1

1 The Futllre of the Sliper Hi.Rise Bllildillgs 3 Z Additioll for tile Press 10 J COllerell·Filled Sleel COllHllIlR for Multistory COlIstrllriioll 12

v- I MODERN TEEl CONSTRUCTION •

Published by VOLUME XIII NUMBER 1/ FIRST QUARTER 1972 American Institute of Steel Construction CONTENTS 101 , , N. Y. 10017 The Future of the Super Hi-Rise Building 3 Less Steel Per Sq. Ft. 8 Addition for the Press 10 O"~ICE". Concrete-Filled Steel Columns for Multistory Construction 12 Gilbert M Dorland. President Van W. Coddington, First Vice President William R. Jackson, Second Vice President Robert P. StuPP. Treasurer 1972 PRIZE BRIDGE COMPETITION John K. Edmonds. Entries are inrited for the Hth Annual Prize Bridge Compe­ Executive Vice President tition to select tlie most beautiful steel bridges opened to traffic Leslie H. Gillette. ASSistant Executive Vice President during the calendar year 1971. William W. Lanigan, The membas of the 1972 Prize Bridge Jury are: Secretary and General Counsel Gerard F. Fox, iU.ASCE Partner, Howard, Needles, Tam­ men & Be"gendoff, New York, N. Y. Rol)er! M. Mai,.. , F.ASC"· ProfessOl', Civil and Environ­ mental Engineering, Washington Unive"sity, St. Louis, • _OITORIAL STAFF Missouri Daniel Farb, Director of Publications Rober! 8. Ridwrtl., F.ASCE President, DeLellw-Cathe,' Mary Anne Donohue. Editor & Co., Chicago, Illil/ois /o/m E. Wnne, F.A~(;J;· President-elect, American Soci­ ety of Ci,'il Engineers; Earl and Wright, San Francisco,

".QIONAL OFFIC.S California Atlanta. Georgia Alan III. '·0"r/.ee8, III.ASCf; Former presidellt, Amaican Birmingham, Alabama Institute 01 Planner .• ; Alan M. l'00rhee8 & Associates, Boston, Massachusetts Inc., McLeaJ!, Virginia Chicago, Illinois Enl>'ies must be postmarked prior to May 27, 1.?72 and ad­ Cleveland, OhiO dressed to the A lL'Urds Committee. AmC1'ican Institute 01 Steel Columbus. Ohio Construction,101 Park Are.we, New York, New York,10017. Dallas, Texas Denver, Colorado 1972 FELLOWSHIP AWARDS Detroit, Michigan Charlotte. North Carolina Four engineaing stue/ellts hal'e been awarded $9,000 'ellole­ Hartford, Connecticut ships in the 10th Annllal Fellowship A It'ards Program. The Houston, Texas progmm is designed to encow'aoe e... pertise in the creative use Los Angeles, California o"abricated strllcillml steel. Memphis, Tennessee Ric" F. David.on New Me;rico State University Milwaukee, WisconSin Adam III. Gla.. Uniursity 01 Wisconsin-Milwaukee Minneapolis. Minnesota New York, New York Er". ! 1I. /"'.0"', II/ Washington Vniversity-St. Louis Oklahoma City. Oklahoma Slephe" JI". ) orlly University 01 Notre Dame Omaha. Nebraska Philadelphia. Pennsylvania Pittsburgh, Pennsylvania OUR APOLOGIES St. Louis, Missouri OJ! page 401 the 4th Q. , 1971 i8slle 01 MSC, the Architectllral San Francisco, California Awards 01 EJ'Cellence willllers !Cere alllloullced. l"n, '·~J· !ff 'llf . Seattle. Washington the name 01 Vincent G. [(lillO and Pal'tllCl'S, Phil _ .. t Syracuse, New York was omitted as olle 01 the architects 101' the Richmond ColiseulIl, Washington, District of Columbia Richmond, Va. • •

EtHel TOWeR STANDARD Oil JOHN HANCOCK CEHTER EMPIRE STATE WORlD TRADE CENTER SEARS TOWER PAitS NEW YORK CH ICAGO CHICAGO NEW YORK NEW YORK CHICAGO 984 feE T 1046 FEET 1136 feET 1127 FEET 1250 FEET 1350 FEET lASO FEEl A Compari,on of the lVorld's Tallest Structure.

