Structural System for Tall Buildings

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Structural syst.erns for ~ a l l ~ u i l d i n g s

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Council on Tall Buildings and Urban Habitat Canlribulon S p o n s o r i n g Soclellcr Internntlonul Asrocintion for Bridge and S w c t u r a l Engineering (IABSE) American Society of Civil E n g i n e e n (ASCE) American Inrtitute o f Architects (AIA) American Planning Asrocintion (APA) Inernalional Union of Architects (UIA) American Society o f Inleriar Designers (ASID) .z~......I:.,, ; ., .~; Jnpon S t r u c t u n l Consultono Arrociotlon (ISCA) ..:; :.~ Urban Lnnd Institute (ULI) International Fedemlion of lnlerior Dcsignen ( I R ) The following identifier those firms m d orgmiwtionr who provide fartheCouncil's financivl s u p p o h Patrons A1 Rnyes Group. Kuwait Consolidnted C o n t m a o r r Internulional Co.. Athens Dnr Al-Hnndnsah '.Shnir & Panncrr." Amman D L F Univcrsnl Limited. Ncw Dclhi Zuhair Fnyez & Arrociales. Jeddvh Juros. B n i m & Bolles. N e w York Kuwait Foundmion for the Advonccmcnt of Sciences. Kuwait Shimizu Corpondon. Tokyo T h e T u r n e r Corpomtion. New Yark

Sponsors Europrofilc Tecom. Luxembourg Gcorge A. Fuller Co.. New York T.R. Hnmrah & Yeung Sdn. Bhd.. Sclangor HL-Technik A.G.. Munich Hong Kong Lnnd Group Lld.. Hong Kong Kone Elevators. Helsinki John A. Mnnin & Aaroc.. Inc.. L o r Angelcr Ahmad Mohnrrom. Cairo Walter P. Moore & Associates. Inc.. Hourton Nippon Slcel. Tokyo Otis E l e w l o r Co.. Forminglan O v e A m p Pmnerrhip. London P D M Strocnl Inc.. Slockton Leslie E. R o b c m o n Associatea. New York Snmrung Engineering Br Conrtruction Co. Lrd..Seoul Snud Consult, Riyadh Schindlcr Elevntor Corp.. Morrislown Siecor Corporntion. Hickory Tukenako Corporation, Tokyo Tishmon Conslruction Corporarion of N c w York, New York Tiihman Speyer Properties. Ncw York W c i r k o p i & Pickwonh. N e w York Wing T a i Conrtmction &Engineering. Hong Kong Wong & Ouynng (HK) Lld.. Hong Kong Donor5 American Bridge Co.. Pittsburgh American Iron and Slcel Institute. \Vushington, D.C. W.R. Grncc & Comp;my. Cambridge Hnscko Corporaion. Tokyo T h c Herrick Corp.. Pleasnnton Hollundsche Belon Mnnlschappij BV, Rijswijk Hong Kong Housing Autl~orily.Hong Kong lffland Kivvnvgh Waterbury. P.C.. New York

O'Brien-Kreilrbcrg & A S T O C ~ ~ ~In=.. ~CI. Pennrlukcn R T K L Associates. Inc.. Bnltimore Skidmore. Ou,ingr & hlerrill. Chicogo Steen Con~ultuntrPty. Ltd., Singspore Syiko & Hcnnery. lnc.. New York nornton-TomorcuilEngineer5. Ncw York Werner Vosr & Ponncrr. Braunrchwcig Wong Hobach Luu Consulting Engineers. La5 Angcles

Office o f Irwin G. Cwlor. P.C., N e w York H.K. Cheng & Pnrtnen Ltd. Hung Kong Douglas Specinlist C o n u n c t o n Ltd.. Aldridgc H n n Conrulwnt Grnup. Snntn Monica The G c o r g ~Hymnn ConsWclion Co.. Balhrsdn Ingenicurburo Mullcr Mnrl GmbH. Mnrl Institute Sulwn lrknndnr. Johor INTEMAC. Madrid J H S C o n s w e n o e Plnncjnmento Ltd.. Sno Pnulo Johnson Fain a n d Perrim Asroc.. Los Angeler T h e Kling-Lindquist P m c n h i p . Inc. Philadclphio LeMessurier Conrultnntr Inc.. Cnmbridge

L i m ConsulU~tts.Inc.. Cambridge Meinhnrdt Auslrnlin Pty. Ltd.. Melbourne Mclnhnrdl (HK) Ltd.. Hong Kong Mucrer Rutledge Consulting Engincen. N e w York Oboynshi Corpomtion. T o k y o O T E P In~crnntional.SA. Mndrid Charles Ponkow Builders. Inc.. Alwdenn Projcst S A Emprecndimentos e Servicos Tecnlcos. Rin d c Jnncim P S M Inlernnllonnl. Chicago Skilling Ward Megnurson B n r b h i r c Inc.. Senltlc Tooley & Company. L a s Angcles Nobih Yourref and Arrocinlcr. Los Angelcs

C o n t r i b u t i n g Pnrtlclponlr Advnnccd Slructuml Concrplr. Danvcr Advicrburnu Voor Bouwwchnick BV. Amhcm Amcrirnn lwti~uteof Slecl Con.uu~Lion. Chicago Anglo Amcricnn Pmpcny Scrviccr (Ply1 Lld.. lohnn"&burg Archituaml Scrviccr Dcpl.. Hong Kong Alelici D'Architcctum, dc Genvnl, Genvnl ~uslnlinnlnstitulc olSlccl Conrwcdon, hlllronr Poinl B.C.V. . Pmnctti Miiono ~ S.r.1.. ~ ~ w.S. Bcllowr conrtriction Corp.. Hourton Aificd Bcncrch & Co.. Chicngo Balro dc lrnovclr Err Sno Poulo. S.A.. Sno Poulo Bomhont & W a d Pty. Lld.. Spring Hill ~ ~ ~ n y cWind ur Tunnci ~ Labornlory d ~(U. Wcrrcm Ontnriol. London Bovir ~ i m i l i London . Bnndow & Johulon ArrociaLcr. Lor Angclcr Bmokc Hillier Porker. Hong Kong Buildings & Dan. S.A. Bwsrclr CBM Engincm Inc.. Houston Ccrmo* Pcerkn Pacnen. Inc.. Fon Coilinr CblA A r h i t u ~& Enginecn. Sari luon Conrfnction Conwlung Lbonlor). Dallor Cmnr Fuhicu Door Cu.. Lnkc Bluff Cmnc & Arloriolcr Ply. Lld. Sydnr) Da(11 Lugdon & Evcnll. London DeSimonc. Ch~plin& Dohr)n Inc. Kc. York D O ~ Arlrlnc ~ ~ g l n r r~nn~r scatllc ~. . Fujilnva lohns~non1 A s ~ o c i l r rCnlcagn . Cunrndgc l i n l t n s k D n r ) Ply Ltd. Sldnc) Holn.5 Lundhcrg U'nrhlcr Inlcmolion~l.Nc* YvrA 1io)ok;i~xAr$ocialcr. Lo, Anerlcr I l r ~ l l l ~Buildtng$ ) lnlrrn:l8vnll In:. F ~ i d r i l l ~ l t m ~O~ h m . & Klsrlboum. lnc S 81, F i a n r 8 ~ ~ o lnlrrnaliond lmn k Slrrl Imlilutc. Brulrcl$ Irwin Iohnrlon nnd Ponncn. Sydncy Infoc~er.S.A. Rio delnoeim I.A. loner Conruuction Co., Charlotic Kcsting Mnnn Iemigan RoacL. Lor Angclcr KPFF Conrulting Engineen. Scuulc Lcnd Lwre Dcrign Gmup Lld.. Sydncy

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~ n n i& n Bmvo, inc.. Honolulu Monin.Middirhrook & Louic. Snn Fmncirco Enriquc Mmincr-Romcm. S.A.. Mexico Mitchell McForlane Brrnlnoli & Paonen Inll. LId.. Honk Kong Miuubirhi Erwlc Co..Ltd.. Tokyo Moh nnd Arrociau. inc..Tnipci Morrc Diesel Inlcmorionrl. Ncw York Mvlriplci ConrWclions (NSWI Pfy. Lid.. Sydncy Nihoasckkci. U.S.A., Ltd., Lor Angclcr NiWIcn Sckkci. Ltd.. Tokyo Norman Dirncy & Young. Brirhonc Pacific Adnr Dcvclopmenl Corp.. Lor Angclcr PcddlcThorp Aururlin Ply. Lld.. Brirhnnc PorkTowrr Gmup. New Yo* Ccror Pclii & Asrociolu. Ncw York Pcrkinr & Will. Chicngo Rnhulnn Zain Arrociacr. Kuolo LumDur RFB Consulting Arrhilcnr, lohunnuhurp Rnrrnunrrrr G m r ~ m mCons Engrr.. PC. llru York E- m~, r n Rod, & Sons lnd. lnc.. New Yoik Rovon Woll8~mrD l r t r l & lruin 1°C. Gurlph ScpllotSaio rcmnding (Sdnl Bhd, K ~ o l oLumpur scrrrn S m : m r Gimi5 dc Encrnhon~S A . Rlo dc lnncim Scvcmd Asrociacr Conr. Engn.. New York SOBRENCO. S.A.. Rio dr Inncim south Africnn lnrtiatc of Srccl Conslrucdon. Johmncrbvrg stccl Rcinlorrcmcnt lnrlilulc of Aurlrnlio. Sydncy STS Conrultnnu Lrd.. Nonhbmok Studio Find. Nova E Coslcilnni. Milnno Tnyior Thornson Whining Ply Lld. St. Lconordr B.A. Vrvnroulu & Asrociacr. Athenr VlPAC Encinrcn & Sricndru Lid. hlclhovmc Worgon Cbpmon Pmnrrr. S)uncy Wndl~nl.crA?ro:irlrl. Nrw Yorl wond~.,d.cl,dc Con~.lurn,. ~ r rYolk .

Other Books in the Tall Buildings and Urban Environment Series Casf-in-Place Concrete in Tall Building Design and Constructio~t Cladding Building Design for Handicapped and Aged Persons Semi-Rigid Connecrions in Steel Frames Fire Sofery in TON Buildings Cold-Formed Steel in Toll Buildings

Systems and Concepts

Structural Systems for Tall Buildings Council on Tall Buildings and Urban Habitat Committee 3

CONTRIBUTORS I.D. Berzrretf~ Joseph Bicnls Brian Coviil P.H. D a y o ~ ~ ~ n r ~ s a Eiji Frrk!ria~ro him B, Ki1,rzister Rpscard M. I;o~~,aicz)k Owerr bJanin Il'iliion! Afuibortnie Sciichi Ml,ra?lrofsll % Okoshi AR,r~adRolrirnian Tltonras Scararrgeiio Roben Si,m Richard Ton!asefri A. )'atnohi

Editorial Group

Ryszard M. Kowalczyk, Chairman R o b e r t Sinn, Vice-chairman M a x B. Kilmister, Editor

McGtaw-Hill, Inc. D.C. Auckland Bogoti Lisbon London Madrid MexicoClty Milan Montreal New Delhi San Juan Singapore sydney Tokyo Toronto

New York San Francisco Washington. Caracas

ACKNOWLEDGMENT OF CONTRIBUTIONS This Monognph uar prepxed h j Commillcc 3 (Slmctuml Syrtcm5)of ihc Council onToll Buitdlngr and Urban Hnbitnt nr p ~ onf the Tali Building, and Urban Environment Series. Thc edtlonll gmup $bas R)szxd hf. Kowatcz)k, chairman; Rohen Sinn, ricc-chnirmln; and hlox B. Kiimister, editor.

Foreword

Special ncknowledgmentir due more individuals whore n k u w ~ i p l formedthe s mjorconvibution UI the chapters in his volume. These individuals and the chnpters or sections lo which they conhibuled ore: Chapter 1: Editorial Group Chapter 2: Editorinl Group Section 3.1: Editorial Group Scction 3.2: Brian Cnvill Section 4.1: Eiji Fukuzawn Section 4.1: Seiichi Murnmulsu Section 4.1: Ahmod Rohiminn Section 4.2: Owen Mnnin Sccdon 4.3: T. Okorhi

Section 4.3: Thomu Scmngello Section 4.3: Richard Tomasetti Section 4.3: A. Yamoki Section 4.4: Editorial Group Section 4.5: Editorial Group Section 5.1: William Melbourne Secdon 5.2: 1. D. Bennettr Secdon 5.2: P. H. Doynwnnrn Chapter 6:Joseph Bums

Project Dercriptionr were conuibuted by:

The Office of Irwin Cantor CBM Engineers, Inc. Ellisor and Tanner. Inc. Kajima Design, Inc. KingiGuinn Associates LcMessuricr Consulrunls. lnc. Leriie E. Roberlson Arnocintes Nihon Sekkei. Inc. Ovc Amp & Pamcn

Paulus. Sokolowski, and Snnor. Inc. Pcrkins and Will Roben Rorenwarser Asrocioter Sevemd Associnter Shimizu Corporation Skidmore. Owings and Merrill Skiliing Ward Magnurron Barkshire. Inc Thomton-Tomaretti Engineers Walter P. Moore and Asrocioter

COMMllTEE MEMBERS Hcrben F. Adigun. Mir M. Ali. Luis Guillermo Aycardi. Prnbodh V. Bnnavnlkur. Bob A. Bcckner. Charles L. Bcckncr. George E. Brandow. John F. Bmtchie, Robcn J. Bmngmber. Yu D. Bychenkov. Peter W. Chen. Ching-Chum Chcm. Pave1 Cirek. Andrew Dnvidr. John DeBremoekcr, Dirk Dickc. Robcn 0. Disque. Richard Dziewolnki. Ehun Fang. Alexander W. Founleh. James G. Forbes. Roben I. Hanren. Roben D. Hnnsen. Toshihnm Hisatoku. Arne Johnson. Michael Kavyrchine. Mnn B. Kiimirler (editor). GcnF. Konig. Ryszwd M. KowaIczyk (chairman). Juraj Korak. Monsieur G. Lacombe. Siegfried Liphardl. Miguel A. Mneiar-Rendon. Owen Mnrrin. Jaime Mnson. N. G. Mutkov. Gerardo G. Mayor. Leonard R Middleton. Jaime Munoz-Duquc. Jacques Nasser. Anthony F. Nnrretta. Fujio Nirhikown. Alexis Ortapenko. Z. Powlowski. M. V. Parokhin. Peter Y. S. Pun. Wcmer Quoscbnnh. Govidan Rahulan. Anthony Fracis Roper. Sntwant S. Rihai. Leslie E. Robenson. Wolfgang Schurilcr. Duiliu Sfintesco. Robert Sinn (vice-chairman). Ramiro A. Sofronie. A. G. Sokolov. Euuro Suzuki. Bungaie S. Tnranalh. A. R. Tonkley. Kenneth W. Wan. Morden S. Yollcr. Nobih F. G. Yourrcf. Stefan Zucrek.

GROUP LEADERS The committee on Structural Systems is part of GroupSC of the Council, "Systems and Concepts." The leaders are: lamer G. Forbes. Chairman Joseph P. Coluco, Vice-Chairman Henry J. Cownn. Editor

This volume is o n e of a series o f Monographs prepared under the aegis o f the Council on Tall Buildings and Urban Habitat, a series that is aimed a t documenting the state of the art o f the planning, design, conslruction, and operation of tall buildings as well as their interaction with the urban environmenL T h e present series is built upon an original set of five Monographs published by the American Society of Civil Engineers, as follows:

Volume PC: Plnrming nrzd En~rironn~enral Crireriofor Toll Beildings Volume SC: Tall Building Sysrems ond Cortceprs Volunze CL: Tall Building Criteria nnd Loading Volume SB: Srrucrurol Design of Toll Sreel Btrildings Voltrme CB: Srmcrural Design of Tall Concrele and Mosorrry Buildings Following the publication of a number of updates to these volumes, it was decided by the Steering Group o f the Council lo develop a new series. It would b e based on the original effort but would focus more strongly o n the individual topical committees rather than the groups. This would d o two things. It would free the Council committees from restraints as t o length. Also it would permit material on a given topic to reach the public more quickly. T h e result was the Toll Buildings and Urban Enr,iron~nenfseries, being published by McGraw-Hill. Inc.. New York. T h e present Monograph joins s i x o t h e r s , the first of which was reieased in 1992:

Cost-in-Place Concrere in Toll Building Design ond Consrrucrion Clodding Building Design for Handicapped ond Aged Persons Fire Safely in Tall Buildings Senxi-Rigid Connecrions in Steel Frornes Cold-Formed Sfeel in Tall Buildings This parlicular Monograph was prepnrcd by the Council's Committee 3. Strucmral Systems. Its earlier treatment was n part of Volume SC. I t dealt with the many issues relating t o tall building structural systems when it was published in 1980. T h e committee decided that a volume featuring cane studies of many of the most important buildings o f the lust two decades would provide professionals with some interesting comparisons of how and why structural systems were chosen. T h e result of the committee's cfforls is this Monograph. It provides case studies of tall buildings from Japan. the United States. Malaysia. Australia. New Zealand. Hong Kong. Spain, and Singapore. This unique international survey examines the myriad o f archirecturni. engineering, and construcdon issues that must b e taken into account in designing tall buildtag structural systems.

Preface

Although tall buildings are generally considered to be a product of the modem indusuialized world. inherent human desire to build skyward is nearly as old as human civilizntion. The ancient ovramids of Giza in Eevot, the Mavan temdes in Tikal. Guatain lndia arcjust a-fiw erampl& eternaily benring witness to mala, and the Kuwb this instincL Skyscrapers in thc modcrn sense began to appear over a century ago; however, it was nnly after World War I1 that rapid urbani'ration and population growth created the need for the conswction of tall buildings. T h e dominant impact of Llll buildings on urban landscapes has tended to invite contrnvenv. o~ticularl; in cities with older historic structuris. The skvscraoer silhouette has transformed andshaped the skylines of many cities, thercby creGing ;he most cbrracteristic and symbolic lrstaments to thc cities' wealth and their inhabitants' collecti!,e

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The ordinary observer recognizes the tall building primarily with respect to its exterior architectural enclosure. This is nnly natural, as when we consider the great pyramids of -~ Eevot -, our overridine imaee is bf their characteristic sharre. It is o d v re&ntlv that we have begun to realize the creativity and colossal effnn expended by these ancient people to erect these swcmres in the desert at that time. So it is with the modem skvscrao;r. The overall soatial form as well as the intricate deWiline , - of the claddine svstems are crucial in defining the architectural expression and in placing the tower within the overall urban environment. The aim of this Monograph, however, is to have a look under the outer covering of the building to reveal the stiuctural skeleton as well as to provide historical knowledge documenting the design and construction techniques used to realize these monuments in today's world. This Monoeraoh is therefore dedicated to the structural systems for tall buildings: their evo~utinn~anh historical development as well as the variety of solutions engendered to allow the tower to be realized safely andcfliciently. As in the pas!, new nchievoments .in material science.. comouter-aided desien. and construction technology -. have opened paths toward more sophisticated and elcgant swcturnl syslems for wll buildings. The rwctuml system organization chosen for a p d c u l a r project determines the fundamen[at oropcnies of the aver;lll buiidinc. the behavior under imposed loads, its safety, and oftin mav,have a drnmatic imoact on the architectural design. - The intent of this volume is lo demonstrate the chmcteristic features of many outstanding syslem form5 while documenting the faclors leading lo their selection for projects aclually realized. The swctural systems for high-rise buildings are constantly evolving and at no time can be described as a completed whole. Every month new buildings are being designed and created, new projects conceived, and new schemes applied. Nevcnheless, we hope it is worthwhile to present the current state of the M while being aware that progress in svstems develooment is oneoine. The planning for thts Monograph began soon after the decision u,nc made by the Council to expand the chapters of the original Monograph into separate volumes. The concept of a volume based-on a survey of some of the most innovative examples of tall building swctural systems conuibuted by leading engineers and design firms of the

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Preface

profession was conceived during the committee workship in Hong Kong in 1990. It was only after estnblishina the editorial lendershir, for the work that the volume began to takc form, will1 tlte scope and content of the book finallred. At this time a buildinf data form wns prepared for collecting thc most essential inform3tion concerning the structural design of the buildings included herdin. The surveys were initiated and the re. s ~ o n s e cs o m ~ i l e dbv Max filmister. This material reoresen& the core of the comoleled dook and the.vast mijority of the work. Bob Sinn then'assembled all of the "looseknds" of the compilation in the summer of 1993 in order to finish the completed volume in time for publication. The ~ o n o g r a as ~ ha uhole is a product of extensive lenmtr,ork. Sincere thanks go to all ofthc conuibutors who offered their valuablc time to share thew cxperirncc with the readers. It Is around this information that the cnurc uork is construc[ed. W e hope that the information included may be presented lo a broad professional audience. This exchange of information is one of the tenets of the Council and is in fact a condition for progress in the design of tall buildings. Supporting information for Chapter 5 from Drs. B. 1. Vickery. 1. D. Holmes. and J. C. K. Cheung is gratefully acknowledged, as is the Australian Research Grants Commission for its suppon of the fundamental research. As mentioned, we are aware that everyday Progress is made in the field of structurnl engineering for high-rise buildings. Thc comn~itlceis already thinking about expmdlng and updating this \,olume. \\'c urge all readers lo enrich and complement thia rrrrrk by writing the Council or ioining the commitke. ~ i n ~ ~wcl lwould ~ . like lochpress our appruui;!lion to Dr. Lynn Beedle, ulto encouraged us to prepare this work and \rho ad\,ised and aupponed tltc efiori. \\'e dudicall: this book to him.

Robert Sirm Vice-Cltoimmn

Mar B. Kilmisrer Editor

Contents

1. Introduction 1.1. Condensed Rererenccs/Bibliography

2. Classification of Tall Building S t r u c t u r a l S y s t e m s 2.1. Condenrcd RererenceJBibliogmphy

3. Tall Building Floor S y s t e m s 3.1. Composite Sleel Floor Systems 3.2. Presmssed and Porttcnrioned Concrete Floor Systems Project Dereriptionr Melbourne Ccnuvl Lulh Hcndqumers Building Riverside Centcr Bourke Plncc Cenuvl P l m One 3.3. Condensed RefercncerlBibliogmphy

4.. Lateral Load Resisting S y s t e m s 4.1. Bnced Frnme and MomentRc;isting Frnme Sysrems Project Derertptions S~nwnBank ACTTower Kobc Portopin Hole1 Nanhi South Tower Hotel World Tmde Center KobeCommercc. Indusuy and Trade Centcr Mvrriott M q u i r Hotel Taj Mnhnl Hotel Tokyo Marine Building Knmognwn Grand Tower Shear Wall Syrlemr Project Dc.cipUonr Mcmpolitnn Tower Embassy Suites Hotel Singapore Treasury Building 77 Wcrt Wuckcr Drive Casielden Ploce Twin 21 Majestic Building Telecorn Corporate Building

Contents Core nnd Outrigger Systems Project Daeriptions Cityspire Chifley Tower One Liberly Place 17 Smle Sueel Figuema at Wilrhlm Four Allen Center Tmmp Tower Woterfmnt Place Two Pmdentinl Plnw 1999 Bmadwvy CilibnnkPloro 4.4. Tubulorsyslemr P r o j s l Descriptions: Frnmed Tuber Amoco Building 181 West Madiron Sueet AT&T Corpamte Cenler Georgia Pacific 450 Lexington Avenue Mcllon Bank Sumitorno Life Insumnce Building Dewcy SquoreTou'er Monon international Nations Bank Coipante Center Bvnk One Center Cenml Ploro Hopewcll Ccnuc Project Descriptions: T-cd Tuber F m l Inlemationol Building Onteric Center John Hancock Ccnter 780 Third Avenue Holel de las h e r PI'ojffL Dereriptions: Bundled Tuber Sears Tower Rinlto Building N6E Building Cnmegie Hall Tower Allied BonkPloro 45. Hybrid Systems PmjeclDiscriptions Ovcrreos Union Bonk Cenler Citicorp Ccnrer CcnTmrusl Center Columbia Seafirst Center First Bnnk Place Two Union Squorc Fist Intersmte World Center Hong Kong Bank Headqumers 4.6. Condensed ReierencesiBibliogmphy 4.3.

5. Special Topics 5.1.

Designing lo Reduce Perceptible Wind-Induced Motions

5 2 Fire Prolection of Swctunl Elements 5.3.

Condensed RcfemnccdBibliognphy

Contents

6. Systems for the Future 6.1. 6.2. 6.3.

6.4.

A~hiEhilecedTendencies Slructural Tendencies Other Tendencies Project Descriptions Miglin-Beiller Tower Deurbom Ccnter Bnnkof thc SouthwertTowcr Shimiru Super High Rise Condensed RclerenceslBibliogmphy

Current Ouestions, Problems, and Research Needs Nomenclature Glorrury Symbols Abbreviudonr Units

Contributors Building lndex Name lndex

Subject lndex

Structural Systems for Tall Buildings

Introduction

Smctural system for tall buildings have undergone a dramatic evolution throughout the orevious decade and into the 1990s. Developments in structural system form and orgnnirntion h m e historically been realized as a rcsponse to as well as an impclus toward emerging architectural uends in high-rise building design. At thc time of publication of the initial Council Monograph Tnll Building Systems and Concepts in 1980. international style and modernist high-rise designs, chanclerized by prismalic, repctilive verticnl geometries and flat-topped roofs, were predominant (Council on Tnll Buildings. Group SC 1980). The devclopmcnt of Lhc prototype tubular systems for lnll buildings was indeed predicated upon an ovcrall building form of constnnt or smoothly varying profile. A representative office building project from the period is shown in R g . 1.1. The rigid discipline of the cxterior rower form has since becn rcplaccd in many cases by the highly articulated vcnical modulations of rhc building envclopc characleristic of eclrclic postmodern. deconslructivist, and nrohistorical high-risrexpressions (Rg. 1.2). This general disconlinuily and erosion of thc cxterior facade has led to a new generation of tall building struclural systems that respond lo the more flexible and idiosyncratic requirements of an increasingly varied architectural aesthetic. Innovntive swctural systems involving megaframes, interior superdiagonally braced h m e s , hybrid steel and high-strength concrete core and outrigger systems, artificially damped structures, and spine structures nre among the compositions which represent a step in the development of structural systems for high-rise buildings. This Monograph seeks to further the plncement of some of the most exciting and unique forms for today's tall building structures into the overall tall building system hierarchy. One of the fundamental goals of the Council has been to continualiy develop a tall buildings dambase. The members of Committee SC-3, Structural Systems, decided that rather than being a collection of papers or a general survey of tall building structural systems, the Monogmph would be organized with respect to such a database-type format of structural and . oroiect . information on actual buildine-.oroiecu. The committee thererore requested detailed informarion from engineers in Lhe profession, regarding the structural design of some: of the most innovative high-rise projecrq throughout the world. An enthusiastic resoonse from the s l ~ ~ c t u r eneineerine nl communirvoro.. vided very spucific engineering informntion such as wind nnd seismic Iondingz. dynamic propenics. materials, and systems for a wide range of intcrnalional high-rise oroiecls, both comoleted and in o&oosal staee. which i r e comoiled in this single &k. These compr;hensive data &e [he p r i m 5 focus of this ~ o n n ~ r n pand h should

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[Chap. 1

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Chap. 11

b e of interest and value to practicing engineers and architects as well as other tall building enthusiasts. This Monograph is organized into six chapters. A general introduction to the classification of tall building structural systems is found in Chapter 2. The section begins to define the parameters and characteristics for which tall building systems are evaluated. Tall building floor systems arc discussed in Chapter 3, which includes recent

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Rg. 1.3 NBC TOCC~, Chicago. Illinois, Cumplclcd 1991. (Cauncry: Skidruorr O t ~ i n ~S sblerriil.1

3

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Introduction

4

[Chap. 1 : , , .,

developments in posttensioned concrete floor systems for high-rise construction in Australia. Structunl systems for tall buildings have historically been grouped with respect to their ability to resist lateral loads effectively. Therefore Chapter 4. "Lateral Load Resisting Systems." forms the core of the work, with system descriptions for nver 50 The oroiects are arraneed within five basic subclassifications for lat- - oroiects. r~ era1 load resistance with generally increasing efficiency and application for taller buildines: braced frame and moment resisting frame systems, shear wall systems, core and ouGigger systems, tubular systems, anhhybrid systems. Each subsection is preceded by a general introduction outlining the system forms. limimtions, advantages, and applications. Chapter 5 discusses special topics in high-rise building structural systems. It presents infor!nation concerning the developing topics of wind-induced motions and fire protection of structural members in tall buildings. The concluding Chapter 6, in dealing with systems for the future, presents examples of projccts on the drawing board and proposals which represent innovative state-of-the-art structural designs for tall buildings.

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Classification of Tall Building Structural Systems

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1.1 CONDENSED REFERENCES/BIBLIOGRAPHY Council on Tall Buildings. Group SC 1980. Toll Btrilding Syrlerm ond Conceplr. The Council definition of a tall building defines the unique nature of the high-rise project: "A building whose height creates different conditions in the desieo, construction. of a cenain reeionand oeriod." For and use than those that exisi in common buildines u the practicing structural engineer, the cataloging of suuctuial systems for tall buildings has historically recognized the primary importance of the system to resist lateral loads. The ~roeressionofiateral load resisiineichemes from eiemental beam and column assemblages toward the notion of an equivalent vertical cantilever is fundamental to any suuctunl systems methodology. In 1965 Fazlur Khan (1966) recognized that this hierarchy of system forms could be roughly categorized with respect lo relative effectiveness in resisting lateral loads (Fig. 2.1). At one end of the spectrum are the moment resisting frames, which are efficient for buildings in the range of 20 to 30 stories; at the other end is the generation 01 tubular systems with high cantilever efficiency. With the endpoints defined, other systems were placed with the idea that the application of any panicular form is economical only over a limited range of building heights. The system charts were updated periodically as new systems were developed and improvemcnts in materials and analysis techniques evolved. Alternatively, the classification process could be based on cenain engineering and systems criteria which define both the physical as well as the design aspects of the building: b

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Material Steel Concrcte Composite Gravity load resisting systems Floor framing (beams, slabs) Columns

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[Chap. 2

Classification of Structural Systems

6

Chap. 21

7

and load transfer. These levels are further broken down into subgroups and discrete systems (Fig. 2.2). This format allows for the consistent and specific identification and documentation of tall buildings and their systems. the overriding goal being to achieve a comprehensive worldwide survey of the performonce of buildings in the hieh-rise =~~~ environment -~ . While any cataloging scheme must address the preeminent focus on lateral load resislance, the load-carrying function of the tall building subsystems is rarely independent. The most efficient high-rise systems fully engage vertical gravity load resisting elements in the lateral load subsystem in order lo reduce the overall structural premium for resisting lateral loads. Some degree of independence is generally recognized between thefloor fmnzing sjsrr,t!s and the loferal load rerisring qsrenzs, although the integration of these subassemblies into the overall structural organization is crucial.

Trusses Foundations Lateral load resisting systems Walls Frames Trusses Diaphragms Type and magnitude of lateral loads

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Wind Seismic Strcngth and serviceability rcquirements Drift Acceleration Ductility

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I

LEVEL A Framing systems

LEVEL B

I

In 1984 the Council attempted to develop a rigorous methodology for the cataloging of tall buildings with respect to their structural systems (Falconer nnd Beedle. 1984). The classification scheme involves four distinct levels of framing-oriented division: primary Framing system, bracing subsystem. floor framing, and configuration

I

framing subsystems (XX)

/

Building configuration and load transfer (XX YY 2)

Elevation TYPE I

I

TYPE 11

I I

TYPE Ill

1)

TYPE IV

Fig. 2.1 Cornpurironof rlruelurol syetcmr. (CTDUH, CrortpSC. 1980.1

I

Fig. 2.2

Clvrrilicoliun of rlrurlurul syrlernr. (Folnl,ler rrnd Beedlr. 1984.1

I

8

Classification of Structural Systems

[Chap. 2

This Monograph therefore divides the discuss~onof tall bu~ldtngsmctural Systems into the subsystems mentioned.

3

1 I

Tall Building Floor Systems

2.1 CONDENSED REFERENCES/BBLIOGRAPHY Falconer and Beedlc 1984. Clarrlficnr!on of Toll Bulldlng S),srem. Khnn 1966, oprlmtzo~lonO ~ B U LS:rucrurer I ~ ~ ~

3.1 COMPOSITE STEEL FLOOR SYSTEMS Composite floor systems typically involve simply supported structural steel beams. joists, girders, or trusses linked via shear connectors with a concrete floor slab to form &I effective T-beam flexural member resisting primarily gravity loads. The versatility of the system results from the inherent strength of the concrete floor component in compression and the tensile seeneth and spannabiliw of the steel member. ~ o m o o s i t e flw; system are advantageous because ofreduced material costs, reduced labor i u e to prefabrication, faster couslruction times, simple and repetitive connection details. reduced stiuctural depths and consequent efficient use of interstitial ceiline soace. and reduced building mass in zones of henvy scismic activity. The composite floor system slab element can be formed by a flat-soffit reinforced concrete slab, precast concrete planks or floor panels with or without a cast-in-place t o.. ~ ~-i slab. n e . o r a metal steel deck, either composite or noncomposite (Fig. 3.i). When a composite floor framing membcr is combined with a composite metal deck and a concrete floor slab, an e x ~ c m e l yeff~cientsystem is formed. The composite action of the beam or truss elcmen1 is due to shear studs welded directly through the metal deck, whereas the composite action of the metal deck results fmm side embossments incorporated into the steel sheet profile. The slab and beam arrangement typical in composite floor systems pr* duces a rigid horizontal diaphragm, providing stability to the overall building system while distributing wind and seismic s h e m to the lateral load resisting system elements.

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1 Composite Beams and Girders

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Steel and concrete com~ositebeams mav be formed either bv com~letelvencasine a steel member in concrete, with the composite action depending on the natural bond caused by the chemical adhesion and mechanical friction between steel and concrete. or by connecting the concrete floor to the top flanee of the steel frnmine member throueh was - shear c&nectors (Fie. . - 3.1). The concrete-encased comoosite steelienm common prior lo the dcvclopment of sprayed-on ccmentitious and board or ball type fireproofing materials, which economically replaced the henvy formed concrete insun found in composite lation on the steel beam. Todny the m o s ~ c o ~ m onrrangemmt

