037 – Standard Test Methods for Evaluating Buildings and frames Properties of Wood-Base Fiber and Particle Panel Materials Test speed = 0.24 in/min Specimen width = 3in Specimen length = 24 in Span (center-center) = 21 in Pressure cell Suppor tlt length = 1 15i.5 in ea. sid e Load and cross head Experimental work displacement recorded
Nagy March 2011 53 Nagy March 2011 54
Coated Plywood
Nagy March 2011 55 Nagy March 2011 56 Coated Plywood Failure Modes of Reinforced 1/2” Plywood
1l1 layer of fP Po lyst rand on each sid e 1/2” CDX Plywood Controls Initial: Shear failure of wood Failure Mode: Tension failure at mid-span Secondary: Tensile Fracture or Delamination of FRP
Nagy March 2011 57 Nagy March 2011 58
Failure Modes of Reinforced 1/2” Plywood Failure Modes of Reinforced 1/2” Plywood
2 layers of Polystrand on each side 3 layers of Polystrand on each side Initial: Compression buckling Initial: Shear fracture of FRP 6l6 layers of fP Pol yst rand on each sid e Secondary: Shear failure of wood Secondary: Progessive compression buckling followed Horizontal Shear failure of plywood followed by by FRP delamination delamination of FRP
Nagy March 2011 59 Nagy March 2011 60 Reinforced 1/2” Plywood Results Reinforced 1/2” Plywood Results*
Number of Max Deflection at Energy Load Energy Layers Load Max Absorbed Index Index E60 X-ppyly (()lbs) (()in) (in-lb) Control 197 0.77 95 1.00 1.00 1 Layer 279 1.33 456 1.41 4.80 2 Layer 275 0760.76 511 1391.39 5385.38 3 Layer 432 1.38 796 2.19 8.38 6 Layer 747 0.82 821 3.78 8.65
*Each entry represents the average of 10 tests except 1 layer is an average of 9 tests Each curve reppgpygresents the average of 10 tests except 1 Layer is an average of 9
Nagy March 2011 61 Nagy March 2011 62
Infusion Process - VARTM
Nagy March 2011 63 Nagy March 2011 64 Coated 2x4 Lumber Failure Modes Ideal Failure Mode
Compression failure of FRP and wood
NA Shift
damage initiation No Coating Flexural Coating Only Continuous Perimeter prior to failing tensile Coating reinforcement
Nagy March 2011 65 Nagy March 2011 66
Coated 2x4 Lumber Coated 2x4 Lumber
Increase Energy Increase Peak Load over Absorbed over control (lb) control (in-lbs) (%) (%)
Control 853 (31%) --- 1139 (36%) ---
1l1 layer 1884 (25%) 121 5915 (41%) 419 Flexural Coating 2 layers 2231 (16%) 162 6904 (26%) 506 Only 3 layers 2396 (9%) 181 11165 (44%) 880
1 layer 2058 (9%) 141 6527 (24%) 473 Continuous Perimeter 2 layers 2020 (10%) 137 8340 (26%) 632 Coating 3 layers 2433 (11%) 185 10362 (23%) 810 Average Load-Displacement Plots Number in parenthesis is the COV
Nagy March 2011 67 Nagy March 2011 68 Coated 2x4 Lumber Coated 2x4 Lumber
Control 1 Layer Perimeter Coating Mean Value Normal Distribution Mean Value • Average bending strength increased 2 to 2 .5 times • Design (5th Percentile) bending strength increased 2.5 to 5 times 128% • Energy Absorption increased 5 to 9 times