These days the record for the world's Unique Design Concept tallest structure has the longevity of a These questions were put to Dr. Faz­ wea ther report. lur R. Khan, the structural engineer, The The 954-ft Eiffel Tower held its rec­ whose unique design concepts have per­ ord 41 years, from 1889 until 1930 mitted the erection of current ultra high whe n New York's 1,252-ft high Empire buildings, including the upcoming Sears State Building was constructed. Sur­ Tower, a IIO-story steel structure which Future mounted by its Zeppelin mooring mast wi II be the world's highest. • and TV antennae, that building held its Ultra high office buildings are a re­ record until the day of October 19, 1970 sponse to mounting socioeconomic when the first of the twin towers of the pressures to produce more efficient land of New York World Trade Center passed use and to create a more attractive the 1,252-ft mark on its way to its final centercity urban environment. height of 1,350 ft. The new superskyscrapers have be­ It is estimated that the Trade Center come possible because of the develop­ will hold its world's record for the ment of revolutionary new steel struc­ the world's shortest time, probably three tural systems embodying economies in years, when Chicago's Sears Tower design, and in the progressive lighten­ passes the 1,350 ft mark on its way to ing of the frame and components of a Super its own new world's record of 1,450 ft, high structure. more than a quarter of a mile high. The new structural systems, in turn, Although stories seem the convenient have come about because of the devel­ way to measure the height of a high rise opment of newer, stronger structura I Hi-Rise building, height in feet is the accurate steels, development of high strength measurement, because a story can vary bolts and welding methods, the more from 9 to 12 ft in height. imaginative use of conventional lighter What has caused the sudden em­ gage steels in floors and curtain walls, phasis on ultra high buildings? Has and using the computer. Building there been a technological break­ Buildings as high as 150 stories may through that's made the supersky­ be expected in the next decade. Build­ scraper possible? How high can a i ngs of 100 stories wi II become more structure be built? Are ultra high build­ commonplace, but the major effect of ings economical? What ultimate effect the economies produced by the new will the superskyscraper have on high high rise structural systems will be the • rise office buildings? lifting of the height of the average office

FI RST QUARTER 1972 Empire Stute BitildiJlU

Sear. T01()tr

building from 30 to 50 stories, up to an architectural partner of Skidmore. past decade. The tallest example is the • 40 to 70 stories. Because of the newer Owings & Merrill, suggested a combina­ . Its shortcoming structural concepts, the premium for tion of two structures in one_ Dr_ Khan 's has been the enormous amount of metal added floors will be very moderate and, unique steel structural system made it required for tall structures. therefore, will justify the added height. possible to do SO with a saving of about So says Dr. Kahn, who is regarded as $15-million in steel. The single struc­ Choosing the Superskyscraper one of the country's most innovative ture consists of seven stories of ga­ To a large extent, four major factors structural engineers. He is the present rages, 29 stories of offices, 47 stories have been primarily responsible for the leader of the rebirth of the original spirit of apartments, along with a 44th floor new ultra high rise office building and its of "Chicago School" of architecture, "sky lobby," and other floors for stores, reduction in weight per square foot, says which "invented" the steel-framed sky­ and the vast amount of mechanical Dr. Khan. The first consists of innovative scraper about SO years ago. It has been equipment required, including emer­ structural systems. He gave two exam· Dr. Khan whose work produced tall gency power equipment for the massive pies. One is the diagonally braced ex· structures which do "scrape" the sky. structure. It is believed that the John terior wall system used in the John Dr. Kahn, born in Dacca. Pakistan. is a Hancock Center enjoys more continu­ Hancock Center. This system requires citizen of the United States, with three ous, 24-hour use than any structure on less steel per square foot than that used graduate degrees in engineering from earth, and may be a practical answer to in a conventional design. In the case of the University of Illinois. He is the en ­ saving central cities. It approaches the the Hancock Center. this meant a sav· gineering partner in the Chicago office Parisian concept of mid·dty living. ings of $15-million. This design is dis­ of Skidmore, Owings & Merrill. "Paris, for example," says Dr. Khan, tinguished by a series of huge vertical Runaway construction costs and in­ "is one of the few cities in the world steel "X's" plainly visible in the e>