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~~

9

~~~

~~

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10

[Chap. 3

floor systems is a rolled or built-up steel beam connected to a formed steel deck and concrete slab. The metal deck tvnicallv - - ~ -. . roans . unshored between steel members while also providing a uorking platlonn for steel erection. The met31 deck slab may be orienled parallel or perpendicular lo the compo>ite beam span and may ilself be either comoosite or noncomnosilr (form deck). . F i-~ u r c3 ? shows a typical .. office building floor that is framed in composite steel beams. ~~

Sect. 3.11

Cornposits Steel Floor Systems

11

In composite beam design. h e stress distribution at working loads across the comnosite section is shown schematicallv in Fie. 3.3. As the tor, . flanee of h e steel section is normally quite near h e neutral axis and consequently lightly stressed, a number of builtup or hybrid composite beam schemes have been formulated in an attempt to use the structural steel material more efficiently (Fig. 3.4). Hybrid beams fabricated from ASTM A36 grade top flange steel and 345-MPn (50-hi)-yield bonom flange steel have been used. Also, built-up composire beam schemes or tnpered flange beams are possible. In all of these cases. however. the increased fabrication costs must be evaluated which lend lo offset the rclalivt: malerial efficiency. In addition. a rcl3tively wide and thickgauge top flange must be provided for proprr and rffr.cli$,e shex slud isslallalion. A n"smat& comnosik steel beam h& two fundamental disadvantapes - over other types of composite floor framing types. ( I ) The mcmbcr !nus1 bc designed for the maximum bending momenl near midspan and thus is oRcn undcrs!rrs,ud near h e sup-

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COMPOSITE BEAM FlAT

wm

MFFlrRElNFORCW CONCRETESLAB

Fig. 3 2 Three First Nntionol Plnm, Chicago, Illiooir, lyplcnl noor.

COMPOSEBEAM W m MEFALOECK A N 0 CONCRETESLAB

C O M P O S E BEAM wrm METAL DECK A N 0 CONCRETE SLAB (RIBS PEAPENDICUldR~

(RIBS PABALLEL)

Fig. 3.1 Comporite benm sjstems.

WORKING LOADS

ULTIMATE LOAD

Fig. 3.3 Composite beam stress dirlribution.

I Tall Building Floor Systems

12

[Chap. 3

pons, and (2) building-serviccs ductwork and piptng must pass beneath the beam, or the beam must be provided with web penc~rattons(normally reinforced with plates or ancles leadinc to hirher fabricatton costs) to allow access for this csui~ment For this . reason, a number of composite girder forms allowing the free passage af mechanical, ducts and related services through the depth of the girder have been developed. They' include tapered and dapped girders, castellated beams, and stub girder systems (Fig. 3.5). As the tapered girders are completely fabricated from plate elemenls or cut from rolled shapes, these composite members are frequently hybrid, with the top flange designed in lower-strength steel. Applications of tapered composite girders to office building construction are limited since the main mechanical duct loop normally runs through the center of the lease span rather than at each end. The castellated composite beam is formed from a single rolled wide-flange steel beam cut and then reassembled by welding with the resulting increased depth and hexagonal openings. These members are available in standard shapes by serial size and are quite common in the United Kingdom and the rest of Europe. Use in the United Stales is limited due to the increased fabrication cost and the fact that the standard castellated openings are not large enough to accommodate the large mechanical ductwork common in modern high-rise, large floor plate building construction common in the United States. The stub girder system involves the use of short sections of beam welded to the top flange of a continuous, heavier bottom girder member. Continuous transverse secondary beams and ducts pass through the openings formed by the beam stubs. This system has been used in many building projects, but generally requires a shored design with consequent construction cost premiums.

-

u

-

.

:>,i;~

j ,. ,:,: . ~

Sect. 3.11

Composite Steel Floor Systems

13

Succc$si~llcnmpnwte hc:m ile.;ign T'LII.IIL.\ the c~nsideri~tio~t ni \.ilriol~<o;b ;IS I~rnn-tsr~tt (clsupl denc:ti~rns ;lnJ nuor vihr;dinns. 0 1 p3rticul;tr cunccrn is lltc iw.c oi pcrc~ptihilityof n:cupaot-indursd tl~tnrr ~ h r ~ l ~ oThe n s . rslnlively l!i;lt II~.rur;ll~ l i l l n c roi~ a1o.l nltnporilc noor fr;lming a)slr.m> rerulls ill relat i t c h lot. !ihralion :~!#,t>litndrc irnm 1r.losilory hcel-dlop d ~ ~ i l : l t ~ oand n s thcr:lore is effective in reducing perccptihility. Recent studies have shown that short 17.6 m (25 fi) and lcss] and rery lollg clcar-sp;ln 113.7 nl (45 St) and longer] cunlposile floor framine svstcnls ncriornl suite well and :!re rarely found to transmit annoying . .vibrations to the occup8tnts. Particular care is requircd for span conditions in thc (9.1- to 10.7-m) 130- to 35-ftl rangc. Anticip.atcd danlping provided by partitions which extend to the sl:lb cthovc. serviucs. ceiling constructiot~,andthe structure itself are used in conjunctiott with htate-of-thc-;lrt prediction tllodels to evalue~ethc potential for pcrceptible noor i~ibrations.

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2

Composite J o i s t s and Trusses

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Preeneinccred nronrictnrv oncn-web lloor ioists. ioisl -rirders. and fabricated noor = trusses are viable composite memhcrs when combined with a concrete noor slab. The advanta~esof an opetl-wcb nour framing 5ystcm include increnscd spannabilily and stiffnus;due to 1he.decocr s~ructuralden& =ncl case in nccomrnodatine- electrical conduit. plumbing pipes. and heating and air-condilioninp ductwork. Open web systems do, however. carry :I picmiuln for itreprunling thc many. rcla~ivelyihin, components of ~

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............................................................ 1 bc:;'TAPERED ;~ .-, . ; .-., C5ZJ -J?C: .... .. - L..

....... ....?..........-....................... .*.,

HYBRID C0MPOSITEBEb.M

..

BUILT-UP COMPOSm BEAM

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-..,. ......................... .......................... ?

.... . . <:. .;-,. 1

a??+-'. V--=d

6C",I~~~~TE TAPERED

DAPPED

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CASTELLATED

Lf4-Z ROLLED

..........

........ .,,.,, . . . . ., . . . . ."

I I <. I TAPERED FLANOE COMPOSITEBEAM

BUILT-UP HYBRID COMPOSm BEAM

Fig. 3.4 Buill-up and hybrid composite bcnms.

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. . .,. . . . . . SYSTEM

Fig. 3.5 Nonprismulie enn~purilcgirdur.5.


14

[Chap. 3

the member. Open-web steel joists have been used in composite action with flat-soffit concrete slabs and metal deck slabs supporting concrete fill with and without sheer conhectors. The desien for these svstems is orimarilv based on manufacturers' test d313 , I s ~~p'n-~veb steel jotbtb and joist girders nornlally are \paced relatively clusaly. rile full polenrial lor composite elilc~cncyis not rcalircd as conlpared to o1hr.r cunlporite floo; systems. Composite design does provide quantifiableadvantages over "oncomoositc desien for oocn-web floor ioisls such as increased stiffness -and~ducdlitv. Ruill-up labricatcd compo\ilu nonr trusses cumbinc m ~ t u r ~ ciilcicncy al io rclnlively long-span 3pplicntions svtlh rn;lxinlom flea~h~lity fnr iscorporaung huildinz-ser\,ic
Sect. 3.21

Prestressed and Posttensioned Concrete Floor Systems

15

shear connectors. The most common floor system in building construction is a comoosite metal deck and concrete slab chosen based on fire seoaration and acoustical requiremenu spanning between composite floor trusses. The floor trusses are normally spaced such that the metal deck slab sonns as the concrete form between the trusses without requiring any additional shoring.

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b

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3.2 PRESTRESSED AND POSTTENSIONED

CONCRETE FLOOR SYSTEMS

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Prestressed floors are commooolnce in buildines throuehout the world.. narticularlv in u low-rise SlNCtUreS such as parking garages and shopping centers. Precast pretensioned floor units have remained popular since the 1960s. and cast-in-place posttensioned concrete floors have eainedwfde acccotance since the mid 1970s Poslrensioncd floors have been widely uscd for high-rise office buildings in Australia since the cnrly 1980s. and there are examples in the United States, the most notable bcing 31 1 South W a c k r Drive, Chicago, which was the tallest concrete building in the world when completed.

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EXTEA1OR STEEL GR4VITI COLUMNS AIIb SPANDRELS

COUPOS~

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TYPICALCOMPOSrrE FLOOR TRUSS Fig. 3.6 One North Fmnkiin, Chiengo. lllinoir.


16

7

[Chap. 3

General Considerations

High-rise oftice buildings usually have long-span floors to achieve the desirable column-free space, and the spans are usually noncontinuous between the core and the facade. To achieve long spans and still maintain acceptable deflections requires a deep floor system in steel or reinforced concrete. However, by adopting prestressed postmumm

WARREN TRUSS

I

I 1 I

Sect. 3.21


17

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tensioned concrete beams it is possible to achicve a shallow floor structure and still m~intainaccepwble deflections witl~ourthe need for expensive prrcamhering. Hirlt-risc residential buildin~susunllv do nor require lona spans because columnfree s b c e is not a selling point;the tenant or buyer ices the spice already subdivided by walls, which effectively hide the columns. Hence continuous spans can be achieved. Unlike office buildings, residential buildings do not as a rule have suspended ceilings-the ceiling may be just a sprayed h~gh-buildcoating on the slab soffit or a plasterboard ceilina on battens fixed to tbe slab soffit. Flat-plate floors are therefore required and deflection control is an imponant design consideration. Where the columns form a reasonably regular grid, prestressing can be very effective in minimizing the slab thickness while at the same time controlling deflections. ~ l f h o u g hit is customary to use posttensioning for prestressed concrete high-rise buildings, precast pretensioned concrete can be used and has been employed in some buildines described in this Monomph (Luth Building: Mnrriott Hotel, New York; Tai Mahal hotell. The maior disadvaitaee of nrecast oretensioned concrete floor beams or slabs is the cranage required to lift the heavy uniu along with the field-welded connections required for stability and diaphragm . - action. Precast prelensioned floor members are usually tied together by and made composite with a thin cast-in-place topping slab. Floor posttensioned systems use either 12.7- or 15.2-mm (0.5- or 0.6-in.) highstreneth steel strand formed into tendons. The tendons can be either "unbonded," " where individual strands are greased and sheathed in plastic, or "bonded," where groups of four or five strands are placed inside flat metal ducts that are filled with Eement eroul after strcssina. On a worldwide basis, bonded systems are preferred in high-rise buildings becausithey have demonstrated better long-term du&bility than unbonded systems. Although unbonded systems used today have improved corrosion resistance compared to earlier systems, there is still a large number of older buildings that exhibit corrosion problems in their unbonded tendons. Another reason that bonded posttensioned systems nre preferred is that cutting tendons for renovations or demolition is both simpler and safer when the tendons are bonded to the concrete. Nevenheless, care musibe exercised as it is by no means unknown for tendons specified to be grouted to have had this vital operation omitted. In this aspect. good quality control is essential. Figure 3.9 illustrates a typical posttensioned floor using unbonded tendons, whereas Figs. 3.10 and 3.11 illustrate the construction of a typical posttensioned floor using bonded tendons. The most common posttensioned systems are:

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Fig. 3.7 Camporilc noor trusr geometries.

Posttensioned flat slabs and flat plates (Fig. 3.12) Posttensioned beams supporting posttensioned slabs (Fig. 3.13) Posttensioncd benms supporting reinforced concrete slabs (Fig. 3.14) Currently with computer programs readily available to carry out cracked section analysis of prestressed concrete, it is normal to design for partial prestress where the concrete is assumed to be cracked at full desien workine food and untensioned steel comprises a significant portion of the total reinforcement. The partial prestress ratio (PPR) gives the degree of prestress

-

PPR =

-

.--! &A,&, +

CHOilOB WEB MEMBERS

hubl~lnglem

IL.%

ri,n

Fig.3.8

Ree?.TUk

IL %. IZX

R L U b

,,-Tub.

Composite trurr romponcnleections.

. .

whereA r-f"2 is the cross section area of orestressed steel multiolied bv its vield shenath and A,J 8 ) is the cross section are3 of normal rcinforccd sleel multiplied by its yisld stress A useful starling point in d:tarm!ning the amount uf prcstrcss rzqi~ircdis lo proride culficicnt prestress lo lh313ncc oboul 15% of the self-weight of the nnor blrUclllrLI.

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i ,: :

,

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18


[Chap. 3

Untensioncd steel is then added to satisfy the ultimate limit state. (This will often result in a PPR of about 0.6.) Deflections and shear capacity must also be checked: The span-to-depth ratio of a single-span noncontinuous floor beam will be about 25; for a continuous beam it will be about 28 and for a flat-plate beam about 45 for an internal span and 40 for an end span.

I/

I

Sect. 3.21


l9 In high-rise buildings it is preferable to avoid running floor beams into heavily reinforced perimeter columns for two reasons: 1. There are difficulties in accommodating tendon anchorages, which compete far space with the column reinforcement. 2. Frame action developed between the beams and columns causes the design bending moment between floors to vary as the fram~sresist lateral load, thereby diminishing the number of identical floors that can be designed, delailed. and conswcted.

Instead of being directly supponed by columns, the floor beams should be supported by the spandrel beams. Prestressing anchorages can be on the outside of the building (requiring external access). at a step in the soffit of the beams [see Riverside Centre and Bourke Place (Figs. 3.15. 3.30, and 3.33)], or in a pocket at the lop of the floor. Top-of-floor pockets have the disadvantage that they usually cause local vnrialions in the flatness o i the floor and rough patches, which may need to be ground flush. Bccause posttensioning causes axial shortening of the prestressed member, it is necessary to consider the effects of axial reslraint, that is, the effects of stiff columns

!

I

Fig. 3.9 Typical porllcnrioncd noor wing unbondcd lendonr.

GROUTING

SRESSING

Fig. 3.10 Typiroi porllcnrioncd noor using bondcd lunduns.

~ i g3.11 .

Construction requcnce Ibr bondcd purttrnrionud conercle.

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.:~. ..3)> ~:?*

20


[Chap. 3

.

'2

,

and walls. Such restraint has two potential effects: it can overstress the co!umns or walls in bending and shear, and it can reduce the amount of prestress in the floor. Fortunately the stiff core of a high-rise building is usually fairly central so that the axial shortening of the floor can be generally in a direction toward the core. This means that the perimeter columns move inward, but because they move by the same amount from story to story, no significant permanent bending stresser occur except in ..., the first story abuus a nonprestressed,floor, which is often the ground floor. As this*:' ,lev is usually higher than a typical ,tory. the flexibility of rhc columns is greater and 1111: induced bdndinp mo~nents[nay be easily accommodated. Horvevsr. the loss of prcstress in thc floor may necessitate some additional t~nte~~sioned reinforcement.

Posttensioned concrete floors will usually result in economics in the total construction cost because of the following: Less concrete used because of shallower floor Structure (Fig. 3.16) Less load on columns and footings Shallower structural depth, resulting in rcduced story height (Fig. 3.17)

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no drop panels

1 Multispan,flat plate, l r o panels ~

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Prestressed and Posnensioned Concrete Floor Systems

21

The last item can be very significant as any height reduction translates directly into savings in all vertical structural, architectural, and building-services elements. The construction will proceed wilh the same speed as a normal reinforced concrete floor, with four-day floor-to-floor construction cycles being achieved regularly on high-rise office buildings with posttensioned floors (Fig. 3.18). Three-day cycles can easily,..be achieved using an additional set of forms and higher strength concretes to shorteb posttensioning time. A major cost variable in posuensioned floors is the leneth of the tendons. Short tendons ;re relativsly expen\c\,e compared lo long tendons. &re 3.1'1 shows tltc cost trend for tendons ranging front 10 to 60 m (33 to 200 it). Tlte relntively high cost of short tendons rssults from fixcd-cost components such as setup costs, asohorapcj, and lcndon stressing being prorated over lesser a m o ~ n t sof itrand. Tlte influence of strmd "retli~tglosses" is also greater with ruv shun strands, thus incrc3sing the area of tendon required. Nevertheless, even though most tendons in a high-rise building floor will be only around 10 to 15 m (33 to 50 it), the system is economical because of savings in floor depth, and it is desirable because of control of deflections and the lack of need for precambering. For grouted tendons. the optimum economical size has been round to be the four- or five-strand tendon in a flat duct because the anchorages are compact and readily accommodated within normal building members and because stressing is carried out with a lightjack easily handled by one person. ~

2 Economics of Posttensioning

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Sect. 3.21

22


[Chap. 3

1

,

Ssct. 3.21


Comparing the cost of bonded and unbonded tendons will generally show the unbonded system as being slightly cheaper. This is because unbonded posttensioning usually requires less strand due to lower friction and greater available drape. Unbonded strand also does not need grouting with its costs of time and labor. As a floor using unbonded strand will require more reinforcement than a bonded system due to lower ultimate flexural strength and code requiremcnls, the combined cost of the strand and untensioned reinforcement will be almost the same as that for bonded systems. The cost of a posttensioned system is funher affected by the building floor geometry and irregularities. For example:

.

The higher the perimeter-to-area ratio, the higher the normal reinforcement content since reinforcement in the perimeter can be a significant percentage of the lolal. Angled perimeters increase reinlorcement and make anchorage pockets larger and more difficult lo form. Inlernal stressing from the floor surface increases costs due to the provision of the wedge-shaped stressing pockes and increased amounts of reinforcement. Slab steps and penetrations will increase posttensioning costs if they decrease the length of tendons.

Fig. 3.15 Bourkc Ploce. Melbourne, Aurlmlin: 53 levels.

23


[Chap. 3

S e c t 3.21

I

3 Cutting Prestressed Tendons

One of the main drawbacks of posttensioned systems is the difficulty of dealing with stressed strands and tendons during structure modifications or demolition. Although .,.. modifications are more difficult, some procedures have been developed to make this .,.: process easier. ,~-r..;.,., :.:,?$ . !y::'J.-c: --2. -~ . . Small penetrations required to meet changes lo plumbing or similar requirernenls are the most common of a11 modiiications that are made to the floor system. The size ' ! of lhcse penetrations is typically from 50 to 250 mm (2 lo 10 in.) in~dinmeter.As a posrlenrioned floor relies on the posttcnsioncd tendons for IS strcnglh, it is prufrrablc to avoid cuttine, the tendons whcn drilling through the floor for the new penetrat~on. Finding the tendons in a floor to permil the localbn of penetrations without damaging any tendons is a very simple procedure that is carried out with the aid of an electronic tendon locater. Tendons are accurately located using this system withon1 any need to remove floor coverings or ceilings.

1 1


Floor being poured7

+ Full access for Finishing Trades

1

Fig. 3.18 Typlcnl noor propping.

Concrete

Reinf Bl3.C.

+ P.T.

R P.T.

Fig. 3.16 hlnteriul hnndling-reinforced concrete versus portlcnrioncd ryrlem.

Average tendon length, rn Fig. 3.17 Exnmplc orstepped beurn sullil; Bourkc Plucc, hlclbourne. Aurlrnlln.

25

Fig. 3.19 Portlenrianing corb.

26


In a typical posttensioned floor it is possible.to locate penetrations of up to 1000 by 3000 mm (3 by 9 ft) belween posttensioned tendons and to require no other modification to the floor. Penetrations that require cutting of the posttensioned tendons will need lo be checked and designed as would any large penetration in any floor system. The procedure commonly adopted in a floor using bonded tendons is as follows: 1. Design the modified floor smcture in the vicinity of the penetration, assuming that any cut posttensioned tendons are dead-ended at the penetration. 2. Install any strengthening required. 3. Locate tendons and inspect grouting. 4. If there is no doubt as to the quality of the grouting, proceed lo step 5. Otherwise strip off ducting, clean out grout, nnd epoxy grout the strands over a length of 500 mm (20 in.) immediately adjacent to the penetration. 5. Install props. 6. Core drill the corners of the penetration to eliminate the nced for overcutling. and then cut the perimeter using a diamond saw. 7. Cut up the slab and remove. 8. Paint an epoxy-protective coating over the ends o i the strands to pre\,enl corrosion. 9. Remove props.

i

!

Project Descriptions

[Chap. 3

If a large penetration through a floor cannot be located within the slab area but must intersect a primary support beam, then substantial strengthening of adjacent beams will usually be necessary. Whcn culling openings into floors built using unbondcd postlensioned tendons the procedures used for bonded posttensioned tendons cannot bc applied. The preferred procedure that has been developed to permit controlled cuttinf of unbondcd strands is to use a special detensioning jack. The jack grips the strand and the strand is then cut. with the force in the strands being released slowly. New anchorages are then installed at each side of the new opening and the strands restressed. Extensive experience has been gained in demolition procedures for posllensioncd floors, and some general comments can be made. In bonded systems the procedures for demolition are the same as for reinforced concrete. The individual strands will not dislodge at stressing anchorages. In unbonded systems the strand capacity is lost over its entire length when cut; therefore the floor will require backpropping during demolition. The individual cut strands will dislodge at stressing anchorages, but will move generally less than 450 mm (18 in.). However, precautions should al!i~ays be taken in case the strands move more than this.

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27

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PROJECT DESCRIPTIONS Melbourne Central Melbourne, Australia ...:,

., ...I, <..

Architect Structural engineer Year of compleIion He~ghtfrom street to roof Number of stories Number of levels below ground Bullding use Frame maanal Typical floor live load Basic wind velocity Maximum lateral deflcction Design fundamental per~od Design accelcrat~on Dcs~gndamping Earthquake loading Type of structure Foundation conditions Footing type Typical floor Story height Beam span Beam depth Beam spacing Slab Columns Size at ground floor Spacing Concrete strength Core Shear walls Thickness at ground flool

Kisho Kurokswa with Bates Smart & McCutcheon Connell Wagner 1991 21 1 m (692 ft) 54 3 Office Concrete core, steel floor beams 3-kPa (60-ps0 beams, 4-kPa (80-psf) slabs 5 0 m/s (112 mph) ullimate. 100-yr return 100 mm (4 in.), 50-yr rctum 4.2 scc 2.9 mg rms. 5-yr return 1% serviceability, 5% ultimate Not applicable Concrete core, concrete perimeter tube in lube Mudstone, 2000-kPa (20-tonlfl') capacity Pads to columns, raft to core 3.85 m (12 ft 7 in.) 11.5 m (37 ft 9 in.) 530 mm (21 in.) 3 m ( l 0 it) 120 mm (4.75 in.) on metal deck

65 MPa (10,000 psi) maximum 600 and 200 mm (24 and 8 in.)

Melbourne Central comprises a 57-level office tower of 60,000 m' (646,000 fl') (net rentable) and a large retail development of a funher 60.000 m' (Fig. 3.20). The overall dimensions of !he tower are 43.72 by 43.72 m (143 by 143 ft). The tower is 21 1 m (692 ft) above street level and 225 m (738 ft) above the core raR. The facade is a glass and aluminum curtain wall.

28


[Chap. 3


.. ,,

29

".

The lower floors consist of steel b u m s spanning from the core to the facade wi composite concrete slab. supported on stoctural steel decking, spanning brtwecn steel beams (Fig. 3.21). The steel beams are generally at 3-m 1 10-it) centers. and typical beam is a 530UBB2 (21UB55). Tlie structural steel decking is I mm (0.04 thick, unpropped.

The column spacing at the facade is 6 m (20 ft). A perimeter beam is required to carry the intermediate floor beams. This is a 900-mrn-deep by 300-mm-wide (36- by 12-in.), prccasl concrete beam. Although this is precast concrete, it is erected in the same way as a sleel beam and as part of the steel frame. The use of precast concrete simplifies the fire rating of the slructure at the perimeter where access is difficult. It . also provides the 900-mm (36-in.)-deep fire barrier between floors required by the building regulations. The fixings for the curtain wall are cast into lhis beam, resulting in reliable and accurate positioning. The floor-to-floor height is 3875 mm (12 ft 8.5 in.) for the typical floors. The floor-to-ceiling height is 2900 rnm (9 ft 6 in.), which allows for a future access floor of 200 mm (8 in.) in height, to be installed by a tenant, providing a minimum 7700mm 18-it 10-in.) occuoied soace. ~ i wind v resistance~- stricture for this buildine" consists of the core cantileverine. from lhe lootin: in combinslion w i l l 1 3 nominal conlribulion from the filcndc rtruclurr. oi ihd column 2nd nrecnst bcnm. This ru,ulls in the fac3de structure cnrqing approximately 10% of the wind load on the building, and, more importantly, it convibutes

-

gig.3.11

LOW-rircfloor

LE-L14 hl~lbourneCcnlml.

I

30



[Chap. 3

significantly to the sway serviceability perromance. The remainder of the wind load is carried by the core element. The central-services core to the building is reinforced concrete from the footings to the roof. All the internal walls are 200 mm (8 in.) thick. This thickness remains unchanged over the full height of the building. The 200-mm (8-in.) internal wall thickness is h e optimum to achieve load-carrying capacity, minimal slenderness effects, and conslructability. The external walls vary from 600 and 550 mm (24 and 22 in.) thick at the bottom of the buildine to 250 mm (10 in.) thick at the buildine too. Concrete strengths in the core walls &y from 70 td 30 h&a (10.000 to 4300 psijat 9'0 days. The columns are a composite of reinforced concrete with a 310UC137 steel column. These steel columns are erected as part o f the steel frame. Subseuuentlv thev arc i the encased within the reinforccd concrete column and oermit erection - ~ n ~ -~ - - sirel ~ - -frame I0 floors J x a d ofconcrc.le cnc3semcn1 ( R E 3 22). This conccpl, in comb!nolion wilh ~ h crtci'l noor b u ~ n ~and s rlructural aleel d:cking. pcrmils bun-fit in^ from 111c~ d v a ~ l tares of steel construction while at the same time minimizine the ouantitv of the relalively cxpun
-

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MELEOURNE CENTRAL TLOm TO FLOOR OlllENYOl6

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f

PRCFLOR~UTED C~GE-'

i l r ~ ~ nrrm ~ n firm i P ~ E F ~ O ~ I C A T ECSE O

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am

R)l,ilOll

O U ~ L D EMI." ~ ELECT m wut~eci T l t i ~ CAGE m nllil STEEL CDLUNII ARD LIFI ltim PJIIIIDII-!YITH STEEL CO.UI4N

-t~n,io L ~ G A r~ lU~~ o ~EL

FLMR STEEL BEAN

Rg.3.22 noor-lo-floor dimcnri~nrand typical torer column reinrorccmcnt details; hlclbournc Ccntmi.


32


[Chap. 3

Luth Headquarters Building Kuala Lurnpur, Malaysia Architect S m c t u n l engineer Ycw of completion Height from slrcet to roof Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity Maximum lateral deflection Design fundamental period Design acceleration Design damping Earthquake loading Type of swclure Foundation conditions Footing type

.

Tvnical . floor Story height Beam span Beam depth Beam spacing Material Slab Columns Size at ground floor Spacing Concrete slrenrlh Core Thickness at ground floor Concrete strength

Hijjas Kasturi Associates Ranhill BersekuN 1984 152 m (498 ft) 38 0 Offices, parking garage Concrete 2.5 kPa (50 psfl 30 m/s (67 mph) Not available Not eswblished Not established Not established Not applicable Tube in tube Stiff silly clay 1500-mm (5-ft)-diameter bored piles. 20 m (60 ft) deep 3.66 m (12 ft) Varies from 19.2 to 8.7 m (64 to 28.5 ft) Typically 640 mm (25 in.) 9degrees radially Precast prelensioned concrete 100 mm (4-in.) precast planks, 50-mm (2-in.) topping 5 by i.2 m (16.4 by 4 ft) 38 m (125 ft) around circumference 32 MPa (5000 psi) Reinforced slip-funned concrete 400 and 200 mm (16 and 8 in.) 32 MPa (5000 psi)

The Luth Headquarters Building is a 38-level office building in Kuala Lumpur (Fig. 3.23). Of the 38 levels. 37 are at or above ground and comprise 7 levels of parking garage, 2 mechanical-plant levels, and 28 levels of office space. All floors are circular and contain a circular central core. However, in elevation the building is most unusual in that the facade is not vertical but formed from several solids of revolution. The facade of the lowest 22 levels is described by one circular

Fig. 3.23

Lulh Hcodqunrl~rrBuilding, Kunin Lurnpur, Mnioysin.


[Chap. 3


36

L 3 5 Fig. 3.27

V Fig. 3.25 Tgpieul midrire noor plan; Luth Hcndquorters Building.

slrands

\4$12

500 4

Fig. 3.26 Typicill noor section; Lulh Hcildquorlcrs Building.

J

Core to noor henm joinl; Luth Hcndqunrlerr Building.


Project Descriptions :.,7 .. . .,...,,: ...

3.'1, .

Fig. 318

Scclion of Lutb Hcndquorters Building.

Riverside Center Brisbane, Australia Architect Struclunl engineer Year of completion Height from street to roof Number of stories Number of fevels below ground Building use Frame mnterial Typical floor live load Basic wind velocity Maximum lateral deflection Design fundamental period Design damping Earthquake loading Type ofslructure Foundation conditions Footing type Typical floor Story height Beam span Beam depth Beam spncing Material Slab Columns Size at ground floor Spacing Concrete slrength Core Thickness at ground floor Concrete strength

Harry Seidler & Associnter Rankine & Hill 1986 150 m (492 ft) 39 2 Office Concrete 4 kPa (80 psO 50 d s (112 mph) 63 mm (2.5 in.), 50-yr return 3.8 rec 2% serviceability, 5% ultimate Not applicable Tube in tube Rock, 5-MPa (56-todft') capacity Pads to columns, mat to core 3.475 m (1l f t 5 in.) 12 m (39 ft 4 in.) 600 mm (24 in.) 3.35 m (1 l ft) Posttensioned concrete 125 mm (5 in.) reinforced concrete 1100 by 700 mm (43 by 27 in.) 6.7 m (22 A) 50 to 32 MPa (7200 to 4500 psi) Concrete shear walls 350 and 200 mm (14 and 8 in.) 40 to 25 MPa (5700 lo 3500 psi)

This 39-story. 42-level building is a totally reinforced concrete slructure designed as a "tube in tube" (Fig. 3.29). However, because the triangular shape leads to unusually long exterior core wnlls. the core has a greater than normal stiffness, and the exterior spandrel beams and columns play only n minor role in the resistance to wind load (Fig. 3.30). The floors nre suppotled by simply supported partially prestressed beams spanning 12 m (40 ft) from core to perimeter. Slabs nre not prestressed. Apart from the office building. the development includes a two-level basement garage, which covers the site and extends into the Brisbane River. The lowest floor is below normal high-tide levels, and the whole basement is designed to continue to function normally during a flood of a height resulting in a head of 6 m (20 11)of water at the lowest floor. The garage is topped by a ground-level plaza, low-rise commercial and retail buildings, and a restaurant which cantilevers 14 m (46 ft) o\,er the river.



[Chap. 3

125 SLAB

8601 4W SPANDREL BEAM

7

XII SLAB

POCKETS IN CORE WALL

Fig. 3.29

Riverride Center, Brirbnnc, Auslrnlin.

I I

PRESTRESSING T E N D O N S ~ DUCTS 4"-

,LO,,

Fig. 330 Floor plnn; Riverride Cenler.

I I


42

The ground conditions comprise hard phyllite. a metamorphosed mudstone, which allowed the use of design bearing pressures of 5000 kPa (50 tunlft'). Footings for the tower are reinforced concrete pads to columns and a raft slab to the core. The surrounding basement columns are supported on either pads or piers, depending on the rock level, which sloped away into the river. Floor slabs are designed for a general live load o f 4 Wa (80 psf) with a 5-kPa (100p s 0 zone around the perimeter of thc core. The use of 4 kPa (80 psi) rather than the statutory 3 %Pa (60 psf) provides for the more ready accommodation of safes, isolated compacting units, and other heavy loads over a small area. The 125-mm (5-in.)-thick slabs span 3.3 m (10.8 ft) and are reinforced with fabric. Floor beams are 600 mm (24 in.) deep nnd 350 mm (14 in.) wide at the soffit. (Sides are tapered to ease form removal.) At each end the beams terminate in a 300mm (12-in.)-thick slab, leaving about a 1200-mm (4-ft)-wide zone in which to locate maior air distribution ducts. The prestressing.tendons, of which there are two per bsnm, usually four-strand. arc contained in uirculnr ducts, but anchored i n ilxb t)pc nnchongus. The s l h nochornpc> are the m o t econo,nicel and lend tbsmsulrss tu ibt uss of rm:lll. linht incks. Tlte circular ducts rdrult in o a r r a ~ e br d i ~ n scu~nparcdnlth the width required ior two flat slab ducts side by side. The partially prcstresscd design provides for a load-balanced condition for about 80% of the weight of the bare concrete. This resulted in a flat floor. Ultimate load canacitv ~, was orovided bv additional unlensioned steel. Untensioned steel stresses ucrc limilcd to 130 hlP:, (?1.100 psi). Bcams were designed for lhe same li\c lu:lds 3s the slabs. chccpt th;tt rcduclions in 3ccurJancr. a!111 lllc luxling code a.r.rc urr.J. ,\I tach end ofth.: btnm. t ~ h ~ ri tl b~comcs : a \\id< 300-mm (I?-i,l ).deep slnb, cnnsidurjble anal)sis eifon *;is undsnaksn to ensure s3ttsf3ctu~stress IL.VCIS.Ilcrc rdirliorielment is predomtnantly untcnsioncd slecl. wilh onl) otle of the tendons uontin.!iltg trl Ihc suooonine s~andrelbeam: the other tendon terminates in a stressing anchorage at the end uf the 6UO-mm (2-i-in.).dcep rection of the bdnnl. This a r n ~ l g e m ot ~i tendons ~ pr0vtdi.J for strtssing off ihd floor bclow-there nerd no externdl scnffulding r?quiremcnts. Strcssinn was carried out in two stares: 50-c 3 d a \ s niter puurinc ths slnb and 100% after? days. These requirements dictated the concrete strength &her than the minimum design strength specified. [The concrete yielded a strength of about 35 MPa (5000 psi) at 28 days. with 25 MPa (3500 psi) having been specified.] A prop load analysis was curried out, tnking into account the load-relieving effect of the prestress. in order to arrive at lhc time when props could be removcd. Plant-room beams support a much heavier load than office floor beams, but the same floor formwork could be utilized bv increasinn- the slab thickness and o\'erall beam depth and by sloping the floor surface upward from the midspan of the beams. (The slab had to be thicker for ocoustic reasons anyway, and a fall for drainage was always required, so the structural requirements matched the other requirements.) The service- care ...- ~-~ ~-~~ has concrete walls. eenerallv 200 mm (8 . in.). thick.. exceot far the perimeter walls. alli;h wry from 350 to 300 tu 250 tnm ( l a in. lo I2 td I0 in.). Some tension in the lowcr rtonc5 occurs under dcsien wind Inads, but in ccncrnl loids ars comprcssion. Concrete was pumped for the full 150-m (492-11) height, with strengths varying from 40 to 25 MPa (5700 to 3500 psi). An architectural limit was ulaced on the column sizes, resulting.in thc use of 50MPa (7100-psi) concrete and 4% reinforccmcnt at the lower levels. Some carly problems were encountered with misplaced bars, which made the placing of spandrel beam reinforcement very difficult, particularly as the column bars w e e 36 mm (1.4 in.) in dinmcter and in bundles of up to four bars, but once a stccl template was employed to locate the bars. the problems disappeared. Where bundled bars were used, all column bars were specified io have splicing sleeves. ~

~

.

..

.

-.

~


[Chap. 3

.

I

Bourke Place Melbourne, Australia

Architect Structural engineer Year of completion Height from street to roof Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity Maximum lateral deflcction Design fundamental period Design acceleration Design damping Earthquake loading Type of structure

Godfrey & Spowers Connell Wagner 1991 223 m (732 ft) 54 3 Office Concrete 4 kPa (SO psf) 39 m/s (87 mph), 50-yr return 200 mm (8 in.). 50-yr return 4.8 sec 3.7 mg rms. 5-yr return 1% serviceability, 5% ultimate Not applicable Reinforced concrete core and perimeter frame tube-in-tube Highly weathcrcd siltstone Pads to columns, raft to core

Foundation condttions F o ~ t i n gtype Typical floor Story height Beam span Beam depth Beam spacing Material Slabs Columns Size at ground floor Spacing Concrete strength Core Thlchness at ground floor Concrete svength

3.7 m (12 it 2 in.) 10.8 m (35 f t 5 in.) 400 mm (16 in.) 4.6 m (15 ft) Posuensioned concrete 125-mm (5-in.) reinforced concrete 1I00 mm (43 in.) square 8.1 m (26 ft 6 in.) 60 MPn (8500 psi) maximum Slip-formed shear walls 400 and 200 mm (16 and a n . ) 60 MPa (8500 psi) maximum

The Bourke Place project includes a lower structure with 5 4 floors above Bourke Street in the city of Melbourne (Fig. 3.31). On top of the concrete tower is a steelframed, aluminum-clad cone roof reaching another four stories and a communications tower rising to approximately 255 m (837 ft) above the street. Alongside the tower there are an 8-storv, narkine raraee (four of which are below eround) and olazas with , rood and retail areas. The total leasable floor space in the office tower is approximately 60,500 m' (651.200 ft'). The tower structure consists of a slip-formed reinforced concrete core, posttensioned concrete band beams, and a reinforced concrete perimeter frame (Figs. 3.32

. --

b

..

.

.

44


[Chap. 3


45

and 3.33). The core structure is approximately 20 m (66 ft) square at the base. Most internal walls are 200 mm (8 in.) thick. with some 150 mm (6 in.). and remain constant for the full height of the structure. The external wails vary from primarily 400 mm (16 in.) thick at the base. using 60-MPa (8500-psi) concrete. to 200 mm (8 in.) lor the top 15 slories, requiring only 25-MPa (3500-psi) concrete [40 MPa (5500 psi) was used for pumpability.] The use of high-strength 60-MPa (8500-psi) concrete allowed the wail thicknesses to be minimized. It wns estimated that the loss of floor space for thicker walls, if40-

Fig. 3.32 Typical tower floor plon; Bourke Place.

?OR

ivn,oxn ,m

"liiiillilC DiiYI*i

Fig. 333 Typicill noor profile, ~ o u r k e~ i u c c . Fig. 3.31 Bourke Piore, hlelbourne, Autrniin. (Plioro by Srjl~ircPlio!ogropi!ic.r.)

46


MPa (5500-psi) concrete was used, represented an effective extra ovcmll capitalized cost to the client of approximately $;100,000 (Australian) per floor. Two substantial core shape changes occur up in the tower as elevator shafts that service the lower levels become redundant. The location of these shaoe changes and the changes in wall thickness were positioned sufficiently high up in the tower to ensure that the cote aould be off the construction crilical path in order to avoid any time delays. The design of the slip form incorporated the facility to reduce the wall thickness and to "drop off' these portions. Cost comparisons during the design dcvelopment phase indicated that slip forming was the most cost-efiicient method of construction, and the Bourke Place core was the largest single slip-formed core ever constructcd in Austmlia. The core conrtruction set an Australian record in Novemhcr 1989 lor pumping concrelc to 2 10131 risc of236 m (77.1 it). A t the tilne of dcs~gn,building rcgulations lor fire prolcc~innrequired 1h3t spandrel benms he a1 least 900 lllln (36 in ) d~wp.11 ulas recoQnized that. In cunjunction with the columns, lllese beams svould therslore m?ke some contnbu~ionlo the oucrall resist2nce lo brnd In3d5 on lhc slnlcturc. Tnr h e ~ m sucr? designed for l l ~ cdead and livc load requircmcnts: then their capacity to resist additional wind load was assessed. This amounkd to approximately 7.5% ofthe total wind load on the structure, meaning that the core need only be designed for 92.5% rather than the full wind load. The "core and partial-frame" approach represented significanl cost savings to the client. A 125-mm (5-in.) normally reinforced concrete slab spans between 10.8-m (35.4it)-long band beams at typically 4.6-rn (15-it) centers. The band beams radiate out from the core and are typically 400 mm (16 in.) deep, but are notchcd at each end to 275 mm (1 1 in.). The notches wcrc introduced to accommodate primary mechanical ducts, and they enable the total floor-lo-floor height to be minimized. This represents savings to the client as the overall height of the building can be reduced without aflectine, the number of Floors. The band beams are posttensioned from underneath, utilizing the vertical face of the notches. This separates the posttensioning contractors from the "work hce." allo!vine- stressine - to be carried but indeoendent of scaffold erection on the newlv poured floor. nnd it r l i m i ~ ~ a ihc ~ e sn<
-

~


[Chap. 3

~

~

CentralPlaza One Brisbane, Australia

Architect Suuctural engineer Year of completion Height from sveet to roof Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity Maximum lateral deflection Design fundamental period Design acceleration Earthquake loading Type of structure Foundation conditions Footing type Typical floor Story height Slab Columns Size at ground floor Spacing Concrete streneth Core Thickness at ground floor Concrete strength

Dr. Kisho Knrokawa. Peddle Thorp Partnerships Maunscll Pty. Ltd. 1988 174 m (571 ft) 44 4 Office Concrete 3 P a (60 psO 49 d s (1 I 0 mph). 50-yr return 350 mm (13.75 in.), 25-yr return 4.4 and 3.8 sec 16 mg peak. 5-yr return Not applicable Central core with perimeter framed tube Marine clay over rock. 5-MPa (5-tonlfi') capacity Spread footings, anchored perimeter wall 3.66 m (12 ft) 10-m (33-ft)-span posttensioned. 275 mm (10.8 in.) thick 1200 by 1000 mm (47 by 39 in.) 7 m (23 fl) 50 MPa (7100 psi) Concrete shear walls 600 and 250 mm (24 and 10 in.) 50 to 32 MPa (7100 to 4600 psi)

Central Plaza One is currently Brisbane's tallest building with a total of48 levels and has a total height of approximately 174 m (571 ft) above sveet level (Flg. 3.34). The building features a four-story avium with an internal running stream and landscaping at the ground-floor level. and a four-level basement garage. A distinctive roof line with a lifting, slewing telescopic building maintenance unit forming the top 2.5 m (8 ft) of the roof structure makes the building unique among modem high-rise buildings in Australia. The tower houses three plant rooms at levels 4.26. and 41. A six-story office block adjacent to the main tower has banking facilities at the ground-floor level and shares the common basement structure with the tower. ThlS "hank annex" incorporntes an additional plant room nt level 5.


.

The tower structure comprises a reinforced concrete core and frame with posttensioned floors and is founded on rock approximately 13 m (43 it) below street level. Design requirements were as follows:

An accurate assessment of deformations due to creep, shrinkage, and load effects to

m

s

Column-free office space requiring floors to span 10 m (33 ft) from perimeter beams to central core Floors to be designed to allow for maximum flexibility in locating penetrations for services Floor edgr beams to be designed and detatled to allow for variations at corners to range from 6-m (20-11') cantilevers to fully truncated corners A minimum number uf minimum-size columns up through t l ~ catrium and above togerhcr with the assurance that accclerat~onsdue to wind-rxcitcd oscillations be within acceptable human response lirnitotions

allow for joint design at critical locations in the curtain-wall system A bosement structure to accommodate 270 cars A roof shucture to support a lifting, slewing. and telescoping building maintennnce unit

j $ ! . Preliminary analysis of the building using a simplified annlyticnl model indicated

I

I II 1

i

I

j

Fig. 3.34 Central Pinzn One, Brisbnne, Aurtmlin.


'

that the tower would be wind-sensitive and accelerations could be excessive. The simplified model comprised the central core as a cantilever linked to the outer frames, with axially stiff linkages representing the floors. the entire assemblage being considered as a plane frame. Having gained considerable insight into the behavior of the structure from the preliminary analysis, the tube-in-tube structural system was chosen for resistance to lateral wind loads. During the preliminary design stage a l:400 aeroelastic model was being developed and tested in a wind tunnel to d e t e d n e and minimize wind pressures by varying the dvnamic earnmeters. Considerable analytical work was carried out to tune the *truckre The stiffness and mass of various structural components were ~- aera~lasticallv. -~ adjusted nnd readj~rstcdin this process to minimize !he aeroelastic forces. Once the slructurai form was finalized. a rigorous three-dimensional tobc-in-tubc .~n~lvclq carried out. This was necessarv toensure that disolacements and acceler,-.- was -~ ations under \vind 1o;ading were brlou acceptable Ie\,cls. In lhc analysis for core-frame interaction. the structure \\,as propped at the ground floor :,nd ;!I each of the basemrnt levclc qo hat lateral loads could be transferrid out to the site oerimeler walls throueh .. .diaphragm action of the floor slabs. Propping of the structure'at the ground floor a i d basements avoided the problem of having Lo deal with large momens at the core fooling and also served to convol deflectioniand accelerations of the building under wind load. Of particular importance was the cross-wind response of the building, which produced a resulting ntoment 1.6 times the along-wind response. The cenval core occupies a space approximately 16 m (52.5 ft) square in the center of the building and is, in reality, two cores with an elevator foyer space between. The two cores are linked together via floor slabs and beams, and in addition, by large diaphragms in the atrium and plant rooms. The atrium diaphragms were found to be particularly effective in reducing deflections by giving the building an exceptionally high point of rotation approximately 45 m (148 ft) above street level. The central core is a multiccll reinforced concrete structure with wall thicknesses varying from 200 to 600 mm (8 to 24 in.). Reinforcement ratios vary from about 1% in the lower parts of the building to 0.5% at the top. The core was designed globally for biaxial bending and axial load using the program FAILSAFE. In this program a particular section of the core is defined as an assembly of square elements within a system of coordinates, and the quantity and location of steel is also defined within the coordinate system. The program outputs a failure surface for axial load versus moment. A detailed dcsiyn of the core at licodcrs. coupling bu.lrns. xnd dii~phr~gnlb \+.IS Carried our using decp-hmm liicury, hear-fricuon theory, and cun\,r.ntion~lrdinC0rci.d concrete theory, as appropriate for the element under consideration. Basement floors u.ere designed as conventional reinforced concrete flat slabs. except that two special effects required particular attention in the design and detailing of reinforcements, namely. (1) transfer of wind loads out of the core to the basement walls. and ( 2 ) differential settlement betwccn the core, maiar columns, and basement columnr. Pcrticulx :!ttention rrar paid to detailing the r~inforcunlentrat thc core-Sl:lh joints, both on lhc dm\r!ng board :!nd on rltc during cnnstruction. ~


50

[Chap. 3

The ground-floor slab was designed in reinforced concrete, incorpomting an extensive beam system. At this level the wind-propping loads were considerably higher than in the basement slabs, and in addition the slab was designed to support a 10-Wa (200-psO conswction live load to allow for scaffolding up to support level 4 plantroom slab over the atn'ltrn The ground-floor slab is a multilevel slab with sloping and stepped purtions, and in the nonheast comer it contained large openings. Special bands of heavy reinforcing steel were required around the perimeler to vansfer wind loads into perimeter walls. A diagonal band of heavy steel from the core to the northwest corner of the site was required lo ensure a load path to compensate for the large penetrations ofthe nonheast corner. Tower floors were designed as posuensioned flat plates spanning approximately 10 m (33 ft) from the spandrel beams to the cenval core. Typical floor slabs are 275 mm (I I in.) thick and are stressed with tendons in bands of six, each tendon comprising five 12.7-mm (0.5-in.)-diameter supergrade strands in 90-mm (3.5-in.)-wide ducts. The banded tendon arrangement provides maximum flexibility of floor layout for the positioning of penebations for services and internal stairs in the tenancy design stage. The flat-plate soffit was important in allowing the builder to speed up the formwork placing and in achieving the specified cycle times. Posttensioning also meant minlmum passive reinforcement, another feature to assist thc builder. Finite-elemcnt analysis of the floor slab indicated the existence of high shear slresses near the comers of the core. This was dealt with by installing some shcar stccl locally in the slab near each corner of the core. Spandrel beams n8ercgenerally reinforced concrete, except for the longer cantilever bcams at the comers of the building, which were posttensioned to minimize deflections. ~

~

Lateral Load Resisting Systems

*

-,

.<.

4.1 BRACED FRAME AND MOMENT RESISTING FRAME SYSTEMS

-'

Two fundamental loteral force resisting systcms are the braced frame (also kno\\'n as shear truss or vcrtical truss) and the momcnl rcsisting frame (moment frame or rigid frame). Thesc systems evolved during the beginning of high-rise construction in the twentieth century. Braced framcs and momcnl resisting frames are normally organized as planar assemblies in orthogonal directions to create ~ l a n a rframcs or a tube frame system. Thc two systems may be used together as an overall interactive SySlem. thereby their individual applications to taller buildings. Both systems arc commonly used today as effective means of resisting lateral forces in high-rise construction ior buildings of up to 40 or 50 stories.

3.3 CONDENSED REFERENCES/BIBLIOGRAPHY Kilmirrer 1983. Design and ConnnlcIia,r offl~eLull?Heodqaunrrs Buiidirtg, K ~ o i oLu,npur Monin 1989, lVirzd Design ofFourBuiidirtgr up to 306 ,n TO!!. L'in*fistrin Irnliimn *el Cementa 1987. T/U Lurb Bsiidittg ir2K ~ , ~ IL~~~~~ O ( ~ f ~ i ~ ~ ~ i ~ ~

I

1,

.

!.,

I '? I 1

.

1 Braced Frames

Braced framcs arc cantilevered vertical trusses resisting lateral loads primarily through the mial stiffness of the frame members. Axial shortening and elongallon of the column memben under lateral loading accounts for 80 to 90% of the overall system deformation lor slender truss systcms. The effecriveness of the system, as characterized by a h i ~ ratio h 01stiffness to material quantity, is recognized lor multistory buildings in the low- to midhcight range. Braced frame geometries are grouped, based on their ductility characlcristics. as either concentric braced frames (CBF) or eccentric braced frames (EBF). In CBFs the axcs of all mcmbcrs intersect at a point such that the member forces are axial. CBFs have a great amount ofstiffncss but low ductility. Thus in areas of low seismic acr~vil)~. wllcre high ductility is not essential, CBFs arc the lirst choice or engineers for lalcral load resistance. EBFs. on the other band. utilize axis offsets to introduce flexure ,and shcar into the frame, which lowers the stiffness-to-weight ratio but increases ducttl~ty. The CBF can take the lorm of an X. Pmtt, diagonal, K.or V, as sho$\,n in Fig. 4. I . The X bracings exhibit hizhcr lateral stiffness-to-\lzeigl~tr ~ l i o sin comparison to K OrV bracings. Ho\ree\'er, the X bracings crcnte a short circuil in the column gravity load

52


[Chap. 4

Sect. 4.11

lransfer path as they absorb a ponion of the column load in proportion to their stiffness. This creates additional forccs in both diagonal and horizontal members of X-bracing svstems which need to be considered in svstem derivn -..=.. To accommodate door and other openings, EBFs are commonly used, a s shown in Fig. 4.2. The shear and flexural action caused by the axis offset in Ule link beam improves ductility. Higher ductility through inelastic shear or bending action of the link beam make it a desirable lateral system in areas of high seismic activity. Ductility is measured by a well-behaved hysteresis loop and achieved through proper connection and member design such that all modes of instabilities and brittle failures are eliminated. Braced frames are most often made from structural steel because of ease of construction. Depending on the diagonal force, length, required stiffness, and clearances. the diagonal member in structural steel can be made of double angles, channels, tees. tubes, o r wide-flange shapes. Besides performance. the shape of the diagonal is often based on connection considerations. Examples of typical braced frame connections are depicted in Fig. 4.3. Vertical trusses are often located in the elevator and service core areas of high-rise buildings, where frame diagonals may be enclosed within permanent walls. Braced frames can be joined to form closed section cells, which logetherare effective in resisting torsional forces. These cells may be bundled to take advantage of additional stiffness and provide a systematic means of dropping off the cclls at the upper levels of a

4 :. ..

....... :. ... ... j..

PRATT BRACING

.

.~. ,

.,

I

/........ ,..

X-BRACING

3;.

DIAGONAL BRACING

Braced Frame and Moment Resisting Frame Systems

lourr where laleral forces are reduced. The strength and stillness of the lruss syslcm is thus sensitive lo the lootprtnt of ihe core area and the arrangement 01the clcvators. When ihe slenderness ratio of a core truss (the ratio of truss height lo le2rt u,idth) Increases. the o,,emll overturning cffecl manifests il5:If in ~ncrcascdaxid dclorn~ntion and uolifr forces of chord columns. While truss chord members may rr3dily be drsigned forces, net foundation uplift forces are generally &desirable. A design be lo spread Lhe chords as far apart as possible while diverting gravity load to these chords to Drevent or reduce the net tensile force. As slenderness increases. the a i a l drformalions of lllc chord columns o f a truss system become more critical in controlling the sway of the slructurc. Increasing the r l ~ l f nrss and strsnath of lhe chord members in proponion lo the work done by those members will prov%e an effective way to minimiz; sway. The bracing system between the chords can be designed to transfer the gravity loads of any intermediate chord columns to the boundary chord columns. As a result the intermediate chord columns could be eliminated or minimized in size and the efficiency of the boundary chords maximized. To further reduce the steel tonnage and cost of the structure, composite steel and concrete chord columns may be utilized. Using concrete in chord columns will most likely provide a lower unit price for strength and axial stiffness.

2

Moment Resisting Frames

Thc moment resisting frame consists 01horizontal and vertical members rigidly connected together in a planar grid form which resists lateral loads primarily through the flexural stiffness of the members. Typical deformations of tha moment resisting frame system under lateral load are indicated in Fig. 4.4. A point of contraflcxure is normally located near the midheight of the columns and midspan of the besms. The lateral deformation of the frame is due partly to the frame racking, which might be called shear sway, and partly to column shortening. The shear-sway camponen1 constitutes approximately 80 to 90% of the overall lateral deformation of the frame. The remaining portion of deformation is due to column shortening (cantilever component or so-called chord drift). >lomen1 rcs~.ting lramrs h ~ v advantages e in high-ri5e conslruclion due lo their flexibility in nrchitsclural planning. A moment reslbling frarnr. may he placed in o r around tltc core, on the exterior. or throughout the interior o f the building with nlinimll con5traint on the olannineu module. ~ h frame ; mav be architecturallv. exposed to express the . gridlike nature oflhs structure. The sp3cing of lhs column: in n moment resisting frame c ~ match n !hat required fur -grnvity lraming. In lac1 ths stecl u e ~ g h prenlium t for iatual frame resistance decreases with increasing gravity londs on the frame ~~~

~~

~

K BRACING

KNEE BRACING

V BRACING Fig. 4.1

Concentric br;lrcd

rromc rorms.

53


54

sect. 4.11

[Chap.


. .. (b) ~ i ~ , 4~3

...

~ ~ ~ ~ ~ n ~dttniis. ~ it i ( no) CBF. ~ n [b)~ EBF. (Codinued) l

(a) Fig. 4.3

Typicul corlncrlion debiir. lo) CUF. (b) EUF.

rig, 4.4

~~~~~t rwirting behavior.

derurmntion under Inter loud. (01 Frame deformntion.


58

[Chap. 4

volves a transfer of shear forces from the top to the bottom of the building. Figure 4.7 shows the truss and frame deflections if each resisted the full wind shear. The distrihution of wind shear between lruss and frame can also be noted. Frame-truss interacting systems have a wide range of application to buildings of up to 40 stories in heieht. In general, core trusses are combined with moment frames located on the building perimeter,where the column spacing and the member proportions of the frame may be appropriately manipulated. Optimum efficiency is obtained when gravity-designed columns are used as buss chords without increasing them for wind forces. These are then combined with gravity-designed exterior columns and spandrel beams with rigid

SEMIRIGID BOLTED CONNECTION

IJ3~ ,

...

sect.