5th Percentile 5th Percentile • Wrapping entire cross section eliminated horizontal shear propagation 369%
02468101214
Bending Strength (1000 psi) Nagy March 2011 69 Nagy March 2011 70
Coated Wall Panel Test Methods Uncoated Wall Panel Failure Mode
Wall Specimen Test Speed = 0.25-0.45 in/min Support Test Span = 92 in Loading Head Load applied across 4ft width at midspan Load and midspan displacement recorded
Stringpots Test Span = 90 in Support Uniformly applied pressure Pressure and midspan displacement of each stud recorded
Water Bladders
Nagy March 2011 71 Nagy March 2011 72 Coated Wall Panel Failure Modes Coated Wall Panel Failure Modes
Nagy March 2011 73 Nagy March 2011 74
Coated Wall Panels Coated Wall Panel Results Results – Hurriquake™ Nails
3-Point Bending (Average of 10 tests) th Energy Absorbed •1/6 the cost of screws Peak Load (lbs) (in-kips) • Much quicker installation CtlControl 3279 (15%) 7517.51
Coated 7824 (6%) 32.69
Uniform Load (Average of 5 tests) Average Increase Energy Increase Moment Panel over Control Absorbed over Capacity Peak Pressure Energy Absorbed FSF (%) (in-kips) Control (%) (psi) (in-kipp)s) (in-kipp)s)
Control 0.87 (23%) 1.63 Control 75.4 (15%) --- 7.51 (23%) ---
Coated 3.66 (4%) 24.68 Coated 180.0 (6%) 139 32.69 (20%) 335 HQN 179.4 (11%) 138 32.39 (15%) 331 Nagy March 2011 75 Nagy March 2011 76 Roof Panels Three Point Bending Roof Panel Moment Capacity
5th Average Increase Percentile Increase Joist Moment Panel Type over Moment over Size Capacity (in- Control (%) Capacity Control (%) kips) (in-kips)
Control T 82 --- 28 --- 2x8 Coated T 202 147 170 510 2x10 Coated T 378 --- 313 ---
= 107 in-kips f or 12ft span
Conventional Wood Wood-FRP Hybrid = 192 in-kips for 16ft span Framed Roof Panel Composite Roof Panel
Nagy March 2011 77 Nagy March 2011 78
Roof Panel Roof Panel Creep Testing Strength and E nergy Ab sorpti on
Roof Panel Increase Specimen Energy Increase Support Test Span = 12ft Joist Panel Peak Load over Absorbed over Control # Tested Humidifier Size Type (lbs) Control (in-lbs) (%) 90 psf dead load applied over (%) entire area Sandbags (90lb/ft2) Temperature = 75-85°F Control T 2271 (34%) --- 4424 (68%) --- 10 Relative Humidity (RH) = 95- 100% 2x8 CdTCoated T 5610 (8%) 147 31912 (17%) 621 10 Dial Gage at Midspan displacement recorded Midspan every day for 90 days Coated 7524 (10%) 231 69812 (9%) 1478 3 Sandwich Skip Creep Testing 2x10 Coated T 7875 (9%) --- 34974 (16%) --- 4 Details
Nagy March 2011 79 Nagy March 2011 80 Coated Roof Panels Creep Testing Results Creep Test Results (ASTM D 6815)
Fractional Deflection Roof 1 Roof 2 Roof 3
Di 0.665 0.581 0.543
D30 0.860 0.722 0.693
D60 0.888 0.739 0.710
D90 09080.908 07490.749 0. 716
FD90 1.37 1.29 1.32
Roof 1 Roof 2 Roof 3 Decreasing Creep Rate D30-Di 0.196 0.141 0.150
D60-D30 0.028 0.018 0.017
D90-D60 0.021 0.010 0.006 Decreasing Creep YES YES YES Rate?