MODERN STEEL CONSTRUCTION • ChrY8ler Building

John HUl/cock Center

Bundled Tube Structural System ure out why billions of dollars should present many feel that 20 stories is a • Dr. Khan also cited the bundled tube be spent to erect a mile-high pylon of reasonable cut off point. All old high structural system used in the Sears almost solid steel that would serve no buildings should also be converted to Tower. The building consists of nine economic, social, or cultural need. emergency equipment. With so much of tubes, each 75 ft square, joined three in our population in the older age groups, a row, to form a "bundle." The rigidity of Height Limitations apartment houses should have emer­ this "bundle" is intensified because the Dr. Khan revealed some of the be­ gency power equipment for even lesser adjoining "tubes" sha re common walls. hind-the-scene considerations that lead height, say over 10 stories. The tenants Had this structure been designed as a to a decision to erect a superskyscraper. feel that eventually such equipment will uconventiona l steel cage," it woul d have First, what are the factors which limit become mandatory. cost about $25·million more. height? Structural cost can be a major The progressive lightening of the problem, but the newer structural sys­ A Look To The Future frame of a steel-framed building repre­ tems can keep such costs reasonable if The advantages of height outweigh sents good design, as well as economical construction costs are within bounds. the disadvantages when one of the mod­ constru ction. Dr. Khan illustrated the Local zoning can limit height, as can ern structural systems is used. More continued reduction in the weight per Federal Aviation Administration regula­ revenue-producing floor space can be sq ft of tall buildings. With a gross area tions when high structures are likely to created without adding to the structural of 2.75 million sq ft the 1930 Empire offer a hazard to airplanes. congestion of an urban area. The top State Building weighs 42.2 psf, in con­ Foundation conditions can be an floors can be above most of the dust trast with the 1968 John Hancock with additional problem because it is neces­ and noise levels of an area. Upper floors 2.8 million sq ft of space which weighs sary for all tall buildings to be con­ produce more revenue than lower floors, 29.7 psf. The 1974 Sears Building with structed on very stable soil. This is help pay the slightly higher premium 4.4 million sq ft will weigh 33 psf. The achieved by driving long piles, sinking cost for the higher floors, and remain as 1972 World Trade Center with 9 million caissons to bedrock which may be more permanent premium income producers. sq ft weighs 37 psf. than 100 ft below ground level, or by Where are the superskyscrapers lead- • Says Kahn, "When optimum struc­ making very deep excavations into the ing us? Dr. Khan says, "To more livable tural systems are used, the 'premium ground and literally "float" the entire ci ties, and a continued profitable con­ for height' in constructing ultra high building. All of these special conditions struction industry when labor costs are buildings is relatively insignificant. can make foundation costs prohibitive. kept in line." The higher rentals which may be charged The penalties of height must also be Dr. Khan said he foresaw a great fu­ for the more desirable upper floors soon overcome. The new structural systems ture for the 24-hour complete city offset the moderate added construction minimize the amounts of steel required. building where garages, offices, stores, costs, and, thereafter the upper floors Vertical transportation can still be a apartments, restaurants, and recreation become a permanent higher income pro­ significant problem for very tall struc­ are combined with open spaces of ducer for the owner." tures. One innovative approach is the plazas and greenery on the ground level. How high are future office buildings sky lobby located at 30- to 50-floor in­ Because these buildings must relate to likely to go? tervals from which passengers on the the total urban scene, there is going to Dr. Khan believes that within the lower bank of elevators transfer to an­ be more accent on overall planning of 1980's someone may build a structure other bank ascending to higher floors. cities with mass transportation systems of 130 stories, although one of 150 is As structures have grown taller and as a key factor in design decisions. not beyond the limit of present tech­ their populations have increased, the Many pessimists say that mid-cities nology. One-hundred story buildings will accompanying increased demands on are running out of land. This notion become commonplace, but the major power companies has led to power fa il­ should cease with the realization that result of the economies produced by ures, which have become a grave con­ much future high rise construction will the new structural steel design con­ cern to tenants, builders, engineers, and be freeing ground space, now cluttered cepts will be to lift the present average building officials. with poorly planned buildings. Future height of office building of 30 to 50 As many safety conscious engineers structures, standing on sturdy steel stories, up to 40 to 70 stories. see it, all tall buildings owe it to their legs, will span the air rights over railroad Dr. Khan brushed aside, as little more tenants to be equipped with their own rights-of-way, tracks and railroad yards, than a conversational gambit, the sug­ fall-back emergency power generating and possibly even over highways near gestion of the late Frank Lloyd Wright equipment. Every office building of sub­ or through large communities. for a mile high office building. Dr. Khan stantial height should then be designed On the whole, Dr. Khan feel s that the . admits that a structure of such height with such equipment. The exact height future of the high rise building and the might be engineered, if anyone can fig- is a matter of judgment, but for the construction industry was never brighter.