4.7,

Braced Frame an. Moment Resisting Frame *terns

connections. If the lateral stiffness of the system is adequate, this then would ~ r o d u c e an oplimal design. If additional stiffness is required. the decision of whether to Increase the core or the frame members depends on the relative efficiency of the two components. The frame beam spans, story heighls, and core uuss depth are key parametcrs. Tension or uplift conditions may limit the possibility of increasing chord columns.

P v:

RIGID FIELD WELDED CONNECTION

DEFLECTION

> FRAME SHEM

RIGID CONNECTION SHOP WELDEDIFIELD BOLTED WITH COVER PLATES

RIGID CONNECTION SHOP WELDEDIFIELD BOLTED WITH END PLATES

Fig. 4.6 Mamcnt resisting frame connection types.

59

SHEAR ~ i g 4.7 .

~mmc-trussinlemeting rsrlcm.

60


[Chap. 4


61

,.

Sect. 4.11

,ir.

together u,ill~the rigid frames. The di3gOIIal members of eccentric K-bmccd framcs do no! intercect . ......-- at the cenkr of the beam. Thus yielding 1 the center of the beams will occur before braces buckle, ensuring ductility and allor;ing for adjustment of the f m e ductility ~. (Figs. 4.9 to 4.11). This hor, been confnned, both experimentally and theoretically. Ductility and strength are ensured by using acomposite beam for the 24-m (78.9-in.) office floor spans. This also minimizes vibration disturbance due to people walking, as was confirmed through a composite beam mock-up test Precast concrete panels faced with granite are used as cladding material, providing a solid appearance to the building (Fig. 4.12). The panel fixings were designed so that during an earthquake, the panels can follow the building deformations without damage or risk of dislodgement. This was checked using a two-story two-span full-scale model.

.I..

PROJECT DESCRIPTIONS

'

L.?

Sanwa Bank Tokyo, Japan

Architect Structural engineer Year of completion Height from street to roof Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity Maximum lateral deflection Design fundamental period Design acccleration Design damping Earthquake loading Type of swcturc Foundation conditions Footing type Typical floor Story height Beam span Beam depth Beam spacing Material Slab Columns Size at ~ o u n floor d Spacing Material Core

Nikken Sekkei Ltd. Nikken Sekltei Ltd. 1973 99.7 m (327 ft) 25 4 Office Stmcmral sleel 3 Wa (60 p ; ~ Not available Not available 3 sec in both directions 20 mg: 40 mp for seismic loading 2% of critical C = 0.10 Combination of rigid frames and eccentric K bracing Alluvium and diluvial gravel Raft on reinforced concrete driven piles 3.84 m (12 f t 6 in.) 24 m (78 ft 9 in.) 850 mm (33.5 in.) 3.15 m (10 ft 4 in.) Steel, grade 400 MPa (58 ksi) 2d floor and above; concrete-encased steel below 2d floor 120-mm (4.75-in.) reinforced concrete -100- by 400-mm (16- by 16-in.) H sections 3.15 m (10 ft 4 in.) Steel. grade SM 490.483 MPa (70 ksi) Shear walls below ?d floor, 800 mm (31.5 in.) thick combined rigid and braced steel frames, grade Shl490, above 2d floor

111designing the Saniva Bank bullding for carlitquakc and \bind loads (Fig. 4 8 ) , it was decided to place ccce~llricK-br3c:d frnmea al npproprio~clucntions such !hat [hey uill act

~

62


[Chap. 4

I

Sect. 4.11

"7

Fig. 4.8

Snnwil Bank. Tokyo, Jnpun.

~k:!



Sect. 4.11

[Chap. 4

i i

I

4

u,m

1

t* %%%%%%%%%% bb 'b Fig. 4.10 Fmme~arL;Snnwn Bank.


Fig. 4.11

Specimen olecc~nlricI( Imme; Snnno Bnnk

65


PLAN

I \ vibration

COLUMN PANEL FASTENING (a) Fig. 4.12

Dclniir otprerut concrele pnnel; Snnwn Bank.

,

,,,,r

',/

"

I..

.I

<;I

4,., - I ,, ..;.,-..,.-....E . - - 2 .-.,< T. .....!?.L::i; ;.., -2 :* :" *.>' ,'I. "

,. C ,.i

,

I

:'

,;

6

,:i

0

0

,.$"

0

A

SECTION

(4 Fig. 4.12

Dctililr o f prcrort rnncrclc pnnel: Scnwn Bunk. (Conrir#ucdl

67

68


[Chap. 4

ACT Tower

Structural engineer Year of completion Height from street to roof Number of stories Number of levels below ground Building use Frame material. Typical floor live load Basic wind velocity Maximum lateral deflection Design fundamental period Design acceleration Dcsign damping Earthquake loading Type of structure Foundation conditions Footing type Typical floor Story height Beam span Beam depth Beam spacing Slab Columns Sire at ground floor Spacing Corc


I

3. A dynamic test to check the dynamic analysis results

Hamarnatsu City, Japan

Architect

Sect. 4.11

Nihon Sekkci Inc. and Mitsubishi Estate Co. Ltd. Nihon Sekkei Inc. 1994 21 1.9 m (695 ft) 47

Hotel, offices, retail space Steel 5 kPa (100 psfJ 30 mlsec (67 mph) Hl2OO. 100-yr return period wind 4.52.4.73 sec 52 mg peak. 100-yr return period 1% serviceability. 2% ultimate C = 0.06 Braced frames Clay, sand, and gravel Piles 1.5 to 2.4 m (5 lo 8 ft) in diameter. 25 to 30 m (82 to 98 it) long

The dynamic annllsis war performed using the mean and the standard dc\'iarion as well as the power spectruln of the ovrnurning moment and the torsional moment cocicienls obiined inthe wind force test i The building response specva are obtained by combining the wind spectra (for the x, y, and 8 directions) and the magnification factors versus frequency curve. As the building cross section is ellipsoidal, special consideration was given to getting the maximum response values used in the design in the x, g, and E directions. The dynamic stability and the possibility of galloping were also checked. Strong winds can occur several times a year, causing uncomfortable building mqtion. In order to avoid this problem, a damping systcm has been installed to reduce the acceleration in they direction. The building site is located in a very active seismic area. The largest eanhquakes in this zone to dare were of magnitude 8. A special seismic analysis was performed using the data of the three largest earthquakes that have originated in this area in order to model the earlhquake waves and the maximum possible accelerations for the ACT Towcr site. These 3 earthquake waves were 416 gallsec (550 mmlsec) (Ansei Tohka earthquake); 150 gallsec (320 mmlsec) (Nohbi earthquake): and 332 gallsec (850 mmlscc) (Tohnankai earthquake).

1

.

1

i

4 m (13 ft) office: 3.15 m (10 f t 4 in.) hotel 17.5 m (57 f t 5 in.) max. office: 10 m (33 ft 10 in.) hotel 850 mm (33.5 in.) office: 700 mm (27.5 in.) hotel 3.2. 6.4 m (10 f t 6 in.. ?I ft) office: 3.2, 4.27 m (10 h 6 in.. 14 ft) hotel 135- to 180-mm (5.25- to 7-in.) concrcte 750 by 600 mm (30 by 24 in.) 3.2 and 6.4 m (10 ft 6 in. and ?I ft) X- and K-braced framer

Braced frames were used lo increase the stiffness of the ACT Tower (Fig. 4.13) and to achieve an optimum structural system (Figs. 4.14 to 4.16). Three u.ind-tunnel tesls were performed:

I. A wind pressure test to evaluate facade pressures 2. A wind force test to measure the horizontal force, overturning moment, and tor. sional moment

I

Fig. 4.13

ACT Towcr. Humnmolsu City, Jnpnn.

70


M i c a 1 Structural Plan (Hotel)

>pica1 Structuroi Plnn (OCrice) Fig. 4.14 'Typical slruelurul plunr; A C T Toner.

[Chap. 4

72


Sect. 4.11

[Chap. 4


73

Ti%-

I!

Year of completion Height from street to roof Number of stories Number of levels below ground F n m e material Typical floor live load Basic wind velocity Maximum lateral deflection Design fundamental period Design acceieration

Ii

Earthquake loading Type of structure Foundation conditions

.

Nikkeu Sekkei Ltd. with Portopia ~ o t ~ l Design O f i c e Nikken Sekkei Ltd. with Portopia Design Office 1981 112 m (367 ft) 31 2 Hotel Structural steel 1.8 kPa (36 psf) Not available 350 mm (13.75 in.) 3.5 sec transverse; 3.6 sec longitudinal 20 mg; 35 mg for seismic loading 2% C = 0.08 Moment frame and braced frame Fill over alluvial and diluvial strata Raft on prestressed concrete driven piles 3.02 m (9 ft l l in.) 7.5 and 6.75 m (24 ft 7 in. and 22 ft 2 in.) 800 m m (31.5 in.) 7.5 m (24 ft 7 in.) Steel, grade 400 and 490 MPn (58 and 70 ksi) 5th floor and above; concrete-encased steel below 5th floor 130-mm (5-in.) reinforced concrete

Columns Size at ground floor Spacing Material Core

I100 by 1100 mm (43 by 43 in.) 7.5 m (24 fi 7 in.) Steel encased in 24-MPa (3400-psi) concrete 600-mm (24-in.) concrete shear walls below 5th floor, smctural steel rigid frames 5th floor and above

Tllr typical floor pi2n of the Kobe Ponopix Holcl (Fig. 4.17) is .an oval, rncnsuring 7j.5 m (24.4 Ir) in the earl-weal dirccrion and 13.5 rn (4.4 fr) in the north-soutl~dirucrion IFlp.

Fig.1.16

Y5A frame elemlion; ACT Tower.

4.18). Above the fifrh floor of the high-rise p m . strength and ductility are provided hy

74


[Chap. 4

using a reinforced concrete rigid frame. The fifth and lower floors, which have a larger story height. have a composite structure of shear walls and rigid frames made of steel encased in reinforced concrete (Fig. 4.19). The site is part of about 500 ha (1200 acres) of artificially reclaimed ground. which has been filled over a oeriod of 10 years, starting in 1965. Before building construction commenced, the site Was preloaded. theoretically completing settlemen~ofthe former 12-m (40-it)-thick sea-bottom clay layer. Because the building weigh1 is about 100.000

Ik

Sect. 4.11


tonnes (1 10.000 tons), a basement withgood foundation load balance was possible, with the weight of h e excavated soil being designed to exceed the weight of the building. Piles of about40-m (130-11) length were used. The building is supponed by using the diluvial layer as the bearing stratum. In pile design, pile groups were used wherever possible to cope with unmeasured ncgative friction. Structural safety was confirmed by performing a seismic response analysis of the building-pilc-bearing stratum composite form against horizontnl seismic loads. The floor plan has an unusual form, so various wind tunnel tests were performed to investigate such factors as the wind force coelficicnt. the wind pressure coefficient, nmbienl wind velocity, and the dynamic stability against wind. In everything from the structure itself to cladding matcrinls, external doors and windoms, and ground-lcvel wind velocity, wind tunnel test rcsulls were used to ensure adequate safety and serviceability.

Fig. 4.18 Typicul slructurul noor plnn; Kobe Purlopin Hotel

Fig. 4.17 Kobc Porlnpiu Holcl. Robe, Japan.

75



8:;:

77

-?,..

.*+.

ah

Nankai South Tower Hotel Osaka, Japan

@

* ,. j..,,

18, &(

Architect

Swctural engineer 41 :Year of completion I $& Height from street to roof @ .,g~, Number of stories ~.~. *.~. :*.: Number of levels below ground , ,:

I,S

'A, : :I:

&~ .?,. 73,'

Building use Frame material

.:.

.,:

Typical floor live load Basic wind velocity Mnximum lateral deflection Design fundamental period Design acceleration .. .,.,,. ,:, . ..

Design damping Eanhquake loading Type of structure

Foundation conditions Footing type Typical floor Story height Beam span

... 2:.

/

\

I

9

VrnrnesorR; Kobe Portoplu Hofcl,

<-

Beam depth Beam spacing Material Slab Columns Size at ground level Spacing Material Core

Nikken Sekkei Ltd. Nikken Sekkei Ltd. 1990 147 m (482 ft) 36 3 Hotel Structural steel upper floors; concrete-encased structural sleel plus concrete shear walls lower floors 1.8 kPa (36 psO 35 d s e c (78 mph) Not available 3.24 sec transverse; 3.03 scc longitudinal Level 1 EQ. 13 to 25 mg; level 2 EQ. 21 to 40 mg 2% C = 0.120 Level 5 and above, rigid frames; level 4 and below, combined frames and shear walls Grnvel Cast-in-place 2-m (6.5-fr)-diameter bored piles 10 m (33 ft) deep 3.2 m (10 ft 6 in.) Primnry. 10.5 m (34 h 5 in.); secondary, 5.4 m (17 ft 8 in.) 850 mm (33.5 in.) 2.625 m (8 ft 7 in.) Steel, grade 400 and 490 MPn (58 and 70 ksi) 140-mm (5.5-in.) concrete on metal deck 1300 by 1300 mm (51 by 51 in.) 10.5 m (34 ft 5 in.) Steel, grade 49 MPa (7000 psi) Shear wall. 34-MPa (3400-psi) concrete. 350 mm (14 in.) thick

78


[Chap. 4

This hotel was constructcd over a railway station, which had been designed and constructed by another firm up to the fourth floor 10 years earlier (Fig. 4.20). An expansion of about the same extent was planned even in the original design, but there existed limitations with regard to theallowable stress of the already constructed parts, including the piles. While over the course of I0 years structural codes had been modified, mal;ing it more difficult to expand buildings constructed before the code changes, the design tech-

Sect. 4.11


niques for high-rise buildings had not fundamentally changed, so the strength ofthc already constructed parts was for the most pan adequate. However, there was n planning regulation change in that guest rooms must now have balconies, and it was necessary to comply with the desires of a desiener. which chaneed the plans considerablv. ?hi increased weight due to balconies was handled by changing the spciific gravity of the concrete irom an original 1.8 lo 1.65. In the original design, slanted columns had ranged from the sixth to the twentieth floors, which was due to changes in thc spans of t h e k o ~ e and r lower floors. and the desiener wanted to reduce thisnnee to dctwecn llourr 9 m d I?. Tu Improxc the ~.nruingreduction in h~lidlngrigidlly, the s n c 01 tile c x ~ c n l dcolumns ~ 3 incrcarcd. s Thir supprcsrcd ihc overall hcnding deformation, and at the same lime the inner coiumns were effectively used as shear columns. External columns are larce boxed members. so in the lencth direction the oerimeter irame is used to rcsirt 111 01 ihe horironnl loading (Figs. 4 21 and I.??). To facilit3te conrtruclion, bnlconics were dcsigncd in ihc L shops uilh 3 length of 10.5 m 134 it 5 in.). Pn:.lr~.swd cuncr2ls. oniv 90 mm 0 . 5 in1 thick. u a i used lo inioimize the weight. A composite floor, fire rated for 2 hours, was used in the typical guest room. The deck has to be of the linked beam type (which covers at least two beam spans). In unit bath areas, which had to be partially dropped, ordinary slabs using a flat deck were employed.

-

..

-

-

Fig. 4.21 Typlcnl noor plan; Nankui South Toscr Hotel.

Fig. 4.20 N ~ n k o South i T u n ~ rHutcl, Omku, Jnpon.

79

I

:g+ .$ +J: .$I

Ssct 4.11

i7.5. ~..=

9

I *.. ji

Architect

*",

'S.

.:

-.:

i

Structural engineer Year of completion Height from street to roof Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity Maximum lateral deflection Design Fundamental period Design velocity Design damping Eanhquake loading Type of shucture Foundntion conditions Footing type Typical floor Story height Beam span Beam depth Beam spacing Matenal

Fig.4.22 Fmmcrork; Nnnkni South Tower Holrl. 80

81

World Trade Center Osaka, Japan

w: *.

~ j < *. .


Slab Columns Size at pound floor Spacing Material Core Material

N i i e n S e k k e i Ltd. with Mancini Duffy Associates Nikken Sekkei Ltd. with Mancini Duffy Associates 1994 252 m (827 ft) 55 3 Office Structural steel 3 kPa (60 psf) 40 d s e c (90 mph) 1300 mm (51 in.). 200-yr return period wind 5.3 sec transverse; 5.8 sec longitudinal Level 1 EQ. 250 mm/sec (10 inJsec); level 2 EQ. 500 mmtsec (20 in./sec) 2% C = 0.05 longitudinal; C = 0.075 transverse Rigid frames with core braced transversely 20-m (65-ft 7-in.) fill over alluvial clay and sand strata Cast-in-place steel-lined bored piles belled at their bust 4.0 m (13 ft 1.5 in.) 16 rn (52 ft 6 in.) 900 mm (35 ft 5 in.) 3.2 and 9.6 m (10 R 6 in. and 31 ft 6 in.) Steel, grade 400 and 490 MPa (58 and 70 h i ) 175-mm (7-in.) concrete on metal deck 650 by 850 mm (25.5 by 33.5 in.) 3.2 and 9.6 m (10 ft 6 in. and 31 ft 6 in.) Steel, grade SM 53B Steel fmmes, braced in transverse direction Stee!, grade 490 MPa (70 ksi)

1 I

82


[Chap. 4

Sect. 4.11


This 252-m (827-it)-high building stands on reclaimed land in the Osaka Nanko (soulh port) area (Fig. 4.231. As a consequence, the design of the foundation structure and the resistance to wind were painstakingly invesligated. A lypical high-rise floor is 36 by 70 m (1 18 by 230 it), and the building has an ex4.24 and 4.25). tremely slender form where the ratio of shorl side lo heieht - is 1:7 (Fies. . Beiuw lhc sevenlh flonr, colu~nnsard trnesiendd lo tltc perimeter, iormiltg a supenruss fr3nlc in order lu slrenglllen lile rusistnnce to !r'~ndand uanhquakcr. and !$idcly distribute nxiill forces of the high-rise building o\cr tht ground. Titis forms n ' h ~ r r "for [he tower, which is integrated with the undeirground slructure. Wind is a more dominant laleral load for this building than earthquakes. The wind load for the design, including vibration assessment, was determined from the rcsull.; of wind tunnel testing. The testing investigated instabilities as well as accelerations likely to affect the comfort of occupants, unstable vibration due to wind, and habitability during swaying of the building duc lo wind forces. As the site is anilicially reclaimed land, and settlement due to canh filling is not complete. the cast-in-place steel-pipe concrele piles used are coated with asphall to reduce friction with the surrounding ground. The bearing stratum is a diluvial sand) gravel layer around 60 rn (197 it) below ground level.

Fig. 4.24

Fig. 4.13 World Trode Ccnlcr, Omkn, h p u n .

Typical noor plnn; World Trndc Ccnlcr, Oruku.

Sect. 4.11


85

Kobe Commerce, Industry and Trade Center Kobe, Japan Architect S~ucturalengineer Year of completion Height from svect to roof Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind vclocity Maximum lateral deflection Design fundamental period Design accclcration Design damping Earthquake loading Type of structure Foundation conditions Footing type Typical noor Story height Beam span Beam depth Beam spacing Material

Slab Columns Sire at ground floor ' Spacing Material Core

I.... 0

I . . - I . . ! . - ! . . - ! 0 9B m

0

Fig. 4.25 Frun~c,vorli:World Trndc Ccnlcr, Osuha.

Nikken Sekkei Ltd. Nikken S e k e i Ltd. 1969 110.06 m (363 it) 26 2 Office Steel 3 P a (60 psfJ Unknown HI400 3.42 scc each direction 20 mg elastic: 40 mg elastoplastic 2%

C = 0.085 Perimeter framed tube \\,it11 diagonally braced core Alternating gravel and diluvial clay strata Raft 3.84 m (12 ft 7 in.) 9.45 m (31 ft) 600 mm (24 in.) 3 m (9 ft 10 in.) . Steel. grade 400 MPa (58 ksi) above 1st floor, concrete-encased structural steel 1 st floor and below 160-mm (6.25-in.) concrctc on metal deck 700 by 700 mm (27.5 by 27.5 in.) 3 m (9 ft 10 in.) Steel, grade 490 MPn (70 ksi) Strucmral steel with prestressing-bar diagonal bracing

This building is structurally characterized by its "tube-in-lube structure." which consists of perimeter wall frames with 3-m (10-it) spans and internal braced frames using prestressing steel bars for diagonal bracing (Figs. 4.26 to 4.28). For the purpose of efficiently increasing the earthquake resisting capacity of a building, it is preferable to design its slructure in a bending failure mode so as to disperse the yielding of frames


86

Sect. 4.11

[Chap. 4

during an earthqualie. To achieve this objective, the tube-in-tube structure was adopted for this building. For the braced frames using prestressing steel bars, F13T steel bars serve as diagonal braces (Fig. 4.29). These braces have a wide elastic range and thus can resist the maximum seismic forces within the elastic region. This enables the overall struchlre to act in a bending failure mode, thereby securing stable recovery characteristics. In this way the structure is designed to be effective from an aseismic viewpoint.


! 1 $3! Ir

g: si,.,,

:? *x:

i?s.j.

Perimeter frame Fig. 4.27

Fig. 4.26

Kobc Cemnlcrre, Industry nnd Trndc center,

J,,~~,,.

Braced

frame

Fmmcnorli: Kobe Commerce, lnduslry and Trndc Cenlcr.

87


Ln

4

Perimeter . frame\

[Chap. 4

Sect 4.11


89

Braced /frame

1 3 6 . 9 0 0 ] Fig. 4.18

Typiutl rtructurnl noor plan: Kobe Commerce, industry nnd Trndc Center.

Fig. 4.29 Specimen of brnced frnme wing prcstruing bars; Kobe Commerce, Industry and Trade Center.

90


[Chap. 4

Marriott Marquis Hotel New York, N.Y.. USA

Architect S t ~ c t u nengineer l Year of completion Height from street to roof Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity Maximum lateral deflection Design fundamental period Design acceleration Design damping Earthquake loading Type of SlNcture Foundation conditions Footing type Typical floor Story height Beam span Beam depth Beam spacing Material Slab Columns

Core

IE

S e c t 4.11

Braced Frame and Moment Resist~ngFrame Systems

John Portman Associates Weidlinger Associates 1985 175 m (574 ft) 50

2 Hotel Steel 2 kPa (40 psO 36 mlsec (80 mph) 300 mm (12 in.), 100-yr return 5 sec 20 mg peak. 10-yr return I% serviceability; 2% ultimate Not applicable Braced and rigid frsmes Rock, 4-lvlPa (40-tonlft') capecity Spread footings 3.05 m ( I 0 h) 8.53 m (28 ft) 460 mm (I8 in.) 3.05 m ( I 0 ft) Steel, grade 250 MPa (36 ksi) Precast concrete. 300 mm (12 in.) thick 610- by 610-mm (24- by 24-in.) built-up I shape from 90- to 203-mm (3.5- to 8-in.) plates, grade 30- to 35-MPa (4200 to 5000 psi) steel Reinforced concrete beam and column frame with 13 columns in a circle

Facing Times Square on a block front between 45th and 46th Streets. the new 167.000m' (1.8 million ft') hotel rises 50 stories above the street (Fig. 4.30). The two sheer fin walls along the two side streets contrast sharply with the stepped and skylit facade facing Broadway. It is surmounted by a projecting, rotating cocktail lounge seven storics above the ground, actually the lobby level of the hotel. Above are five-story packages of hotel rooms that are stepped back and forth between the tin rraallslike a giant's ladder. The first six floors of the building contain public facilities, including a 1500-seat theater, a ballroom, exhibition and meeting rooms, and revail space.

Fig. 4.30

hlnrriott hlnrqnir Hetcl, New York, undcr construction. (Pl!aro b),Jennreier Leby.)

91

I

92


[Chap. 4

A circular concrete core, wilh 12 Tivoli lighted elevators and four enclosed elevators, rises from the street level through the public levels, breaking free at the lobby level, into a spectacular 35-story atrium (Fig. 4.31). I1 terminates at a multilevel rotating rooftop restaurant Skylights on the east facade, between the five-story packages of hotel rooms, bring daylight into the atrium, shining down onto the hotel lobby. The 3 5 guest room floors,. wilh 1876 rooms, are disposed in rectangular bands around the atrium. From the guest floor corridors, with their projecting planters presenting an image of the hanging gardens of Babylon, one can look down at the parklike lobby surrounded by colorful restaurants. As a structure, the building is equally unique, consisting of a steel-framed structure surrounding the slip-formed concrete core. Between the two I I-m (36-it)-deep fins, a 34-m (1 12-it) clear span is framed using girders below the lobby and five-story Vieren-

.

Sect. 4.11


93

.

-

.

.

~

~

~

-

I. 2. 3. 4.

~~~~

~

Support dead and live loads Transfer wind iorces to bracing members Transfer column-stability forces to bracing mcmbcrs Transfer forces between bmcing members

Since the planks are an inherent part of the stability of the structure, p l a n k were placed, grouted, and welded in sequence with the erection of the stccl irame. A rapidsetting, nonshrink grout with high early strength was specified for the grouting o f t h e joints between ulanks. These ioinls. which have shear kevs with castellations.. have been -~~ ihuirn hg cp&itncnt tu proCldu adequate shenr strcng;h for diaphragm action with n grnut strength of 17 >!Pa (2500 psi). Fur this project. a design strength of 35 hlPn (5000 psi1 w:!s spec~liudto prnvidc higher carly strcngth and 2 magin ofs;tf
Pig.4.31 Elcvntar core rises 180 m (600 10 through ntriurn to r~volvingrc;tnuronls: hlnrrintt hlurquis Hotel.

.

deel frames for the packages of hotel rooms. These hotel room oackares were oririnallv conceivrd to,be supponed by slerl trusses. The Vierendeel irames nor only climinatcd rhc trusses, but being tied into the s~de-wingvenical fr3mcr. pro\.ide stiifnes in the north-south direction. Stmctumlly. the building is a U with coiumns 8.5 m (28 it) on center along the thrcu sides, with the closure pro\*idcd by the 31-01 ( 1 12-fi)-\pan V~rren.deel frames. The two sides of the buildingmd the back are rigid iramcs above the lobby and arc vuased hctween lobbv and round floor. To urovidc the reuuircd 131~ra1stiffness in the iront, the vierendeel;, combined with a ÷d vertical frame on the two sides, form superframes. In order to avoid the added columns at the ground level, the columns placed 6 m (20 fl) from the nonh or south side are. in fact. nosts with vertical slip joint5 at midhe~glttbetuecn floors. At the hack of the building, along column line I?, a single irantc. cross hrsced bclow the lobhv. oro\,ides the stiffness in the north-south dirxrion. Sincc the -eroun of ~ - ~-~r three superfr&nLs in the front (at column lines 3.4, and 5 ) have substantially different stiffness, a process of fine-tuning wns undertaken to match deflections betwccn the packet of superframes and the single frame as closely as possible. The purpose of this exercise was to avoid torsion in the building. In this connection it should be noted that even if the two were perfectly matched, a 5% eccentricity is required by the Uniform Building Code (UBC) between the centroids of mass and rigidity. This has the effect of requiring a 10% increase in shear carried by the diaphragm above that, resulting from lateral wind iorces. Below the lobbv.. the floor construction is conventional metal deck and concrete fill. For the guest room floors, this construction was originally specified. However, since a ceiling is required and since spans for the metal deck are limited, necessitating more beams, an alternative, using long-span precaslconcrete plank without topping, wus chosen, based on economic considerations. Not only did this result in a reduction in the number of steel beams, but it also eliminated a hung ceiling since the underside of the plank is a finished surface. The more than 93.000 mz (I million it2) of plank used makes this a most dramatic application of plank floors in a high-rise building. As a result ofthe innovative use of both the Vierendeel msses and the concrete floor plank (which are only. mar~inallv .heavier than the orieinal metal deck and concrete solution)... the steel structure with less thon 117 kglm' (?4 psO is extremely efficient and economical. The planks. a p m from providing normal \enicaI load-carrying capacity. arc required tu provide the d ~ a p h r a ~ rrsisuncc, rn transicrring all lateral force5 to the vcnical \rind irorncs. Becnuse of the height of the building and the unujual configomtiun, this implied special rcquircmel~tsfor the plank Bas~cally.the plank l~tusldo rhe fi~llowrng:

94


[Chap. 4

Taj Mahal Hotel Atlantic City, N e w Jersey, USA

Architect Structural engineer Year of completion Height from street to roof Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity Design wind load deflection Design fundamental period Design acceleration Design damping Eanhquake loading Type of structure

Foundation conditions Footing type

Typical floor Story height Truss span Truss depth Truss spacing Material Slab


Francis Xavier Dumont Paulus Sokolowski and Sanor, Inc. 1990 128 m (420 ft) 42 0 Hotcl Steel with precast concreie perimeter beams Rooms 2 P a (40 psO; corridors 4 W a (80

P~O 40 d s e c (90 mph) 254 mm (10 in.) 3.0 sec 1.8 mg rms, l-yr return period 1% scrviceabiiity C = 0.037; K = I .O (did not govern design) Staggered steel trusses and braced steel core transverse, rigid perimeter frame longitudinal direction 27 m (90 ft) of loose sand and thin organic strata over dense sand 355-mm (14-in.)-diameter steel-shell driven cast-in-place concrete piles. 1500-ki-4 (165ton) capacity 2.69 m (8 ft 10 in.) 20.7 m (68 ft) 2.69 m (6 ft 10 in.) 9.14 m (30 ft) Structural steel

.

100-mm (4-in.) precast slabs with 100mm (4-in.) cast-in-place topping: 3 5 . ~ ~ ~ (5000 psi) concrete Built-up steel. 2230 kglm (1500 Iblft) 9.1 by 20.7 m (30 by 68 ft) Structural steel, grade 350 MPa (50 ksi) Braced steel frames, g n d e 350 MPa (50 hi)

r

S e c t 4.11


95

When the developer wanted a 1200-room high-rise luxury hotel right on the exposed oceanfront, a prime concern ofthe designers was occupant comfort. Building sway and acceleration had to be minimized. Preliminary analyses and cost studies were made of four basic structural systems: Steel staggered truss with concrete floors Concrete frames with shear core and other shcar walls Concrete-fnmcd lube with concrete shear core Steel-framed tube with shear core

.

.

All svstems excenl the staeeered -- truss reouired relativelv laree shear wallr to control ssra).. and the hciv~lyl o ~ d e dwills rcquircd l;lrgc and cxpcnsivc fueling s)ste,ns. In iddillon lhe slccl-ir:mi.d lube h:!d p r u b l ~ mof~ uplift. Rcl;,tive car15 w r e . Steel staggered truss Concrete frames and shear rvnlls Concrete-framed tube Steel-framed tube

~

~

1.00 1.25 1.10 1.40

The stagg~.rr.dtruss fr~mingsyrlcm rvas dcvr.1npr.d Ry a U S . Steel-spunsured rcs23rch learn n o r l i n g 21 hl.1.T. i f , the inid-1960s. Its hilsic ~ I C ~ I C I I is I thc \ I U T ) - ~ U L . ~I ~ U I I which spans the full width of the buildine at alternate floors on each coiumnlinc. ilcncc the floor spans from the top chord of one truss to thc bottom chord of adjacent trusses so that each truss is iondcd on both the lop and the bottom chords and is laterally fully restrained. Because all & eravitv .load is suooorted at the oerimeter of the buildine. the tvholc of th? huild~nga d i ~ l c3n ~ t hi. ~ I I O ~ I ~ I L10 L rdsist .~ ovcrturnlng eff~.cls. Lxcral iorc~.sare transmitted from floor to flour d0u.n the building via the llonr dlaohraems and I N S S web members. The oerimeter columns c a m onlv-axial load in the transverse direction and can therefore have their strong axis oriented longitudinally to form part of a longitudinal rigid frame. The layout of the Taj Mahal Hotel (Fig. 4.32) with a central double-loaded corriddr suited the staggered truss arrangement as it allowed the provision of a Viercndeel panel midspan, where the shear is least, for the corridor. With the structural svstem selected. a wind tunnel studv rvas canied out to determine atruculnl forces, d)n:trnic bch:,\,ior, c1;ldding pressures, 2nd cnr,irnnnicst31 eifccts s1 ground level. Frdm this. the design l;ltcr:,l looding, building driit, 2nd acceleration ncrr. established. Because this is a tall buildine for a staeeered truss svstem. the shears in the floors were an important design consideration. The 200-mm (8-in.)-thick slnbs comprise precast pretensioned concrete plank tapered on their top surface from 127 mm (5 in.) thick midspan to 76 mm (3 in.) thick each end, where they are supponed on top of the 254-mm (IO-in.) -!vide flange steel truss chord, and a cast-in-place topping. The shear connection between floors and trusses is achieved by stud shear connectors (Figs. 4.33 and 4.34). Because of functional and architeclural requirements, the staggered truss systcm could not be used at all locations. As a consequence, two other systems were used, a core frame and an end frame. The core framc consists of a truss system with n truss at every floor. but with n vertical stiffness to match the staggered trusses. The truss at every level !\,as required to carry shears from lateral loading without reliance on the floor diaphragm which, at this location, is heavily penetrated by service openings.

..

.

-

. .

uu

96


[Chap. 4

The three-bay end frame comprises a diagonally braced center bay and outer bays of rigid framing connected to large perimeter columns. This frame is 13.7 m (45 ft) wide compared to the 20.7-m (68-ft) width of the typical frames (Fig. 4.35). Wind shears are transferred to the foundations by embedding the bottom chords of the lowest trusses in large concrete-gnde beams. On the lines where the lowest truss

Sect. 4.11


97

1

:..i' gi

was one story above the footings, a diagonal brace was provided at the columns to transfer the load to a steel beam embedded in the footing, similar to the adjacent truss hot(g: ._. tom chord. A pile cap at a typical staggered truss bay is 7.6 m (25 ft) square and 2.9 ,. , , 4 . , (8 fi) deep, supported on 36 piles. , ..:.Both structural steel and concretespandrel beams wereconsidered. with the lnnerh.ino selectcd as they best suild architectud and fire-nting rquiremenk. lllc mrn (48- by 12-in.) beam rigidly connwtedtothc largrrxtcriorcolumns nnd the small .... I .*;. height created a f n m e easily capable of resistine. the lon~itudinalwind forces . r~.:; fab&alor cut the 44- and 57~mm~diameter(+l4 &d 818) reinforcing b m and uclded them lo sael Trectians h o l d for bolting nt each end before delivering thcm lo the Prucalcr ~.... h . ,,,~ ~~. ; finished beams included a shear key and reinforcement for connection to thislabs. .,:,. , .

.@:,

I I

--.

.;$; .,.. ,-.,,. .

~

... ,.->.,

!

-21

<.,%I

,..**

Fig. 433 Typical noor plnn; Tnj Mnhnl Hotcl.

0

1" Elg. 4 3 2 Toj hfnhnl Hotel,AtlnnUe City, New Jcmey.

Typical building exterior column I " + A490X bolls

Section

Fig. 4 3 1 Spandrel beam delnil; Tuj Mnhnl Hulel.


98

[Chap. 4

It

Sect. 4.11


Tokyo Marine Building Osaka, Japan

Architect Structural engineer Year of completion Height from street to roof Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity Maximum lateral deflection Design fundamental period Design acceleration Design damping Earthquake loading Type of structure Foundation conditions Footing type \Piles (typical) INTERIOR STAGGEREDTRUSS BENT

CORE FRAME

END FRAME

Typical floor Story height Beam span Beam depth Beam spacing Material Slab Columns Size at ground floor Spacing Matenal

Fig. 4.35

Fromewurk and typical buy reelion; Taj hlnhul Hotel.

Kajima Design Kajima Design 1990 118 m (387 ft) 27 3 Office, retail space, parking Steel 0.79 kPa (16.4 psf) 35 d s e c (78 mph) a1 10-m height Seismic conlrol 3.31 sec longitudinal; 3.95 sec transverse 4 mg peak, 5-yr return 2% Base shear coefficient 0.08 hloment resisting frnmc Fine sand Cast-in-olace concrete oile: 22-m (72-ft) length, 5.4-m (7.9-ft) djameter, wiih 4-4 (13-ft) bell 3.9 m (12 ft 9 in.) 21 m (69 ft) 900 mm (36 in:) 6.75 m (22 ft) Steel, grade SM 490, 483-MPa (70 ksi) tensile strength and below 155-mm (6.1-in.) lightweight concrete slab on cormgated deck 500 by 500 mm (20 by 20 in.) 10.8, 21 m (35, 69 ft) Steel. grade SM 490

Tlic Tokyo hlcrine building i s n 27-story officl: building locatcd in the Osaka burinsrr park district bring develuprd just cast of Osaka Castlc. Japan (Fig. 4.36). The burld~ng urovide~about 69.000 m' (743.000 11'1 of arca for offices. ret~il.and ,n~rkina.Cun. . struciion was completed in 1990. i\rchitccturaily the buildins a.as conceived to fir into tht c~~viroo~nentof thc Osaka business p3rk and ro runect the imagl: ofthc cl~ent.Tokyo Marine. As the base of operations in western Japan for Tokyo ~ & n e the , building tvis

-


I

Sect. 4.11


designed to have high-tech capabilities, to reflect ils prestige appropriately by its external appearance. and also to be attractive to tenants as office space. The building has a rectangular plan to fit into the site surrounded by two high-rise buildings on the longer sides. The exterior facade, exposing columns and beams outside the building, brings to mind the simple lines of traditional Japanese wood-frame details and gives a clear identity as well (Fig. 4.37). The lateral force resisting system of the

Fig. 4.36 Tuk).u Rlurlnc building. Oaaku,Japun. Fig. 4.37 Pilotis columns: Tokyo hlurtnc building.


102

Sect. 4.11

[Chap. 4