Nagy March 2011 81 Nagy March 2011 82
Before
After
Blast Testing Blast Testing Results Nagy March 2011 83 Nagy March 2011 84 Seismic Effects on Wood Structures (Photo courtesy APA-The Engineered Wood Assoc.) FRP-Reinforced Wood Shear Walls
Bill Davids, Habib Dagher, Eric Cassidy, Keith Martin
Supported by: The National Science Foundation The US Dept. of Agriculture NIST No sheathing on garage walls
Nagy March 2011 85 Nagy March 2011 86
Wind Effects on Wood Structures Wind Effects on Wood Structures
www.nationaltrust . org/hurricane/christman. html www.nationaltrust . org/hurricane/christman. html
Nagy March 2011 87 Nagy March 2011 88 Shear Wall Performance Motivat io n fo r Di sastesaster-Resista nt Sheathing-to framing connectors are critical Construction R&D • Single-family residential construction represents over 30% of the U.S. annual construction budget
Nail head • Wood-frame construction constitutes the majority of pull-through single-family houses • Substantial damage and economic loss have resulted from earthquakes and hurricanes Connector edge tear • Maine produces many wood building products (dimension lumber and OSB, for example)
Nagy March 2011 89 Nagy March 2011 90
Research Objective AOSB Panel Characteristics Develop and assess performance of an Advanced OSB panel (AOSB) that is selectively reinforced with FRP at the panel edges to enhance diaphragm performance 6.4mm OSB
Desirable panel properties: – Improved strength and performance – Decreased damage due to load cycling 12mx24m1.2m x 2.4m – Installed with conventional construction methods FRP hot press
Nagy March 2011 91 Nagy March 2011 92 Material Screening Single Nail Connection Tests Two reinforcing schemes were assessed – Two outer layygers of reinforcing ASTM D1761-95 – Single layer sandwiched within the panel Lateral Nail, Staple, or Three different FRP types were tested Screw Resistance Test – E-glass fabric + PRF adhesive AOSB strip – E-ggasslass f abri c + th erm opastcoplastic r esin Nail loads similar to Sing le na il – E-glass fabric + vinyl-ester adhesive shear wall demand Inexpensive and fast Various fiber architectures were examined DCDT FbhFor both monoton ic an d – Woven, unidirectional, chopped strand mat cyclic tests – Final configuration combines two of these Framing
Nagy March 2011 93 Nagy March 2011 94
Failure Mode Differences Nail Lateral Load-Displacement* Conventional OSB 500 • Single nail curvature • Edge tear failure 400 • Less ductile ) 300 • LtthLower strength bb AOSB 200 Load (l AOSB Controls 100 (7/16" OSB) • Double nail curvature 3/8” • More ductile 0 1 2 3 • 90% nail pull-out Displacement (in) • 39% stronger * Each curve is the average of 10 tests • 249% tougher Nagy March 2011 95 Nagy March 2011 96 CUREE Protocol for Cyclic Cyclic Connection Test Results Connection Tests 300 0.6 200 AOSB
0.4 100
0.2 0
0 d (lbs) (inches) -100 OSB aa
Lo Control -0.2 -200 -300
lacement -0.4 -400 Disp -0.6 -1 0 1 2 0 40 80 120 160 Displacement (in) Time (seconds)
Nagy March 2011 97 Nagy March 2011 98
Nailhead Pull-through Nailhead Pull-through • Common in roof sheathing during hurricane events 3100 • Problem is magnified by rain and soaking of OSB sheathing 2990N AOSB Dry 2400N AOSB Wet
1320N oad (N) LL
Control Dry Control Wet 0 0 12.5 Dispp()lacement (in)
Nagy March 2011 99 Nagy March 2011 100 Monotonic Tests of Two-panel Walls (ASTM E-564) Instrumentation Plan
1,2
3 Wall Test Matrix List of channels: Sheathing Nail Spacing Type 150 100 1. Applied load 2. Applied displacement Control 3 3 3. Translation at top AOSB 3 3 4. Uplift displacement 5. Uplift displacement 6. Slip at base 5 4 6 Nagy March 2011 101 Nagy March 2011 102
Wall Construction Typical Results for Walls with
2x4 SYP studs @400mm. o.c. 100mm Perimeter Nail Spacing Simpson HD10A tie fastened b y 16d na ils 40 down fastened with 22mm bolts Sheathing fastened by 8d nails AOSB N)
@ 100mm or 150mm edge kk OSB control @300mm field al Load ( rr Late
Double e nd studs f asten ed by two 10d nails spaced at either Double top plate fastened 0 100 or 150mm depending on By two 10d nails @ 400mm 0 50 100 150 perimeter fastening of Horizontal Displ. (mm) sheathing. Nagy March 2011 103 Nagy March 2011 104 Cyclic Wall Tests MtiWllTtRltMonotonic Wall Test Results Carrying Beam + X - Actuator Peak Perimeter Nail Failure Mode Nail Wall Load Spacing Type (kN) % Edge % Pull % Pull Tear Through Out Pinned Supports