6 MOOERN STEEL CONSTRUCTION • LESS STEEL PER SQ. FT. •

THE PROGRESSIVE REDUCTION IN THE POUNDS

OF STEEL PER SQUARE FOOT IN STEEL-FRAMED

HIGH RISE STRUCTURES

A significant trend to more econom­ Ibs of steel per sq ft, compared with 4. The increasing use of composite ical use of steel in high rise construc­ 42.2 Ibs for the Empire State Building. floor construction where steel beams tion is well under way. Its symbol and a A 50·story building can be constructed act compositely with concrete slab. In measure of efficient design and tech­ with only 20 Ibs and an II-story struc­ some cases the steel deck acts com­ nology has become the weight per ture with as few as 6.3 Ibs. positely with the concrete slab. square foot of a steel-framed structure. The following table indicates the 5. The use of computers which (a) The weight·per-foot figure is derived progress made in the reduction of speed up and refine analysis for deflec­ by dividing the total number of square weight per square foot since the 102- tion and stress and thus result in the feet of gross floor space into the total story Empire State Building was con­ more accurate and economical use of weight of the steel in the frame of the structed in in 1930. The steel, and (b) let engineers make alter· building. tabulation can not reflect all conditions nate choices with speed and economy. Weight per sq ft has become an im­ and factors which influence the reduc­ 6. The "details" which consist of the • portant kind of relative cost index be­ tion in weight. However, eight major fac­ arduous, painstaking steps taken by en­ cause the weight of a frame is related tors have significantly contributed to gineers in evaluating alternatives at to its cost, even though it is frequently weight reduction and have helped to each step of design, the total of which impossible to compare either the cost make steel the most economic and com­ can produce substantial reductions in or the weight of one structure with an ­ petitive construction material for high the weight of a frame. other because of many variables. Also, rise buildings, both office and residential. site conditions and other factors can Here are the major factors identified 7. The gradual increases in allow­ sometimes make a relatively heavier as chiefly responsible for slimming down able stresses on the basis of continuing frame more desirable. the weight of a steel structural frame: research, as indicated in the AISC 1969 The progressive reduction factor in Specification for the Design, Fabrica­ the weight per sq It is indicated in a 1. Dramatic and innovative design. tion & Erection of Structural Steel for Buildings. The new AISC Specification study made by the Steel Products News 2. The use of high strength low alloy Bureau which highlights the weight-re­ thus more accurately predicts the steels which are up to 100 percent strength of steel structures. ducing contributions of some of the na­ stronger than conventional structural tion's foremost engineers and architects, steel for buildings. Quenched and tem­ 8. A reduction in the weight of other whose pace-se tting developments have pered steels used in high strength bolts construction materials has permitted ranged from spect~cular design con ­ are even stronger. use of lighter steel frames. Lighter ex­ cepts to the use of eight major factors ternal and internal walls, lighter floors which reduce weight. Many are less dra ­ 3. The use of welding for fastening. using cellular steel panels and light­ matic, some are innovative, others are Welding saves from 8 to 15 percent of weight aggregate, the lightening of pedestrian, but the total of which is re­ the steel required in a structure that is other components and reduction of floor flected in substantial savings in steel riveted or bolted because it results in height all combine to reduce the dead­ structures ranging in height from 110 continuous construction, and it elimi­ load a frame must carry. Elimination of to 11 stories. nates or minimizes the angles and concrete fireproofing and the SUbstitu­ Today, a 100's tory office building can plates which must be used when struc­ tion of light sprayed",n material also be constructed with no more than 29 tures are fastened with rivets or bolts. produce a big saving. •