~~~

~~~~

I. At 250-mdsec (10-in./sec) peak input level. the long-span beams developed large bending moments, in particular high up in the building. It was verified that even including these stresses. the beams remained within the short-term allotvable stresses according to the Japanese design criteria. 2. At 400-mdsec (80-in./sec) peakinput level, due to the effect of the vertical component of the earthquake. elastic hinees - at the ends of lone-snan beams develooed , ~ ~ early on, but the structun remained elaslic in its overall heh3vior and did not degrade its ovsr-ll dynamic stiffness charactarislics. Thc reason for this 1s that scrtically the period of vibration is much shorter than horizontallv. such that thc stmciurc isnblc to recover its clastic characteristics. From this risult it was concluded that using horizontal earthquake time history records only for the main reu

I

I

I ' FRAMED COLUMN

Fig. 4.38 Framing pcrspcclivc; T n k ~ ohlurinc building.

103

The structure was planned with an unusually long main span of 21 m (70 ft) across the full building width. In such cases the vertical component of an earthquake can have a significant effect on the beam slresses. This was investigated by modeling a typical bay as a two-dimensional frame. Dynamic analysis was carried out using the time history of four earthquake records, inputting their lateral and vertical components simultaneously. As a preliminary step, the modes of vibration of the structure were obtained, from which it was found that the fifth mode was the first mode in the vertical direction nnd involved axial tension nnd compression in the columns, with all the beams vihrating together. Only at higher modes did the beam vibration become more complex. The analysis was carried out at two levels of earthquake input. The following were the results.

building consists of the framed columns interconnected with long-span beams [10.8,21m ( 7 0 4 ) spans]. This allows for an open public urea at the plaza level of the building and column-free space across the width of the building with a 2.7-m (9-ft) ceiling height on the office floors. The building is framed in slrucluml steel (Fig. 4.38). Each frame column consists of four vertical membcn joined by short 12.7-m (9-ft)-span] beams to create a three-dirnen~ional ~swcture. The combination of the short beams in between the framed column cicnlcntr and the long-span bcamr cre:ttes unusual static charoclerisrics: migrntiun of column loads. the shorn-span beams being loaded more lightly in bending than the longswan beams. and an unusunl failure-hinge mechanism for extreme xismic events. m 3 mpiium-rise buildine. under relatively -~ .. -. short-sean beams yield at their SuppoN low loading levels due 10a conccntmtion of bending stiffness. Houevcr, in this case the effect of axial deformation; of the frame columns was the dominant mode of behavior. An incremcntallv increasine static analysis on an elastic-plastic model C'pushover" analysis) was c a k e d out to obr3in the sceleton cun,cs for story shear. From this analysis thc formntion of plastic hinges at the supportsof the long-span beams. with the shornspan burns remaining claslic even at high eanhquake le!,cls, was notablc. ~~


.

sponse analysis was appropriate Although the bullding is not of irregular shape, wind tunnel testtng was carned out to investteate - the effect of the cxeosed column frames on the surface rourhness dnd effcctive lront~l; m a o i the building 11 was also dcsir3ble to prcdiot the vibration bthariur of llte build~tigunder wind loading, since its period is rei;!tlvclg long. Using ihc prcssurd cnefficienls from the uind lunncl test. the base shear from u.ind is ahout giro that of seismic ct,ents. In terms of acctl.aation. it uns pr~.dicted(ha1 although the upper levzls u,ould e~pcricncca peak ncceicration of around 4 mK. his ,\auld nut cause any discomfort. It was considered that since the exposed frame was outside the main building glartng Itne, it would not be subject to the same intensity of fire as a normal frame, and therefore could be fire-vrotected to an anoroor~atelvlesser deeree. An annlvsis was oeriannedonthcframe\<,~rn rubjectedio n.&rtCsdisc/lsrgingfro; insidu 1hc ioilding.!~hc rcsults shou,vd that the beams uould hc heated 10 273'C and the columns to ?81'C the outside of their aluminum claddine. - Since the critical lemverature for steel in a firs nlay bc lakc,! ar 350°C ;,\,crape (with 3 n~nximulnuf 45O'C). the conulusiolt unr d n w n tIt:!t no fire protection was needed at ail for the cxlcrn.ll froinc. llpon craminxinn b) the Building Csnlcr Flre Safety and Protection Commitlcc. 10 rnm (0.4 in ) o f fire-res~sl;tnt cladding material was finoily agreed upon, which represented a substantial reduction in fireproofing material.

-

~

~

104


[Chap. 4

Kamogawa Grand Tower Kamogawa, Japan

Architect S m c n t n l engineer Y e x of completion Height fmm slreet to roof Number of stories Number of levels below ground Building use Frnme material Typical floor live load Basic wind velocity Design fundamental period Design damping Earthquake loading Type of smcture Foundation conditions Footing type

Typical floor Story height Beam span Beam depth Material Slab Columns Size at ground floor Material

Kajima Design Kajima Design 1992 105 m (344 A) 33 1

Hotel and condominium Concrete 1.77 !@a (36.9 psO 35 mlsec (78 mph) at 10-m (3341) height 1.92 sec transverse; 1.55 sec longitudinal 2% Shear coeficient0.085 Moment resisting frame with honeycomb damper wall Fine smdy layer over clay layer over shale rock layer Cast-in-place concrete pile; 19-m (62-ft) length. 1.7-m (5.6-A) diameter, with 2.8m (9.2ft) bell 2.85 m (9 ft 4 in.) 4.5 m d 9 m (15 and 30 ft) 700 mm (27.5 in.) Reinforced concrete, normal weight 160-mm (6.3-in.) concrete 900 by 900 mm (35.5 by 35.5 in.) Concrete. 23 to 41 MPa (3400 to 6000 psi)

The Kamogawa Grand Tower is composed of ductile moment resisting frames (Fig. 4.39). The high-rise reinforced concrete (HiRC) conslruction method developed by Kajima Corporation was used. It consists of pure reinforced concrete columns, girders, and floor slabs tvhich are cast on site (Fig. 4.40). The typical floor plan is a stairshaved vlan alone the catcrior zones. which consists of rceular souare units ~- 4.5 - rn (1 5 11) i n a kide (~i~.-4.41). The standard p a n is chis? 5 m (l
~

106


I

:@f j ig&a.

[Chap. 4

COMB DAMPER

4.11


107

columns are installed in each typical story. The seismic response of the building is re. duced by the hysteresis damping effect due to the yielding of the steel plates. The seismic design criteria for two levels of design earthquake were established as follows:

On typical floors, steel plates with honeycomh-shaped openings are installed in the central corridor connecting to the cross girders (Fig. 4.42). Post columns extending from the midspan of upper- and lower-story girders are spliced at midstory using these damper plates, connected by high-strength bolts through gusset plates. Thus the story shear drift is concentrated in the damper plates. Sixteen units of damper plates and post WALL WITH hONEY-

Sect.

1. Severe earrhquake: The stresses in all slructural members must be less than the allowable values and the story drift must be less than 11200. 2. Worsr earrhquake: Even if the structural members exceed allowable limits, excessive large plastic deformation should not he caused and the story drift must be less than 11100.

COMPRESSIVE DESIGN STRENGTH OF COhCRETE

Referring Lo the preliminary earthquake response resulls in considcrntion of the hvslrresis steel dlmper, the slory shear coufficienls 3rc dcltrm~ncdThe design a ind sbc;!rs arc nbnul56Sn of the seismic valucs. In order to secure tbc 111tirn;llustrung11 olthu structural lrame, it U 3 S cst;~bli~hed that th~.m r y shunr cap;,city . . rrould hc 1.5 times !hat of the design earthquake shear forces. The uldmate hcnding and shear strength of the columns was designed to he at least 1.25 times greater than that of the girder, so that yielding to bending in the girders precedes yield in the columns: hut at the tops of the columns, in the lop story and at the bottom of lhc first story, thc bending yield in the columns is considered. From the earthquake responses of the structure to both severe and worst-case events it was assured that the final desien - of the moment resistine frame structure was complclsly s3t1sf~ctog. rvilh respuct tu the design criteria. hlnrco\cr, "ring the huncycor~lb sICL.I plates 35 hysleresi dampcrr. not only a well-bilanced structurs hut also s2vints i n the volume of reinforced concrete may hc realized.

I

Fig. 4.40

Framing rlcvulilln In tllc). dlrcctinn: Knrnugurn Grund Tu$vrr. j

Fig. 4.41 Tgplcnl nuar plun; Knrnogonn Grnnd Tosrcr.

Sect. 4.21

Shear Wall Systems

4.2 SHEAR WALL SYSTEMS

I&

%$I";

i!.

.,:

I

;

I ' I ' I100 600 SHAPE OF HONEYCOMB DAMPER PLATE

1001

0 0

.

I

"

BEAM

w

' .

Shear walls have been the most common structural systems used in the past for smbiiir ina- building- structures aeainst horizontal forces caused bv wind or earthsuakes. With the advcnt oircinforced concrete, shear wall systems have become widely uscd to stabilize efficiently even the tallest building slructures. In the last 10 yc-rs, concrete tcchnology has nd\,anccd lo a point where concrete streneths of over 130 hlPa (19.000 psi) arc achievable in the field. T k s has led to the design o f the proposed 610-m (2000:itj Miglin-Beitler Tower in Chicago (which would become the world's tallest building), relying heavily on a shear wall svslem of verv-hieh-slreneth concrete to resist horizontal forces. A common shear w d l ; y s t ~ mused-for tall office buildings groups shear walls around service cores, elevator shafts, and stairwclls to form a stiff box-type structure, such as for the Melbourne Cenlrnl building in Auslralia (Chapter 3.2). In this example the need to enclose and lire-protect 21 passengerelevators, service elevators. two stainvells. lobbies, and service risers created the framework for a niff concrete box-type shear wall system. In contrast with oftice buildings, high-rise residential buildings have less demand for elevators, lobbies, and services, and hence do not usually have large stiff concrete shear wall boxes to resist horizontal forces. A more common system will incorporate a small box structure around a smaller number of elevators and stairwells, and include discrete shear walls between apartments. In both shear wnll systems noted, the walls are designed lo canulever from the foundation level. To deslen - shear walls -need around service cores. the bcndine.- shcar, and !<,arpingstroses duc to !\ ind or cmhqoake lo3ds arc combined eith slr:sses due to pmvll) loldc. Indi\,idunl wdl, within thc box system can then hc designed as unit-length u,alls spannine either noor to flour or bctu,ccn return walls. Reinforcrmcnt is proponioncd as iollon,:

-

-

HONEYCOMB

.. .. ..

N

,

..,.~ . .

i

b ; > ,'

. i.

I

I 1

L600-l

MAIN REBAR 10-032 HOOP D13-a100

Fig. 1.42 Shilpeand tnrtntlolion olhoneycornb dornpcr ptolc; Knrnogn~mGrnnd Toscr.

..

1. Minimum shrinkage restraint reinforcement where the wall stresses are low, which can be for a subsmntinl ponion of the shear wall. 2. Tensile reinforcement for areas where tension stresses occur in walls when wind ~ ~ l islresses f1 exceed eravitv. stresses. 3. Compressive reiniorccmcnt with conlinumunt ties u hcre high cumpressi\,e forces rcquir: that ualls b~.des~pnedas c o l ~ m n sIndividual . shcnr walls, say at the edge of a tall huildinp. are dcsiknrd either 3s blade walls or as coluo~nsrer~sling - shcar and bending as required. -

-

Multi~leshear walls throuehout a tall buildine-mnv.be couoled to vrovide additional iramu action and hcncc increasr ovcr2ll building stilfncsr. Coupling can bc realized hy rulalivel) shallow hrader or link b u m s within the ceiling cavil) at each Irvcl or by means of one- or two-story-high shear coupling walls. By adding a coupling shear wall at a single level, reverse curvature is induced in the core above the coupling shear wall, significnntly reducing lateral drift by increasing thc overall building stiffness. As the increase in mass is minimal, there will be an increase in the building's natural frequency. This can be a desirable effect.. in oarticular with resoect to achievine an accentablc uind-induced ncr~lcmtionresponse tu cnsurc occupxn~comforr. Ccntrnl cure hnxus can 31ro hc coupled \In slifi beams nr lri.,sus, ol discrule lc\uls, Id urlcm>l shear u;ills or columns to achieve a similar and more pronounced effect than that noted. Thus the concrete shear wall becomes the central component in a core and oulrigger system. Many tall buildings undergo torsional loading due to nonalignment ofthe building shear cenar wilh the location of the horizontal load application. Such a situation occurs in the CitySpire Building (Chapter 4.3) due to the asymmetry of Ule location of the shear wall boxes. Torsional loading can also be induced in a building such as Bourke Place (Chapter

.


110

[Chap. 4

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3.2) due to theneriodic sheddine of windvoltices altemalelv fmmeachside of h e shucntre, moving the insvmtmcous center of pressure oul nf line aid) thc building's shearcenat. Boxed shear all systems pro! ide an efficient means of resisting such lnrsinn. Torsion is resisted bv both wa&ine . &d uniform shear. Particular care must be tnken during- compurer modeling of boxed shear u d l s lo reflect penetrations forelevator and stair doon. Calculation of incltiv based on a reduced uall thichess, depending on the number of shear wdl nenemtions. is common. Boxed shcar wall systems &e very well suited to regular plan . oMice buildings. as demonsmled in many of ale project examples in this section. Conslruclion advanwges ofr
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Sect. 4.21

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6. Wcll-detailed reinforced concrete will develop about twice as much damping as , structural steel. This is an advantage where acceleration serviceability is a critical limit state, or for ultimate limit state dcsign in earthquake-prone areas. Although thcse advantages make concrete shear wall systems a compclitive construction method, the following must also be considered: 1. Shear walls formed around elevator and service risers require a concenvation of openings at ground level where stresses are critical. 2. Torsional and flexural rigidity is affected significantly by the number and size of oocnines around the she& wails throuehout the heieht of the buildine. 3. In 1 and 2 it is difficult to gauge the effect of openLgs precisely wilhout undertnking time-consuming finite-element analysis. 4. Shear wall vertical movements will continue throughout the life of the building. n ~ e impact ~ r on the integrity o f i h r sIructure nlust b;rvalu31rd at the design slag;. 5. Consuruclion lime is gsnerally slou,er I I I for ~ n sleel-framed building. 6. The additional ueirhl of the \er~icalconcrete elemcnts as compared to steel will induce a cost penalty for the foundations. 7. An incrense in mass will cause a decrease in nntural frequency and hence will mast likely produce an adverse effect of the acceleration response depending on the hequency range of the building. But shear wall systems are usually stiff and cause a compensating increase in nntuml frequency. 8. There are problems nssocialed with moving formwork systems, including the following: a. A sienificant time lae will occur between footinc u - construction and wall construction beenuse ofthe fabrication and ureclion on rile ofthe moving formwork system. O. Time will be lost at levels !s,hcru aalls are lerminatcd or decrrased in thickness. c. Reeular survcv checks must he undertxken to ensure that the vertical and twist xlignmcnrs of the s h r x walls are uithin tolerance. d. In pneral it is difficult ru achieve a good finish from slip-form formwork systems, and hence rendering or sollle other Ispc of finishing may be necessary. E. When walls IW 100 thin [such 3s 150 iIlnt(6 in.)] it is not unusual for friction betrrccn ~ h cforms and cuncrcle lo lift lflr concrcle in slip-form conatmction. Icading to cracks or gsping holes in the wall.

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111

Project Descriptions Metropolitan Tower New York, N.Y., USA Architect

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1. Central-services core shear walls can be efficiently constructed using slip-form orjump-form techniques. In the case of 120 Collins Skeet, a 4%-day cycle was achieved, ensuring that core wall construction was well off the critical path. 2. High-strength concrete hns enabled wall thicknesses to be minimized, hence maximizing rentable floor space. 3. Technology exists to pump and place high-strength concrete at high elevntions. 4. Fire rating for service and passenger elevator shafts is achieved by simply placing concrete of a determined thickness. 5. The need for c o m ~ l e xboltcd or site-welded steel connections is avoided.

Shear Wall Systems

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Structural engineer Year of completion Height from streel lo roof Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity Maximum lalcral deflection Design fundamenlal period Design accclererion Dcsign damping Earthquake loading Type ofslmclure Foundation conditions Footing type Typical floor Story height Beams Beam depth Slab Material Columns Material Core Material

Schuman. Lichtenstein. Claman and Efron with design input from MackboweIDenmanl Werdiger Robert Rosenwasser Associatcs P.C. 1985 21810 (716 it) 68 2

Office lo 18th floor; residential above Concrete 2.5 P a (50 psi) office; 2 Wa (40 psi) residential 47 d s e c (105 mph), 100-yr return HI500 5 and 4 sec horizontal; 2 see torsion I5 mg peak 1 2 % servic~ability;2%% ullimatc Not applicable Coupled shcar walls plus perimeter frames Rock. 4-MPa (40-tonlit') capacity Spread footings 3.45 m (I l ft 4 in.) office: 2.95 m (9 ft 8 in.) residential Span and spacing vary 508 mm (20 in.) at perimeter 216-mm (8.5-in.) flat slab Concrete, 42 to 28 MPa (6000 lo 4000 psi) Size and spacing vary Concrete. 58 to 39 MPa (8300 to 5600 psi) Coupled shear walls: thickness varies Concrete, 58 lo 39 MPa (8300 to 5600 psi)

A rectangular towcr \vould not work because of restrictions on the north-south-oriented site. This problem was solved with a triangular tower whose longest face is oriented northeast, with setbacks designed to conform to zoning regulations. The L-shaped commercial base is 18 stories, whereas the upper .. trianeular condominium towcr is 46 storits p l ~ lsa u sluiies iur IllL. 1nec11:~nical and stn~cu!raiIransiiion. 'l'hr. Iksding edge of lhu Inangular lower being north on 57th S1rcr.l 1s continued for lhc enure 21X.m 1716-11) Ihti~bIof the bull din^. - inlcgrating - thu 1r.o b ~ s i ciorms. In !his w a y lhl: unique lrilneular Yower mximizes one of its greatest assets-the views (Fig. 4.43).

Sect. 4.21

Shear Wall Systems

..

The uooer condominium tower contains 246 luxurv apartments tolaline 39.300 mz (423.000 ft'). The lower commcrci~lbase has 21.000~"(2?5.000 ft') of;ental office space and 460 m' (5000 it2) for relail rental. The lotal project amuunls lo 60.600 m' (653.000 11') and required approximately 23.000 m' (30,000 yd') of concrete and 3300 tonnus (366-3 tons) of reinforcing steel. To keep an efficient column grid on tlte commcrcia1 floors, a double-height reinforced concrete mechanical floor was crcned at the nineteenth floor to allow thetransfer of loads from the triangular plan ofthe building's upper tower to its L-shaped base (Fig. 4.440). In effect this was a new foundation for the triangular tower, accomplished by using an exlmordlnaiy volume of concrete, an unusually dense mass of reinforcing stvel. and bcams up to 4 m (13 it) deeq. Thesc transfer girdcrs ucre c a t in two stages. the bottom 600 to 900 mm (2 to 3 it) belng cast first to s e n c as suooort for the remainder of the concrete in the second placemenL The depth ofthe meandering shear wall (the main btmctura~support ofthe triangular footprint) is about 21 m (70 ft) (Fig. 4.446). 0:the three available faces. the west face was a lot-line face. and therefore obloce to accommodate the elevator shafts for the high-rise structure. It was recognized, and later verified in a wind tunnel tcst, that the structure would support larger wind forces acting perpendicular to the hypotenuse of the trianele. Vnncx rhedding, u,hich ~lsuallypruduces larger forces ironsverse tn ths wind dirdclion, did not matcriallzc for this structure bscausc of its triangul:lr foulpnnt. Shear walls then migrate from the west lot line, meandering alongside the apartment lobby and corridors, to the hypotenuse side ofthc triangle, where additional columns were engaged via Vierendeel action of the spandrel beams. Other frame elements. 508-mm (20-in.)deeo soandrel beams alone the .oerioherv . . and 216-mm (8.5-in.) slabs at the interior of the structure, were needed to help counter large torsional loads since it was impossible to minimize torsional forces for all possible wind directions. This slender lower was somewhat stiffened bv a wider bascbelow the eiehteenth floor. However, part of the shear tva11 and nlany of the columns bad to bc transferred utilir~ngdsep concrets girders nt this levcl. These deep girders w r r . utilized. via outrigger action, lo ungxgc nddltional supports to help d i v e s hold-down loads for the shear wall and to equalize the strain in the supports. The flat slab floors are supported by a hybrid building frame of columns and shear walls. in purt because of the developer's desire to leave the perimeter as column-free as possible.'~n the triangular tower. \\;ind on the long side of ;he triangle governs the dcsign, so the shear walls were placed at right angles to that face of the building, meanderine alone partition lines in a horseshoe shape to the opposite side o f t h e tower and hackio theidne side of the trianele. Scveml factors contributed to the decision to use concrete rather than steel. Thesc included the easier modeling oishapes. the ability to make last-minute changes, and the knowledre that a lareer miss reduces vibration and the .perception . of motion. The choice ofconcrute raflucls ths needs ofthe u\tremi.ly ?all slel~dsrstruclurc S\ray ofthe huilding u a s an impnnanl uunccm. In high-nsc hu~ld~ngs i t may range from 11500 tn 1/600 of the buildine hcieht in a lUU-\u~rwind (tl13t is. thc slronwst uind lhilt inns bi. :~aticipatcJlo occur a 160-"car oeridd). When comoarine buildiks of structural steel and reinforced concrele having similar stiffnesses and movcmenlr. the perceived motion in the concrete building will be less bccausc the larger mass of the concrclc structure slows do\isn its swayini motions, that is, the period isincreased and the accclcration reduced. In the Metropolitan Tower the typical slab floor thickness of 216 mni (8.5 in.) of stone concretc is important in achieving the mass of t h e building. Nevertheless, the huildine was designed with provisions lo support - o f a pcndulum-type .. dnmper . . the \vcieht should it be needed. Using thrcc nccclcrometers, field measurements wcrc tekcn when the structure reached its fifty-fourth floor and, latcron, at its sirty-sixth floor (at the last ~

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FIR. 4.43

hlclrupulilun T u ~ e rNPW , York. (Coi,ncr). o~RobenRarmm~nsrcrA.~rucl 112

113

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Sect. 4.21

Shear Wall Systems

115

possible date, allowing time for a "galno go" decision with regard to the installation of a damper), indicating that adamper was not needed. Theexlra cost to the owner resulted orovidine a double desien from - lavout, . with and wilhout lhe damper. No materials, except those nrcded to support the damper's weight on the footings 2nd columnr. were octually expended in the svucturz. This suucture can accommodate a future damper, if found necessarv durine its service liir, with some nunor modifications and rerouting of some mechanical pipes. Slab formwork was cycled by the "preshoring" method commonly used in New York (Grossman, 1990). The first 18 stories, larger in floor area, were completed at the rate of about 4 to 5 days per story. In the triangular tower, two floors per week was typical progress, with columns and shear walls cast on Mondays and Thursdays and floors on Tuesdays and Fridays. Near the top of the tower, work speeded up to 2 days per story. The concrete framewas topped out on October 2. 1985 ~

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(4 Fig. 4.44 hlctrnpulllnn Tuscr. to1 L-sllupcd borc. ( b ) hleundrringshcor ,,,,11.

114


[Chap. 4

Embassy Suites Hotel New York, N.Y., USA Architect Structural engineer Year of completion Height from street to roof Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity Maximum lateral deflection Design fundamental period Design accclerstion Design damping Earthquake loading Type of structure

Fox and Fowie Architecls DeSimone, Chaplin and Dobryn 1990 146.3 m (480 it) 46 I Hotel Concrete above 8th floor: concrcte-encased steel below 2 kPa (40 psQ 36 mlscc (80 mph) Hl.150, HI700 5.4.7.4 sec 21 mg peak 2% serviceability Z = 0.375; C = 0.030 and 0.025; K = 1.0 Shear walls above 8th floor; encased-steel trsnsfer trusscs to steel supercoiumns be-

Shearwail Systems entire wsses were encased in concrete. The ballrooms, kivhen, and mechanical spaces are located between the 14.9-111 (49-ft)-high trusses. The system is efficient and economical and solved the problems associated with constructing over a landmark. The hotel superstructure is a reinforced concrete flat-plate system with a 8.5- by 8.5m (28- by 28-it) column grid and was built on a Zday cycle. Wind is resisted by shear walls ns well as moment f n m e acdon of slab strips and columns. The total weight of the reinforcing steel used for the concrcte tower was only 36.7 kglm- (7.5 pSO.

IO\V Foundation conditions Footing type Typical floor Story hrigllt

Columns

Core Material

Rock. 4-MPa (40-tonlft') capacity Concrete piers 2.65 m (8 fi 8.5 in.) 200-mm (6-in.) flat plate, spanning 7.32 by 7.32 m (24 by 24 R) 4 supercolumns built up from five 200rnm Win.) plates on 14.63- by 39.63-m (48- by 130-ft) grid Shear walls. 300 to 450 mm (12 to I8 in.) thick at ground floor 56-hlPn (8000-psi) concrete

1568 Brondway is the site ofthe Embassy Suites Hotel in the Times Square district of New York Cily (Fig. 1.45). I t is built over the historic Palace Theatre, a landmark dating back to 1919. Bccausc of the theater's landmark status, New York City would not permit any disturbance to tbc theater by the new hotel. It was therefore necessary to suppon this 46-story. 146-m (480-TI)-tallbuilding by building e "bridge" over the theeter [Fig. 1.46). The transfer was accomplished with a hybrid composite steel and concrete structure consisting oftn,o 40-m (1.X-f11-lung compnsile trusses and steel cross trusses. Four superculun~ns.two on either side ofthe theater, come down to ground to suppon the structure. Thcsc columns n'erc built up out to thick grsde 350-hIPa (50-ksi) steel plates and n'eigh up tu 6000 kg/m (4000 lhlfl). The truss menlhers were dcsi~nedto bc light enough to pern~iterection on an estremcly diflicuit site. To give them the necessary stiffness, the

Fig. 4.45 Emburry Suilcs Hotcl. Nss York.


Sect.

4.21

Shear Wall Systems

119

Singapore Treasury Building Singapore

Architect Swctural engineer Year of completion Height From sueet to roof Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity Design fundamental period Design acceleration Design damping Eanhquake loading Type of structure Foundation conditions Footing type

Typical floor Story height Beams Beam depth

Columns Fig. 4.46

"Bridgc" rupportlng hotel over thcotcr. Embnsry Suits Hotel.

Core Material

Hugh Stubbins and Associates LeMessurier Consultants with Ove Amp and Partners 1986 234 m (768 fl) 52 5 office Concrete core, steel floor beams 2.5 Wa (50 psf) 30th floor and above: 3.0 kPa (60 psf) below 30th Floor 38 mlsec (85 mph) 5.6 sec Not estimated ~ p p r o x2% serviceability Not applicable steel floor beams cantilevered off cylindrical concrete core wall Clay over rock 6 8.m (26-ft 3-in.)-diamctcr caissons. 35 (I 15 ft) long, under a 2.9-m (9-ft 6-in.)thick mat 4.25 m (13 ft 11 in.) Cantilever 11.58 m (38 fr), spacing 4.9 m (16.42 ft) at core 1470 mm (58 in.). facade w s s 1260 mm (50 in.) deep, continuous 80 mm (3.25 in.) on 77-mm (3-in.) steel deck only erection columns embedded in core wall Reinforced concrete cylinder. 22.95-m ( 7 5 4 ) I.D., 1.65 to I m (65 to 39 in.) thick Concrete cube. 40 to 30 MPa (4500 3400 psi)

This cylindrical 48.4-m (I 59-Ft)-diameter mixed construction office lower, loca!ed in the center of Singapore, has an area of more than 132,000 m' (1.42 million h') (FIE.4:-17). Although the Singapore wind climate is relatively benign, avoidance of resonsnt vlbration caused by wind-induced vortex shedding conlrolled the required latcral stlffness Of the tower. This required setting the first vibralion mode period at no more than 5.6 set.

120


[Chap. 4

The architect and owner wanted to have little or no visible StNCtUre obstructing the 360" panoramic swcep u l the \vinduu,s at each floor. The simple jet elegnnl structural solution was lo cantiicvsr evcry floor from an inner cylindrical wall enclosing tile clc1,3101and service core. This required radial beams ubich cantliever I 1 6 m (38 h) from the 24.95-m (81.8-ft)-outside-diameter reinforced concrele core wall. Each cantilever girder is welded to a steel erection column embedded in the core wall (Fig. 4.48). The cantilevers on successive floors are connected at their outer ends by 25- by 100-mm (1by 4-in.) steel ties, hidden in the curtain wall, which reduce relative vertical deflections

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Sect. 4.21

Shear Wall Systems

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of adiacent floors. A stiff continuous nerimeter rine truss at each floor minimizes relalive deflcc[ions of adjacent cantilevers on the same floor pruduced hy any unrvrn live loading. This w s s plus the rrnical tier also provide some redundancy in the unlikely event of a cantileve; failing. All gravity load and all the wind loads are resisted by the concrele core wall. For . strength alone, the core wall would have been a constant thickness almost to ground .level, bur in order to meet the building period limitation, it was necessaq to thicken the wall from its typical 1.0-m (3.3-fl) dimension lo 1.2 m (4 ft) and then 1.65 m (5.4 ft) helow the sixteenth floor. A concrete core wall was selected in lieu of an all-steel diago-

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b Fig. 4.47 Singuporc Treasury Dullding. Singnpurc. ICounerj olT11ileSr.libi,n r\.~saciorion.)

Fg.4.48 Typicnl noor plan; Singopore Tmsury Dullding.

1

1

122


[Chap. 4

nally braced "wall" for reasons of economy. The core is spanned by two plate girders. ~ h h c o r ewall has four doorway openings on each floor. The headers over these openings consist of rigid steel Vierendeel girders, which allow duct work to pass lhrough (Fig. 1.19). Structural steel floor framing was used to facilitate a modular electrified underfloor steel deck, including trench headers, and to make the long cantilevers quite stiff. Typical live-load deflection at the end of the cantilever was less than 25 mm ( I in.). Girders were cambered to countcnct dead-load deflection. Web openings were provided in the cantilevers for ducts and nines. T o vcrifv the dcsirn and fabrication oualitv, and reassure theowner that deflections would not be excessive, a full-size prolotype cantilever girder welded to a two-story steel column was tested at the steel fabricator's laboratory in laoan. Thc test was ouite successful and verified the accuracv of the structural analvsis within a few percent This ,&aslhc first significallt slcel-iromed building lo bs built In Sing;.purr.. m the ICSI u.ns also hulpful in pruviding arsurnncc to the huilding ullisials of the competence ofthe design and steel construction team. Because of the somewhat unusual s t ~ c l u r a framinr l &svslem. . the concrete core wall WAS designed conscn,alivcly lo rusisl porciblc, slthuugh very unlikely, p;.tlurn lise l o x incr i n srhicb scrersl cons~.cutirefloors had live lnods i n ccrlain quxlraols and no li\c load in others. The result of such loadinr oatterns was to induce throueh-thickness bending stresses in the wall due to these asymmetrical forces. The core wall was anslyzcd using detailed finite-element analyses. and reinforcing stcel was provided to resist !he in-plane and through-thickness forces and bending moments due to gravity loads with and without wind loads.

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M Fig. 4.49 Framing perspective; Singopare Trensury Bullding. 123

124


[Chap. 4

77 West Wacker Drive Chicago, Illinois, USA

Architect Structural engineer Year of completion Height from street to roof Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity Maximum lateral deflection Design fundamental period Design acceleration Design damping Earthqunkc loading Type of strucmrc Foundation conditions Footing type

Typical floor Story height Beam span Beam depth Beam spacing Material Slab Columns Sire at ground floor Column spacing h4atcrial Core Wall thickness at ground floor Matcrial

'

Richard BofiillDeSteiano and Goettsch Cohen-Barreto-Marchcrtas, Inc. 1992 203.6 m (668 ft) 50 2 Office Concrete core, steel perimeter 2.5 kPa'(5O ps0 Chicago building code Less than HI500 6.67.5.88 sec horizontal; 6.67 sec torsion 29 mg pesk 2% serviceability Not applicable Cnncrete shear core, perimctcr stcel frames Hardpan, 1700-kPa (40.000-ps0 capacity 21-m (70-it)-deep caissons. 900- to 3000mm (3- to 10-11) shaft diameter bcllcd to 1370 to 7000 mm (1.5to 23 it) 3.96 m (13 ft 9 in.) 13.72 m (45 11) 533 mm (21 in.) 3.43 m (I l ft 3 in.) Steel 110-mm (5.5-in.) concrete on metal deck W350 X 1086 ( W i 4 X 730) plated 3 m (10 ft) min. 13.7 m (45 it) max Steel. F, = 350 MPo (50 ksi) Central concrew shear core 559 and 355 mm (22 and 14 in.) Concrete. 52 to 35 MPa (7500 to 5000 psi)

This 50-story 96.600-m' (1,040,000-TI') office torver is located at the southwest corner of Wacker Drive and Clark Street (Fig. 4.50). It is a classically styled addition to the Chici~noskyline on North \\'ackcr Drive. which is graced by several outstnnding architectural and structural originals.

I

Fig.450 77 West Wnckcr Drivc. Chicago, lllinuir.

126


[Chap. 4

The building. which is rectangular in shape. 50.29 by 42.67 m (165 by 140 ft) with 4.57-m (15-R) reentrant angles at the four corners, is the first high-rise tower designed by the Spanish architect, Ricardo Bofill. It was designed in collabontion with the Chicago architectural firm of DeStefano and Partners. The framing system is a central concrete core surrounded by a structural steel h m e with a composite floor deck (Fig. 4.51). The core, which is extremely slender [ I 5 5 5 by 27.45 m (51 by 90 ft) with a height-to-width ratio greater than 13:1] incorporates all the mechanical, electrical, and verticnl transportation amenities. The column-free floor spans allow for a very flexible 13.72-m (45-ft)-wide tenant soace. Another outstanding feature in the building is its magnificent entrance lobby, which extends from the ground to the fiflh floor, with a completely unobstructed space of 50.29 by 13.72 m (165 by 45 it). 13.72 m (45 it) high.

Sect. 4.21

127

Casselden Place Melbourne, Australia

Architect S I N C I U Iengineer ~~ Year of completion Height from street to roof Number of stories Number of levels below ground Building use Frome material Typical floor live load Basic wind velocity Maximum lateral deflection Design iundemenlal period Design acceleration Design damping Earthquake loading Type of structure Foundation conditions Footing type Typical noor Story height Bcam span Beam depth Beam spacing Slab Columns Size at ground noor Material Core Material

Fig. 4.51 hlidrise noor framing plnn, l l d to 36th floors; 77 Wesl Wneker Drive.

Shearwall Systems

Australian Conswction Services with Hassell Architects Connell Wagner 1992 160 m (525 ft) 43 3 Office Concrete core, steel frame 4 kPa (80 psfl 41 mlsec (92 mph). 50-yr return 150 mm (6 in.). 1000-yr return 3.45.5.00 scc 4.5 mg rms. 5-yr return 1% serviceability; 5% ultimate Not applicable Core for all lateral load Siltstone. 2-MPa (20-ton/ft2) capacity Pad footings 3.75 m (12 f t 4 in.) I 2 m (39 R 4 in.) 610 mm (24 in.) 3 m (9.83 it1 130 mm (5 in.) on metal deck 950-mm (37-in.)-diameter composite concrete-filled steel tubes Concrete, 70 MPa (10.000 psi) Concrete shear walls. 500 and 200 mm (22 and 8 in.) thick at ground floor Concrete, 70 MPa (10,000 psi)

This building is interesting for several reasons: 1. Construction over Melbourne underground rail loop 2. Use of high-sbenglh concrete 3. Use of composite concrctc-filled steel-tube columns ~h~ conswctian of Casselden place (Fig. 4.52) orrcr the Melbourne underground rail loop necessitated two unusual design features. (])The removal of rock for the three-


128

[Chap. 4

If

S e c t 4.21

Shear Wail Systems

story basement rclnxed the overburden pressure on the tunnels. (2) To prevent heaving of the tunnels, 26 30-tonne (33-Ion) vertical anchors were inslalled to Lie the tunnels t were reimposed, there anchors are permanent. down. In the areas where only l i ~ h loads but where heavy loads are imposed by the new struch~re,temporary anchor; only were used. In addition, piling was used in some areas to provide load transfer to below the level of the tunnels in the event of ground movement The mosl inluresting pan of the c~nstructionis the columns construction. Thts method is the firs1 of i n type in Austrnlia. with only a small number of buildtngs knnwn lo b: constructed using- similar methods anywhere in the world. The tube columns are erected in two-slory lifrc, wilh (he bare steel able ro suppon up to six stories of construction. Concrete is p ~ m p e dinto the b;lse ofthe lube, and up as man) as six slories at a lime. No 1% bmtinn of the concrele is required. Conncll \'fagner ha.. dcveluped design methods for this tjpc of column. including lltc use of thin-walled lubes. No codified mclhod for rhe design of thin-walled concrete-filled lubes is av~ilableanywhere in the world. This form of construction orovides a column for a steel-fmmine-svstem ~~. at a cost equal to that of a reinforced concrete column. The cost of the columns has been a major stumbling block in the economies of steel-framed buildings, with the penalty for using all-steel columns on a building such as this as high as 3% of the total building valuemillions of dollars on projccls of this size. This solution benefils from the economy of concrete. with the simple concrele placement method -giving the system constructabilily lhal ir couivalent lo that of a full sicel column. 'llie cure and columns on llic project use concrete olup lo 70 hlPa (10.000 psi). T ~ L culuinns arc considcr:d to bc an ideal u.3). raluring br~h-slrcnglhroncrele of good curc confines the concrete, enhancing ability, which is being placed inside btube. ~ h tube ing the ductilily of the high-strength materials. ~

Fig. 4-52

Cmscldcn Place, hlelbourne, rlunrn)jn.

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130


[Chap. 4

Twin 21 Osaka, Japan Architect Smctural engineer Year of completion Height from street to roof Number of stories Number of levels below ground Building use Frame material

Typical floor live load Basic wind velocity Maximum lateral deflection Design fundamental period Design velocity

Design damping Earthquake loading Type of structure Foundation conditions Footing type Typical floor Story height Beam span Beam depth Beam spacing Material Slab Columns Size at ground floor Spacing hlatcrial Core Thickness at ground floor

Nikken Sekkei Ltd. Nikken Sekkei Ltd. 1986 157 m (515 ft)' 38 1 Office, shops, showrooms Steel core and perimeter on upper floors: concrete core and concrete-encased steel perimeter on lower floors 3 kPa (60 psO 35 rnlsec (78 mph) 400 mm (16 in.) 3.9, 4.0 scc 250 mmlsec (10 in./sec) for medium earthquakes: 500 mmlsec (20 in./sec) for maximum-level earthquakes

Sect. 4.21

Shear Wall Systems

spaced at 3.2-m (10-ft 6-in.) inten,nls, connected by the floor slabr to the slucl-fmnlcd core. This suucture is eflicient in resisting horizontnl 2nd torsional deformations due to earthquakes and wind. Below the sixlh floor the building smcture consiss of steel frames encased in reinforced concrete, and rigidity is provided by reinforced concrete shear walls around the core. The majority of the horizontal force is borne by these shear walls (Fig. 4.54). Had the tower building columns been continued down through the low-rise section at 3.2-m (10-ft 6-in.) centers, space utilization would have been adversely affected. Hence the 3.2-m (10-ft 6-in.) spans are increased to 12.4-m (40-8 8-in.).soans bv,onestory-high concrelc-encased ste.el transfer beams at the fifth-ljoor level, thereby pro\,iding for shops and showrooms in the lou,rr floors of the building. The uind load response due to the tuin towers bcinr in close proxim~tv*,as checked using wind tunnel testing and the results were reflectea in the design. The atrium of the low-rise pnrt is surrounded by the low-rise parts of the two towers and the gallery building (four stories wilh an L-shaped floor plan). It is composed of a large space [about 47 by 47 m (156 by 156 ft)] nod is covered by alarge steel-pipe space buss roof suucture. There are large forces on the roof due to the uplift of the wind blowing between the twin towers and the down wash off the buildings.These factors were evaluated by wind tunnel testing. The atrium roof trusses are supported on slide bearings, which can absorb horizontal deformations of the high-rise part during an earthquake. Stoppers are provided to prevent uplift under upward wind loading.

.

270 C = 0.10

Primarily perimaer rigid moment frames Clay 18-m (59-(1)-long. 1.5- to 2-m (5- lo 6.5ft) shaft-diameter belled concrete piles 3.75 m (I? f t 4 in.) 13.7 m (45 ft) 820 mm (32 in.) 3.2 m ( I 0 ft 6 in.) Steel, grade SS 400 and SM 490 165-mm (6.5-in.) concrete on metal deck 1400 mm (55 in.) 6.4 and 12.8 m (21 and 42 it) RcinSorced concrete and structural steel Reinforced concrete lower levels: steel upper levels 700 to 900 mm (27 lo 35 in.)

Twin 21 comprises t\vo identical 38-story office towers with sbaps and showroom.; on the lowcr floors (Fig. 4.53). The perimeter frames above the sixth floor have columns

131

Elg.453 Twin 21. Osoko. Jopon.


[Chap. 4

S e c t 4.21

Shear Wall Systems

133

:q 5' Majestic Building ,@i,

1

Wellington, New Zealand

.@/: E . ,

Architect Structural engineer . .:,:Year of completion Height from street to roof Number of stories Number of levels below ground

Manning and Associates Wass Buller and Associates

.

Building use Frame material Typical floor live load Basic wind velocity Design fundamental period Design acceleration

Fig. 4.54

Typimlstrurhrnl floor plan; sin 21.

Design damping Earthquake loading Type of structure Foundation conditions Footing type Typical floor Story height Beam span Beam depth Beam spacing Slab Columns Size at ground level Spacing Material Core Thickness at ground level Material

1991 116 m (380 ft)

.

29 3 Office Concrete 3.5 kPa (70 ps0 50 d s e c (112 mph) 2.9 sec 10 mg peak, I-yr return period . 1% serviceability (wind). 5% EQ

C, = 0.0132 Core and perimeter frame Weathered rock over rock Pads and 1.8-m (6-ft)-diameter bored piles 3.7 m (14 ft 2 in.) 12 m (39 f t 4 in.) 750 mm (29.5 in.) 10 m (32 ft 10 in.) 365 mm (14 in.) Dycore 1400-mm (55-in.)-diameter 10 m (32 ft 10 in.) Concrete. 50 MPa (7100 psi) 400 and 600 mm (16 and 24 in.) Concrete, 50 MPa (7100 psi) max

The Majestic Building (Fig. 4.55) comprises 32 levels tolnling 42,000 m' (452.000 it'). including four levels of parking garage, extensive retail, arcade, and public plaza areas. a fitness center with a 33- by 4.5-m (1 10- by 15-ft) swimming pool, a crkche, an art gallery. and approximately 24.000 m' (258.000 it2) of office space. Wind engineering played a major part in determining the building shape, podium features, and strucmre of the building. Three separate wind tunnel studies were undertaken to investigate environmental wind effects, cladding pressures, as well as overturning moments and acceleration levels. Following completion, further studies of the

I, ...

134


[Chap. 4

structure were cnrried out usinf: - a mechanical vibrator and also recording wind displacumenls using scnsili\,c occelcromclers. The building is located in the most active cismic zone of Sew Zeal;~nd,with knoun fault lines running lhrouyh the ccnlral business dislricl of \Veilinglon. The first floor of the tower is I2 m (40 fl) above street letel and the column spacing around the perimeter i s !O m (33 fl). These fentures were critical to crtnlc a spncmus lobby and enlrancc to the building; however, such features in seismic zones require special design to prevent the occurrence of a "soft story." For these reasons a "ductile hybrid structure" was chosen as the lnleral load resisting system. The concrete core walls and the perimeter frame work together and were designed using capacity design methods lo be fully ductile. Foundations ~ ~ ~ - . and lower levels were designed - to resist the overslreneth . capacity . . forces from the superstructure. The unique floor system comprises prelensioned hollow core planks 1200 mm (4 fl) wide and 300 mm (12 in.) deee, at 2400-mm (8-ft) centers. A thin metal may was . seaced . plscud hctaccn lllc hollow core planks, and 65 mm (2.5-in.) of in-situ cuncrele ~ 3 s placed over the whole floor.Tlrc floor is only 115 mm 1.1.5 in.) dccp in parts, uhich nllous for~ffic1~111 duct I ~ ) O U II S t neighs . only 3.6 kPa (75 psQ and can suppurl in excess of 3.5 P a (73 psf) overi2.5-m (41-fl) spans (Fig. 4.56).

Sect. 4.21

Shear Wall Systems


[Chap. 4

Sect. 4.21

Shear Wall Systems

137

I

Telecom Corporate Building Melbourne, Australia

Architect S l ~ c t ~ rengineer al " Year of completion Height from street to roof Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity Maximum lateral deflection Design fundamental period Design acceleration Design damping Earthquake loading Type ofstructurc Foundalion conditions Footing type Typical floor Story height Beam span Beam depth Beam spacing Material Slabs Columns Size to ground floor Spacing Material Core Thickness at ground floor Material

Perrott Lyon Mathieson Connell Wagner 1992 192 m (630 ft) ~,. . , ... ....* ~.. 47 3 Offices Concrete 4 kPa (80 psO 41 mtsec (92 mph). 50-yr return 123 mm (5 in.) at 25 mm (1 in.), 1 return 4.5 sec 4.4 mg rms, 5-yr return 1% scrviceability; 5% ultimatc !,J@ Not applicable Concrete core and perimeter lrame tube~a @!' tube ,:%I*:

,$#

Pads to columns. raft to core

..:,., :.s::. !stt

3.85 m (12 ft 8 in.) 12 m (39 ft 4 in.) 440 mm (16 in.) 5 m (16 f t 5 in.) Partially preslressed concrete 125-mm (5-in.) reinforced concrete 1000 by 1200 mm (39 by 47 in.) 8.1 or 9 m (26 ft 7 in. or 29 ft 6 in.) Concrete. 60 MPa (8500 psi) Shear walls 500 and 200 mm (20 and 8 in.) Concrete. 60 MPa(8500 psi) mas

This all-concrete building achieved impressive conslruction times (Fig. 4.57). The entire 50-level concrete core was complclcd in 14 months, using a jump-form system. Typical cycle times for the core averaged 4 % days per floor.

I

ID

'w:


[Chap. 4

.*

Se.

4.21

Shearwall Systems

with three 15.2-mm (0.6-in.) strands was tensioned from the opposite end. The bands were top-sucssed. Grinding in b ~ c kof the surface ofthe anchorage pockcs was no1 nrcessary because access flooring is being provided throuphout the tower One hundred percent of the prestrr5s force was appiisd to cach tendon u hen the concrcte had reached a strength of 22 hlPa (3 100 psi). Using a high early-strength concrete e of mix, this uas achieved on lhc second d3y after the pour. This, togeli~erwith d ~ use two sets of table forms, alloued floor-to-noor cycles of three d3ys lo be achieved. The tendons arrive on site prefabricated with suands already threaded into the ducts. The connection to the corc is ;imply and posili!,cly affected b; Ihe use of 600-mm (24in.)-long 20-mm (0.75-in.) bars which wrap around the vertical rcinforcrme~~t in the core wall. The prrimeter spandrel beams are 775 mm (30.5 in.) deep by 350 mm (14 in.) wide, spanningup to 9 m 730 ft). Reinforcement cages for these biams were fabricated on construction decks on the podium roof and craned directly into position. Loose bars were added at column locations to provide continuity. The main enlrance to the building is a dramatic three-story-high entry auium. The nerimcter of this alrium is elass on exoosed architectural steelwork fabricated from 250by 250-mm (10- by IO-in.)-square hollow sections. This steciuork IS hunp from 3 2200mm by 950.mm (86- by 37-in.) posrtensi~ncdcnntiicvcr ring beam at lcvel 3, giving the imnression of a glass cube susnendrd in midair. The rinc beam is clad !r ith 200-mm 18in.)-thick polished precast panels used as formwork. The e n y space is further enhanced by the termination of one of the tower columns above the lobby level. The column load is 24,000 kN (2640 Ions). This is achieved using slage-stressed 3950- by 1000-mm (155- by 39-in.) posttensioned beams, each spanning 18 m (59 ft) in a cruciform la you^ The beams hove eight and six tendons, respectivelv. with 19 12.5-mm (0.5-in.)-diameter strands in each tendon. The beams are stressed in three stages as load from the tower is progressively applied, achieving essentially flat beams throughout the construction phase.

The tower floor band beams. typically 400 mm (16 in.) deep. are notched to 275 mm (11 in.) thick at the core to allow the major mechanical ring duct to encroach into the structural depth, thereby reducing the floor-to-floor height. The band beams were designed as ~Ktially and are offset from the - prestressed . columns. A typical beam has three tendons. Two tendons, each with four 15.2-mm (0.6in.)-diameter strands, were stressed from the external end of the beam. A single tendon

-

F~E.4.57 Talccam Carpornte Building, Melbourne, Aurlmlio. (Pboro by S ~ U I TPEI I O I O ~ T O ~ I)~ I C I

I

140

4.3


IChap.4

Whilc outriggers have only brcn incorporated into high-risc buildings nithin the last 25 veors. the o u v i g ~ e as r a structural rlcmenl has a much longer Itistn~y.The great sailing ;hias .~ -- to help resist the wind forces in their r - of the oastand nresent have used outriggers sails, making the adoption'of tall and slendcr mas& porsible. In high-rise buildings lllc corc can be related to the marl of the ship, with rhe oulripger acting like the spreadrrj and the cxterior columns like the stavs or shrouds. The typical of a core and .. oreanization oulriggcr system is picturcd in Frg. 4.58. Just as in sailing ihipb. there outriggers serve 10 reduce the oven urn in^ moment in the core that would otherwise acl as a pure cantilever. ...- - .and- to transfer th; reduced moment to columns outside the core bv . way. o f a lensiun-comprcssion couple, uhich takes ad\,antage of thc incrcascd momenl arm betu.cen these columns. In addition lo reducing the size of lhe marl. [lie presence of uutri:pers n l ~ serves n where the mast is sreoned to th? keel beam -~ to ~- reduce the critical conn~ction In high-rise buildings this same bench1 is re3liz~dby a reduc~ionof !be hare core oterturning moments and the associaled reduction in potential core uplill forces. Tlic same overtuLing moment which is taken through a couple between the windward stay and the mast to the pretensioned ties in sailing ships, is transferred to gravity-loaded precompressed columns in the high-rise building. The structural elegance and efficiency of outriggers are well rooted in history. The outriggers have also becoine key elements in the efficient and economic design of highrise buildings.

.

~

~~

~

~~~

..

Core and Outrigger Systems

141

Why Outriggers?