Control 26.3 43 54 3
150mm Data Acquisition AOSB 26. 1 11 0 89
Control 32.6 41 53 6 100mm Floor Beam AOSB 40.4 20 0 80
Nagy March 2011 105 Nagy March 2011 106
Cyclic Tests of Two-panel Walls Hysteretic Response of Walls with • Same test matrix as for monotonic specimens: 100mm Perimeter Nail Spacing 40 Nail Spacing Sheathing Type 150 100
Control 3 3 0
AOSB 3 3 oad (kN)
• Wall construction and test rig same as monotonic OSB control Lateral L • Separate CUREE loading regimes for OSB-sheathed controls and AOSB -40 AOSB specimens developed from monotonic wall test data -150 0 150 HiHorizon tlDiltal Displacemen t(t (mm )
Nagy March 2011 107 Nagy March 2011 108 Failures Observed in Cyclic Failures Observed in Cyclic Tests of Control Walls Tests of AOSB Walls
Nailhead pull-through Edge tear Nail Fatigue Nail Pull-Out
Nagy March 2011 109 Nagy March 2011 110
Cyclic Wall Test Results Wall Allowable Loads
• Computed per ICC-ES Acceptance Criteria for Prefabricated Wood Shear WllWalls (AC130) Peak Relative Perimeter Nail Failure Mode Nail Wall • Based on first-cycle envelope of cyclic response Load Energy % Edge % Pull % Pull % Fatigue Spacing Type (kN) Absor be d Tear Through Out • Minimum safety factor of 2. 5 assumed • Allowable load is computed as minimum of: Control 21.91.0 46 54 0 0
150 1) Vmax/SF = V max/2. 5 AOSB 24.31.51 4 0 77 19 2) Load corresponding to drift limit ∆ = ∆m/(1.4x0.7R) • R = 5.5 (seismic response modification factor) Control 30. 2 1311.31 37 62 0 1 • ∆m = min. (0. 025x 2. 44m, disp l. atkld)t peak load) 100 AOSB 38.42.27 6 0 48 46
Nagy March 2011 111 Nagy March 2011 112 Wall Allowable Loads Wall Allowable Loads
Peak load V = 38.4/2 . 5 = 15.4kN = 38.4kN all First-cycle envelope AOSB, 100mm nail spacing Nail ∆*m Vall Vall
ad Wall Type oo Spacing (mm) (kN) (kN/m)
Vall = ∆m = 60.5mm Control 54.6 8.77 3.60 ateral L 15.4kN
LL 150 AOSB 56.4 9.75 4.00 Control 58.2 12.1 4.96 100 ∆m/(1.4*0.7R) AOSB 60.5 15.4 6.32 = 11.2mm 50 100 150 * Upper limit of 0. 025h = 61. 0mm Horizontal Displacement (mm) Nagy March 2011 113 Nagy March 2011 114
Conclusions of Initial Studies The Next Step • AOSB panels increase diaphragm load and displacement cappyacity with code minimum nail ed ge distance (9.5mm ) • We are not fully utilizing AOSB capacity • Strength increase appears dependent on nail spacing – 27% increase with 100mm spacing • Weak links in the wall – 11% increase with 150mm spacing • Perimeter sheathing nails • AOSB panels increase energy absorption through bending • Tie-downs ofthf the nail s (dou ble curva ture )
• Within the range of nail spacings considered, allowable • AOSB in prefab narrow-panel shear walls? load increases follow strength increases • Market is strong on west coast of U. S. • AOSB panels provide as much capacity as the framing, • Competitors are Simpson, Truss-Joist, etc. tie-downs, and the sheathing nails will allow
Nagy March 2011 115 Nagy March 2011 116 A Better Fastener A Better Fastener
• Cutting tip penetrates AOSB • Stainless steel is strong and ductile • Collated screws install quickly
Nagy March 2011 117 Nagy March 2011 118
Better Tie Downs: Glued Rods Better Tie Downs: Glued Rods
A hole is drilled along the axis of Splitting failure is caused by epoxy expansion the member
A threaded rod is bonded in the hole with epoxy
Tension is transferred from the rod to the wood through shear in epoxy
Nagy March 2011 119 Nagy March 2011 120 Better Tie Downs: Glued Rods E-glass fibers wrapped around Summary the rod confine the epoxy layer
• Selective reinforcing improves lateral capacity • Full benefits require modifications to wall design • AOSB is a potentially viable technology • Most likely to succeed in niche markets • Engineered shearwalls • Industrial building horizontal diaphragms Splitting forces are reduced, failures shift to wood shear and tension
Nagy March 2011 121 Nagy March 2011 122
Thank You Edwin Nagy, PhD, PE [email protected] http://www.aewc.umaine.edu/
Nagy March 2011 123