MODERN STEEL CONSTRUCTION .,

Pounds of Steel Gross Area Ht·Width • per Square foot Year Million Square feet Stories Ratio Building . City 42.2 1930 2.75 102 9.3 Empire State New York 38. 1969 2.2 60 5.7 1st Nail. Bank Chicago 37(*) 1965 1.46 31 4.4 Civic Center Chicago 37. 1930 1.1 77 8.5 Chrysler New York 37 . 1972 9. 110 6.9 World Trade Center New York 33. 1974 4.4 109 6.4 Sears, Roebuck Chicago 32.1 1961 2.8 59 6.1 Pam Am Bldg. New York 32. 1950 .9 42 7.5 UN Secretariat New York 30. 1971 3.1 64 6.3 U.S. Steel Corporation Pittsburgh 29.7 1968 2.8 100 7.9 John Hancock Center Chicago 29.5 1974 1.4 62 7.1 United California Bank Los Angeles 29.5 1962 1.77 50 3.5 277 Park (Over RR) New York 28. 1957 .85 42 5.1 Seagram Bldg. New Yorl< 27.2 1945 .625 32 4.4 Esso Bldg., Radio City New York 26.6 1950 .3 9 27 5.5 Sinclair Oil New York 26.5 1971 2. 54 5.1 One Liberty Plaza New York 26.5 1971 1.84 54 5.75 IBM Bldg. Chicago 26. 1969 .4 26 4. Alcoa Bldg. San francisco 26. 1971 2.4 51 6.5 McGraw·HIII New York 25.7 1951 .51 30 4.1 Alcoa Bldg . Pittsburgh 25.6 1960 .258 ZO 4.1 United Engineering Center New York 25. 1972 .6 40 4.1 1st Natl. Bank, Oregon Portland 24.5 1969 .875 50 4.9 Seattle-ht Natl. Bank Seattle 23. 1963 1.3 46 6.1 I. C. Penney Building New York 22.5 1967 .31 25 3.5 Connecticut Mutual Chicago 22. 1968 .3 7 30 5.1 Owens·Corning fiberglas Toledo 22. 1957 .46 26 3.1 Corning Glass New York • 22. 1972 1.2 40 4.1 One Beacon Street Boston 22. 1956 1.7 42 5.5 Socony Mobil New York 21.6 1963 .231 13 1.67 IBM Bldg . Pittsburgh 21.3 1970 .206 30 4.1 Two first Natl. Plaza Chicago 21. 1970 .8B 42 4.1 Boston Co. Building Boston 20.3 1950 .64 25 4.2 Mutual Life Insurance Bldg. New York 20. 1960 1.92 43 3.1 1290 6th New York 20. 1968 1.8 50 4.1 Burlington House New York 19.1 1955 .44 33 4.1 641 Lex. Ave . New York 18.9 1967 .84 41 3.4 437 Madison New York 18.7 1958 1.10 38 2.3 80 Pine Street New York 17.9 1959 .69 22 4.5 Gateway Center Bldg. #4 Pittsburgh 17.9 1971 1.5 54 6.t lOS Center Minneapolis 16.8 1957 1.50 30 1.7 2 New York 16.7 1958 .15 8 1.2 Deering·Millikin New York 16. 1969 .5 29 3.1 77 Water Street New York 8.78 1970 .15 10 6.1 200 No. Glebe Road Arlington, Va. 6.5 1969 .148 17 3.1 Housing Project St. Paul 6.3 1966 .168 11 6.1 Stevenson Apts. Bladensburg, Md. 6.3 1971 .13 10 5.1 Low income Housing (HUD) Brockton, Mass.

NOTE- Gross area Includes all framed area fn buildinl above and below ,rade. Number of stories are above crade.

·The 37-psf weight of the Chicalo Civic Center Illustrates the need to consider I number 01 variables In comparl;3 structures on the basis of their dille rent per-foot-welghts. The Civic Center rises to • height of 640 II yel Is only stories high and has 87-ft spans due 10 architectural requ irements and variations In the size and loc.Uon of the mlny • court rooms in the structure. FIRST QUARTER 1972 •

ADDITION for the PRESS.

Architect: Ratcliff-Slama-Cadwalader Berkeley. California -- Structural Enlineer: Alan R. McKay and Associates Berkeley, California --.. General Contractor: -- Rai se r Construction Com pany San Mateo, California