1

CORE AND OUTRIGGER SYSTEMS

~~

Sect. 4.31

Modem high-rise buildings frequently incorporate central elevator cores along with generous column-free floor space between the core and the cxterior support columns. While this results -~ ~~-in greater functional eficiencv.. it also effectivelv disconnects the two major SWcNral elements available to resist the critical overturning forces present in a .?';"Hieh-rise building. . - of the interior core and the perimeler frame reduces - This uncoupling the overall rerislance of llte StNClUre lo the ovenurning forces lo the sum of llte indepcndcnt resisrances of the individual rlrmcnrs. The incorporation of outriggers in this Same svstem couales these two comonnents and enhances the system's abilihl lo resist overturning forces dmmatically. For buildings of up to 35 lo 40 stories, reinforced concrete shear wall or steelbraced cores have been effectivelv utilized as the sole lateral load resisting- svstem. . These iystems are very effective in resisting the forces and associated deformations linearly with Lhe builddue lo shear racking- since their resistance vnries approximately ~. ineu heieht. However. the resistance that core svstems alone arovide to the overlurninecomponent of drift decreases approximately with the cube of the height. so that such core syslems become progressively more inefficient as the height of the building increases. In addition toatiifness limitations. a core svstem alonican also -eenerate excessi\u uplift forces in the core structure along with prohibitively high ovenurning forces in the building's foundation system. With !he sysrem's inability lo take adv;~nngr. oftlie overall building depth, designing for lhe resulting uplifl forces can be problematic. In reinforced concrete cores, excessive or impractical wall elements where large net tension forces exist can negate the inherent efficiency of concrete in compression resistance. In steel cores. large and costly field-bolted or -welded tension splices greatly reduce steel efficiency and the ease of fabrication and erection. In the foundation system, these uplift forces can lead to the need for the following: ~~~~

~~~~

~

~

~

.

-

-

The addition of expensive and labor-intensive rock anchors lo an otherwise "simple" foundation alternative such as spread footings. Greatly enlarged mat dimensions and depths solely lo resist overturning forces. Time-consuming and costly rock sockets for caisson systems along with the need lo develop reinforcement throughout the complete caisson depth. Expensive and intensive field-work connections at the interface between core and foundation. These connections can become particularly troublesome when one considers the difference in construction tolerances between foundation and core StNClUre. n i e climinarion from consideration of foundation systems which might have bcen considerably less expensive. such as piles, solely for their innbilily lo rcsist significant uplift.

2 Outrigger Benefits For many bnildines. - the answer to the problems and restrictions of core-onlv or tnbulvr struclures is the incorporation of one or rnorc lcvcla of oulriggers. Typical oulrigger organization consisls of linking the core o f a high-rise building to h e exterior columns on one or morc huildins faces with lruss or wall elements (Fig. 4.59). The outrierer -- sys. tems may be iormcdin any combination of steel, concrere;or composite conswction. When properly and efficiently utilized, outriggers can provide the following structural and functional benefits to a building's overall design:


142

. . .

[Chap. 4

Core overturning

moments and their associated induced deformation can be reduced tltrouglt ths "rc\r.r,c" momdnt applied to the cur< at each outrigger intersection (Fig. 1.60). This applies to titc core at r3ch outrigger intersection. This momtnt is created by the forcc couple in the exterior columns to which the outriggers connect. It can potentially increase the effective depth of the structural system from the core only to almost the complete building. Significant reduction and possibly the complete elimination of uplift and net tension forces throughout the columns and the foundalion system. The exterior column spacing is not driven by structural considerations and can easily mesh with aesthetic and functional considerations. Exterior framing can consist of "simple" beam and column framing without the need for rigid-framc-type conncctions, resulting in economies. For rectangular buildings, outriggers can engage the middle columns on the long faces of the building under the application of wind loads in the more critical direc~

.

Uond Uuilding, Sgdnry, Austrnlin. Toncr bracing, ccsl-~wstlints, looking north.

Sect. 4 31

IF


143

lion. In cure-;!lone and tuhuiar systcms. IIIL'SC columns which ;my siglliiicnltl gr;!vit! load nrs either not incorporntcd or ~nderutiiized:In aomc c3ser. oulrigsur s)stems can elficicntl\ lncomorate almost e\crv. :rs\,ily - . column tnto !he laieral load rrsisrinc system, leading to significant economies.

$,

9. .,.

3

Outrigger Drawbacks

The most significant drawback wilh the use of outrigger systems is their potcntiai interference with occupiable and rentable space. This obstacle can be minimized or in some cases eliminated by incorporation of any of the following approaches: Locating outriggers in mechanical and inlerslitinl levels Locating outriggers in the naluml sloping lines of the building profile Incorporating multilevel single diagonal outriggcrs to minimizc the member's interference on any single ievcl Skewing and offsetting outriggers in order to mesh with the functional layout of the floor space

Fig. 4.60

1650 hlnrkcl Slrccl,

I'hiludelphlu.

144


[Chap. 4

Aitolllcr potential drawback is the impact tile nutrigger isstallation cnn have un the crcctiun pruccss. As a typical building rrcction prouceda. the repelitlve nature of thc structurai framinr and th~reduetionin member sizes generally result in a learning curve which can speedbe process along. The incorporatioiof an outrigger at intermediate or uppcr levels can, if not approached propqrly, have a negative impact on the erection process. Several steps can be taken to mtnimtze this possibility.

. .

Provide clear and concise erection guidelines in the contract documents so that the erector can anticipate the constraints and limitations that the installation will impose. If possible, avoid outrigger locations or design constmints that will require "backlncking" in the consvuction process to install or connect the outrigger. The incorporation of intermediate outriccers -- in concrete construction orlarcc - variations in dead-load column suesses bctuccn the core and the exterior can in some cases result in the nccd to "backunck." Such a need can be minimized if issues such >%creep and differential shoncning are carefully studied during the design process to minimize their impact. Avoid adding additional outrigger levels for borderline force or deflection control. Outriggers provide diminishing returns for each additional level added. Incorporate outriggers in less optimal numbers or locations when doing so will haven significant positive impact on the overall construction cosls.



g, -

,,

Cityspire N e w York, N.Y., USA ,;

ATehitect Svuclural engineer Year of completion Height fromstreet to roof Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity Mnximum lateral deflection Design fundamental period Design acceleration Design damping Earthquake loading Type of swcture

t

Foundation conditions Footing type Typical floor .. Story height Beam span, spacing Beam depth Slab Thickness Columns Material Core

Mumhv . .Jahn Robert Rosenwasscr Associates 1987 248 m (814 ft) 75 2 Office and residential Concrete 2.5 and 2 W a (50 and 40 psO 47 mlsec (105 mph), 100-yr return HI500 5.5,5.4 sec horizont;U; 2 sec torsion 15 mg peak. 10-yr return 1 2 % serviceability; 2 2 % ultimate Not applicable Shear walls with outriggers at transfer levels and interior diagonals in olfice levels Rock. 4-MPa (40-ton/ft2) capacity Spread footings 3.5 m (1 l ft 6 in.) office; 2.85. 2.95. 3.05 m (9 ft 4 in., 9 ft 8 in.. 10 ft) residential Vary 508 mm (20 in.) at perimeter Flat slab 216 mm (8.5 in.) office; 241,267,305 mm (9.5, 10.5, 12 in.) residential Size and spacing vary 56 MPa (8000 psi) Concrete walls of varying thickness

CitySpire. 156 West 561h Street, displaced Metropolitan Tower as the tallest concrete structure in New York CitySoncrctc placement reached to 244 m (800 it) and aluminum-dome fins extended the height to 248 m (814 ft) above grade. When completed in 1987, it was the second fallestconcrete structure in the world (Fig. 4.61). With a 1O:l ratio, it is the tallest, most slender structure (concrete or steel) in the world today. CitySpire has about 77.100 m2 (830.000 it') of floor space and required 33,000 m3 (43,000 yd3) of concrete and 4300 tonnes (4700 tons) of rcinforcing bars for its 77 construction levels (including mechanical and below-grade levels).


S e c t 4.31

[Chap. 4


;g: &?: Floors 6M9

&jj

.,:.. ,@ .*,,

Si,

(a)

Floors 2645

-:; ,

(c)

fl:

?g; 5

!a .-+

'8.

r:

1!

,~,: .a.. ,I..

; a: ,.a.

:*,: 4f J" >If

".-L1. %,I

f>L?r& , '**

i x*': "i,

Floors 47-61

(4 Fig. 4.62 Floor plans; CitySpim.

.:ST

-@,

3, ?db3 :t$q ;L.L

,rb:

-~.

gY

: r 7L.

Office

(4 Fig. 4.62 Floor plnm; CilySpire (Conrinurdl

149

150


[Chap. 4

Chifley Tower Sydney, Australia

Architect Structural engineer Year o f completion Height from street to roof Number of stories Number of levels below grol~ n d Building use Frame material Typical floor live load Basic wind velocity Maximum lateral deflection Design fundamental period Design acceleration Design damping Earthquake loading Type of structure Foundation conditions Footing typc Typical noor Story height Beam span Beam depth Beam spacing Material Columns Material

Kohn. Pedersen. Fox with Travis Partners Hack and Kurtz Australia with ThorntonTomasetti 1992 215 m (705 ft) 50 4 Office with 2 retail levels Steel 3 kPa (60 psO 50 mlsec (112 mph) ultimate, 1000-yr return Hl400.50-yr return 5.0 sec 20 mg peak. 5-yr return, with operating tuned mass damper 7 lo 2.5% s~rviceability;6% ultimate Not applicable Steel perimeter frames, braced steel core with outriggers at levels 5, 29-30.42-43 Sandstone, 5-MPa (50-tonlft') capacity Spread footings plus rock anchors ilp to I8 m (60 it) long 4.075 m (13 ft 4 in.) 10 to I5 m (33 to 49 ft) 530 mm (21 in.) 2.5 to 3 m (8 ft 2 in. to 9 ft I 0 in.) Steel, grade 350 MPa (50 ksi) Braced steel frame Steel, grade 250 and 350 MPa (36 and 50 ksi) Rnccd steel frame. grade 350 MPa (50ksi)

Chiflcy To\+,erhas been designed to house financial service organizations. Wiring needs were met by raised "computer" flooring, by generous riser closets, and by the open nalure of a steel-framed core. (Less accessible concrete cores are most commonly used in Austmlia.) Steel rraming was also used to speed erection and occupancy (Fig. 4.63). Its 90,000-m' (969.000-ft') tower rises from a 32.000-m' (345.000-11') full-site "podium." The building has a highly articulnted facade \+pithnonparallel sides, setbacks at different levels on different elevations, and a mix of flat, gently curved, and circular

Sect. 4.31

core and Outrigger Systems

151


faces. This desicn serves to define and enclose Chiflev Souare. reflect the street uerid.. maximize the views ofharbor, park and ocean 1; the'north and east, break up the bulk ofthe tower, and enliven the Sydney skyline. The numerous setbacks, the variety of facade geometries, and the desire for open views made a framed-tube shuctural solution impractical. A braced core would avoid involvement with the facade, but the tapered nature of the tower floor plans redulted in an inverted T-shape core plan (stepping back to an L at level 31) whose limited width would require unreasonably large columns to contra1 deflection (Fig. 4.64). To control deflections more efficiently, outriggers (or heavy trusses) link the core to perimeter columns at levels 5.29-30, and 42 (top) in the east-west direction and at levels 5 and 42 in the north-south direction. The middle east-west outriggers also serve as transfer trusses for a setback.

Core and Outrigger SYStemS

Sect. 4.31

[Chap. 4

The irregular building shape, irregular core geometry, and involvement of outriggers reouired analvzine and desienine- the wind system structure by means of a complete three-dimensional computer model since no planes of symmetry exist and three-dimensional interaction was critical. A oackaee of analvsis-and-desicn - p.r o-g m s was developed for this projecL An interactive deflection control routine determined "optimal" member areas to meet drift criteria by usinc virtual work establishing relative efficiencies of members, resizing the most ...--~ effiiient ~~members to meet deflection limits, and reanalyzing. A "final" analysis with optimal areas used precise loadings. Another analysis in;estigated dead loads ap'olied to the incomolete structure under consmction. A load combin;tion program look the member-force results of lllcse runs and appllcd forccs following an "overluming wind envelope" using directionalily from wind tunnel Icsts, sclected maximum and minimum wind forces for each member. and used combinations of the load cases lo dclermine maximum design forces for cnch mcmber. Wind allouablc suers incrrascs (force reductions) were included. A member selection program used the "optimal" arcas. Ihe design forces, and a table of acceplahlc member sizes lo select a uial member size, with an arcathilt was near "uplimal," in order to check the load capacity in accordancc with the Auslralian stecl code AS 1250-198I.The loop was thcn repratcd with a larger trial size if necessary. Memhrr selection marks were piotted on diagrams of the core bracing for ease of use. Member forces were also plotted in various ways to aid in the design of connections. It is inlerestine to note that ofice dead load plus reduced live load is about 20 lo 25% g lonnage figures lo Asshigher in ~ u s t m < nthan in U.S. practice, so u ~ ~ p o l a l i nU.S. tralinn projects could be m~sleadingunless faclorcd up. Australian practicc also affecled the conslruction delails. Available hot-rolled member sizes me more limiled lhan i n the United Stntes. For floor bcams this mcant using a hunvicr size than onc might athcrwisc choose. As a result floors have a higher-than-minimum load capacily. For girders, builtun sections were common. Also, since tl~eavailable plate is 100 mm (4 in.) thick or less. &e largest column sections use flanges and web of doubled and tripled plates. Chifley Tower includes a tuned mass damper (TMD) in the original consmction lo keep building movement below objectionable levels. Its help is not considered in the wind response for strength. The TMD mass is 400 tonnes (440 tons) of steel plate. suspended from eight 11-m (36-ft)-long cables anchored at level 46. Its period is adjusted by a tuning frame, which slides along the cables to vary their active length. Damping is provided by eight hydraulic cylinders which push fluid through a control valve and a heat exchanger in a closed circuit Movement is permitted in any lateral direction (NSEW), but torsion is restricted by an antiyaw yoke. The TMD is anticipated to increase damping from 1 to 2.5% and to decrease 5-yr acceleration from 0.03 to 0.02 g.

.

,!$.'!.?$:'

153

. -

u

-

154

Sect. 4.31



One Liberty Place Philadelphia, Pennsylvania, USA

Architect Structural engtnccr Year of completion Height from street lo roof Number of stories Number of levels below ground Building use Frame material

Typical floor live load Basic wind velocity Maximum lateral deflcclion Design fundamental period Design acceleration Design damping Earthquake l r ~ d i n g Type orstructure Foundation conditions Footing type Typical floor Story heiglll Bcam span Beam depth Beam spacing hlnterial Slab Columns Size at ground floor Spacing Core fvlateriol

Murphy Jahn Thornton-Tomasctti Engineers 1988 288 m (945 it) 61 I Office Structural stcci-braced core with superdiagonal oulri:gcrs 2.5 kPa (50 psi) 3 1 mlscc (70 mph) HI450 5.5 sec 15 111gpcak, 10-yr return I to 2% Nol applicable Braccd slccl core linked by steel girders to cxlerior columns Rock. 4-hlPa (40-tonlf~') capacity Caissons 3.81 m (12 rt 6 in.) 13.4 m (44 rt) 530 mm (21 in.) 3.05 m ( I 0 rt) Steel, grade 350 MPa (50 kst) 63-mm ( 3 - i n . ) concrete over 76-mm (3in.) metal deck W350 by 384 (W350 by 257) built up to 2788 kglm (1870 lb/ft) 6.1. 13.4.21.3 m(20.44.70ft) Linked braced frame with nutriggcrs Steel, grade 250-hlPa (36-ksi) hracing. grade 300-MPa (43-ksi) and 350-h,lPa (50-ksi) beams and columns

One Liberty Place at 288 m (945 11) is located on a prime block ofdowntorvn Philadelphia (Fig. 4.65). The orlice floors range from 2230 m' (24.000 ft') in the lo\ver portions to 120 ni' (1300 it') at tllc pcak. The 61-story tower contains o\,er 120,000 m' (1.3 million ft') of floor area.

I

Fig. 4.65 One Libcrty Piocq Philndclpinin, Pcnnrjlronio.

155

I

156

[Chap. 4


Structural steel framing was chosen for its flexibility and high strength-in particular, its ability to transmit large tensile and compressive forces efficiently while keeping the size of the members to a minimum. Built-up wide-flange sections were used for ail outrigger diagonals and core and outrigger columns due to the large forces and required thickness ofthe plates. Their use also facilitnted fabrication and erection. The typical floor framing consisU of composile W2I ASThl A-572 gmde 50 stecl beams spanning 13.4 m (44 it) from the building core to the cxterior face. As a result, thc cntire lease space within thc tower is column-free (Fig. 1.66). The structural slab is compuscd of a 76-mm (3-in.) composile decking with 64-mm (2.5-in.) stone concrete topping. Floor beams were cambered lo compensate for dead-load deflection under wet concrete placement. The selected lateral load resisting system is a superdiagonal outrigger scheme composed of a 21.3- by 21.3-111 (70- by 7041) braced core coupled with six four-stom diaea. buildnal oulriggers at each face of the core located at three points over the hcight of the ing. The system works in a similar manner lo the mast of a sailboat, with the bncud core acting as the most and the outrigger superdi~gonnlsand vcnicolr forming the spre.lder ~

~

--

Fig. 4.66 Typical noor plan; Onc Liberty Plorc

Sect. 4.31

Core and Outrigger systems

157

and shroud system. After various studies utilizing in-house optimization computer programs, three sets of eight outriggers were found to be the most efficient solution. Although simplified models showed that they would be the most effective if spaced at equal intervals, optimization programs showed that these outriggers could further reduce wind-induced drift without addins additional steel by simply modifying their spacink o>erthel~cight of the building. ~ l t k a l ethe l ~ design warc~mpletedwith thr outside ends of tllc supcrdiagonnls placed at floors 20, 37, and 51. The outrigger supcrdiagonsls are connected'at theexteri& of the building to vertical outrigger columns. To reduce uplift forces on comer core Folumns and the ;itrigger columns it was desirable to concentrate most of the building's dead load on these columns. This was accomplished by introducing exterior transfer Wsses at floors 6,21, and 37, which span between the outrigger columns within the exterior face and thus funnel dead load, into the outrigger columns to compensate for uplift dueto wind pressure. Uplift in the extenor outrigger columns was totally eliminated with this approach. The uplift on the corner core columns was reduced to 5800 kN (1,300,000 lb). In developing the superdiagonal outrigger system, an intensive effort between the building's architects, interior planners, and developer was undertaken to determine that the presence of diagonal outriggers penetrating down through certain lease space at eight locations on 12 floors would not interfere with theefficient layout of the space. Interior planners made various layouts for full-floor and partial-floor tenants and concluded that the presence of the inclined superdiagonal columns would not hinder the real estate leaseability of these spaces. Wind forces were generated using prevailing codes and also utilizing a force-balance wind tunnel lest undertaken by CermakPeterka of Fort Collins, Colorado. It was determined that average wind pressures on the building varied between 0.25 kPa (5 psO at the bottom lo 2.9 kPa (58 psf) at the top. Both planar nnd three-dimensional static and dynamic analyses were performed for combinations of gravity and lateral loads. The period of the building was determined to be 5.5 sec. The lateral load resisting system was initially designed using a purely ailowable strcss criterion. During the optimization effort, members were increased in size, which contributed to increasing the building's internal stiffness. As stiffness was increased, the acceptable limits of building drifl (Hi450) and acceleration (15 mg) were met. In addition, because of the vertical compatibility between ouuigger columns ald core columns created by the outriggers, analyses were required to determine the gravtty load magnitude in the lateral load resisting system. This nnalysis was performed in steps lo properly model the actual building erection and loading sequences. Utilization of the optimization program vimmed on estimated 9.8 kgim"2 psf) from the wind-resisting system, a savings of some 15% by weight. More imporlnnt were the savings gained by eliminating cntire components such as two interior bracing lines above the twentieth floor, which greatly simplified design and consuuclion.

I I I

, ,, $

'i

j

158


[Chap. 4

17 State Street New York, N. Y., USA

Architect Structural engineer Year of completion Height from street to roof Number of stories Number of levels below ground Building use Frame material Typical floor live load Bnsic wind velocity Maximum lateral deflection Design fundamenlal period Design acceleration Design damping Earthquake loading Typc of structure Foundation conditions Footing typc Typical floor Story height Beam span Beam depth Beam spacing Slab Columns Spacing Material Core

Emery Roth and Sons Desimone. Chaplin and Dobryn 1988 167.3 m (542 ft 2 in.) 44 I Office Steel 2.5 Wa (50 psO 17 mlsec (105 mph). 100-yr return Hl500. 100-yr return 4.7. 5.0 sec 20 mg peak I% serviceability Not applicable Bundled braced core tubes with perimeter monicnt irame and an outrigger hat truss Rock. Concrete piers and steel piles 3.66 m (12 it) 5.5 to 12.2 m (18 to 40 ft) 305 to 530mm (12 to 21 in.) 3.2 m (10 ft 6 in.) max 63-mm (2.5-in.) normal-weight concrete on 76-mm (3-in.) metal deck Built-up W350 (W14) core, W610 (W24) perimeter 8.53 m (28 ft) core. 5.69 m (18 fi 8 in.) perimeter Steel, grade 250 MPa (36 ksi) Braced tubes, grade 250-MPa (36-hi) concrete encased through lowest two levels

17 State Street is a 44-story office tower located ncross from Battery Park at the tip of Manhattan (Fig. 4.67). To maximize the unobstructed views of the Statue of Liberty and the New York harbor, the architects chose a quarter-circle floor plan of 1160 m' (12,500 ft') (Fig. 4.68). Although the perimeter of the plan is symmetric, the core of the tower is offset to optimize the arrangement of rental floor space. The first level is 10 m (33 ft) above grade, and typical floors are 3.66 m ( I 2 ft) high.

Sect.

4.31

Core and

Outrigger Systems

159

160


[Chap. 4

Wind tunnel testing predicted that the wind coming off the harbor would produce loads 40% higher than those required by the New York City building code. The structural system consists of bundled braced core tubes coupled to perimeter moment frames by means of an outrigger hat truss. The three core tubes are braced with X, diagonal, and inverted V members, as dictilted by core functional requirements. Core

Fig. 4.68 Typical floor plnn: 17 SLnle Strcer

Sect. 4.31


161

columns consist of W350 (WI1) series rolled shapes in the upper ponion of the building and built-up membcrs below. Pcrimeler moment f m e s have W6lO (W24) series coiumns. rolled and built uo. a . soaced at 5.7 m (18 h 8 in.). The nerimeter hame; do not form a tube, as architectural notches at the comers of the quarter-circle prevent effective economicd transfer of vertical shear forces around the corners. The hat truss is a three-dimensional outrigger two stories high, with diagonals sloping downward from the core to the perimeter. At the first level. which rises I 0 m 133 ft) above the sidewalk the ~erimelercolumns and spandrel beam; are encased in cincreie to provide additiooal siffness for the tall story. Below the ground-floor level, the cores are also encased to add stiffness. Footings consist of concrete oiers lo 6-MPa 160-ton/h2) bedrock and end-bearinr steel oiles. Eight columns are Gchorcd for uplif;with postiensioned threadbur rock Gchors.'

.

~~~

162


IChap. 4

Sect. 4.31


163

Figueroa a t Wilshire Los Angeles, California, USA

Architect Structural engineer Year of completion Height from street to roof Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity Maximum lateral dcflcction Design fundamental period Design acceleration Design damping Earthquake loading Type of structure Found~tionconditions Footing type Typical floor Story height Beam span Beam depth Beam spacing Slab Columns Size at ground floor Material Core

Albert C. Martin CBM Engineers. Inc. 1990 218.5 m (717 ft) 53 4 Office All stccl 2.5 kPa (50 psO 3 1 mlscc (70 mph) 380 mm (15 in.), 100-yr rclurn 6.5 scc 17 mg pcnk, 10-yr return I% scn2iceability;7% ultimate Magnitude 8.3 from San Andrcas fault Braced corc "spine" with outrigger ductile frame Shnle, 750-kPa (15,000-psn capacity Spread footings 3.96 m (13 ft) 18.3 to 10.7 m (60 to 35 ft) 914 to406 mm (36 to 16 in.) 3.05 m (10 it) 133-mm (5.25-in.) lightweight concrete on SO-mm (?-in.) melal deck 1067 by 1067 mm (42 by 1 2 in.), cruciform shape nl 18.3-m (60-ft) centers Stcei. grade A572.350 MPe (50 ksi) Braced steel, grade A572

This 218.5-mm (717-ft)-tall 53-story office torvcr is located in downtown Los Angcles (Fig. 4.69). Tltc floor plan of the tower is 45.7 m ( I 5 0 It) square, exhibiting notches and multiple step backs as it rises above the plaza ( F i g 4.701. The square ton8erplan offers internal spacc appropriate to banking and law firms. The granite-clad building has a three-story-tail stepped grccn-colored glass crown, wi~ichis lit from within at night and makes a distinct mark on the Los Angeles skyline. Turo six-story ntriums, botit rectangular in plan, which rise like glass and steel staircases, arc attached to two of the building's corners at 45' angles. Tile plaza of the tower at the corner of Figucron at Wilshire is articulated by fountains and a 12-m (40-it)-high sculplure.

Fig. 4.69 Figucroo nl Wilrhirc, Lor Angels, Cnltiarnio. (Co~rrresyojCBnf Engiriccrr. Inlc 1


164

..

[Chap. 4

the conceot of n saine As onnosed to conventional nerimeter ductile tubular frames. ~~~~, ~~~~- ~~r~ - r ~ structure is used for [his tower. The spine, the unintempled ponion of this lower, consists of a 17.4- by 20.4-mm (57- by 67-h) concentrically braced core linked to perimrler columns by aductile frame of outrigger beams. The 'pine in this case has three components (Fig. 4.71): ~~

~~

1. A rectangular concentrically braced core anchored at its extremities by steel columns of a maximum size of 1067 mm (42 in.) square at their base. The interior core bracing and beams are proportioned in such a way that, in case of an inadvertent failure of the diagonals, the vertical load-carrying ability of the floor is not affected. 2. Outrigger beams linking the internnlly braced core to the perimeter columns. These beams not only carry the floor loads, but along with the perimeter columns perform the function of ductile moment resisting frames for the entire structure. The beams are laterally braced to prevent lateral torsional buckling and are con-

Sect. 4.31 ~

~

-

Core and Out?ggwr Systems

. - .

nected to floor dianhraems bv shem studs lo m s m i t horizontal shew forces to Ihc frame. Nolchcs at the midspan of those beams, which provide for the passage of mcchanlcal ducts, are sllffened lo prevent the formation of a three-hinge mechanism when the ends of beams yield-during a major seismic evenl. 3. The 914- by 762-mm (36- by 30411.) steel perimeter columns which. because of their importance in the overall stability of the frame, nre checked for the loads created by the plastification of all outrigger beams. Because of the closeness of lateral periods of vibrations with torsional vibration periods. the- smciure was checked for the nhennmenon of modal counline. . The spine struclure nor only provided column-frcc uninlcmptcd lease spaces, bul also %asstruciurally very efficient. Designed lo remain essenlially elaslic for the maxof steel. as imum credible ~ ea&ou&e. ~ -. the structure ~ ~ uses~I10 kelm' - 122.5 . .~ s.n ~structural opposed to aconventional ductile frame, which would have required 132 kglm2(27 psO. ~~

~~~

-

~

.

$ SYMM.

i

OUTRIGGER

Fig. 1.70

Comporlle flwr plan; Figucroa o l Wilrhire.

165

Fig. 4.71

Spine slruehre; Figuemn st Wllrhire.


[Chap. 4

Four Allen Center Houston, Texas, USA Architect S t ~ c t u r aengineer l Year of completion Height from street to roof Number of stories Number of levels below ground Building use Fmme material Typical flqor live load Basic wind velocity Maximum lateral deflection Design fundamental period Earthquake loading Type of SINclurl Foundation condilions .Footing type Typical floor Story height Beam span Beam spacing Beam depth Material Slab Columns Size at ground level Spacing Material Core

Lloyd Jones Brewer Associates Ellisor and Tanner, Inc. 1984 210.5 m (690 ft 8 in.) 50 2

Office Steel 2.5 kPa (50 psf) 41 mlsec (92 mph) H/400,50-yr return 4.03 sec Not applicable Braced steel core with outriggers to steel perimeter lramed tube Deep still clay Continuous mat 3.96 m (13 11) 12.2 m (40 ft) 4.57 m (15 ft) 610 and 915 mm (24 and 36 in.) Steel, grade 250 MPa (36 h i ) 82-mm (3.25-in.) light!vcight concrete on 76-mm (3-in.) steel deck 915 by 280 mm (36 by l l in.) 4.57 m (15 ft) Steel, grade 250 MPa (36 ksi) Braced steel frame, grade 250 hlPa (36 ksi)

The Four Allen Center building rises 50 stories above grade and extends two stories below (Fig. 4.72). The elongated plan, combined with the slenderness of the tower, yields an illusion of exceptional height when viewed from street level. The 133.800 m' (1.44 million it') ollice building is connected to parking and retail facilities by an air-conditioned pedestrian tunnel and an overhead pedestrian bridge. Figure 4.73 shows the typical floor freming plan, and Fig. 4.74 illusvales the building section of a typical floor. The geometry of the slender airloil shape is susceptible lo dynamic oscillation in hurricane-speed winds, thereby establishing a complex and challenging series of structural frame and foundation problems. Wind tunnel tests of an aeroelastic model of the building were recommended and coordinated by the structural engineers. The testing resulted

Fig. 4.72 Four Allen Ccnler, Hourtun, Tcxnr

167


168

[Chap. 4

in developing a laternl wind-resisting system to control predicted dynamic oscillation of the building. A four-celled tube structure was develooed which includes a nerimeter fmmed tube and three vertical trusses m s v e r s e to the eievator core. linked t i t h e perimeter tube by tree-beam elements. The unique wind-bracing system was subjected to a full-scale test during hurricane Alicia in August 1983, and it performed exceptionally well. A refinement of the traditional solider pile was developed to retain the 11.3-111 (37ft-deep foundation excavation. The improved shape reduced the number of piles and

Sect. 4.31

tiebacks nomaily required, thus enhancing economy and shortening the schedule for the basement and foundation construction. The structural develooment. svslem - were facilitated by devel. anaivsis. and desisn oping a compmhcnsive series of computer analjses and design progmms. The automated analysis and d e s i ~ nprocessing ofall elements in the wind-rrsistun~system of the buiidine sbucture resulted-in sienifiiant savincs in material costs. and enabled the en-- u gineen to complele the design and drawings in a short4-month schedule. Advanced methods were also employed control during construe. . . to assure quality lion. in pmicular. Ihe project set new slandards of assurance regarding the Gghtness of high-suength bolls. Uilnsonic cxtmsomelers were usrd lo measure bolt lightness accu~atelyfor the first time on a commercial projecL The 45.7- by 91.4- by 2.6-m (150- by 300- by 8.5-ft) mat foundation containing 11,127 m3 (13.308 yd" of concrete was poured in just over 19 hours. This was made nossible bv. usine-a svstem by concrete pumps. . of belt convevors su~olemenlcd .. Thc structural stcel was crccled by fabriculing the exterio;lrcc cuiumns.
.

J!Q!

!

I

I

!

!

.

ED -

"

I.. I % _ "'3"B-

Fig. 4.73 Typical noor framing plnn; Four Allen Center.

F p . 4.74

Enlnrgcd building reelion-lypicnl noor; Four Allen Center.


"One of the Ten Outstnnding Engineering Achievements in the' United States of America," National Society of Professional Engineers, 1983 "Grand Award Winner for High Professional Execution of Engineering Design," American Consulling Engineers' Council. 1984 "Eminent Conceptor Award for the Most Outslanding Engineering Project" Consulting Engineers' Council of Texas. 1984


[Chap. 4

I

Sect 4.31


Trump Tower New York, New Vork, USA

Architect Structural engineer Year of completion Height irom sLreel to rooi Number of stories Number of le\'els below ground Building use Framc material Typical noor live load Basic wind \,elocity Maximum lateral deflection Design fundamenVal period Design accelcretion Dcsien damping Eanltqunkc loading Type of structure Foundalion conditions Footing type Typical floor Story height Slab Columns Size at ground floor Spacing hlatcrial Core

Swnnke Hayden Connell Oftice of Irwin G.Cantor 1982 1 0 1 m (664 It) 58 3 Retail, offices, residential Concrclc 5 kPa (100 p r o rerail: 2.5 kPa (50 psi) ofliccs; 2 kPa (4D 11~1)rcsidcnti:~l Unavailable: iorcc = 1.0. 1.25. 1.5 kPa (20.25.30 psi) Hl600. 100-yr return 5.2 sec 16.5 mS peak. 10-yr rcturll i.5% Not applicable Concrctcshcarcoie linkcd by cuncrelcoutrigger walls lo conarcle pcriltielcr rralncs hlonhattan mica schist Sprcnd footings 4.8.3.66.2.9m(lh,12.9.5111

400-mm (16-in.) waffle slab: 190-nlnl (7.5-in.) flat slab 813 by 513 rnm(32 by 37in.) 12.2 to 7.3 m (40 lo 24 it) Concrete. 49 MPa (7000 psi) Shear walls, -157 mm ( I 8 in.) thick at ground floor in 49-MPa (7000-psi) concrctc

Trump Tower is n multiuse building occupying a prime site on 5th Avenuc in New York City. T h i o u ~ the h purchase of the air rights for adjacent sites and irom bonuses awarded for the provision of public atncnities, a plot ratio (building floor arcJ lo site area) o f 2 1 was achieved, making this a very slender building. A perimeter tube lateral load resisting sysleln was unacceptable due to the impact o i closely spaced columns on the views from the condominiums and on t l ~ cshop fronts at street level. Also, structural steel was rejecled due lo the lead lime required Tor supply to the site. The adopted all-concrete solution u!ilized concrcte shear !\,ails for l;~leral load resistance and deep concrete lransier girderr to chon%cthe structural column grid (Fig. 4.75).

Column and rnll lond and lnlcrnl dirplnccmcnt;Trump To~ucr,New Ynrk.

172


Sect. 4.31

[Chap. 4

Through the 38 condominium levcls, loads are carried by 52 concrete columns and concrete u d i s around the service corc. At moflcvei, twin oulrigger beams 6 m (20 11) high and 450 mm (18 in.) thick link the corc with perimeter columns on two opposite sides to reduce Extended core walls do this iob in the other direelion ~ - - latekdisolaczment. ~ Below the twentieth floor a system of lransler girders 7.3 m (24 it) high and 450 to 600 mm ( I 8 to 24 in.) thick allows for the 52 columns to reduce to only 8 columns through the 13 office levels. The transfer girders nlso act as outrigger beams to further control lateral displacement. The girders are pierced by many openings for doors, pipes, and ducls. Another transfer system comprising an inclined-column A frame was introduced between the eleventh and seventh n o o n lo allow mother two columns to be removed in order to open up the atrium, which rises seven levels through the retail floors at the base of the buildine. The 1087-m' (I 1.700-it2) rcsidcntial floors wcrr poured on a ?-day c)cle. n ~ 56c and 49-hlPa (8000- and 7000-psi) concrete for the columns contained a superplasticizer to increase workabilitv. for . vlacine- around dense reinforcement. Tieht manGement of concrete delieerics uas requ~rcdto ensirre that high-strength concrete %,asavsilablc at the right time for placement in s l ~ b over s and around columns.

-

-

-

@

? @;


173

Waterfront Place Brfsbane, Australia ;.5'

Architect

...,

Stmctuml engineer Year of completion Height from street to roof Number of stones Number of levels below ground Building use Frame material Typical noor live load Basic wind velocity Maximum lateral deflection Design fundamental period Design acceleration Design damping Earthquake loading Typc of structure Foundation conditions Footing type Typical noor story height Beam span Beam depth Beam spacing Material Slab Columns Size at ground floor Spacing Material Core Thickness at ground floor Material

Cnmeron Chisholm and Nicol (Qld.) Pty. Ltd. Bornhorst and Wnnl Pty. Ltd. 1990 158 m (518 ft) 40 2 Office Concrete 3 Wa (60 psfJ 49 mlsec (110 mph) 185 mm (7.25 in.), 50-yr return 5 see 2.3 mg (standard deviation), 5-yr return I % serviceability; 5% ultimate Not applicable Shear core with outriggers to perimeter columns 17 m (56 ft) of soft clay over rock 25-m (82-it)-long 1.5-m (5-it)-diameter bored piles socketed and belled in rock 3.6 i (12 it) 11.5 m (38 ft) 420 mm (16.5 in.) 6.8 m (22 ft 4 in.) Posttensioned concrete 130-mm (5-in.) reinforced concrete 1350 mm (53 in.) in diameter 6.8 m (22 ft 4 in.) Concrete. MI to 35 MPa (8600 to 5000 psi) Concrete shear walls 600 mm (24 in.) max Concrete. 45 to 35 MPa (6-100 to 5000 psi)

Waterfront Place is a 42-level reinforced concrete framed office tower, located at tile rivcr edke of Brisbane's central business district on a 15,000-m' (160,000-flZ)site (Fig. 4.76). A steel-level plaza provides access to the river edge for the public, whereas bclow and abow river level there is parking for 500 cars. River cdge boardwalks connect

174


[Chap. 4

S e c t 4.31


175

ncifhboring developmenis with thl: p1311. ilnd mooring is pro!,ldedon the a;1ierfroot for plc~surr.craft,tour boats, and ferries. The 42-level tower provides 36 office floors, three plant-room floors, a ground-floor foyer, and two basements. The configuration of a typical floor provides 12 m (40 ft) of column-free space between core and glass line, with four cantilevered bay windows on both the east and west facades, effeclively contributing 10 "corner" windows on each floor (Fig. 4.77). High-rise buildings taller than approximately 35 stories may not be structurally cconomical if the core alone is used to resist wind loads. This is particularly thc case for a building rectangular in plan loaded about its weak axis. Such was the case with Waterfront Place, which has 40 levels above plaza level. Wind tunnel model testing was undertaken, and the results indicated that it would be impractical to use the core to fully withstand wind forces. Wall thicknesses and reinforcement quantities would be excessive, as would be the sway of the building in the east-west direction. Instead the design concept was changed to that of a core-perimeter interaction structural system where the core "tube" is connected to the exterior columns at specific locntions, in this case at the plant room at levels 26 and 27 (Fig. 4.78). At these levels, four stilC"wind beams" cantilevering from the core are connected to perimeter transfer beams between three columns on each lace ofthe building. This induces participation ofthe axial capacity of the exterior columns in resisting wind-induced loading (Fig. 4.79). The core is used to resist all horizontal shear, but vertical shear resistance is transferred from the core to the exterior columns, thereby utilizing the total overturning capacity of the SINClUre.

Fig. 4.76 Wnlcrlront Place, Brirbone, Auztrolln.

I

3

Fig. 4.77 Typieul rnidrire noor plon; WnlcrCront Plorc.

I

.

Y__I


176

Sect. 4.31

[Chap. 4


177

Research indicated that the most effective location for the wind beams was at the top levels of the tower. However, this was impractical due lo the stepped profile of the topmost three plant levels (levels 37, 38, and 39) and the marketing potential of tenancy 29 to 36. As a consequence the wind beams were placed at levels 26 and 27. two . ' levels floors containine mechanical rooms and ofice space. This loca~ion~hri~htcned the possibility of diifcrentiai axial shoncning between the reinforced concrele core and the colu~nns.A ,lee1 joint was developed to link thc outrieeer beams with the fransfer beams at the columns lo allow controlled slippage .. - as Lhe dilfcreniial movement occurred. Thc use of the cantiicvcring wind beam syslem introduced some architeclural and siructural cncinecrine dcsirn challenecs. In order to rcrist the 820-tonne (180.000-lbl l o ~ dappiied;o thc end ofcach wind hiam. the h e m s had lo be t u o stories high and 900 mm (36 in.) thick and prefenbly without any penetrationr. To have no pcncvations would have meant the ldss of o f f i e soace: th&efore laree were made in these - ooenines . beams. This precluded the use of conventional beam design theory for these beams. Consequently the beams were desipned using "strut and tie" theory. Concrete of 55MPn ff800-osil streneth and ties cinsistine i f 45 36-mm f 1.4-in.1-diamcler bars were required to ;ra;mit &! working load of 86 tonnes (1 80,000 lb) per beam. The noor slabs at levels 26 and 28. which are locally 420 mm (16.5 in.) thick. participate in the wind-beam action by working as flanges for the wind beams. The force paths in the wind beams and the floor slabs arc shown in Figs. 4.79.4.80, and 4.81. Differential venical shrinkaee betureen core and ~erimetcrcolumns at level 26 subsequent to construction of the entire building was caiculated. Consvuclion history, material propenies, and in-service loads were used in this calculation.

.

CORE

--

WALLS

- -

WIND BEAMS

COLUMN LOAD SPECIAL

-

JOINT

.

Fig. 4.78

.

- -_ - _A * . TOWER AND P L A Z A E A S T WEST SECTION Tower nnd plnm wt-wstserlian: Waterfront Place.

+L-LrL FIG. 4.79

Level 26 noor plun-r,,reer

trnnrmlttcd througtlnnorLanungc"; Wnlcrrronl Plncc.


[Chap. 4

Sect. 4.31


179

The wind beams are extremely stiff. Design load deflection was calculated to be only 2 mm (0.08 in.). Unless some means of allowing movement between wind beam and columns was found, the wind beams would have attempted to support the 15 stories above level 26 and several stories below. This it could not do, and s w c t u n l failure would have resulted. A sliding friction joint between wind beams and the column transfer beams was developed. This is shown in Fig. 4.82. The joint is in effect a multiple clutch with the slip load determined by the clamping force provided by the through bolts. Tests were canied out at the Queensland University of Technology to determine the co-efficient of friction between the brake-pad material and the stainless-steel plates. Size, clamping force. and loading rate effects were investigated. Typical load-slip graphs are shown in Fig. 4.83. Eoch joint is fitted with four strain gauges to monitor stresses in the plates and hence the load being transferred through thePclutch." This allows the clamping force to be adjusted to slip at the required design load. When the clamping force is finally adjusted, it will not require any fudher adjustment in its life. A typicnl plot ofstress versus time for one of the joints is shown in Fig. 4.84.

Fig. 4.80 Str~Ulietmrr-rt~rce up; \Vulcrrronl Ploec.

Fig. 4.81

SlruUtic truss-rorec

dcmn:

Il'ulurlronl t'larc.

180

[Chap. 4


!

Sect. 4.31

I81


75% of maximum

Slip (mm)

Section

9 Slip (rnrn) Fig. 1.83

Friction ! e r e Wolerfrunt Place.

Elevation on slip joint

T I M E (WEEKS1

Plan detail of slip ioint

rig.4.82

Slip joint; \\'alcrfmnt Plituc.

Fig. 4.81

Typicnl rlruin-gouge rcudingr on vind-beam juinl: \!'nlerfrunl Pincc.

I


[Chap.

Two Prudential Plaza Chicago, Illinois, USA

Architect Structural engineer Year of completion Height from street to roof Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity Maximum lateral deflection Design fundamental period Design ncceleration Design damping Eanhquake loading Type of structure Foundation conditions Footing type Typical floor Story height Beam span Beam depth Beam spacing Slab

Loebe Schlossman and Hackl CBM Engineers. Inc. 1990 278 m (912 ft) 64 5 Office Concrete to level 59, steel above 4 kPa (80 psf) 31 d s c c (70 mph) 488 and 419 mm (19.2 and 16.5 in.). 50-yl return 7.2.5.8. 4.4 sec 19 mg peak. IO-yr return 2% serviceability Not applicable Shear core with outrigger beams and perimeter frame 14-m (45-ft) fill over 11-m (35-ft) hardpan over rock 15-m (50-ft) hardpan caissons and 24-m (80-fl) rock caissons 3.96 m (13 ft) 12.2 m (40 ft) 610 mm (24 in.) 6.1 m (20 ft) One-way 150-mm (6-in.) slabs, typically 28-MPa (4000-psi) concrete

Columns Size at ground noor

890 by 1140 mm (35 by 45 in.) at 6.1-m (20-ft) centers Material Concrete, 84 MPa (12.000 psi) . Core Shear walls 840,610. 460 mm (33. 24. 18 in.) thick at ground floor Material Concrete, 84 MPa 112.nnn ,,;r ,--- r-., Two Prudential Plaza, a 64-story office building, is located in downtown Chicago, Illin01"Fig. 4.85). At the time of completion it was the second tallest concrete building in the world. The building has a gross area of about 130.000 m' (1.4 million ft'). It has five levels of basement, which are primarily used as a parking garage for 325 cars. The low.

~

~

.

Fig. 4.85 Tno Prudcnlinl Plaza. Clxicngu. Illinois. ICoirnen ojCBAl E , r ~ t n ~ . ~i,,c rr

)


184


[Chap. 4

cst bxcment is locatrd nt elev3lion -6.477 m (-21 fi 3 in.) CCD (Chicago Cily dntom). The lobb) ofthe building is locatrd at elevation T 10.668 m ( 7 3 5 ft 0 in.) CCD. Levels 4.5.38, nnd 39 are used for mecltmical equipment, and level59 for siorace of uindow-washing equipment Level 58 is the last office floor. Levels above 59 are mcchnnical floors. The building- is rectannular at lhe lower levels. 37.4 bv 40.4 m (122 ft 6 in. bv 132 ft 8 in.), but becomes square at the fifty-ninth floor due lo a series of rcrb3ck on the nonh :and south faces. Above lhr. fifty-ninth floor. lhr building sti\nq tapering to form a "cone held." which is torrrred bv a 25-m (82-11)architectural soirc. The 10" rlcvniion of the spire is 304.8 m ( i i 0 0 f t j c c (~~ i g1.86). . The lateral stiffness in each direction is mainly provided by the four shear walls located in lhe core of the buildine. Their deoth is 13.8 m (45 ft 4 in.). The flanees are 838 rnm (33 in.) thick a d the wzb; are 610 aid 380 mm ( i 4 and 15 /n.) thick Tor the intenor and extcrinr ualls. rcspeclively. The south shear wall drops off nt level 27 where&$ the nonlt w11l drorrs off at leiel 40. Tile middle ualls conlinue 111 !he wav lo floor 59. The flanges of wails arc connected together in the north-south direction by k86-mm (27in.)-deep link beams. The columns at the east and west faces are soaced at 6.1-m (20-ft) centers.. whereas . on the north and south laces they arc spaced at 9.15 m (30 11). The typical extrnor column sire vJries from 8'10 by 1140 mnl (35 hy 35 in.) at the lo\ver floors to 600 h\ 600 mm (24 bv 24 in.) e the ton floor;. A maximum concrete streneth of 84 MPe 11$.000 psi) u'as used for columns and shear walls at the lower floors. The concrete strength was reduced to 42 MPa (6000 psi) at the upper floors. The floor beams have clear snan 3 aooroximarelv I 2 m (40 . ft). from the oerimetcr columns to the shear r\,311 cure. Typical floor bcam size is 965 mm (38 in.) by 610 lrlm (24 in.) deep. Floor framing consists of a 150-mm (6-in)-thick norrn>l-weightconcrelc sllb u,ith o clear span of 5 13 in (16 f l I0 in.) be1ncr.n rhc noor beams. spaced st 6 I m (20 ft) centcr5. In addillon tu carrying the gmvity load. rbe floor beams carry some 01 the wind shear frum the shear ivalls to the outside columns. At the fortieth and 111cfillynineth floors the core is tied to the outside columns at two locations with the helo, of oilrigger ivnlls to control the wnd drift and reduce Ihe overturning monlent in thu core shear walls The beams are 5.03 m (16 f16 in.) deep (in other words. a full nory high) butwcci~floors 39 and 10 ind 1.68 m (5 11 5 in.). deep. ar floor 59. The foundation system consists of straight shaft caissons up to 3 m (10 ft) in diameter. These caissons rest on the bedrock, which is about 30 m (100 fr) below the existing ground level. The allowable bearing capacity of this rock is 19 MPa (200 tonlft'). To fully utilize this capacity, 56-MPa (8000-psi) concrete was used in caissons. In the parkinggange adjacent to the main tower, belled caissons were used. These caissons extend to hardpan about 21 m (70 ft) below existing grade. The allowable bearing capacity for this hardpan is about 3.4 MPa (36 todft').

+1!22'-6'+

- .

.

-

a

~

.

..

-.

:% C

m:

X

at

LON

\

Fig. 4.86

Typlcnl floor plnru: Two Prudenlinl Plnm.

186


[Chap. 4

7999 Broadway Denver, Colorado, USA Architect Structural engineer Year of completion Height from street to roof Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity Maximum lateral dctlcction Earthquake loading Type of structure Footing type Typicnl floor Story height Beam span Beam depth Beam spacing Slab Columns Size at ground level Spacing Core Material

C.W. Fentrcss and Associates P.C. Sevemd Associates 1985 198 m (650 it) 43 3 Office Concrete corc, srcel frame 2.5 W a (50 psi) 36 mlsec (80 mph) HI400 USA zone 1 Concrete corc with outriggers to perimeter stccl fmme Caissons

S e c t 4.31


formed core. The perimeter frames act with the core to resist lateral loads and effects due to the eccentric form of the building. Footings comprise cast-in-place caissons founded in claystone and sandstone some I5 m (50 ft) below grade. A single caisson supports each column, and caissons at a minimum spacing of three caisson diametem are distributed around the core. The design end bearing pressure was 3350 kPa (70,000 psO, and skin friction in the rock was 335 W a (7000 psf).

3.81 m ( I 2 ft 6 in.) 9.14m (30 it) 406 mm (16 in.) 3.43 m (I l ft 3 in.) 83-mm (3.25-in.) lightweight concrete on 50-mm (2411.) metal deck W350 by 1088 kglm (W14 by 730) 4.57 m (15 ft) Shear walls 610 mm (24 in.) thick at ground floor Concrete, 42 to 28 MPa (6000 to 4000 psi)

1999 Broadway is an unusual 43-story office building built on a triangular site. The presence of an historic church on pan of the site resulted in the plan of the office building having the shape of an arrowhead which wraps around the church, creating from it a piece of sculpture on the plaza (Fig. 4.87). The facade comprises alternating bands of limestone and green reflective glass and a concave cunain wall having seven angled facets around and above the church. The building has been raised 15 m (50 ft) above ground on 22 limestone-clad columns to create views ofthe church from within. The slroclurc cunsists of^ rr.inforccd concrde curvicc core. stccl perimeter columns. and stcci flnor b s m s and g~rdcrsco~nposilewith tile rlah. At Ic\r.lr 3 10 5 and 29 lo 31. two-story-high outrigger trusses between core and perimeter columns reduce thc lateral deflection. Girders are connected to plates field-welded to cast-in plates in the slip-

.-.

Fig. 4.87 Typicnl noor plnn; 1999 Broadway, Denver, Colorado.



[Chap. 4

Citibank Plaza Hong Kong

Architect Structural engineer Year of completion Height from street to roof Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity Maximum laleral deflection Eanhquake loading Type of structure Foundation conditions Footing type Typical floor Story heighr Beam span Beam depth Beam spacing Columns Size at ground floor Spacing Material Core Material

Rocco Design Partners Ove Amp and Partners 1992 220 m (722 it) 41 4 Office Reinforced and posttensioned concrete 5 kPa (104 psO 64 mlsec (144 mph). 50-yr return, 3-scc gust 370 mm (14.5 in.). for50-yrrcturn period wind Not applicable Concrete core with outriggers Dccomposed granite over granite bedrock Hand-dug caissons to rock 3.9 m (12.8 it) 9.4 m (31 ft) 500-mm (20-in.)-deep ribbed slab Reinforced concrete ribbed slab 3000 by 1900 mm (120 by 75 in.) mnr 9.4 rn (3 1 ft) Concrete with 40-MPa (5800-psi) cube strength Shear walls 1.0 and I.?, m (3.3 and 4 it) thick at base Concrete with 1 0 MPa (5800-psi) cube strength

The four-level basement of Citibank Plma (Fig. 4.88) was formed using top-down construction techniques. Stability \vas achieved with the internal cores acting in combination with the perimeter columns, using outriggers at two levels (Fig. 4.89). Part o f t h e building is seated above a major entryway to a neighboring development. To achieve this, the perimeter columns rake outrvnrd along one face of the building over a one-story height (Fig. 4.90). The resulting lateral forces were resistcd by a prestressed beam system tied back to the internal cores. prestressing being applied in stages as construction progressed.

hg. 4.88

Cllibank

Plnzo. Hung Kong. (Cac,ncrr o f o l e A n q orxdporinrrr]

190


Sect. 4.31


7B.& Fig. 4.89 Fioorplnn; Citibnnk Plnrs.

Pig. 4.90

Section through mking columns; Cilibnnk Plorn.

191


192

4.4 7

[Chap. 4

Tubular Systems

Sect 4.41

TUBULAR SYSTEMS Historical Perspective

The development of the initial generation o f tubular systems for tall buildings can be t.. r... n r ~ dto . .- the concurrent evolution o f reinforced concrete construction followine World War 11. Prior to the early 1960s. reinforced concrete was utilized primarily for low-rise construction of only a few stories i n height. Ti~esrbuildin~swere chancterized by planar Viercndeel beak and column arraneemcnts with wid;soacines between membcrs. The basic ~ncfficieacyof the frame wcleln for rsioforc:d concrete buildings or more t1r~11 ahnut I5 slnrlcs rusulttd in m:,ober proportinns or prohthit~te.ire and rlruclur;~l material cost or~miums.and thus such svitcms were economicallv inviable. Concrete shear uall systems arr;lnged i \ ~ t b i111s ~ t huilding int~.riurc o ~ l be d utilirud. b.11 lhcy uerr. oftc~tof insul'licicnt sire for aliifne,~and rcsil;,ncs ;lgain%torcrturnlng. Thi, Icd tu lhr. dcvclonment ofstructur~lsvstems with a hirhcrdcrrcc orcfficicncv toward lateral load rci\t.lncs lor 1311~.rh~ildings.The nntlon n i i fully t h r ~ u ~ d i m c n ~ i oiruclur;~l naI sjrlum utiliz~ncth~.cnlir~.build:nc inertin lo rcrirl l s l ~ . r loads ~i b:wn lo cmcrec ;I[ lhls time. Thc main ,orooonent o f thi;desien trcnd was Fszlur Khan. who svstem~icallv , ,oursucd a logical evolution of tali building structural systems. The pervssivc international-style approach 10 archilecture a1 the lime included lergcr open spaces with longer spans, a well-oraanized core. and a clcarlv ocrceotiblc interior-exterior column grid. Wilhin this ;~rui~iteclur:tl 2nd ecnnnmic clinl:!lc. Ihc fr-1111cdIuhi. h).\tcin i n rd IIIOICL.~ c~lncrct: i : t l l hi. \c:n ;lr bull) ;I n;~ttlr-l2nJ 3,) innur:.l!\u ~ : ~ ~ I O ~ in I I tidl I S Ib.tilcling II
-

~

. -

-

~

-

~

,.

2

-

.

.

The Framed Tube

-

-

The orcnniration ofthe framed tubc svstcm is acncrallv one ofciosclv soaccd exterior < . columns and deep spandrel bcama rigidly connected together. with the enlire assemblaee continuous aionr each facade and around the building corners. The system is a loekal cxansion o f the moment resirline frame. whcrebv the beam and coiumn s t i r ussses are 1 1 1 c r r 3 dram;!ric:ill! ~d hg ruducirlg ltle clear sp;tn dirnensionr and incrr3stng thl: rnclnbcr d c ~ ~ l tThd s . monoiilllic oaturr. u f rcinfurccd corlcrcte runrlructinn is ide311y suited for sucha svstem. in\,olvinr- fully. continuous interconnections of the frame members. Depending on the heighl and dimensions of the building, exterior column spacings should be on the order o f 1.5 to 4.5 m (4.9 lo 14.8 ft) on center maximum. Spandrel beam de~thsfor normal office or residentinl occupancy applications are t v ~ i c a l l v600 to 1200 m k 124 to 47 in.). The resuitine arranremcnt a o ~ r ~ x i m a t eastub; cantilcvcrcd

-

svsiem costs. Exterior columns mav eliminate the need for intermediate vcrtical mullion elcntunls of ti>cuur1;lin \$:dl 133~11311) ur 1.)1311g. A iIrUClUr.lli51 ?Xpr~:isinnfur tile e \ l ~ ridr envelope msy hc lull? rc;~liz~.J b! <\pnslng IIIC~.xldrinrtuhul;,r mernb~.~;,IIIUS dclinong >hexil1,>r.~!-r31Jen~.str:,li~~~>. TI,< ~ L i l l d n !!L~i l l l i).st?rn 15 1hc.n infilled i,etre~.n the coi&~ and spandrel beams. with II resultino reduction i n claddine cost. An eariv * exampie o f such a iubuiar b u i l d i n in rcinforccd~oncreteis shown i n Fig. 4.91. The behavior ofrrarnrd tubes under Interel load is indicated in Fig. 4.92, which shows the distribution o f axial forces i n the exterior columns. The more the distribution is similar to that o f a fully rigid box cantilevered at the base, the more efficient the system will be. For the case o f a solid-\$,all tube. [he distribution of axial forces would be expected to bc uniform over the windn.nrd and Iccivard \tSsllsand linear over the sidcrvnlls. As the tubular walls are punched, creating the beam-column frame, shear frame deformations

Fig. 4.91

Brunrwiek Building, Cl~icugo.lllinoir.

193

~ d ~ r ~r o a a~ o n e s ~ s r ~ nhysrems g

[Chap. 4

Sect 4.41

Tubular Systems

ore introduced duc lo sltear;lnd flcxurc i n the tubular mumbcrs as u u l l as routtons 01thc ntcmber loin&. This rcdtlccs the eilecti\e stlffnrss Of lbe systeln as a cantilever. The extent to which h e actual axial load distribution i n the tube columns dcoartr;- from the ~. idesl is rcnndd the ",hear lag effect." I n behavioral terms. the forces i n the colurnns toaard lltu lniddls u i t h e flange frnmus lq behind those nearer the conter and are tltua less than fully ulllized. Limiting the shear lag ellect is essential fnr oplimal de\.elopmen~o f the :ubulnr system. A rc3son;1blr. objcctit,e is l o strivc toward a1 least 7% effiricncy sucll [hat the cantilever component in llte oterall rystcln deflection ondsr u i n d load dnminatus. Thc 1r;tmed tubu i n structural slsel rsquirus wcldinp oftlte heam-column join1 tu du!clop rigidity and continuily. Tllc ~ o n n 3 t i o n ofahric~tcd f 1rr.u elemenlr, rrltcre all welding is p:rformcd i n llte shop i n a horizonwl position, has made the alrsl-frame tuhe s ~ $ . tem more practical and efficienl, as shown i n Fie. 4.93. The trees are then erected-bv ~, bolting the ipandrcl bcotn* togelher ak Inidspan near thc pnint o f innrxion. The column spacing i n steel-fmntrd tubular buildings lnust be ~.ralualcdto b~l;tnce llte nerds for higher cantilever dfiicicauy throuph clorcr anactnkr rvitll increased F ~ h r i cation costs. The use ordeeper, built-up sectioni versus roiled G m b c r s is also a matter o f cost-effectiveness. A survey o f steel quantities for completed tubular buildings is s l ~ o w nin Fig. 4.94. The buildings range from 40 to 110 stories. and column spacings generally range from 3 to 4.5 m (10 to 15 ft) on center, with spacings as close as I m (3.28 ft) i n the case of the 110-slory World Tradc Center twin towers. New York (fig. 4.95). These towers are examples whereby the structuralist notion o f a punched wall tube with extremely close exterior columns is architeclurally exploited to express visually the inherent venicality o f the high-rise building.

~.

~

Fig. 4.93

Typical tree crcction uniL

Cantilever componenl Shear frame component

I

I

Elevation

Sway

Dlslribullon w l h w shear lag Actual axial stress

shear lag Wind lorce

Fg.4.92

t

Frulncd tulle i~clv~rior.

HEIGHT (in) Vlg. 4.94

Conlilcv~rsystems, stccl qunntity versus hciglxt

195


196 3

The Trussed Tube

,\, ihc tubular concept; were being dcreloprd in ihr 19605, il became Jppdrent that

thcrr was a cenain building height n n g e for which the framed tube could be elficlenll) adaoled. For rrry 1311 buildings. lhe dense grid of beam and column members has a d t =id;d impact onihe facade aGhitecture. The need lo control shear lag and improve the

I

9

\Ysrld Trndc Center, New Y n k .

Tubular Systems

[Chap. 4

lCo,mrry rfLrrlii. Robcrrrnr, n ~ i ~ l . i r m r 1

systemefficiency can only be realized by relatively small perforations in the tubular walls. The problem becomes particularly acute at the base of the building, where archi1 @$ teclural plannine lypically. demands open access to the bulldine interio; from ihe surrounding infrastruaurd will1 as lilrlc encumhr;mre 2s possible {om the sxlerior fr;~mek.; n,orI;. A number ofulcgant solutians inrolving Ole transfer and rcmovnl oftlle e~turi,,r columns at the base of the building have been iomulated (Figs. 4.91.4.95, and 4.96). '".~~t~pcharnc~eristically include an associated material premium. The trussed tube system represents a classic solution for a tube uniquely suited to thc qualities and c h m c l e r of structural steel. The ideal tubularsyslem is one which intercon-

I.,

~. Lateral Load Resisting Systems

,

.

Sect. 4.41

[Chap. 4

Tubular Systems

The bundled tubc concept allows for wider column spacings in the lubulu walls lhan w o ~ ~ ibr d oossible with unlv lhc eatrrior framed lube form. 11 is his sp3cine uhicll rnnkes it possible to place inierior frame lines withoul setiousiy c ~ m ~ r o ~ i s i n g ~ i n l e r i o r space planning. In principle, any closed-form shapemay be used to create the bundled form (see Fig. 4.102). The ability to modulate the cells vertically can create a powerful vocabulary for a variety of dynnmic shapes. The bundled lube principle therefore offers great latitude in the architecturnl plnnning of a very la11 building.

*.?;s.::!:s .,2

,

ENDCHANNEL TRUSSEDTUQE

MOMENT RESISTING FRAME OR

FRAMED TUBE

Fig. 4.99 Pnrtiul Lubulnr ryslcrn.

-COLUMN

AXIAL LOADS DUE TO WIND CASE (A1

::: s.. 0

0

114 PLANS

ttttttt Fig. 4.98 Trurrcd tubc, grurity loud rrdlrlribstion.

TUBE

TYPE

EXT. TUBE

EXT.

SIZE

69m x 69m

46m r 4 8 m

HIW

6.65

9.60

0c0101

0.61

0.75

EXT. TUBE

BUNOLEO TUBE

23m x 23m 19.00 0.66

6.65 0.78

Fig. 4.100 Sludy of tul~ulorcllicicnry.

69m x 6 9 m


202

Sect. 4.41

[Chap. 4

Tubular Systems ,03

PROJECT DESCR~PT~ONS,FRAMED TUBES

r

COMPRESSIVE STRESS

Amoco Building Chicago, Nlinois, USA Architect

STRESS

(a1

FRAIAING PLAN

1:ig. 4.101

Ibl

Uundlrd

SHEAR LAG BEHAVIOR

tube bchuriur: Sears Tower, Clnicugn, lilineir.

Footing type

Typical floor Story height Truss span Truss depth Truss spacing Material Slab

Columns Spacing Material Core

i

I

3.86 m (12 ft 8 in.) 13.7 m (45 fr) 965 mm (38 in.) 3.05 m (10 ft) Swctural steel 140-mm (5.5-in.) lightweight concrete slab; 35 MPa (5000 psi) on 38-mm (1.5in.) steel deck Folded plate, size not available 3.05 m (10 ft) center lo center Stcel, grade 250 MPa (36 ksi) Structural steel frames carrying gravity loads only

Fig. 4.102 hlndular tuher.

/, ,!j

l

Edward Durrell Stone with The Perkins and Will Partnership The Perkins and Will Partnership 1973 342 m (1123 A) 82. 5 Office Structural steel 4 Wa (80 psO 1.4 X Chicago code HI400 Not applicable Perimeter fnmcd tube Silty clay, sand, and gravel over massive dolomitic limestone Concrete caissons. 1.5 to 3.8 m (5 fl to 10 ft 3 in.) in diameter. approximarely 24 m (79 ft) long

Swctural engineer Yenr of completion Height from street to roof Number of stories Number of levels below ground Building use Frnme material Typical floor live load Basic wind velocity Design wind load deflection Earthquake loading Type of svucture Foundation conditions

MASTER GRID OF COLUMNS AT BASE

1

The innovative structural concept applied to this 342-m (1 123-ft)-high building resulted from the desire to achieve an efficient, simple to erect structure utilizing a perimeter tube whose behavior would closelv anoroximate that o i a oure cantilever (Fie. 4.103). . The lubc compriaca uolulnns uf V-rhaped kcel plaw 3nd du:p ubxnnul.shapud bcnlplat: spandrel bcams shop-fabncalcd Inlo 3-stor) Irccs. Tb:r< arc 64 sucll columns ;,t 3-

.

..

-

I

I

f&'


204

Sect. 4.41

[Chap. 4

Tubular Systems

205

i: : i.

m (10-11) centers around the perimeter, plus solid steel plate walls to the reentrant corners. The free inner edges of the columns are stiffened by heavy angle sections. Connections between spandrel beams comprise simple high-strength bolted joinL5, whereas column splices are welded at lower stories and bolted or welded at upper stories. The floors are generally supported by 13.7-111 (45-11)-span trusses at 3-m ( 10-ft) centers. Trusses at successive floors attach to alternate sides of a column to effectively cre-

Fig. 4.103

Amoco Uutldtng, Chtcugo, lllinuis. (Pl>ninh? Jrrr BairB.)

::

ate a concentric load in the vlane of the wall. At the buildine corners the shorter-soan diagonal girder and attached'beams are wide-flange sections. ?he 4000 essentially identical lrusses and the comer beams were mass-produced in an assembly line. r irom thin steel olate .;oread Economv was achieved bv creatine a ~ e r i m e l c frame !,.,.i,over as much of the facade as was architecturally acceptable and by maximizing the ;?:?'number of geometrically identical elements. The arraneement also negated the need for sublramine - for the exterior curtain wall. The space within the V-shaped columns was used Tor air s h a h and hot and chilled water pipes for the perimeter zone. The interior zones were s u e ~ l i e dfrom vertical shafts in the bore The building contains45.900 lonnes (50.506 tons) ofsteel,ofwhich 37% is in beams and trusses and 63% in columns and reentrant corner wnlls.The r\reieht ofsteel amounts

- .

'

.

. -.

Sect. 4 41 181 West Madison Street Chicago, Illinois, USA

Archilcct Structural engineer Year of completion Height from streel to roof Number of stories Number of levels below ground Building use Frame malcrial Typical floor live load Bnsic wind selocily Maximum lateral deflection Design fundemenla1 pcriod Design acceleration Design damping Earthquake loading Type of slructure Foundation condiiions Footing type

Typical floor Story height Benm span Benm spacing Benm depth Slab Columns Spacing blalcrial Core Thickness a1 ground floor

Cesar Pelli and Associates with Shaw and Associates Cohen-Barreto-Mareherlas Inc. 1990 207 m (680 ft) 50 1 omce Concrete corc, steel perimeter frame 2.5 kPa (50 psf) -13 mlsec (97 mph). IOO-yr rclum period 400 mm (16 in.). IOO-yr return period 8.3. 6.7 see horizontal: 6.3 sec lorsion 18.4 mg peak I .5% senaiceability Not applicable Concrete core lube with stccl perimeter tuhc Hardpan. 1.7-MPa ( 2 0 . ~ ~capacity 0 Caissons. 24 m (80 ft) long. 1370 mm (4 fl 6 in.) in diameter, belled to 3-m (IO-ft) diameter 3.96 m (13 ft) 10.36 m (34 ft) 3.05 m (10 fr) 530 mm (21 in.) 140-mm (5.5-in.) composite metal deck W350 by 745 kglm (14 in. by 500 Iblft) 6.1 m (20 ft) Steel, grade A572. 350 MPa (50 ksi) Central concrete corc. 62 lo 28 MPa (9000 to 4000 psi) 400. 500, 660 mm (16, 20.26 in.)

The I 81 West Madison Sbcet lowe r is a 50-story office building located at Madison and Wells Streets in [he Chicago Loog1 (Fig. 4.104). It is a point lower, with multiple setbacks and a distinctive cro\r8nthat recalls the sculpturally expressive skyscrapers of the 1920s. This is also n tower for the 1990s. It is clearly organized as a square floor plen with n center square concrelc core and column-free office space (Fig. 4.105).

Fig. 4.104

181 \Veal hlidiron Slrccl, Chicngn, illlnoi~


208

[Chap. 4

181 West Madison is the tallest combination core building in Chicago. The central concrete core is surrounded bv a sWctuml steel frame and a com~ositefloor svstem. The squa~ccore is 50 stories tA11. for a totnl height of 207 m (680 fi). rile core and columns a the base of ihc building are rupponed by cnissons and gradc heams. Of the cnissons in the uroiecC 25% existed. Transfer-crade beams between new and existing cnissons were uskd io take the tower's wind an; gravity loads. The foundation wall on the east side of 181 West Madison required underpinning as it is a common wall with its neighbor, 10 South LaSalle StreeL Interior spans of 13.1 m (13 ft) ailowa column-free interior space for maximum user flexibility. The many setbacks at the top of the building require all the perimeter columns to be fransferred several times. In addition, the columns on either side of the

I

I

I

I

I

@?

sect. 4.41

Tubular Systems

loading dock at ground level are also transferred to increase clearance for trucks. E stcel is less than 59 kg/m2 (12 psO. lobby. Clad in warm white, grey, and green marble, the lobby's

;.?&$

I

-

-

,

-

I -+ I I I I I I I Fig. 4.105 8th to 14118 noor rramine pian;

181 \Vest hlndirun S t r c c ~

210


[Chap. 4

Sect. 4.41

Tubular Systems

AT&T Corporate Center Chicago, Illinois, USA Architect

Skidmore Owings and Mcrrill

Structural engineer

Skidmore Owings and Merrill 1989

Year of completion Height from street to roof

270 m (886 R)

Number o f stories

61

Number o f levels belo\%,ground

2

Building use

Oflicc

Frame material

Conlpositr slccl-concrete perimeter liarlie. steel interior columns. stccl floor beams

Typical floor live load

4 kPa (80 psr) lct,cls 3 to 30: 2.5 kPa (.iO psi) Ic\,c~s 31 to 59

Basic wind \,elocity Maximunt lateral deflection

35 mlsec (78 rnplt). IOU-yr return HI700

Design fundantcntal period

6.5 sec

Design acceleration

20 rng. IO-yr return

Dcsign damping

I to l.5<> aurrice;lhility Not applicable

Earthquake looding Type o f structure

Exterior concrcte-fromcd tubc with iliterior frfieity-luad culunins. t m r r s . :lnd bei~o~s

Foundation conditions

18 m (60 i t ) o f clay over liardpan

Footing type

Belled caissons on 1iardp;ln

Typical floor Story lheigltt

4.0111 (13 ft 2 in.)

Truss span

14.6 m (48 i t )

Truss depth

914 rnm (36 in.) 4 . 6 m ( l 5 It)

Truss spacing Illaterial

Steel. grade 230 and 350 h,IP;1(36 and 50 ksi)

Slah

63-nun (1.5-in.) light\\,cight cuncrctc on 76-mm (3-in.) o~etaldeck

Columns Size at ground lloor

I422 by 813 oim (56 by 32 in.)

Spacing

4.6 ~n( 1 I 5 111

ivlnterial

Nornt;il-\\,cigltt concrstc, 56 tu 35 MP;t (5000 to SUOU psi)

Cure

Steel he;~msand columns for gravity load only

Tlte ATSlT Cnrporatc Center (Fig. 4.106) consists o f a 61-story uflicu to\i,cr \\,it11 rentable areas o f fluor plates ranging front 3250 m2 (35.000 1'1') on the lowest floors to

. .

Fig. 4.1116

ATST Corpunltc Ccntcr, C ~ I E I ~Illtnots. ~ C ~ . (Pimr
I

216


[Chap. 4

I#

Sect. 4.41

Tubular Systems

~

TYPICAL HIGH-.RISE M O R

TYPICAL LOW.RISE. F L W R

Fig. 4.lllY

Fig. 4.108

Gctwgio P I I E ~A~ tCl l .m l ~ ,Gcorgiu.

Typirni flours; Gcorgio Pocific.


[Chap. 4

222'-0" Fig. 4.illl

Pruming piun; Gcargiu Pacific.

Fig. 4.111

Snalooth locnde; Georgia Pneilic


[Chap. 4

450 Lexington Avenue N e w York, N. Y., USA

Architect Structural engineer Year 01completion Heighl from street to roof Number 01stories Number 01lc\pelsbelow ground Building use Framc malerial Typical floor live load Basic wind velocity hlaximum lateral dencclion Design lundnmental period Design acceleration Design damping Earthquake loading Typc of structure Foundation conditions Footing type Typical noor SIOVheight Bcnm span Beam depth Beam spacing Malerial Slab Columns Spacing Material Core

Skidmore Owings and Mcrrill Olfice of Irwin G. Cantor 1992 168 m (550 h) 40 0 Olfice Steel 2.5 kPa (50 psfl 36 mhec (80 mpit) HljOO, 50-yr rcturn 5.5 sec Less than 20 m S peak 1Su No1 opplicablc Perimeter tube with broced core Rock. 4- to 6-hlPn (40- to 60-lon/lt') capacity Piers socketed into rock

Tubular Systems terference wilh train clearances. The key to the structural solution was the use of a egacolumn syslem. The megacolumn system lonns the "legs of a table," which carries e tower's gravity and wind loads within the existing building's shell (Fig. 4.113). Tlte megacolu~il~~s are placed 24.4 m (80 11) apart in the north-south direction and 1.8 m (170 11) apart in the east-west direction. Two are 6.1 by 7.6 m (20 by 25 ft) in p an. and two are 6.1 by 2.6 m (20 by 8.5 11). The plan sizes were governed by the avail-

3.81 m(12116in.) 13.4 m (44 fi) 460 mm (18 in.) 3.05 m (10 11) Stccl. grade 350 MPa (50 ksi) 64-mm (2.5-in.) concrete over 76-mm (3in.) metal deck 6.1 m (20 11) Steel. grade 350 hlPa (50 ksi) Braced steel. grade 350 hlPa (50 ksi)

Placing n high-rise tower abo\'e a landmark post olfice structure which sits dirrclly above a mnjor urban rail line is a highly formidable task, which requires an unusual and innovalive engineering concept. The 450 Lexington Avenue building (Fig. 4.112) is such o project and posed many challenges to lhe designers and conlractors. Thc existing landmark post ollice sits directly over the railroad tracks leading into New York City's Grand CcnIr.nl Station. The congested system of tracks made it impossible to bring t l ~ e54 totr'er columns down to the loundation. In addition, the track layouts ~otellyprecluded the placcnlenl of a conventional a,ind resisting system due lo

Fig. 1.1 13 450 Lcringlon ,\venue. New York.

Sect. 4.41

Tubular Systems

223

able space bcrween tracks. The megacolumns arc solid reinforced concrete as they rise from tltc foundation through tlie train area. At the first floor. theu are comnosed of a steel-fr3mud iruhs stru:tdre t01:111) enc3scd in cu,!crets. ~ . i t t Jioicrtrinn\ ) :i. ~UIL.U. R ' i ~ n rtu the third-flour - u ~ c c t. h ~ m . e e : t ~ ~ I ~ conne:t ~ n t ~ s to rnas\trc 76-11] 25.11,tall trusses. The trusses estcnd in both the nonh-south and east-rvcsl directions and connect all four megacolumns. Tlie resulting megaframe systcm was referred to as the "table ton." I t wa; the table top which picked up all the tower's columns and transferred their load to the mcgacolumns and to 13 strategically located con\'entional steel columns. The 12 intermediate columns reduce the truss spans bet\\,een llte megacolumns and aid i n thc sunnon o f zrauitv loads. Ultimatclv it was this frame which transferred all the ,, nind I t v ~ Jillid r gr3$it! Iu~JI to llle f o ~ n d ~ l i u n s . I l r e tlu\~hilityn l \IL.L.Imxdc i t the choice m3teri~1for 111~'luaer illttl lhc hdlk u f the merasustem. However. the concrete encasement added the needed mass and stiffness.

-

-

L

I

I

1

.

tween the adiucent train tracks iormcd concrcle wall columns. Composed o f 55-MPa (6000-psi) these walls supported the intcrmcdiate columns o f thc mega truss system above. Utilizing concrctc meant that the construction could proceed while the existing building above !\,as still in plnce. Tlie towcr.5 structural svstcm is cornnosed o f a oerimetcr tube of columns naced at 6.1-m (20-it) ccntcrs. The colunins arc W36s and W30s for maximum efficiency. The four corners of the pcrimotcr tube arc reiniorccd wilh a vertical Vierendeel truss. \tshich stirfens the tube sienificuntlv. Inside the corc t\\,o vertical trusses are locrttcd. \\,hich rise

concrete.

-

Tltc to\ve;'s lrasc suacc beeins at the sixth floor. ~ e l o $the i sixth floor. a11 the towcr's columns slope through tlic fiftli-floor mechanical area to positions upon the top chord ofthe megutrussea. Figure 4.1 I 4 illustrates thc thirteenth through thirty-fin1 odd floor framing plan. Rccagnition that the existing past office facility is a national landmark mcont that the facade had to be maintained in its current form, whereas the central area of the existing structure was demolislied lo make way for the new mcenstructurc. Consequently Lhe facade and one adjacent bay of the structure were left inplace, thereby providinf the slability to the facade while demolition and construction proceeded. The remaining bay of the existing structure \\,as known as the "douohnut" area. which \\.as uperaded struc. turalty ;lnd ulum;ltcl! \ia n u ~ ~ t loi ~ cthree-dimtnsiond r cump.ller models for 3n3lysi. L;ilr.r:ll a.nd vertical movement bad to be determined accuratciv due to tlic imnact u&n the [and-

-

ihe 90-year-old bunts and limcstonc perimeter.

-

I

226


[Chap. 4

As tall buildings become more slender, the dynamic behavior of thc building bccomes more critical. The results of the wind tunnel tests showed that the Mellon Bank lower (Fig. 4.1 15) had a vortex shedding problem with the cross-wind structural response being 50% larger than the response due to the code wind forces. A comoarison of various ootions for sliffeninr - and damninr" the svucmrc rvas studled and tl~ecusts ofuach method were estimolcd. I t ass C O I I C I U ~ L . ~11101111s L ~ S of:! S cornposits struclural systsm would bc most eco~tomicnl.Conwqucntly a concrr.lc.uncared

.

Tubular Systems . ,

{

1.%', ?:'

perimeter column system coupled with s composite steel pnd concrete supertruss wrrs utilized. Figure 4.1 I6 shows the resultin% floor plan. The concrete encasemenl of the steel structure provided the needed damping, stiffness, and additional strength. The cost analysis performed by the construction manager proved that the composite system resulted in a more economicnl structure lhan an allstccl building. Thc inter3ction of stcul nnd concrclc and their bchwior under the dcslgil loads were studied utilizing a detailed finite.elemunt nnalysis. The building's lateral system is formed by the comoosite nerimeter columns soaccd 7.95 m (9 11 B h.)on ccnlfr, forming a pcri&eler l u b C [ ~ i gi.117). . Typical composite column xhemes ulili7.c the slecl columns sol:ly fnr erection purposes, uith the bulk of thc v~.rticaIload carried by the concrete. In this slruclure, restrictions in the overall sire of the columns required the use of a truly shared composite system, with the concrete encasement and the steel columns each c a w i n g significant portions of the vertical load.

,

Fig..

hl~llnnDunk. Philodrlphin, Penns?.lvaniu.

... :::., .*,

.

.,>A. - , ,., . .. .

.,i?.. .,.

227

Fig.4.116 Framing plan for noors 14 l o 23; hlcilon Dank.

Tubular Systems

Sect. 4.41

- ..

229

Comolicatine the nroiect was that none of the 52 columns in the tower continued directly to the ground. Instead, all of the perimeter columns are either sloped o r picked up bv msses. The sloped column system enabled the transfer of columns into new positions, allowing for the enlargement of the lower floor plates while still maintaining col,:.u.mn-free 2. . lease space. .*.. - I , Depending on the architectural constraints, groups of columns slope at different floors. The sloped columns always form a symmevical system, whereby sloped columns on opposite sides of the floor balance out the overturning forces resulting from the slope. In numerous cases, columns are terminated upon pick-up tmsses, which are also sloped to link up with their repositioned supporting columns. A unique sloped column system occurs between the tenth and thirteenth floors, where the four inside comer columns are supported by an A-frame. Each A-frame generates significant lateral forces, which are all balanced out by again balancing one corner against the opposite corner. The floor diaphragm, being the link between all columns, plays a kcy role in transferring these balancing forces across the floor. The mosi critical diaphragms arc the fifth- and sixth-floor diaphragms where, in addition to supporting most of the sloped columns, the lateral wind forces are transferred from the nerimctcr to the core vertical w s s . r With some slopcd columns generating 7000 liN (450.000 lb) in lateral force, the designer chosc lo place a 13.4-111 (a-ft)-deep steel horizontal truss within the floor dian-hraam. ~hese'trusses helo transfer the bind forces to the core while passing the ~~r~~~~ sloped column forccs around the core to the opposite sloped column. At the core a vertical supertruss extends from the foundation up to the sixth floor. The supertruss is constructch of steel wide-flange shapes, with the four comer columns encased in 3000- by 3000- by 600-mm (10- by IO- by 7-ft)-thick L-shaped concrete shear walls, thereby forming a composite steel nnd concrete supenruss. The supenruss is divided into two parts, a large 13.7-111 (45-ft)-high truss between.levcls 6 and 3, and a single X truss on each face of the core, extending from the third level down to the foundation. The transfer of latcral loads out of the oerimeter and into the core at the sixth floor forntr an optimum conibin3tinn 01 the core and perimdtcr 1stur:il system,. Triinjfcmng the wind lateral force\ to the core ;it ilie r i ~ i hflour results in zero uplilt forccs upon the foundations.

-

I-+&&+.. Fig. 4.117

Eurl and

west lncrr of pcrirnelcr tui,c: i\lcllnn Dunk.

! 230


{Chap. 4

Tubular Systems

. S a d . 4.41

Sumitorno Life Insurance Building Okayama. Japan

Architect Structural engineer Year of completion Height from strcet to roof Number of stories Number of levels below ground Building use Frame material

Typical floor live load Maximum lateral dcnection Design fundamental period Design acceleration Design damping Earthquake loading Type of structure

Foundation conditions Footing type Typical floor Story height Beam span Beam depth Beam spacing Material Slab Columns Size at 2d floor Spacing Moterial Core

Nikken Sekkei Ltd. Nikken Sekkci Ltd. 1977 75.3 m (247 ft) 21 2 Office Structural steel from 4th noor up: concrete-encased structural steel and shear walls below i t h noor 3 kPa (60 psO Not available 2.08 sec transverse: 2.01 sec longitudinal Level 1 EQ, 20 mg; level 2 EQ, 25 mg 2% C = 0.14 Structural steel perimeter tube from 4th floor up: arched conciete-enca5ed steel fnrncs and shear u-alls from ground to first noor Gravel Raft

3.5 m (1 I ft 6 in.) 9.9 m (32 ft 6 in.) 700 mm (27.5 in.) 2.5 m (8 f t 2 in.) Steel, grade 400 MPa (58 ksi) 150-mm (6-in.) concrete on metal deck 400 by 300 mm (16 by 12 in.) 2.5 m (8 ft 2 in.) Steel, grade 190 MPa (70 ksi) Steel frame

The main structural system of this building is a nearly square tube structure, which employs a peripheral frame in an integrated fashion (Fig. 4.1 IS). In appearance, tile tube structure has no directionality. The peripheral hearing walls of the l'irst and second floors support the upper structure a ~ i dhave a large arcli-shaped opening. The axial forces of the external columns of the upper tube structure are transferred by the nrcli-

Fig. 4.118

Sumito~noLife Imurnncr Building, Okoynmo, Japan,

232


Tubular Systems

[Chap. 4

shaped bearing walls of the first and second floors to the L-shaped wall columns at the four comers and thence to the foundations via bearing walls below grade. The arch-shaped bearing walls of the first and second floors are of reinforced concrete construction with internal steel msses (Fig. 4.119). The embedded steel structure is designed to remain elastic for long-term vertical loads and for short-term horizontal loads. The bearing walls were modeled as flat plates and analyzed by finite-element analysis. (The steel msses were taken into consideration.) Analysis of the earthquake response was performed using a rnultimass model, which combined the upper tube struchlre with the arch-shaped bearing walls of the fust and second floors. For accelerations of 3500 mmlsec2 (1 1.5 ftlsec2) during a large ennhquake. the arch-shaped bearing walls remain within the allowable elastic stress range. The primary natural period in the vertical direction (considering vertical rigidity of the arch-shaped bearing walls) is 0.179 sec, so there was almost no response from the arch-shaped bearing walls due to venical earthquake motions. The typical floors (Fig. 4.120) are supported by 700-mm (27.5-in.)-deep trusses at 2.5-m (8-ft 2-in.) centers spanning 9.9 m (32 R 6 in.). The spnces between the truss web members allow for the passage of ducts and pipes. The truss top chord is connected via stud shear connectors to the concrete slab. The increase in stiffness results in a frequency of vibration of h e floor in excess of 9 Hz.

Fig. 4.119

Fmmcnork; Sumitomo Life Inruruncc Building.


Sect. 4.41

Tubular Systems

Dewey Square Tower Boston, Massachusetts, USA

Architect Structural engineer Year of completion Height from street to roof Number of stories Number of levels below ground Building use Frame material Typical noor live load Basic wind velocity Maximum lateral deflection Design fundamental period Design acceleration Design damping Earthquake loading Type of structure Foundation conditions Footing type Typicnl floor Story height Beam span Beam depth Beam spacing Material Slab Columns Size at ground floor Spacing Material Core . .. ......