E ....!!Iit: "%;:::--~ new steel structure '0 =• u -• '- ... I• I ;c• • o 20 ft 10 MODERN STEEL CONSTRUCTION The new Press Box for Memorial Sta­ west rim of the stadium, using a mini­ Two tiers accommodate the working dium, at the University of California, mum of the existing seat space, and press, radio and television coverage, Berkeley, replaces a smaller wood frame avoiding any visual blind spots. coaching staffs, statisticians, and VIP's. structure, built in 1923, which was sup­ The planning of the Press Box is Along the back of both tiers are the ported on the reinforced concrete struc­ based on obtaining clear visual sight supporting functions, snack bar, toilets, ture of the stadium_ Since the stadium lines. The metal-framed plexiglas win ­ storage, film changing room, and the is built over a major earthquake fault, dow panels are constructed in such a like. An elevator connects with the it was felt that a new and larger struc­ manner as to swing up and out, thus ground level entry, 90 It below. ture would have to be structurally inde­ eliminating posts and mullions from The use of steel is based on several pendent In addition, the University view. The transparency of the front face factors. Of primary importance is the preferred a scheme that would only is further expressed by the use of structure of the Press Box itself. I n­ eliminate a minimum number of spec­ bronze-tinted plexiglas spandrels, re­ stallation, accessibility, the need for tator seats_ vealing both the floor line and structure. long spans, and the necessity of a rela­ The solution to the problem was, The siding material is made of fac­ tively lightweight material were prime therefore, a steel and plexiglas sheathed tory-finished corrugated steel, which considerations in choosing steel as the steel frame structure, cantilevered on spans from floor to floor. Its "skinlike" building material. huge wide-flange steel columns, which character is visually expressed by re­ Aesthetically speaking, the character are embedded in a new concrete foot­ vealing thin edges, wrapping around the of steel and glass were employed to con­ ing system_ This new structure, 24 ft back corners and ending with sharp trast with the existing stadium in both • wide x 180 ft long, hovers above the edges at the front corners. form and texture. FIRST QUARTER 1972 11 Concrete­ • Filled Steel Columns for Multistory Construction •

by Alexander G. Tarics

• • - The ('ollnml. i".idc 0/ the Bhadtd area participatr in lateral load resistance. • TheBe aTC inl(,Tconnecteci with 6 It deep girders. The lat(,Tal load re.iBtillg framc closely upproximatc. the shape 0/ a canti- BUILDING ELEVATION [('vcr 0/ equal 8tre8'. The colum"s outsicie' of the shaded arca carry 1..' crtiealloatl oJlly, alld are illtercon­ "feted 1dth shallow girciers uncler the floor slab. Herr the floors cantilever out­ side the lillc 0/ caltom'l', adding 80,000 sq It 0/ usable arca fa the building.

In conventional construction the high tensile strength of structural steel and the high compressive strength of con­ + crete are successfully combined into a single structural unit in composite con­ struction. In another kind of combination of • steel and concrete, the high compres­ sive strength of the two materials is efficiently utilized when large diameter '"Of. o structural steel pipes are filled with o concrete to form a column. Such col­ ...J umns of several feet in diameter are ex­ u.. tremely efficient, not only to carry grav­ >­ ity loads, but also to resist lateral wind I­ and earthquake forces in high rise con­ u.. struction due to their greatly increased u.. stiffness gained by the use of the more efficient pipe section and by the addi­ tion of concrete inside of the pipe. These concrete·filled columns can sig­ nificantly contribute to the solution of several major problems associated with high rise construction, the control of sidesway, the elimination and simplifica­ tion of highly stressed connections, pro­ visions for fireproofing, and provisions for damping in earthquake areas. Depending on the floor load, the clear span of the floor beams, and on the mag­ nitude of the lateral load for which the building is designed, the steel required for the framing of a typical 50·story building is in the range of 24 to 28 psf • of the tower floor area. Or. Tarics of Reid & Tarics Associates, San Fran­ CISCO, Calif., IS principal in charge of design.