Fig. 4.1ZU Txpicul structurui flour pins; Sunnitunls Lilc lniurdnru Uuilding.

Pietro Belluschi Inc. and lung Branncn Associates Inc. Weidlinger Associates 1983 182 m (597 ft) 46 2 Office Steel 2.5 Wn (50 psf) 42 mlsec (95 mph) 450 mm (I8 in.). 100-yr return 5.5.4.3 sec 23 mg peak. 10-yr return I % serviceability: 2% ultimate Not applicable Perimeter tube Stiff silty clay over compact glacial till Mat. 1800 lo 2600 mm (6 to 8 ft 6 in.) thick 3.81 m (12 ft 6 in.) 9.1 m (30 ft) 400 mm (16 in.) 2.3 m (7 ft 6 in.) Steel 133-mm (5.25-in.) lightweight concrete an metal deck W350 by 1088 kglm (W14 by 730 Iblft) 4.57 rn (15 ft) Steel, grade 350 MPa (50 ksi) Braced steel frame, grade 350 MPa (50 ksi)

After having examined many alternative systems, project designers at Weidlinger Associates concluded that a steel structure with a rigid frame around the perimeter was most economical for this 46-story building and would resolve the requirements for integrating the structure with the curtain wall (Fig. 4.121). Ressstance to wind and seismic forces is provided by the framed tubc forming the tower's penmeter. To economize


Tubular Systsms

[Chap. 4

on field work, particularly field welding, spandrel units consist of trees with columns and welded eirder stubs. Field connections of the girders at the centerlinc between cnlumnr are golted shear connections. Spandrel girders on lyptcal floors arc gcncrally 1143 mm (-15 in.) deep. \.:lr).ing irom a minimum or900 mm (39 in.) at the lop oiihe building lo 1245 mnl (49 in.) a! lllc boltom. Columns are built-up members 760 mm (30 in.) deep along the building face. except where rollcd sections are used above the thirty-third floor. Perimeter columns arc ~

arranged to provide open comers, that is, the ladder section always ends with a beam stub at the comer. This scheme avoided the complication of three-dimensional corner columns with welded stubs eoina in two directions as well as the hiaxial bending problem of a comer column. since ail of the structure's lateral stiifness is proridednr~ound the penmcter. nil interior bean-lo-beam connccliuns arc o i l h e simple sllcar type. A varietv of steels is used throuehout - the struclure. Exterior columns and inlerior ~:&floor framing are of A-36 steel, girders and interior columns are A-572 grade 50, and built-up interior columns are g n d e 42. High-strength steels were chosen where the desien w& eovemed bv streneth considerations. Where the desien aovemcd - is .primarily. . b) dcfor~nalioncriteria. as for drturiur columns, lower-strength l e e i s ware oscd. The lower has o slructural dcpth u i 36.57 m (120 it) ulth a height-lo-depth ratio of almost5:I. This.. couoled with its unusual shaoe.. sueeested the useof a windtunnel test !o verify both the magnitude and the local variations of wind forces. The wind tunnel test results very closely matched the overall forces required under the Massachusetts code. Local hoi soots here found to exist oarticularlv a t the intersection between the tower and the atrium. The analysis of the suucture for lateral forces yielded information useful for future oroiects. It is well known that the effect oishear deformation becomes mnenified with an a increase in the depth-to-span ratio of the beam. Since in a frame such as this, the depthto-span ratio is on the order of 15. shear delormations contribute a large part of the total lateral deformation of the swcture. Soecificallv. in this case it was found that the lateral deflection due to drift of the buildingLan be aGibuted in roughly equal parts to:

-

-

-

.

. --

.

-

Overall deformations of the frame (shear deflections) Column shortening (bending defleclion) Shear deformation of beams and columns Since the girder webs are relatively thin compared to the column webs, the major portion of the shear deformation is attributable to the beam web. Wherever possible in the eslablishcd program, the steel fabricator elected to substitute fillct weldine- for this connection between the spandrel -eirder flanees and the penmuter columns. This was cltoscn w c r the specified full-pcnclmlion weld. \VBcnevcr the ercction equipment uouid nllo!, the iabricnlor uscd 1-0-stor). tiers for !hi. e~teriorcolumns. There cunsisted of the lull 7.62-m (25.11) columo. ~ i l htuo sp;indrel girder stubs oo each side. The spandrel girders were then bolted togcthcr nl mldsp~n This method kept field \$,elding to 2 m~nimumas well ns expediting the erc:tlon In erectine- the steel tower, three self-climbine - tower cranes were used in lieu O F the more conventional two. This ensured maximum erection speed and facilitated the ercction of the precnst concrete panels, also p a n of the steel contractor's work. Dewey Square Tower is granite-clad on the lower two floors, with precast rain-screen panels reachine from the third floor to the s l o ~ e d-class crown of the fanv-sixth starv. Continuous bands of tinted reflective glass alternate with bands of exposed granite aggregate l for the panels were dcvclopcd wilh input set in white cement. S l ~ c t u r a connections from both the panel fabricator and the steel contractor. The typical panel is attached by two load-bearkg connections and two lateral connections shop-welded to the perimeter columns. Floor construction consists of a 50-mm (2-in.) composite deck with an 83-mm (3.25-in.) lightweight concrete topping. erade and rises 180 m (590 it). The torvcr starts on a concrete mat two stories below . f l ~ sI t - ru 2-m (6- to 8-frl-(hickconcrete m:ti reris on hardpan, nhi:h protrdcr ; ~ neconnnli;;ii i b ~ n r l ~ t i uTilt n are;, uf lhr. building surro~ndingthc i.>\\cr 113s cnlumns rdsting on spread footings and incorporates an undcrdrain system below the subbasement slab.

.

-

Fig. 4.121 D e w y Squure Tower, Boston, hlnrsnchusctb. (Phoin lir S a w Rorrrirbn1.l

.


[Chap. 4

Morton International Chicago. Illinois, USA

Architect Structural engineer Year of completion Height from street to roof Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity Design wind load deflection Design fundamental period Design acccleration Design damping Eanhquake loading Type of structure Foundation conditions Footing type Typical floor Story height Beam span Beam depth Beam spacing Material Slab Columns Size at ground floor Spacing Material Core

Perkins and Will Perkins and Will 1990 170 m (560 ft) lo top of clocktower 36 plus clocktower 1 Office, parking, and retail S l ~ ~ t ~steel ral 2.5 W a (50 psfl 34 mlsec (75 mph) 330 mm (13 in.). 50-yr return 4 sec Estimated 15 mg peak, 10-yr return I lo serviceability Not applicable Perimeter framed tube with transfer truss at low level Stiff clay Belled caissons bearing on hardpan

Sect 4.41

Tubular Systems

239

The 36-story structure has typical floor spans of 12.6 m (41 ft 6 in.). but spans varying from 19.8 lo 21.3 m (65 to 70 it) were required to span the railroad tracks. This was achieved with n series of 6-story-deep Vierendeel frames consisting of two 3.05-m (10ft)-deep plate girders, one at level 2 and one at level 8, connected by fully welded vertical and horizontal members. For a building of this height, a braced core would have been the obvious means of resisting wind loads. However, in lhis case the railroad tracks

3.81 m (12 ft 6 in.) 12.6 m (41 f t 6 in.) 533 mm (21 in.) 3.05 m (10 ft) Steel, grade 350 MPa (50 ksi) 140-mm (5.5-in.) lightweight concrete on steel deck Built-up 1640 kglm (1100 Iblft) max 4.57 m (15 ft) exterior; 9.1 by 12.6 m (30 ft by 41 f t 6 in.) interior Steel, grade 350 MPa (50 ksi) Steel frames supporting gravity loads only

The Morton International building comprises a 13-story base containing commercial floors and parking for 450 cars, topped by a 23-story ofice tower (Fig. 4.122). The site fronts the Chicago River and contains existing railroad tracks, which had to remain fully operational during consmction. Almost a quarter of the site was unable to accommodate any footings and the remainder rcquircd large spans across the tmcks. Several interesting transfer systems were designed lo overcome the site restraints. Pig. 4.122 Morton lntcrnnlionol. Chicago, lliinoir. (Plzoro I,? Hrdrich-Blerring)

240


Tubular Systems

[Chap. 4

made this impossible and instead, a perimeter framed tube with columns at 4.57 m (15 ft) was adopted. The columns and spnndrel beams were shop-fabricated into 2-storyhigh "ladders" with site-bolted web plate connections at midspan of the beams. This design saved 1360 tonnes (1500 tons) of steel compared to an original design with perimeter columns at 9-m (30-fl) centen. The 13-storv structure presented major challenges, which were overcome by three separate transfer structures and unusual construction rrquirrmcnts. Street-level concrete transfer beams 2.3 m (7 ft 6 in.) deep nt 9-m (30-it) centers span the mcks lo allow a regular and efficient column setout above. T h e recond transfer svstem occurs above the roof to the southern end of the build~~~~~~-~ ing, where no footings were able to be provided in the tnck zone. Trusses with major members built uo from six 100- by 600-mm (4- by 24-in.) plates suspend one side of the

--..-...-.

n l e third transfer system occurs between levels 2 and 4 and serves to redirect two rows of upper columns into one row located to avoid the tracks. The entire vrnical structure above these transfer frames u a s erected to the roof lcvel, and the roof top trusses were erected cantilevering bcyond the floors belon. This section of thc bullding was erected 90 rnm (3.5 in.) out of plumb to dlow for the sway induced when the cantilewred section was erected and partially loaded. With the roof top trusscs erected, perimeter columns wrre suspended ham the free ends of the trusses.and the floors were erected in a conventional manner from the boltom up. To equalize dcfl:ctions and minimize difrcrentinl movement, a load-distributing longiludinal truss mas installed at level 8 between the suspcndcd columns.'lhis truss served 3 dual purpose in that it was also designed lo redistribute the column load to adjacrnt columns should aroof-top truss fail. The roof-top trusrrs were providcd u,ith sufficicnt capacity to allow them to cnrry t h ~ additional s load. This challeneine proicct - -. - received an nwnrd for Most Innovative Design of 1990 from the Structural Engineers Association of Illinois

.

'

Height from street to roof Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity Maximum lateral deflection Design fundnmental period Design acceleration Design damping Eanhqualie loading Type of structure Foundation conditions Footing type

Typical floor Story height Beam span Beam depth Beam spacing Slab Columns Spacing Material

Cesnr Pelli Associates Walter P. Moore and Associates, Inc 1992 256 m (840 ft) 62 2 Oftice, corporate headquarters, retail Concrete 2.5 kPa (50 psf) 1.0-kPa (20-pst) partitions 35 mlsec (80 mph) at 10-m (3341) heighl HnOO, 50-yr wind 5.3 sec 12 mg peak, 10-yr wind 1.5% serviceability; 2.5% ultimate C = 0.53, Z = 0.15. Ru, = 7.0 intermediate moment resisling frame (IMRF) Perimeter tube Clay of variable thickness, 4.6 to 7.6 m (15 lo 25 it) over weathered bedrock 2.4-m (8-ft)-thick core mat on weathered rock: 9- to 30-m (30- to 100-it)-deep caissons (150 ksO. 1.5 to 1.8 m (5 to 6 it) in diameter

+

3.86 m (I2 ft 8 in.) 14.63 m (48 ft) 457 mm (18 in.) posttensioned 3.05 m ( I 0 it) 117-mm (4.625411.) lightweight concrete one-way. 35 MPa (5000 psi) 1370 mm (54 in.) in diameter 6.1 m (20 ft) 55 MPa (8000-psi) concrete

The Nations Bank Corporate Center is a 60-story. 256-m (840-fl) tall building in the central business district of Charlotte. North Carolina (Fig. 4.123). The building is the tallest in the southeastern United States and will dominate Charlotte's skyline into the 2151 century. From a heavy stone base, the building rises with curved sides and progressive setbacks culminating in a crown of silver rods symbolizing Charlotte's nickname, "The Queen City." The exterior surface materials arc rcddish and beige granite

242


[Chap. 4

and mirrored reflective glass; the granite piers narrowing at each setback. The building will serve as the corporate headquarters for Nations Bank. A number of different feasible structural schemes were analyzed before Nations Bank and the developer selected an economical concrete frame. A reinforced . together concrd~cframe U 3 S ssl~ctcdbec3use it met both thc intricate geumetric rcquiremsnt, 01 thr. arcl~~tucr ;~ndthe d-munds of the detcloper for economy Sh3llow posttensioricd concrete floors were used to span the 14.6-m (48-ft) lease depths and to achieve the desired 3.9-m (12.5-ft) floor-lo-floor heights.

Sect. 4.41

Tubular Systems

243

The smctural system selection followed an intensive four-phase scheme development process. This process has been used successfully in swctural system selection for many other high-rise projects. The purpose of the structural scheme selection process is not only limited to finding the most economical structural system. but to finding the system that best resoonds to the overall buildine eoals. Nonswctural oorameters such as impact on lc~sing,column sizes and locations, shcar wall drop-offs, construction duration, floor-to-floor heights, fire nling and intcgrntion wilh mechanical systems arc also considered. The entire-team oaiicio&d in theselection orocess Thr. srleclcd all.concrcte scheme consists of a reit~forcudconcrele perimclrr lube struculre witl~calum~is spaced on6.1 rn (20 ft)centers.Thc perimeter lrwnr utilizes normal weleht concrele with slrenclhs rancinc from 41.300 lo 55,000 Wa (6000 lo 8000 psi). ~h;external tube was selected because it was the most efficient late& load resisting system. The tube also proved to be an economical method of dealing with the many setbacks and column transfers imposed by the building architecture. The floor system consists of a 117-mm 14.5-in.)-thicklichtweieht concrete slab soannine to 457-mm (18in.)-deep post-lension;d beams. The pasttenzoned beams are spaced 3 m (10 ft) =enters and span as much as 14.6 m (48 it). The 14.6-111 span provides column-free lease soacc from the core to lheperimeter.The shallow structural devth allowed the low floorto-floor height resulting in additional savings in skin cost. ~ i ~ h t w e i gfloor h t concrete was selected to minimize the building weight and to achieve Charlotte's unusual reouirements for 3-hr fire separation. A normal weirht - concrete slab would have needed lo be I50 mm (6 in.) tltick in order lo proiidc tlie Err. separation, substantially incrcasing not only the b~ildlngwcighl but also ths floor-lo-floor hcight. All lateral loads are resisted hv the external frame. The floor framinn- and core columns 3re sized for gravity loads. Lateral load niumcnls imposed by compatibility uf deformation uilh the cxtcrior frame were found lo bc ~nsignificanl.The corc columns were shaped to be wall-like Column sires ranecd from 0.6 by 5.5 m (2 by 18 it) at the lower le&l to 600 by 900 mm (24 R by 35 in.i at the top of the building;~hewalllike colunm shapes integrated very well with the building core. u

-

on

Fig. 4.123 Nutions Bunk Corporule Ccntcr, Ci~orlstle.North Cilrollnu.


[Chap. 4

Sect. 4.41

Bank One Center Dallas, Texas, USA

Architect Stmctural engineer Year of completion Height from skeet to roof Number of stories Number of levels below ground Building use Frame material Typical noor live load Basic wind velocity Maximum lateral deflection Design fundamental period Design damping Eanhquake loading Type of structure Foundation conditions

.'

John Burgee Architects with Philip Johnson The DatumIMoore Pafinership 1987 240 m (787 ft) 60 4 Office, parking Concrete-composite perimeter frame, steel core 2.5 kPa (50 psO + 1.0-kPa (20-psO pnrtitions 31 mlsec (70 mph) at 10-m (33-11) height Hl500, second order. 50-yr wind 6.8, 6.5. 3.5 sec 2.0% serviceability; 1.5% ultimate None Perimeter tube 6.1-m (20-ft) shnie and weathered limcstone over unweathered limestone

Tubular Systems

The engineering for the 148,000 m' (1.6 million ft') project is as complex as the architecture. Extensive value engineering studies were done during design development to analyze six floor framing systems and four wind framing systems. Design information for each was provided to the general conuactor, who in turn smdied scheduling and prices. All four wind schemes were variations of the perimeter tube. For the early compar:alive design studies, Dallas building code wind forces were used. The selected scheme

Footing type design allowable Typical noor Story height Beam span Beam depth Beam spacing Material

Columns Spocing Material

3.84 m (12 ft 7 in.) 14.69 m (48 R 2 in.) 457-mm (18-in.) 2.74 m (9 ft) Steel. A572 grade 50.50-mm (?-in.) composite metal deck + 89-mm (3.5-in.) 1i:httveight concrete 610-mm (2-it)-square 100-mm (4-in.). thick box column 7.6 m I25 ft) Steel. A572 grade 50

Bank Onc Ccnlcr is a postmodern to!\'er compictc rvith a monumental arched entry and curved roo[ line (Fig. 4.12-1). The 60-story oflice tower also Ins an atrium banking hail in its 6-story podium, semicircular arched roofs at the t\\,ent)'-sixth floor and quartercircle i,aulted skylights at the fiftieth, where the shope changes from rectangular to cruciform. On top is a cross vaulted arch clad in copper and pmnite.

1 :!.

Fig.J.124

Dunk Onc Ccnlcr, Dallus, Tcsar

246


[Chap. 4

has punched concrete walls at the building corners with infills of composite columns and steel spandrels; floors have a composite steel heam framing system. The building's nrchitecture requires a number of geometric changes as the stmctural frame rises above the below-grade levels. The cruciform shape above level 50 created two major structural problems. First, the perimeter tube had to be broken, leaving only two-dimensional rigid frames on each building facade. To control frame distortions under wind loading, two-story X-braced frames were added in the core. This required strenathened diaphragm . - floors to allow the transfer of wind shear forces from the irames to the pcrimetsr lube system btlou. Second, comer columns at the rccnuant corncrs of the cruciform hod lo be transferred lo provide culumn-free lease space bclow Icvel 50. Story-deep Vicrendccl trusses spanning 13.7 m (45 it) move these gravity column loads 10tltc perinieter wind frame and to the cure. Because of the relationship bet!\e:n corc and perimeter columns. lhr trusses ltad lo be supponed nt the corc by twoslury Vicrcndecl lrusscs spanning 8.5 m (28 it) to the building corc columns.

Sect. 4.41

Tubular Systems

Central Plaza Hong Kong

Architect Smctural engineer Year of completion Height from sweet to8 roof Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity Maximum lateral deflection Design acceleration Earthquake loading Type of structure Foundation conditions

Footing type Typical floor Story height Benm span Beam depth Slab Columns Size at ground floor Spacing Material Core Material

Nu Chun Man and Associales Ove Amp and Partners 1992 314 m (1030 ft) 78 3 Oifice Reinforced concrete 3 P a (63 psfJ 64 mlsec (144 mph). 50-yr rcturn, 3-sec gust 400 mm (15.8 in.), 50-yr return period wind Less than 10 mg. 10-yr rcturn period (typhoon wind) Not applicable Perimeter tube and corc Fill over clay over granite bedrock; granite bedrock. 25 to 40 m (80 to 130 it) below ground Machine- and hand-dug caissons to rock 3.6 m (11.8 ft) 12 m (39 ft) 700-mm (27.5-in.) reinforced concrete 1 6 a m (6.3-in.) reinforced concrete 2-m (6.5-A) diameter 8.6 m (28 ft) Concrete, cube strength 60 Nlmm' (8500 P") Shear walls 1.3 m (4 f t 3 in.) thick at base Concrete, cube strength 60 to 40 Nlmm' (8500 to 5800 psi)

When completed in 1992, Central Plaza was the tallest reinforced concrete building in the \vorld (Fig. 4.125). The site is typical of a recently reclaimed area with sound bedrock lying between 25 and 40 m (80 and 130 ft) below ground level. This is overlain by decomposed rock and marine deposits, with the lop 10 to 15 m (33 to 1 9 ft) being of fill material. A permitted bearing pressure of 5.0 MPa (56 ton/ft2) is allowed on sound rock. The maximum water table rises to about 2 m (6.5 fl) below ground level.

248


[Chap. 4

Tubular Systems

Sect. 4.41

Wind loading is the major design criterion in Hong Kong, which is situated in an -& fluenccd by typhoons. TheHong Kong code of practice for wind effects is bared on amend:, hourly wind speed nf 44.3 d s e c (99 mph). 3-sec gusls of 70.5 m/Sec (158 mph), and give$r, ,. rise to a l a t e d design pressure of 4.1 kPa (82 psO at 200 m (656 h),above pound level. 11 was clear from the outset that a multilevel basement of mnxlmum noor area be required. The design of a diaphragm wall. extending around the whole slte perimeter, i:f
:!$!id,

1 7 STRUCTURE

Fig. 4.125 Ccnlrol Plnzu. Hung Kong. (Cotarrery of O w Anlp und Pnrrncrs.) Fig. 4.126n

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Ccnlrnl Plnm. Eicvnlion of building.


250

[Chap. 4

Sect. 4.41

Tubular Systems

An initial planning assessmcnl had indicated that up to four levels ofbasement could be required and the design produced catered for this. By the lime construction commenced, it had been decided that only three levels would be necessary, and the construction drawings were amended accordingly. The diaphragm wall design allowed for the basement to be constructed by the lopdown method. This provided three fundamcnlai advantages:

TRANSFER PLATE

Elg. 4 . 1 2 6 ~ Ccntrnl Plnm. Derign wind prrsrurc concrcte scheme

A- A

B-B Fig. 4.126b Centrnl Piuro. Slruclurui rterl rehcmc.

KEY PLAN

251

1 I I


254

[Chap. 4

(1 11 ft 10 in.). The core hns an arrangement similar to that of the steel scheme and, just above the lower base, it carries a .~.~ r o x i m a t e 10% l v of the total wind shear. Thc tnwcr b.asr slrtlcturc edge transfcr beam is 5.5 m ( I 8 it) deep by 2.8 m ( 9 i t ? in.) u,ids around the pc"nletcr. This allnws 3llernatc 2olumnr to be dropped from the fac;!dc. thereby upunirlg up ihc public srca at ground lcvel. The incrmsed column rpacinc, together with the elimination ofspandrei beams in thc tower base, results in tl;e external frame no longer being able to carry the wind loads acting on the building. Over the height of the lower base. the core transfers all of the wind shears to the foundations. A I-m (39-in.)-thick slab at the underside of the transfer beam transfers the total wind shcar from the cxternal fmme at the inner core below. The uind s h c x is taken out from lhc core ot the louert bosctncnt leucl, whcre it is transftrrcd lo thc punmetcr diaphragm u,nlls. In ordcr to rcducr large s h c a rc\.ersals in the core !rails in lhc bnsumcnt and nl the top of the tower basc lu,cl. thc floor slobs 2nd beams arc separated horizontally from the core wnlls at the ground floor, basement levels 1 and 2. and the fifth and sixth floors. To comolete the dramatic imoact ofthir building, the tower top incorporntcs a mast, which will be constructed of S l ~ c t u r a steel l tubes with diameters of up to 2 m (6 ft 6 in.). The performance of tnll building structures in the strong typhoon wind climate is of particular importance. Not only must the structure be able ;isis1 the loads in general. and the cladding system and ic; fixings resist higher local loads, but the building must also perform dynamically in an acceptable manner such that predicted movements lie within acceptable standards of occupant comfort criteria. T o ensure that all aspects of the building's performance in strong winds will be acceptable, a detailed wind tunnel study was carried out by Professor Alan Davenpon in the Boundary-Layer WindTunncl at the University of Western Ontario. When complelcd, this project became the tallest reinforced concrete building structure in the world. For such a tall building it is not appropriate to adopt the strength of

.

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tbl Fig. 4.127

Central Pinm. (n) Typlcol oficc noor plum. ( b ) Foundnllom. (Continued)

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Tubular Systems

Sect. 4.41

255

materials commonly used for normal buildings in Hong Kong. In ordcr to reduce the size of the vertical structure it was decided to use high-strength concrete 128-day cube strength of 60 MPa (8500 psi)]. This is the first private-sector development in Hong Kong for which approval has been granted by the Hong Kong building authority forthe use of such a material. Considerable research took olace into materials and mix design. and man) t r i i s were ~3rrir.dOJI, includtng mock-ups of the large-diamcler columns to check on icmperaturc uffccls. As n result ofthis, cooling was introduced into the major pours. The use of hirher strcnrths was considered. but it was decided against - it since it was conidtrcd by the dt\,r.lopment team thlt the material chosen could bc produced without difficult) front matcri=ls readily wailsblc in llong Kong.

-

-

256


Sect. 4.41

[Chap. 4

Tubular Systems

Hopewell Centre Hong Kong

Architect Structural engineer Yevr of completion Height from street to I O O ~ Number of stories Number of levels below ground Building use Frame material Typical noor live load Maximum lateral deflection Design acceleration Earthquake loading Type of structure Foundation conditions Footing type Typical floor Story height Bcam span Bcam dcpth Slab Columns Size at ground floor Spacing Material

Material

Gordon Wu and Associates Ovc Amp and Partners

1980 216 m (708 ft) 64 1 Offices above parking and commercial podium Rcinrorced concrete 3 kPa (63 psfl 150 mm (5.9 in.). 50-yrrctum period wind 16 mg peak. 2-yr return period Not applicable Pcrimctcr tube and inlcrnul core Srrund granitc very close to cround level Pad footings an rock 3.35 m ( l l . 0 f t ) 12.3 m (40 It) 686-mm (27-in.) reinrorccd concrete 100-mm (5.9-in.) reinforced concrete 1A5 by 1.22 m (4.75 by 40 fi) 3m(10ft) Concrete, cube strength 40 Nlmm' (5800 .psi) Shear walls. 762 mm (30 in.) thick at basc; circular in plan Concrete, cube strcngth 40 Nlmm' (5800 psi)

The I-lopervell Centre is situated on a steeply sloping site, one entrance being at ground floor and asecond main entrance to the rear of the building at the seventeenth floor (Fig. 1.128). The tower itself is rounded on pad footings at levels varying between the underside o r the basement and the third noor. Stability is principally providcd by thc perimeter tube structure rormcd by 48 columns at a spacing o r 3 m (10 ft), linked by 1670-mm (66-in.)-deep spandrel beams at each floor levcl. Some assistance is also provided by the internal corc. Shears nre transferred to the foundations at the third-noor level through a 157-mm (19-in.)-thick noor slab (Fig. 4.129). The entire verdcal structure was constructed using slip-formin€ techniques. The main office floors use a radial h u m and slab system and were formed using fiberglass molds (Fig. 4.130). Uring these techniques, construction progressed at a rate of 4 days a floor.

>.

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24.

xi

Fig. 4.128 Hoperell Ccntrc, Hong Kong. (Colmcry o/Ol,e Antp nnd Porrnrrrl

Tubular Systems

Sect. 4.41

r

2 2 4 m rndiul

1 i

260


[Chap. 4

Sect. 4.41

Tubular Systems

PROJECT DESCRIPTIONS. TRUSSED TUBES First International Building Dallas, Texas, USA

Architect Slructural engineer Year of completion Height from street to roof Numbcr of stories Number of levels below ground Building use Frame material Typical floor load Basic wind velocity M a i m u m lateral deflection Earthquake loading Type of structure Foundalion conditions Footing type Typical noor Story heigbt Beam span Bcnm depth Beam spocing Slab Columns Size 31 ground noor Spacing hlatcrial

Hcllmurh Obata and Kassabaum. Inc. Ellisor and Tanner. Inc. 1974 2 1 7 m (714 ft)

56 2 office Struclural steel 2.5 kPa (50 psn 31 mlscc (70 mph) Hl500.50-yr rcturn period Not applicable Trussed tube Limestone. 4.3-hlPa (-IO-ton/ft2) capacity Spread footings

3.81 m (12 ft 6 in.) 12.27 m (40 f t 3 in.) 460.530 mm (18, 21 in.) 3.81. 10.97 m ( I ? It 6 in.. 36 ft) 83-mm (3.25-in.) lightweight concrerc on 76-mm (3411.) metal deck 533 by 584 mm (21 by 23 in.) -7.62 rn (25 it) Steel. gmdc 350 hlPa (50 hi)

The 56-story First Internnlionnl Building with a Ihcighl of 2 17 m (71-1 i t ) lhas 176.500 m' (1.9 million TI') of space (Fig. 4.131). There are an adjacent 13-story scli-perk gerngr and a 10-station drive-up banking facility. Tendcm clcv;~torsllandle the venical movement of building occupants during peak traffic pcriods. Each of the 2-1 passenger clevator shafts has two elcvalar cabs, mountcd one on top of the other and moving on a single set of cables. Thc exicriar dimensions of the onice tou.er arc 5 5 by 55 m ( 1 8 1 by 181 it). The sxterior column spacing is 7.62 rn (25 ft). Thcrc is n column-free span irom the core to the exterior columns of 1 2 2 7 nt (10 ii 3 in.). The design incorporalcs the trussed lube struclural syslcni in the exterior frame, utilizing large X braces, each covering 28 floors. two lo a side. Because nftlte usc of large X-bracing clcmcnts on the four exterior \valls to resist lateral wind forces plus some

Fig. 4.131 Firs1 lnternolionni Uuilding. Dullas, Tcxor,

261

i E Lateral Load Resisting Systems

262

[Chap. 4

wind fmmes or m s s e s in the interior core are eliminated. The two X breccs on each side consist of diagonal steel wide-flange mcrnhrrs whose ouuide dimensions arc approximalcly 610 by GI0 mm (24 by 24 in.). The gusset plates art approximately 3 m (10 ft) wide and 3 6 m (12 it) tall (Fig 3.132). Comer box columns 610 mm (24 in.]. sauare are used in the basement and are fabricated from 152-mm (6-in)-thick stucl plates. These Inkc the henvieit loods accumulating from the diagonal bracing of two ridrwnlis. Tlts comer gusset asscmblics a r t Lshaped in section and were welded by the electroslag process. Another structural design concept is the stub-girder system. This minimizes structural costs lhroueh a reduction in the amount of steel reauired far floor framing and a ~=~~ lessening of the building's floor-to,floor hcight. The built-up girder system consins of stubs that arc fabricated onto ruucturnl beams (Fig. 4.133). nts \ride-flange beam acts as a bouorn chord whcrcas lhc rhorl slubs act ;is u e b mumbcrr.'Ths 159-tnm (6.3.in.) liehtweiaht concrete slab functions in c o m ~ o s i t eaction with h e steel or the too chord. The overall effect is that the slab and beam'function as flanees. the stubs func- ~whereas . lion as wch struts in a Vicrcnducl truss. Ills stub girders p~.rmitunubrrrucrud runs o f m c chanical ducts without web openings in llic beams. n ~ e also y suppun the scmicontinu-' .. our floor beams. An electrified floor svslem was used for the first time with the stub-eirder~~conceot. Alro, a longer girder is uacd than in prcwous applications o f t h e s)slr.m. In addition to I! detailed cumputer anslysis of the stub.girder design for this project. actual load tests were made to funher verify the desien concept The buildine was tonoid out i n 6 6 weef;; from rroundbreakine and in 10 months from the erection ofthe first piece ofsuuctural steel. Tlti; projcct recui\ed ~ l i cfirst Consuiting Eng~nccrrCouncil of Texas "Emincnt Conccplor Award for the h l o n Outsv,mding Engineering Project" in 1974.

Sect. 4.41

Tubular Systems

eravitv. loads. -

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7

7 spaces at 25'4" = 175'4''

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263

264


[Chap. 4

.I

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-k

3'4'' Ic

7 spaces at 2 5 ' 4 = 1754'"-4

S e c t 4.41 Onterie Center Chicago, Illinois, USA .!,?i!: A'&hitect Structural engineer Year of completion Height from w e e l to roof Number of slories Number oflevcls below ground Building use Frnme material Typical floor live load Basic wind velocity Maximum lateral deflection Design fundamental period Design acceleration Design damping Emhquake loading Typc of structure Foundation conditions Fooling type Typical floor Story height Slab

9 'n


Tvoicai low rise floor lrarnino oian Mechanical duct

7 6114"

W14 girder (ASTM A572 GR.50)

Seclion-builluo oirder Fig. 4.133 Tspirnl fmming pian and built-up girders; First lnlcrnntionnl Building.

Tubular Systems

265

Skidmore Owings and Merrill Skidmorc Owings and Menill 1985 174 m (570 it) 57 I Commercial, parking, offices, apartments Reinforced concrete 2.5 kPa (50 psO 34 mlscc (75 mph) Hl500, 100-yr return period Not available Not available I to 1.5% serviceability Not applicable Perimeter diagonally braced frames, flatplate floors 27 m (90 it) of clay over hardpan 1.5-m (5-ft)-diameter caissons, belled to 3.6 m (12 ft) Apartments 2.62 m (8 ft 7 in.) 178-mm (7-in.) flat plate, spanning 6.1 by 6.7 m (20 by 22 ft) 483 by 533 mm (19 by 21 in.) 1.68 m (5 ft 6 in.) at perimeter 49-MPa (7000-psi) reinforced concrete Not applicable

Onterie Center is n mixed-use 58-slory building near the Lake Michigan shoreline in downtown Chicago (Fig. 4.134). The building has a total area of 85.000 m' (920.000 it'), which is divided into five distinct areas by function. On the ground floor is lhc main public lobby and 1860 m' (20.000 ft') of commercial space. The single-level basement and the four floors above the lobby are a parking garage. Floors 6 to 10, at the tapering base, provide ofiice space grouped around two interior atriums. The sky lobby at level 2 includcr a health club, swimming pool, hospitality room, and mechanical equipment space. The remaining floors 12 to 58 consist of593 one-, two., and thrcc-bedroom aparlments (Fig. 4.135). Because mixed-usc buildings need flexibility of core layout and column spacing, it was desiiable lo utilize only the exterior frame for thc resisiancc of lateral loads. In ihe

266


[Chap. 4

t, y ,

Sect. 4.41

Tubular Systems

267

3 '

i),

j ;'

;

Onterie Center tower all of the lateral forces are resisted by closely spaced reinforced concrete exterior columns and spandrel beams. Additional lateral stiffness and structural efficiency were achieved by infilling window spaces with concrete in a diagonal pattern. These panels act not only as diagonal braces but a shear panels as well. The diagonal effect of the shear panels tends to even out the gravity load on the columns and also to reduce shear lag in the tube frame under wind loading. The entire lateral load is thus resisted by two diagonally braced channels, located one at each end of the tower structure. Interior columns carry gravity loads only. The absence of a lateral load resisting core wall system allows a maximum of flexibility in planning interior space and eliminates the problem ofdiifercndal axial shortening. Threc-dimensional computer modcling was used to analyze both gravity and wind load cases. Pcrimctcr columns arc 480 by 510 mm (19 by 20 in.) at 1.68-m (5-ft 6-in.) centers. The510-mm (20-in.)-thick infill panels contain diagonal reinforcing bars as well as horizontal and vcrtical bars. The concrete strength for the exarior frames and interior columns varies from 5 2 to 28 MPa (7500 to 4000 psi). The floors me flat slabs with thicknesses of 178 mm (7 in.) for apanmcnts and 216 mm (8.5 in.) for commercial floors, using 35-MPa (5000-psi) concrete. Interior columns are spaced at 6.71-111 (22-it) centers. The external structural mcmhcrs are insulated lo minimize differential-temperalurc indurud dcfonnations bctu,cen purimctrr and inlcrnsl culumns. The d~3gon;llshear panels used in the Otllcnc Center pruducc 2 high I c \ d ofstractural efficiincv and create a distinctive architectural appearance. A similar systcm has been used on 780 Third Avenue. New York (see Fig. i . i 3 7 ) .

Fig. 4.134 Onterie C~ntcr,Chicago, lilinuis. Fig. 4.135 Typieol pion, 13th to 57111noor: Ontcrie Center.

270


[Chap. 4

floor (the first of the residential floors) and the larcest . office floor at the bottom. The tnp:r ir.:,, c\tendcd u p r ;,rd until JII ofthr. dc\clupcr's requircrn:ntr u.L.rc mL.1. The ~spcrcd fnrni .~lloa?dit c o r i l i ~ ~ u SoI~N Cs ~ U T L . In bc U I U ~nn lhe iilc:~dcI11 create 3 tapcrcd I U ~ C . 'Tllr. ,lnr~.turnl r!ilcrn consi~lsu i cnlumnb and spandrel bu:,ms ;tad diacal~nlcross bracing, all acting together to form an exterior tube. The requirements of th; diagonals imposed a very rigid geometric discipline on the building. The diagonals from each face had to intersect at a common point on the comers so that wind shear, carried as axial loads in the web side diagonals, could be trnnsfcrred directly to the flange side diagonnls. The diagonal X bracing is continuous from face to face and is connected to the columns, allowing load lo be transferred from bmcing to columns and vice versa. The beams are provided at the levels where diagonals intersect corner columns so that the diagonals could redistribute the gravity load among the columns. The gravity load in the diogonals causes them to always be in compression under wind loud, leading to much simplified connections. The redirtribution of gravity load also allowed all columns on each face to be made equal in size. A typical tier of the tube consists of a primary systcm comprising columns, diagonals, and spandrel beam ties at levels whcrc the diagonals intersect columns at a noor level, and a secondary syslem comprisin~ ~. . - the spandrel beams at other levels. The- nrim:ir!' ctruclurc \ \ a 1 r ~ . q u ~ r c10d dc\,~.lnp conunuity 3nd to tmos,nit ari:,l l o ~ d sThc . 131t r h l load is rcsislcJ ROC> hy c:~ntil~.iur aslion ano ?OF b) f r ~ r n cxlion. 'fl~isis duc 10 111sdiayol~'llsc~calit)E:In almu\t onifur~ncolutnn lo;d dirtribu~iun:lurus5 tllc flancc face: thcre is \,cry little shcar lag. Thc struclural cfficicncy is demonstrated by a steel weight of only 1-15 kglm' (29.7 ps0. The floors are a composite systcm of stcel bcams and a 127-mm (5-in.) semilightweight slab. On aportmcnt levels the bcams arc arranged in such a way that lhey align with partitions and thcsoiiil oftlieslab is plastered and used as the finished ceiling. The geometric discipline of the extcrior diagonal module is maintained by three typical office story heights equaling four typical apartment story heights. T o achieve simple joints, the columns, diagonals, and ties are all fabricated I seclions. The thickest plate is 152 mm (6 in.) and the largest column is 915 by 915 mm (36 by 36 in.). Interior columns were designed for gnvity load only, using rolled and builtup sections. A36 steel was used for nearly all members. Joints consist of double gusset plates to which diagonal members are connected by grade A490 bolts. Spandrel ties are field-welded to columns above and below, similar to typical column splices with bolted webs and partial-penetration flange rvclds. All gusset plate assemblies were shop-welded with comer gusset plate assemblies requiring stress relief. The simple derailing resulted in an crection rate of thrce floors per ureck. ~

. -

~~

Sect. 4.41

Tubular Systems

780 Third Avenue New York, N.Y.. USA Architect Swctural engineer Year of completion Height from street to roof Number of stories Number of levels below ground Building use Fromc material Typical floor live load Wind lood Maximum lnleml deflection Design fundamental period Design accelenlion Dceign damping Earthquake loading Type of structure Foundation conditions Foodng type Typical floor Story height Spandrel benms Slab Material Columns

Core

Skidmore Owings and Merrill Roben Rosenwnsser Associates 1983 174 m (570 ft) 50 L

office Concrete 2.5 kPa (50 psfl New York City code. 1 to 1.5 kPa (70 LO 30 psO 180 mm (7 in.) at design load 4.8 sec E-W: 2 sec N-S 12 mg peak. IO-yr return period I 4a serviceability; 2% ultimate Not applicable Diagonally braced cxterior tube ~ o c k4. - ~ (40-ton/ft2) ~ a capacity Spread iootings 3.5 m (I1 ft 6 in.) 380 mm (15 in.) deep 380-mm (15-in.)-deep one-way joist and two-way waffle slab Concrete. 31 and 28 MPa (4500 and 4000 psi) 1220 by 610 mm (48 by 24 in.) at ground noor Concrete, 41. 34. 28 MPa (6000. 5000, 4000 psi) Concrete walls and columns: concrete strength ns columns

The trend toward very high-rise construction in concrete has received a big boost due to the adaptation of the first diagonally braced tube system to concrete swclures. The fifst of its kind is the 50-story office building located at 780 Third Avenue, York ( F I ~ 4,137). which was completed in March, 1983. Its very slender aspect ratto of over 8:l IS what suited it to this design approach. e 46,500 m2 (500,000 it') of office space. Its struclural The building contains ~ l 0 s to system is a hybrid, utilizing thrce varied systems-a truss, a tube, and, to a minor extent, frame and sheor wall interaction of its remaining structural componenls. All SYS-

fiew

272


[Chap. 4

[ems interact to provide gravity and latenl load-carrying capacity at an efficiency not previously available. This hybrid system appears to rcmove any practical heigllt limit from design in reinforced concrete (Fig. 4.138). The "concrete tube" consists of closely spaced perimeter columns which are connected at each floor level by spandrel beams. In addition, thc tube is braccd by a diagonal pattern of rectangular panels, in place of window openings, betwecn adjacent columns and girders.

S e c t 4.41

Tubular Systems

The building is 38 by 21 m (125 by 70 ft) in plan, with an overall height of 174 m (570 ft), consist~ngofa4.4-m (14.5-ft)-high first story and48 3.5-m (11.5-ft)-high standard stories. Perimeter columns are 1.2 m (4 ft) wide, with window openings 1.6 m (5.3 ft) wide. The column h i c h e s s reduces From 610 to 457 to 406 to 356 mm (24 to 18 lo i d t i 14 in.) a floors 2.20. and 32. The spandrel beams, which arc the solid edges of the floor construction and are flush bottom with the one-way and two-way joists. are 380 mm (15 in.) deep by 1 m (39 in.) wide, except for those at the second floor. which are 762 mm (30 in.) deep by 610 mm 174. in I wide ----, -~ 'The concrete bracing panels arc of the same thicl;ness nr the ndjncent columns 2nd are placsd integr~llyuith thc~ti.The purpose of adding bracing to the lube is lo reduce illear log cffccts. and hence improvc the pcrfurmnncc of the struclurc for bnth gravity and wind loading. Thc wide iscer o f t h c huilding h a w double diagonol bmcinp. w h c r e ~ s thu nmoa iaccs hnvc only singlc diqonal bncinz in a rlgz;iy p;lltcrn. 'lhc concrsts rtrcngth of the columns and p:tncls varies 310110 IIIC huilding hcight. Thc slrenath of 41 hlPa (6000 mi) is rcduccd lo 35 hlPa (5000 psi) in the - ~ maximum ~ middle third and to 1 8 MPa (4000 psi) in'& top third of the swcturc. ~ h concrete e strength of the floor members matched 31 MPa (4500 psi) with 41-MPa (6000-psi) columns and 28 MPa (4000 psi) with the lesser-strength columns. Another structural element in the building is thc set of elevator core walls. Because oithcir small size and central location they are considered to be of secondary imparlance in their influence on the braced tube's behavior. The wind pressure applied to the building is in accordance with the New York City building code, increasing with lmight in steps up to a maximum of 1.44 Wa (30 psO at thc 91.4-111 (300-ft) levcl and above. The results o f a wind tunnel aeroelastic test verified that thc code's wind-pressure requirements for the design of the structure frame

.-

-

Fig. 4.137 780 Tllird Avcnuc, Kwr Tsrli. (Coi8rtc.r~r?rRnbm Rorm,>mrrer~s.~.roc)

273

Fig. 4.138 Typicul l r n m i n ~pin": 780 Third Arcnur.


274

[Chap. 4

were not exceeded. The cladding design requirements were, however, upgraded on the basis of the wind tunnel test results. The projected 10-yew return maximum acccleralions of 12 mg registered well within the occepled industry limits for office structurcs. Results from B e analyses performed for 780 Third Avenue that are of particular interest are those that indicate increased cracking and reduction in the effects of shear lag by the bracing on the column forces of an unbrnced tube structure. Results of sensitivity studies and the influence of the panels on lateral sdffness are illusmated by the deflection curves in Fig. 4.139. Evidently cmcking in floor members is very detrimental to the stiffness of unbraced tube structures (curvcs I and 11). but of only secondary importance in braced tubes (curves 111 and IV). The stiffening effect of the brncing is demonsvnted both in the reduced sway and in the modified-mode shape of the deflection curve (curve I versus curve Ill). The unbmced lube deflccts in a wallframe configuration, with concnvity downwind in the lower pan, concavity upwind in the upper part, and a point of contraflexure at about two-thirds of the height. The braced tube deflects in a more strongly flexural shape with a much higher point of contraflexure. The component of Lhe mbe's deflection due to racking shear of the columns and

Tubular Systems

S e c t 4.41

275

spandrels was, lherefore, reduced significantly by the bracing. This is further supported bv the small increasein the overall deflection when the spandrel stiffncsses are asigned . t i e large (50%) reduction to account for cracking. The deflection curve for the braced suucture with cracked bcams shows an increase in drift of 4% at the top, and a minimum increase of approximately 7% at about midheight. The maximum drift per story, however, which occurs in the middle region of the building, was hardly affected. The small influence on the overall lateral stiffness of the braced structure of a 50% va~iationin the moment of inenia of ihc spandrel beams indicates that their flexural stiffness, and therefore their depth, in the braced tube strucmre are of secondary importance. Their primary rolc is to nct as ties or struts in developing the axial forces in the intermediate columns. Figure 4.140 indicates ihc placement of the panel reinforcing. The column and spandrel bcam reinforcing was extended through the panel, which was also reinforced with lieht orthoronal reinforcements to minimize ihc size of accidental cracks. Collector reinforcing. suppicmunliog litc rpandrcl rcinforccmcnts, war added to i i ~ clop and buttom of the panel tu ;lugmcnt the lcnrile ruquiir.munts at the intcr,uctions Splicer an the m ~ i n rw~odrelrcinforu:mcsts aerc slaggurtd tu providc for lcnsilc forccr in the .p:!n~lrcl -beams. The construction of the concrete structure, from first footing to roof level, took 13 months to complctc. Thc building required 16.000 m' (21.000 yd') of concrete and 21 SO tonncs (2400 tons) of reinforcing bars. A 3-day construction cycle was easily maintaincd for the typical floors (a Z d a y cycle would have been possiblc with ovcrtimc). L

Direction ol force in diagonals

Spandrel reinfc. Collector reinfc. Column reinfc. Diagonal reinfc. Collector reinfc.

IV

111 II

--

HORIZONTAL DEFLECTION (fl) BRACED TUBE-UNCRACKED RFAMS - -- -- - BRACED TUBE--CRACKED BEAMS TUBE ONLY-UNCRACKED BEAMS (1.1

Spandrel reinfc.

-

Fig. 4.139

Dclleclionr olrlructurc.

Fig. 4.140

Urucing punel rcinfureirlg luseul.

276


[Chap. 4

Hotel de las Artes Barcelona. Spain

Architect Structural engineer Year of complclion Height from street lo roof Number of stories Number of levels below ground Building use Frame material Typical noor live load Basic wind vclocily Maximum lateral dcflcction Design fundemcntal period Design acceleration Design dantping Earthquake l o ~ d i n g Type of structure Foundation condilions Footing type Typical noor Story height Bcam span Bcom depth Beam spocing hlateri;~l Slab

Colun~ns Sizc st ground floor Spacing hlolcriol Corc

Skidmore Owingr and Merrill Skidmore Owings and Merrill 1992 137 m (450 fi) 43 1 Hotel Structural steel 2.87 kPa (60 psD 40 m/sec (90 mph) at 30 m (98 St) H/50O, 50-yr return period 5.2 scc Not applicnblc I % sensiccobility No1 applicable Diagonally braced lube in tllc form of mefa portal frames Dense sand Aufcred straighl sltnft piles construc~ed undcr bcntonitc slurry 3.00 m (9 it I 0 in.) Office 9.2 m (30 St) Orlice 157 mm ( I 8 in.) Office 4.6 m (15 ft) Sleel. A572, grade 50 75-mm composite metal deck 60-mm 12.4-in.) concrete + 55-mm (2.1 in.) sccand-pour concrctc

+

W350 by500 1bIf1inlerior: \\TA4 21 e h l e k r 9.2. 13.8 m (30. 45 St) A572 grddc 50 Braced lo p a n belr.cen mega brncing pencl points; rlcel-braced rrilrnes in orthogonal directions

The Motel dc las ilrtcs tower is the ,must prominent par1 of n multiusc cornplcx in

Barcelona. Spain. consislinf o i 5-slur luxury huteliapartment units. commercial oiiics space. retail. porkin.. and beallll club f:~cililics(Figs. 4.141 and 4.142). Thc project is

S e c t 4.41

Tubular Systems

277

278


[Chap. 4

luc3tcd along Barcelona harbor, overlooking the hlcditcrranetln Sea, and u a s colnpielcd in time for the 1992 So~ltmerOlgmpic G m e r The Hole1 d r 13s Ancr- i.;- o:tn -..of:$" -. - n,.p,. all plan to provide new infrastructure and private development of individual building parcels in the Olympic Village area. The lower is envisioned as one of the focal points in the reawakening of Barcelona as a major European capital.

..- .-.

Sect. 4.41

Tubular Systems

279

Continuing a long tradition at Skidmore Owings and Memll. thc uchiteclural form. crnression. and aniculalion of the tower a 2 all bascd on thc beauty and esrccnce of the expused, pninled stmclurol stecl fume. The archi~ecturnllyexposed X-braced framer located on the building periphery nrr organized on a Cslory [I?-m (39-R)] module. These frames form a fully three-dimenrianol iystern resisling nll wind and seismic 1atcr.xl forces as abortion o f t h e tower siavitv.load. o st he Full building inertia is uti. ~ .nr--well ~ ~ lized, n very eifici'ent lalcnl load resisting system is obmincd, with very lillle stecl abort that requircd lo resist the toucr gravity load. ueight From thr: archileclural point of view. a clear articulationof the cxtcrior slmclurc was desired. which is charactcnzed by the crisr, aro~ortionsof steel I b e a m , columns, and hilf-an .,. members. ~-~ . as well as the honest exbressfon of thc connectins ioints. both bolted 2nd ucldr.d.The cxtenor cunnin wail is set back 1.5 m (5 It) from the pcrimrler. thereby nrovidins n c l e u architsctural expression of the exposed X-braced slcrl frame. An open. ; e b l i k e ; ~ c ~ r e allowing the play of daylight through the frame, much desired by the architcctural design team; was-bainncedbythe need for robusmess and slructurnl integrity, particularly at the memberjoinls. Exterior frame members were chosen on the basis of erectabilily, connection detailing, nccessibility for slcel painting and future maintenance, and visual considerations related to the architectural aesthetic. The issues of corrosion and fire protection were addressed in engineering the exterior exposed steel fmme. Corrosion protection for the exposed steel members is providcd by a durable fluorocarbon paint system designed for long life under the coastal marine environment, consisting of a shop-applied primer, undercoat, and finish coat. with a sccond finish cont applied in the field after erection of the stecl frame. The nonfireproofed exterior structure was anolyzed using the latest slate-of-the-art fire engineering mcthods developed in Europe and the United States. Analytical methods to determine the steel lempcrnturcs as well as the charncler and nature of n number of hypothetical design fire events were stndied. High-tempernNre structural analysis of the entire huildine frame comaleted the fire eneineerins - desipn. A simple, straightforu,nrd architcctural cornpoiition expressing thc inhercnt function of the Slruclural frame, thl: Hole1 de Ins Ancs loner represents n prominent !\or),comhinine architccmre and ,uuctur~lrngincuring, marking a major intcm3Uonnl cclubration in Barcelona during the summerbf 1992.

-.

~

Fig. 4.142 Frurnvsurli: Holcl dc lur Art-.

280


[Chap. 4

PROJECT DESCRIPTIONS, BUNDLED TUBES Sears Tower Chicago, Illinois, USA

Architect Structural engineer Year of complelion Height from street lo roof Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity Maximum lateral deflection Design fundamcnlal period Design accclcration Design damping Earthquokc loading Type of structure Foundation conditions Footing type Typical floor Story height Truss span Truss dcplh Truss spacing Material Slab Columns Size at ground floor Spacing Material Core

Skidmorc Owings and Merrill Skidmorc Owings and Mcrrill 1974 443 m (1451 it) l I0 3 Omce Structural steel 2.5 Wa (50 p s 0 34 mlscc (75 mph) H1550. 100-yr relurn period 7.8 scc 20 mg peak. 10-yr relurn pcriod 1.25% scrviceabilily Not applicsble Bundled framed lubes 18-m (20-it)-deep steel-lined concrcie caissons Roft 3.92 m (12 fl 10.5 in.) 22.9 m (75 fi) 1016 m n ~(10 in.) 4.6 m (15 ft) Steel, grade 250 MPa (36 ksi) 63-mm (2.5-in.) lightweight concrete on 76-mm (3-in.) metal deck 990 by 610 mm (39 by 24 in.) built up 4.6 m (15 it) Steel, grade 350 MPa (50 ksi) Not applicable

The Sears Torvcr is the world's lellcsl office building with a height o f 4 4 3 m (1454 it) above ground (Fig. 4.143). It conloins 362,000 m' (3.9 million it') of oflice space in 109 slorics. The setbacks in tile facade result from reducing floor areas required by tenancy considerations. Sears. Roebuck and Company required large floors for their opcrotions, whereas smaller floors were best for rcnlal purposes. The adopted bundled tube concepl

282

'

Latsral Load Resisting Systems

[Chap. 4

provided nn organization of modular areas which could hc terminated at various levels to create floors of different shapes and sizes (Fig. 4.144). Each tube is 22.9 m (75 ft) square, and nine such tuhes make up n typical lower floor for an overall floor dimension of 68.6 m (225 ft). This square plan shape extends to the fiftieth floor, where the first tube terminnlions occur. Other terminations occur a1 floors 66 and 90, creating floor areas of 3800 to 1100 m'(41.000 to 12.000 ft21. The structurr: acts as; venicni canlilc\,er Lxcd at the hase lo resist wind loads. Nind square rubes of varying heights ;Ire bundled together lo crcale ihr larger ovcnll tube. Ench tubr comprises columns at 4.58-m (15-11) centers connected by stiif bcnms. Two adjacent tuhes share one sel of columns and henms. All column-to-he& connections are fullv welded. At three levels. the lubes incornorate trusses.. orovided to axial ~- m&e the ~~~column loads more uniform where tuhe.drop-offs occur. Thesc trusser occur hclow floors 66 and 90 and between floors 29 and 31. The two inarior frames connect opposing facade frames at two intermediate points, therehv reducing the shear Ian effect in the flanee frames. This reduces the oremium for hcigbt~onsidcr;~bly as shoun by the relnli\ely-lou unit stmctur;il rtccl qu;oli~g of 161 Lglrn' (33 pro. The uind-induced sway is nbout 7.6 mm (0.3 in.) per atory, and tltc fundamental period is 7.8 sec. The 22.9-m (75-ftl-square floor arcos of each tube are framed hv one-wav trusses spanning 22.9 (75 ft) i t 4.58-m (15-ft) ccntcrs. Each truss conneci dircctly'to a column with a high-strength friction-grip bolted shear connection. The span direction o r these 1NSScs was alternated every six stories to equalize gravity loading on the columns. The tmsscs are I020 mm (40 in.) deep and utilize all of the available depth in the space between the ceiling and the floor slab above. The spaces between the diagonal truss wch members allow the passage of up to 530-mm (21-in.)-diameter air-conditioning ducts. Benms and columns are built-up I sections of 1070- and 990-mm ( 4 2 and 39-in.) depth, respectively. Column flanges vnry from 609 by 102 mm (24 by 4 in.) at the hottom to 305 hv 19 mm (12 hv 2.75 in.) at the too. and henm flanres from 406 bv 70 mm (16 by 2.75 k.)to 254 by mm (10 by 1 in.j. A total of 69.000 tdnnes (76.ion tons) of structural steel was used in the project, consisting of grades A588, A572, and A36. The steel-tube structure was shop-fabricated into units of two-story-high columns and half-span heams each side. tvoicallv weiehine 14 lonnes 115 tons). The shoo fahrication climinatrd95560f field uelding. ~ u t o m a t r d r l r c l r o s l aweldini ~ was usedior thc hull aulds of hcnms to columns. The continuity plates ocrors columns at the joints ~ c r c fillet-welded by the innershield process. Because site storaee sonce wns unavailable. the frame units were delivered exnctlv when needed and lift&! oif the truck into place. Except for column splices, all field con'neclions were grnde A490 high-slrength friction-grip bolts in shear connections. Exterior columns were insulated to limit the average temperature differential between these columns nnd interior columns.

.