FIRST QUARTER 1972 HORIZONTAL SECTION @ COLUMN S 8- 8

1,5 ' . /- , connections • 10 ' · 1- 2 The conventional high rise steel structure is composed of an assembly I !I c r 0 of columns and girders. Where columns U .. and girders meet, stresses are the high­ I est, yet this is the point where the .;. • 8 , girders are spliced for the necessary continuity. The cost of the preparation :. I ~ ;., I L of the connections in the shop and the , ':- cost of the field work associated with it are significant components of the total •, . •, cost of the structural steel. A typical " 50-story building may have thousands I • . ~. .. . \ of such connections . , - .. The use of large tubular concrete­ , filled columns simplifies the construc­ I ] tion, because it permits columns and 3 girders to go through at their point of . I '" • , intersection without interruption. The s concrete in the pipe columns prevents 6 1 ~ the buckling of the web of the girder 1'-' ,- from the usual high shear stresses in­ '--. '0 - . side of the connection. The girders "pierce" the columns and only the web [ .1f11 of the girder is connected to flanges of 1 the steel columns in the most simple I c J I 1- 0 manner. Girders are spliced where stresses are lowest, specifically, in be­ FRAMING ELEVATION @ EXTERIOR WAll • tween columns. The number of highly l..JL--.J stressed connections under lateral load A-A o 1 3 6 can be also reduced to almost half byex­ LEGEND cluding certain columns from the lateral load resisting frame. mech. duct (optionol) .. column connection 2 cantilevered floor 5 ,t.. 1 pipe - cone. rill Fireproofing 3 girder connection 6 girder The fire resistance of building ele· ments is determined through standard fire test procedures adopted by appro· priate agencies. It is expected that dur­ Si desway for all steels. Consequently, when these ing fire tests these columns would ex­ steels are used in a high rise structure, hibitgood fire resisting qualities-similar In the design of steel framed high the higher working stresses under lat­ to partially water·filled columns - be­ rise buildings, the control of sidesway eral loads are accompanied with high cause of large amounts of water of crys­ under lateral wind and earthquake strains and with increased sides)"ay. tallization in the mass of concrete in­ forces represents a major problem. With This does not exclude, but puts a limit side the steel pipe. Until such tests conventional structural systems it is to, the broad utilization of high strength are performed on these proposed col­ customary to use more steel than re­ steels in multistory construction. umns, they can be fireproofed as con­ quired for strength alone to keep the The st,ffness of the proposed con­ ventional steel columns. sidesway below acceptable levels. crete-filled tubular columns is so many The round shape and uniform diam­ There are several commercially avail­ times more than the stiffness of the eter make it practical to consider the able steels which have significantly equivalent weight wide flange columns, use of simple prefabricated fireproofing. higher yield point than the commonly that less steel and higher strength steel Those columns which do not participate used A36 steel. The modulus of elastic­ can be used in the buildings without in lateral load resistance and conse­ ity, however, does not increase with the excessive sidesway. The saving in steel quently have simple connection details higher yield point; it remains the same alone offsets the extra cost of concrete. can also have shop applied fireproofing. •

1~ MOOERN STEEL CONSTRUCTION • Damping Substantial Savings Seen • Minimum steel quantity per sq It of Investigations of the effect of actual Experience has taught us that prog­ building area earthquakes on high rise structures in­ ress in construction technology is grad­ • Reduction of the number and sim­ dicate that stiff masonry elements, act­ ual; ideas emerge along lines already plification 01 highly stressed con ­ ing in unison with steel frames, crack started. In that sense the idea of using nections and field connections and yield after their elastic deformation concrete-filled large tubular steel col­ • Reduced fireproofing requirements reaches its limit and help to dissipate umns in high·rise construction to con­ Concrete-filled steel pipe columns the destructive kinetic energy in the trol sidesway is ana logous to the con­ mean better buildings as they reduce building. The concrete in this case will cept of "composite design" for horizon­ sidesway and contribute to essential reach the limit of its elastic deforma­ tal beams which carry gravity loads. damping in seismic areas. tion, when stresses in the steel pipe are A new idea in construction has im­ This novel structural concept, devel­ still very low, beyond that it will crack, mediate value only if it produces build­ oped by Reid and Tarics Associates, has yield, and help to dampen the lateral ings which can be built at less expense been presented as it appl ies to a 50- movements of the building, without than buildings designed with already story office building. The concept is also losing its ability to carry design loads, existing ideas. The concept presented suitable to the framing of any multi­ being in an ideal state of confinement here yields substantial savings through story building: hospital, apartment inside the steel pipe. accumulation of the following: house, research building and the like.

• ERECTION OF STRUCTURAL STEEL

Coltwtn, alld girders are a,· CO/UJntl 'tction. are fabri­ ,enthlcd on ground 1uith cated in halvn, ll·ith /latlge. ftangt. 0/ hall cohunn ue­ lor a•• tntblv at tltt .itc. tion, bolted to rach otheT and to web. 0/ virden.

Co[urn,,, 1dtich art alreadJl ill piau art' fil/ed tt'ith concrete. Next, column-girdtr a.,('ntb/II 18 put into place, Field CQllll('C­ • tion. eompleted. FIRST QUARTER 1972 15 AMERICAN INSTITUTE OF STEEL CONSTRUCTION 8UlK RATE 101 Pork Annue New York, New York 10011 US POSTAGE Address Correction Requested PAID DAN8URY, CONN PERMIT NO 97 •

•

•