~~~~~~~~

.

Sect 4.41

r

..

b "7

N

3' cellular deck

N

I1

21/2"

D

'ul r-

z

m

Typical lraming plan (levels 1 lo 50) (a)

Li5

..

.

283

Tubular Systems

-

Modular lloor conliguralion (bl Etg. 4.144

ScorJ Tower.

It. wt. cond

284


[Chap. 4

Sect. 4.41

Tubular Systems

Rialto Building Mdbourne, Australia >,.'.,

Architect ..... .. . ,

. .

Structural engineer Ycar of compiction Hcight from sUcel to roof Number of storles Number of levels below €101 Building use Frame nlatcrial ~ y ~ i cfloor a l live load Basic wind velocity Maximum lateral deflection Design fundamental pcriod Design damping Earthquake loading Type of strucmrc

Shear lag behavior

F ~ R4.144 . Srnrs l'cmrr. ~ C ~ ~ n r i r , , , ~ d ]

Foundalion conditions Fooling type

:-,, .

g; ?t:

,?I; ,.*a

2. ..?. rt :,z

s!.

.< ,.,: L.

.-

"~:

Typical floor Story height Beam span Beam depth Bcam spdcjng Slab Columns Size at ground floor Spacing htaterial Core hlatcrial

I

~ e m r dde PrcuPenott Lyon Mathieson Pty. Ltd. Meinhardt Australia Ply. Ltd. 1985 243 m (797 fi) 63 2 Office Concrete 4 W a (80 psfl 39 mlsec (87 mph). 50-yr return 230 mm (9 in.). 50-yr return 6.1 scc 3% serviceability: 510 ultimate Not applicable concrete core with concrete perimeter frames ~ a s a l tover sands and clays over mudstone Caissons 1500 or 1800 mm (5 or 6 ft) in diameter. 18 m (59 ft) long, socketed inlo rock 3.9 m (12 f 9 . 5 in.) 10.5 m (34 ft 6 in.) 500 mm (20 in.) 5 m (16 ft 5 in.) 120.mm (4.75-in.) lightweight concrete 1.2 m (4 ft) octagonal 5 m (16 f t 5 in.) Concrete. 60 MPa (8500 psi) Shcar walls. 750 mm (30 in.) maximum thick at ground floor Concrete. 60 MPa (8500 psi)

A number of structural systems for the Rialto Building (Fig. 4.145) were initially investigatcd and a reinforced concrete swctural system was finally adopted, with speed of construction being a prime consideration in the dcvclopment of formu,ark and reinforcement dctails

:>,

.2,: ;.


Sect. 4.41

Tubular Systems

The external frame or coluntns and beams, urhile being designed for the direct dead and live loads aoolicable. acts as an external tube i n resirtine lateral load. Althoueh the plan shap: i r uns)t~t~aetricaI 3ad tltc colutons arc 5 m (16.4 i t ) apart. ;lnaly$is 01 lhu i n ~ d tmnsfer ardund the uurners indicated re>runxblc thrce-din1:nsiunal action. l h l : corner beams connecting the end columns are most oecessary for Lhis action. The tube effect also provides forsome latcrnl distribution of load from thc more heavily loadcd columns (Fig. 4.146). Thc service cores, being the major elements i n the structure, were the subject o f a number o f detailed considerationr. No sizable penerrations or rebates were permitted i n the main walls. Sizine ofthe walls was not oolv for Iondine considerations. but !v\'as the suhjcct ofrhrinkngc 2nd 2rr.r.p usti~natiun~ 2nd r~.fiocmcntfor buildlng pcrfornlsncr.. F i n d checking afthc intcrnctillc corcl rind r.\tr.rn;jl frames u.2~cxried out using n tl>r~.i.. dimcnrionxl l i n i t u - ~ I ~ . , l ~on:~l)sis. snt Design u i n J 102ds i n th? b.ulding wcrc calculated ~ ~ i mctcorological n g d313 3s13ilz~hlc.Thc huil~lingi r of S L C ~3 beigttt, rile. 2nd s l e e d ~ r ~ ~ that ~ aths s diifr.rcnt : ~ p p r u ~ c h tclocitiu* 2nd wind dcrcctiurl, nurr qignilicant ~n the dciig~t.\ \ ' i d tunncl tsats dutr.rmlncd design prcssurds 10, hoth the iruilding ;and the facade. Frntn thc north, elst. and rvrrt. terrain category 4 (1.36 applicable. ~ l t i l c[ram th~.south, with Port Phillip R3g bein^ 3 k m (?, . mi) distnnt. tcrrain~cnteeorv - . I was considered above level 30 Tlic i;,icr>l projcctirm of thc h ~ ~ l d i n being g, s.ynmctric31. inducer 3 $rind fnrcc un n.ll >luj!s cnnfc,rrn a1111lhs c ~ n l e ruf J t i f i n ~ s rTi16 . pr,r1111dlr.r thc s t r ~ c l t ! rt~h ~ t bcnms and cores have bccn modilied to align thc ta,o centroids as closely as possible at all lcvels: homevcr, a section of tllc building between levels 24 and 40 is subject to a twisting force. Thc calculnted drift at the top of the tower undcr maximum design wind forces and incorporatina this twisting i s 230 m m (9 in.). A major consideration addressed and rcrolved early i n the design phase was the aspect o f shrinksge and creep o f lhc concrete structure. Most buildings of [his size r\,orldu,ide are steel framed and not subicct to these tvocs of mo\~emeots. ,, .An nsaussmeol i,i111~1C I :xnd ~ shritlkagl: U VL.~ICII I ulemcnls in llic prujecl $$asc:lrr i ~ out d i ~ r ~ h i use n g uf rurcar:lt dht3 i l v ~ i l btcurnlhe l~ United Srille~.USL~~LLI?~~:C \;$Iucs derived for material properties and predictions wilh regard to weather and building orouram. a comouter .oroeram was deselooed taking = = into account member size. concrete str~.ttgth,r:inforcr.m~.nt ratio, age ;I 1o:iding. I~umidtty,loldittg condit~uns.and cre:p and sIirink3g~.d~velopm~.nt. I t N ~ anticip:~tr.d S th;it thc total nonelartic .~hon~.nisg oithe 65storv to& would be on order of 1% to 200 mm (6 to 8 in.). Provided allowances are ~itsdei n tlte atlachntest of non-ln~d-bu3rinb ciements such its l ~ frt~ i l atid s the faode, the magnitude u f l h i r nnnvlastic dsform;~tiottis ttot i i g n ~ i l c i n t .HU\I~\L.I, cliff~r~.nccs i n tltc msnilude uf ihnnkage ;md crsup inirltirt :1 1x11 concrete structure 15 3 ntajur .ulljcct n f concern, and this is p&ticularly rclc~,anti n the case o f the Rialto towers. Lone-term differential shortenine bcr~veenthe central core and nerimelcr columns at the top of a typical tower building can be readily catered for as the distances between thcsc elements are usually large. Thc combined shrinkage and creep lo be expected after construclion of the upper levels o f the Rialto lO\\.er5 indicntcd differential rnlucs of 10mm (% . .. in.). i n thecase o f towerB and 1 1 m m (% . . in.). i n thecascofto\verA.Thc mini m ~ nsp:~ns l i n ~ n l l ~r c~9.7~ 01 d ( 3 2 11) 2nd 7.0 i n (23 it), r-sp:cli\ely. I-lot\c\r.r. o * tun d r i \ 2nd B furm a n intugr~tr.ditruclurc. 3 differr.nti:~l\i~lul:un the urdcr of 38 inn1 (1.5 in.) could he -.\PL.CIC~ bct~ee11 >di;lc~.nlc ~ l u t ~ l ill n r I~.!el -41 (IoNL.~ B rnnfj ~ U L . 10 effects o f the addiiional I 7 levels o f k w e r A. The distance between these columns is only .I111 (13 ft). ;~ndclcnrlg ru;h inotcntcnt, u:tn~tut hu tolr.r3tsd in a ~ o n s t c ~ ~ cu ti ti t~l inr !lalore. Jointing oflltc t u ~ c r se l r not 3ccepli~hlc.2nd tlte ~rovisiortnfi!.'h:lt"xt this l e \ ~ 1 was unsuitnblc to Lhe architecture, as !,,ell as inducing a long-term out-of-plumb ofthe top o f tower A.

..

-

~

.

-

Fig. 1.115 Riulto Building, hlrlbuurnc, Austmliu,

287

.

-

288


[Chap. 4

S e c t 4.41

Tubular Systems

289

The solulion arriied at uas to "play a cunfidcnce lnck" on lo!rer 5,nlabng lhe structure '.bcliwc" it is 17 slorics Inllur. Prcrtrcrsing cohles are provided from lcvel I to level 38 and stage stressed as tower A conslrucdonproceeds. Thereby nll columns below level 38 are subject to the same loadings at the same time, and therefore elastic and nonelnstic shortening values are relatively consistent for the lifetime of Ule building (Fig. 4.147).

Fig. 4.147

Fig. 4.146 Fluor pions; Riallo Uuilding

SLnged slresring; Rlnlla Building.

290


Tubular Systems

N6E Building Shinjuku-Ku, Tokyo, Japan Architect Strucmnl engineer Year of completion Height from street to roof Number o r stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocily hlavimum lateral deflection Design fundamental period Design acceleration Design damping Eanhrluakc lr~ading Type or structure Foundation conditions Typical floor Story height Beam span Beam depth Beam spacing Slab Columns Size at ground level Spacing Core

Nihnn Sekkei Inc. Nihon Sekkci Inc. 1996 189.6 m (622 it) 46 4

Offices and retail Stccl 5 kPa (100 p s n 35 mlsec (78 mph) HtZOO. IOO-yr rctum 4.56.4.75 scc 35 mg pcak. 100-yr rcturn 1% rcrviceability; ?% uldrnate c = 0.0533 Dundlcd tube Clay and rand o\,eigravrl 3.95 n~ 113 ft) 19.6. 16.4 m (6-1 f t 1 in.. 53 it 10 in.) 800. 600 mm 131.5.23.5 in.) 3.2. 3.6 m (10 fi 6 in.. I I it I0 in.) 135-mm (5.15-in.) reinforced concrcte 600 by 600 mm (24 by 24 in.) 3.z.3.6 m ( I 0 Cl 6 in.. I I It 10 in.) Fremcd tube

The plan dimensions of the N6E Building ore 92 by 39.2 m (302 by 128 it), which is quite large (Fig. 4.148). The core location caused eccentricities that could not be rcduced using shcar \raallsor bracing systems, so the bundled tube r).stcm was adopted to ochicve a symmetric structure and lo avoid torsional problems (Fig. 4.1491. This mas done at the expense of reduced span lengths and incicased numbers ofcolumns. The building response was estimated using ail available data as well as the alongwind and cross-wind power spectra end cospectra, which vary with the building heighL Ail cslculetions were donc forl: J. and lorsional directions.

Fig. 4.148 NGE Building, Tekyo, Jupnn.


[Chap. 4

Sect. 4.41

Tubular Systems

293

Carnegie Hall Tower New York, N.Y., USA . :.. . 2,: L

Fig. 4.149 Typical structural plnn; N6E Building.

Structural engineer Year of completion Height of street to roof Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity Maximum lateral deflection Design fundamental period Design acceleration Design damping Earthquake loading Type of structure Foundalion conditions Footing type Typical floor Story height Beam span and spacing Beam depth Slab Columns Material Core

I

C e s u Pelli and Associates (desim) Brennan. Beer, G o m a n Associates Robert Rosenwnsser Associntes 1989 230.7 m (757 ft) 62 I Office Concrete 2.5 kPa (50 psf) 47 mlsec (105 mph). 100-yr rcmm period Approx Hl500. 100-yr return 4.8 sec E-W; 3 scc N-S: 2 sec torsion 20 mg peak. IO-yr remm period 1% serviceability: 2x7'0 ultimate Not applicable Side-by-side concrete tubes Rock. 4-MPa (40-tonlft') capacity Spread roolings 3.66111 (12 ft) Vnrying 457 mm (18 in.) interior; 762-mm (30-in.) spandrels One- and two-way, 230 mm (9 in.) thick Size and spacing vary Concrete. 58 MPn (8400 psi) S h e u walls ( p u t of tubes); thickness varies; concrete as for columns

At 230.7 m (757 11) in h?iphr. Camepie IJall Tosser ia the iccond 1:~llestconcrcle rlruclure in N r u York Cily and thssighth tollssl in the wnrld ludly (Fig. 1.150). With a 15.2nl (50-TI)-ulde~nnnllTdce and 1 2?.9-m (75-r1)-wide south race. which olfsc.1~lu a 15.2m (50-it) face above the forty-second floor, this 62-story SlNClUrc is the most slender habitable building of this height ever constructed (Fig. 4.151). The structure occupies the narrow site bctween the five-story Russian Ten Room and the 100-yeor-old Cornegie Music Hull. The structure's nrchitect. Cesar Pelli Associates, dictated the structural scheme by "sculpting" the structure to complement the existing music hall. The double (side-by-side) tube structural system that resulted rvss actually defined by filling in all the available spaces bctmeen the desired windows with concrete. This resulted in nonuniformity in column size and spacing.

I i!


Fig. 4.i5U

Curneglc Holi Tower, KEIVYolk.

[Chap. 4


296

The nonuniformity in the size o f the columns at a level was also extended venicolly as -~offseu -~~~~- and larecr or -~ smaller window sizes dictated relocation or alteredcolumn sizes. Often Viercndcel nction u,as nerdcd to terrninntc venical eletncnls at vlrious locations without the benefit of trnnlfer girders. This occurred on the nonh and south walls and above the fortv-second floorrif the south half of the west wall, which spans over the enlareed haze: Vicrendcel action was also reauired direcllv above lhe ihroueh-block plrjags at the ground floor and at sevcral othcr localions. A center u r b (perforated by lobby egress requirements), common to ihc1u.o side-byside tubes. w m needed to heln Ule north- and soulh-wall columns to efficienllv connect l the C ~ S I nDngc. wall to l c w&t flange wall with minimum shmr lag. A ~ l e r c n d e ecolumn (skipping alternate floors to minimize the lobby obstructions) u,as introduced to rcducc the clear span u f ihc center wcb. This Vicrcnducl column i s the only intcrior culumn i n the stru;ture. which othewisc s u. .o o o ~dl rrnvitv loads b v thhexterior tube uolutttns and t h ~~. . I e v a l n r c o rwi!lls. ~ The large c l x r spms o f 9.1 m (31 it) and more bc1,vccn the elevator core and tlic u c r t wall wcrc spanned wllh 230-mm (9-in.) slabs nnd shnlluu beams ,157 mm (18 in.) deep. This f r a n l i n ~for gravity loads proved to be [nore economical than one-way ioisu; o r w a f f l e slab coislruction bccausi i t orovided more mdss to rcsist uplift forct~s?rolnwtnd loads and to reduce bullding acccl~rations.I t also pro\idcd c x t n height to accommodate mcchanic:,l systems so that with 3 lutal slog. height 013.66 m ( I ? it). 3 ceiltng height o f 2.7 m (9 i t ) uas maintained. TIISdouhlc tuhc design relics hcavily on 760-mm (30-in)-deep spandrel beams to tnpage 211 tltc vcntcnl suppuns to rcsist thc rxind actio~iand to equalize the SI~L.SSCS due to gravity l o ~ d si n all suppons rugardlcss ofthcir smr. The tube's venical rttcmhers vari t d bstr\,cen l R O and 2590 mm (19 and 102 in.) i n length (parallel lo tltc cxtcrior) and included a solid concrete wall behind the service core &a to the cast. The structural design cnnsidcrcd hoth the relasation duc to long-tcrm crccp and 5hrinkagc ofthe concrew mumbur, dnd the instnntaneous demands ofthe wind iurcer. Ennugh gmvity loads % v ~ . r:lassmbled r. to clitninatc the possibility of tension duc to wind in the vertical supporn and to ict the gravitational loads anchor the structure. A few rock anchors at the west end o f t h c center web were added to enhance the vbilitv of < -~ the web l o cngspc llie flanges cv6.n under larger lateral loods than dicvatcd by the Nerr York City cndc or the wind tunnul ru,ults. 'lllc prelintinary design considered both steel and concrete. Conuol ofthe ourceotion of motion w i t h o u i a u x i l ~ mmeans such as damoers was found to be nttainableonlv -- - ,with --.. tit: concrete allerrtalivc because of ihs larger damping 2nd weight of a concrete stmclure. H u ~ c v L . ~1S. a prt~iluliun.because o f its extreme slendcmcss. the stlucturc was dssigned to accommodate a pendulum-type damper. Field meaurements, after the structure was topped out, indicated that dcsign predictions were accurate and n damper was not needed. The anticipated accelerations, projected from these load mcnsurcments. should not exceed 20 m g for the 10-year return pcriod. Concrete was pumped i n to the full height o f the structure. Concrete strength i n the columns did not exceed 58 MPa (8400 psi) because the use of silica fume i n New York City was still questionable at the time the structure was designed. For this and other slender structures, stiffness, weight. and damping are the important parameters diclating the slructurc's behavior. The design for acceptable perception o f motion oRen ovcrrides othcr more mundane design requirements such 3s strength and stability.This aruclure together with its earlier slender siblings (Metropolitan Tower. Cityspire, and the Concordia Hotel) ore prototypes of the future mcgastructures of the neat generation o f I d 1 SLIUCLUres.

-~-

~~

Sect. 4.41

[Chap. 4

-

~

Architect .Y.*::.:,h Stru=tuml engineer

Skidmore Owings and M c r r i l l

Year o f completion Height from sueet to roof

1983 296 m (972 it)

Number of stories

71

Number o f levels below ground

4

Building use Frame material Typical floor live load

OlEce

Maximum lateral deflection Design fundamental period

Not available

Design acceleration

Not available

Design damping

I% serviccnbility

Earthquake loading

Not applicable

Type o i structure

Pcrimeter framed tube; diagonally braced core with outrigger trusses Stiff clay

Foundation conditions Footing type Typical noor

~~

4.0 m (13 i t 1 in.)

Bcam depth

530 mm (21 in.)

Beam spacing

4.6 m (15 it) Steel, grade 250 MPn (36 ksi)

Slab Columns

Spacing Material ' i .

Mat 2.9 m (9 f t 6 in.) thick

Story height Beam span

Material

1:~. ~-:

Skidmore Owings and M e m l l

Stmctural steel 2.5 W a (50 psO Unavailable [force = 196 k N l m (13,400 Iblft) for 100-yr rclurnl H/500. 100-yr return

Basic wind velocity

. .

~

297

Allied Bank Plaza Houston, Texas, USA

~

-

Tubular Systems

core

15.2 m (50 ft)

83-mm (3.25-in.) concrete on 76-mm (3in.) metal deck Built-up. 1016- b y 610-mm (40- by 2 6 in.) pcrimctcr: 610- by 610-mm (24- by 24-in.) interior 4.6-m (15-ft) perimeter: 9.15- b y 6.1-m (30- by 20-it) intcrior Steel, grade 250 and 350 MPa (36 nnd 50 ksi) Braced steel frame, gradc350 MPa (50 h i )

%..

3.22

h

:I<

?!:

,:2.

:$ .*., 4: ;?2 ~:&:

&?. *P~

Allied Bank Plazn was designed to relate strongly to the buildinps around it. Situated on a site which is essentially the center oldowntown Houston, the building has a major tmpact on the western iacadc ofthe city; which is the most dominant view of its skylinc. In form and mnterials, a design was sought which would be distinctive but would Scr\pC


298

[Chap. 4

to complement and tie together its surroundings. A form that tnovcd and flowed was felt to be nppropriatc, one that wns sort and sheer rather tltan 1t;lrd and opaque like the granite and steel rectnnnulnr buildines around it (Fie. 4.1521. The resulting semicurved lower was uchievcd by juxtaposing two quarter-cylindcr shafis (Fig. 4.153). The 71-story tower is sheathed in dttrk green rcflccdve glass, chosen for its sheer quality and rcsponsivencss to light. Tite combination o r p l a n s and curves in the building's design will allow a cconrtant intcrplay of sunlight un its surface.

-

-

-

Sect. 4.41

Tubular Systems

299

Givine" the buildine a human scale was another imoonant asoect or the desianer's intcnlions. Unlike many recent buildings, which are sheathed in reflective glass and appear only as a huge mass. the swcture of the Allied Bank Plaza is subtly cxprcssed with venical&d horizonml mullions. A formal o o m l on theeastsideoflhe b$ldi"eorovides asense of cnlr).. Slncc h5rc or the public u n e r r the tun~~el-cotittccted dounloun buildings st the underground lcrel. Allied Bank PICA o l r ~ r st l i ~olily entnnce directly from the SU~L.Iand combines the tunnel with M open-air plaza, including landscaping and a fountain. A bundled tube frame is the ~ r i m a r vlnrcral svstem for the 71-storv 296-111 1972-ftl1211 186.OUU.m' I? mtliton 11') .iilisd 63nk lorie;. The shape is forme> by luo'quanr;circlcs placcd ~nus)mmctricall! bout thc m ~ d d l ctuhulir line. Tiis colun~nsp~cing5brc 1.57 m ( l j it) \kith the usuil tres-l)pe construction. Thc systcm ilso uses irvo v~micll trusses in the core, which are connccied to the exterior tube by outrigger and belt wsses. Sienificant imorovemenl in tubular behavior is obtained bccause o r the oarticioation of the INSSeS. This sysrcm, thcrcrorc, embodies elements from the framed tube, bundlcd tube, and truss rystcme with bcit and ouvigger trusses. The truss system provides another transverse frame linkage in the curvilinear part to improw its shear lngchnrnctciisticn. The structurai system for the Allied Bank Plaza towcr was sclcctcd after study of both steel and composite systems. Tite system permitted a substontially reduced cons w c t i o n time. The tower's form and slcndcrness arc a radical departure from past rcctnngularbuildings of this height. yet the inherent rigidity or the bundled tube system dcveiooed for the tower limited stccl w c i ~ h to t 128 ke/m2 126.2 nsn. b

-.

-

cant reductions in design wind pressure belorr' that experienced by square or rectangular rorms. The tower is founded on a 2.9-m 19-ft 6-in.)-thick mat roundation aooroximalely 20 m (65 ft) below grade, which pc;mits utilization of four lowcr lcdels for necessary retail, mechanical, and parking lunctions.

Fig. 4.151 hliird Unnli I'inzn. Hoartun, Tcsits. tPbrlio I?HedN'rS-Blcrriag.1


300

[Chap. 4

4 ~ 5 HYBRID SYSTEMS

Tall buildings hdve been lraditionllly designed lo n l o k use of 3 rlnglc type uf Inlcr~l In3d resisting system-inttially s ~ m p l cmoment resisting frames 2nd then shcar wall s\,rtcms and frimed rubes. Until ~ h radvent . of economical, c3sy-lo-use. high-capacit) cbmouter hardware and software. structural svstems had to be amenable to hand calcuI;ttioc or cumpuler a n ; ~ l y s ~usit~g s limitcd-c:tpacity nlach~nts.Notvnda).~computcr capacil) l s nu1 ;an issue, and decisions on slructural syilcms art made on 1h~'basisof1h:ir r.ficcts on the xppcdrance and funclioning of the building and on its cnnaln~ctahil~ty. This is not to sieeest that on,*l/~i,in~ musl still be aware of . " is nc&otable-lhe e&ineer 111,: pi1p~II5 ofcrc3ting ;~bruptdiscnntimriticr in building sliffncrs. the Ions-tcrm cffecls nf dilf:rcntial ixi31 siloncninp. and other side effccl, of using mired systems and multiple materials. as Bank Center in SinAn excellent examnle of a hvbrid svslcm is the O ~ ~ e r s eUnion gdporc. Here :.b r x t d stcvl fr:,n:c rvas used b:causc ofils lightnos. lnng sp:inniog ihd. )I!, small metnbcr aizss, absence of crccp shancning. and. combined with ioncrcle a h e ~ tralla. r for iL\ r c r \ cost.r.fficicnt contribution to l>ltral stiffn~ss. Another tvoe of hibrid svslem " eaininr! oooulsritv is the concrete-filled steel lube , column, u.berc lhe r.rcct3bility of n str.ci framr: is 111iinlaincd.but the c o s l . ~ f f c c l i ~3 ,~- c i;! In-d uapacily ufhiglt-rlrcnpth concrete is u ~ e dThe stecl tube pruvidcs cunfincmcnt lo the concrelc much more eificiently than normal reinforcement does, and it is on the extreme outside. where il is most effective. Of course fire orolcction must bc considered. If the slecl tube is considered ns sacrificinl in a fire, then inlernal reinforcement sufficient for the reduced loading normnlly prescribed for the fire limit state must be provided. If external fire protection is provided, lhcn internal reinforcemcnt may not be needed. If concrete can be oumocd into the column from ihc base of each Dour. then a number ofstorics can be concreted at one time and vibration of the concrele is not necessary. Examples of such a system are Cnsscidcn Place. Melbourne, and Two Union Square. Seattle. The rrends of modem architecture sometimes force the structural engineer away from convention in a search for a struclure that will nccommodale ocsthctic and functional demands while meeting struclurnl requiremen*. The result may be a structure which on one face of the building is of a different type than the other faces, as in Georeia Pacific. Atlanta. or a S I N C ~ U ~ ;with a number of quite different clemenls formine i s Lateral load resisling frame, an exccllenl example being First Bank Place. ~ i n n e a ~ o l i s . Here the engineer has provided a braced steci core connected via outilggcr beams to large high-strength concrete perimeter columns, incorporating cast-in fieelwork lo aid erection and connection. Although this systcm provides in-plane stiffness. its lack of torsional stiffness required that additional measures be lakcn. which rcsultcd in one buv oi tr.ruu.ll cxterior hr:lcinp 2nd ;i iturnher ui l:vcl. of pcriln~.lr.r\'lerc,dr.cl 'b..oJ.iges."-pr.rl~aps unc of lhr h~.rtcaamplcs of the an uf$~ructuralcngin~'rring. Wilh t l r adtctll of high-r~renglhcottcrcle [uuncrclc ;1buv~'50>!PAor (70UU psi,] 113, come ihe era of the "sipcrcolumn." where the stiflncss and damping cnpabjlities of larre concrete elements are combined with the liehiness and conslructabilitv of stecl li:unus. I-l~gI~-r~rungtlt uortcmte. \$hen 11 irlclrrdu, silicz fumc ;mi 3 high-rarrge ivu:
.

-. .

. .

.

Hybrid Systems

Sect. 4.51

301

The Intcrtirst Plaza in Dallas (not described in this Monograph) uses supercoiumns in conjuncrion with an almost conventionai steel frame, and the Columbia Seafirsl Ccnler in Scatllc incorporates very large supercolumns connected by slecl diagonal members.~?a braced steel core. Another example, although never built, is the Bank oTt11c Sou*\t.est tower in Houston. Hcrc eight giant concrete columns form the chords of four vcrtiFi\ steel megawsses. The orcvious cxamnles sueaest that hvbrid slructures are likelv to bc the rule rather I I I ; ~the exccplion for'luture r e g 1x11 buildings, a hsther lo crest; scccplahle dynaloic ~ l ~ i ~ r ~ c I ~ ~orr i10 s t ilccun~~nodatc ics thc cu,npie\ .Il:tp~.s dtm3ndvd by modern ;!rchilccture. Hybrid structures are not somcthlng be tackled by the novice cnginccr armed with a oarveriul microcornouter and a structural nnalvsis software 'oackaee. as a sound knowicdgc and undcrstanding of material behavior (such as ductility, damping, creep. and shrinkage), which is not included in analysis and design packages and mostly no1 codified. is essential and construclabilitv must bc a oarallel consideradon. However. \vithour hybrid structural systems many of our modern tall buildings may n e w 1 have heen bull1 in their presenl form.

..

u

302


[Chap. 4

PROJECT DESCRIPTIONS Overseas Union Bank Center Singapore

Architect Structural engineer Year of completion Height from street to roof Number of stories Number of levels below ground Building usc Frame material Typical floor live load Basic \\find velocity Maximum lateral deflection Design fundamentnl period Design damping Earthquakc loading Type ofstructure Foundation conditions Footing type

Typical floor Story height Beam span Benm depth Beam spacing h'lalerial Slnh Columns Sire at ground floor Spacing htoterinl Core Thickness at ground floot htalerinl

Kenzo Tange and Unec/SAA Poflncrship Meinhardt Asia Pty. Ltd. 1986 280 m (919 it) 63 4 Commercial. rctuil, office Stccl with concrae walls to sL-~irsand core 2.5 kPa (50 pso 37.7 mlsec (84 mph). 1000-yr return 448 mm (17.5 in.) 7.3 scc 1% ser\'iceability; 3% ultimate Not applicable Hybrid system of steel frames rvith concrctc ~ i ~ stol incrcasc l~ rigidity Silty sand. sandstone. siltstone, claystonc 7 caissons 5 lo 6 m (17 to 20 it) in dismeler. 100 m (328 i t ) deep. belled to 9-m (30f i ) diameter 4 m (13 it 1.5 in.) 20.3 m (66 ft 7 in.) 950 mm (37.5 in.) 4.32 m ( I 4 it 2 in.) Steel, grade 5 0 and 43 150-mm (6-in.) concrcte on metal deck 800 by 600 mm (31.5 by 31.5 in.) Varies Steel, g n d c 55 and 50 Hybrid stecl frame with concretc wall zoncs 600 mm (24 in.) Slccl. g n d e 55 and 50; concrete. 45 MPa (6400 p i )

The Oversear Union Bank Ccnler (Fig. 4.154) is a prestige state-of-the-art dei,elopmcnt designed to house the bonk's lleed oflicc and provide renval office, commciciul, and

304


[Chap. 4

Hybrid Systems

Sect 4.51

parking space in Raffles Plnce. Singapore. The high-rise section is conceived as two visually scumate triangle towers (although structumlly~. integral) facinp. each other on the hvooienure. A service core and a w i a n i ~ ecolumn in one comer oroAde suooort for the , higher tuwcr. The loner tower is supponcd on n smaller triangular colutnn and no Lshaped column. The slructurc has hei~ht-to.widthratios of 10:l on the south cluvxion and 8:l on the north elevntion. he hirh-rise structure ~rovidescolumn-free soace throuehout its full heieht above nround 6. i r . 4.155). The high-nsr slruclurc is framed using high-jicld structural steel. The princip,l rolumnr we fabricated box columns framing the cieratur ,hafts and flanged T si12pea IU conform to the wall lines and minimize encroachment into the elevator shaft arca: Simply supponed stt.el w s r r s 950 mm (37.5 in.) dccp spaced at4.32-01(14-it) ceoters in an cast-west direc1i.w support the large column-free areas. These trusser xrc dcsigned to act compositely with the concrete floor system. The floor system consists of areinforced concrete slab composite with a 63-mm (2.5in.)-deep ribbed steel deck. The concrete slab is a total of 150 mm (6 in.) thick in order to maintain a sufficient concrete thickness, after reticulation of services. for the rcquircd fire separation between levcls. Fire protection of the s s e l frame is provided by liphtweirht mineral fiber (Firs. 4.156 and 4.157). The high-rise structu& is supported on h total of seven caissons ranging in depth from 96 to I10 m (315 to 360 ft) and in diameter from 5 to 6 m (16.4 to 19.7 ft). Thc caissons are belled at their bxse and carny Lheir load in end bearine on solid rack Development of the most efficient siucmrai system is the essintial prerequisite to optimization of the design. The choice of ryslcm drsmatically affects the quality of the material required in the design. The family ofstructural systems based on the tubular concept has provided the types most widely used to date for high-rise and ultra-high-rise structures. However, it has become necessary to seek new structural systems lo respond to changes which have taken place over the last decade, including the very strong influence on high-rise buildings of evolving architectural forms with many large open arens which extend through m;ltiple floor heiehts. 'The d'ecision to use structural strcl in lieu oiru~niorccdcuncrelc for thc?SO-m (91% (1)-hlph O U B tou'cr e a s dicta1c.d by ruuctural consideralions rxhcr t h ~ necnnunlics (Fig. 4.158). The following are the principal f3ctors that dcturmincd the ndoptiun o i structural steel in lieu of concrete.

.

-

..

-

I. T h e asymmetrical geometry of the.structure resulted in higher stresses in the columns supporting the higher triangle thnn in those supporting the lowcr triongle. This caused unequal column shortening from creep and a consequent lateral movcmem of the slruclure. 2. Differential movement (creep) occurred between the reinforced concrete supcrcolumns in the primary megasystem and the swctural steel secondary system within the portal frames of the megastrcturc. 3. The dimensions of the vertical structur~almembers had become gross. resulting in loss of floor space and presenting substanrial planning difficulties, both archirccturally and in the distribution of building services. 4 . Tile sujl conditions were poor. jnd :! sp:cihl and cos~l'yfnusdatinn wr.3~nccus5:lry. Structural hIcrl kccpr \he weight down cu~npsrcdlu v cuncrct: stmcturc, rsdu:. Ink buth the difficulty and the cost of footingr. 5. 'The use uf high-yield steel restllted in light:r, snlaller, and leas cnstly structural nlembcri nhich svuuld sa~isf>the system stiifncas crilsria.

LEVEL

FLOOR

RISE

LOW

RlSE

FLOO"

ELEVATION

~ 1 64.155 .

~ ~ ~ r npiln~ gnnod r elcmlion; Ovcrscns Union Bunk Ccnlcr.

I


306

[Chap. 4

Sect. 4.51

Hybrid Systems

307

The composition of the structure is one where lhe stcel frame provides the skelcton ofthe structural system, with the bracing and reinforced concrete walled zones acting to increase the rigidity of the building (Fig. 4.159). The individual elemena (steel frnme and concrele walls) nre both capnblc of functioning independently in the trnnsfer of vertical loads from the top lo the foundations. However, as elements used in conjunction. h e concrete provides restrain1 to the slecl. allowing the steel frame to be fully stressed as an isolaed component. Control of dilferential creep between concrete and smctural steel was investigated extensively, taking into considcrntion axial shonening of the 5 t ~ ~ l u rslcel a l columns. the construction program, and the bracing of the steel smcrure during erection. The likely stresses in the concrete elements and thc steelwork were considered in both the short term and the long term. The analysis indicated that the oplimum was for the concrete clemcnls lo follow behind the steelwork by approximately four lo five lcvels. The maximum allowable differential was the concrctc elemcnls lagging 24 levels behind the steelwork. The final optimized solution for the OUB structure is a mixed-frame hybrid structure, providing an effective SlNClUrc utilizing the hest properties of slccl and concrete to achieve the minimum cost.

SERVICES ACCESS

1

/

LIGHTWEIGHT FIREPROOFING

Fig. J.156

Flctor plan: Olcrrcns Union Dunk Ccnlcr.

Fig. 4.157

Piun of reinrorccd concrcle wollr: Orerreus Union Bunk Centur.


308

[Chap. 4

Sect 4.51

Hybrid Systems

Hhbrid .,truclurs in n u n h g n f cottaidsra~iunas 3 cnttsciot>rdesign ilppr03cl1. 7.111: US? 01 reittfurccd coucrstc ulsmcne l o contrul thc dcflcclion and dynamics o f loll steel 51mcturcs provides an effeclive altcrnadvc smclural svstcrn that bill ailow the dcsiener to" malrerull use o f the higher allowable stresses o f 'high-yield steels when other bracing systems are inefficient or unacceptable architecturally.

TYPICAL BRACED FRAME

TYPICAL -R.C. SHEAR WALL

PLANT F:LOOR TRUSS

Fig. 4.l5Y

fig. 4.158

Slrutturirl r l c c l ryslunl; O ~ u r l r i ~Usian r Bunk Ccster.

I'rinlurysl,cur $ ~ usyslcrn; ll 01.errcus Uniun nonh Cunlrr.


[Chap. 4

Citicorp Center New York, N.Y., USA

Architect Slructuml engineer Year of completion Height from street to roof Number of stories Number of levels below ground Building use Fmmc material Typical floor live load Basic wind velocity Maximum lateral deflection Design fundamental period Design acceleration Design damping Earthquake loading Type of structure Foundation conditions Footing type Typical floor Story height Beam span Beam depth Beam spacing Material Slabs Columns

Material Core Materiol

Hugh Stubbins and Associates with Emery Roth nnd Sons LeMessurier Consultants with office of James Rudeman 1978 279 m (915 ft) 60 3 Office, retail Steel 2.5 kPa (50 psf~ 41 d s e c (92 mph). 100-yr return HI600 at I-Wo ( 2 0 . ~ ~seniceability 0 load 6.9. 7.2 scc Less than 20 mg peak. 10-yr return Measured 1.1 and 0.9% serviceability increased by TMD to 4% each direction Not applicable Braced perimeter tube with braced core below 9th floor; TMD at top Manhnnnn schist Steel bore plates on grout on rock 3.89 m (12 ft 9 in.) 10.3, 12.8 m (33.9.42.1 ft) 530 mm (21 in.) 3.81 lo 3.91 m (12.5 to 12.84 ft) Steel, grade 350 MPa (50 ksi) 63-mm (2.5-in.) lightweight concrete on 76-mm (3411.) steel deck Pairs of 965 by 762 mm (38 by 30 in.) max by 3421 kg/m (2294 Iblft) at 5.74-111 (18.83-ft) centers at center of each side of building Steel, grade 350 MPn (50 ksi) Moment frame above 10th floor, braced frame below Steel, grade 350 MPa (50 ksi)

This 60-story tower contains an area of 102,200 m' (1.1 million it') of the project total ' (1.8 million ft'). The 47.8-m (157-ft) square lower has a dramatic and of 167.200 m

I

Sect. 4.51

Hybrid Systems

3 (76 it) unsupportc~Crom daring appearance, with all four of its corners jutling 0 ~ 1 2 m only four exterior columns, one centered on each side, which free-stand for a he~ghtof 34.7 m (1 14 it) at the base (Fig. 4.160). The central core also suppons the tower. This unique structure was not designed this way arbitrarily just lo achieve a dramatic effect. Thc site. a city block in Manhattan, was purchased fully except for St. Peter's Lutheran Church on one comer of the block. The church agreed to sell its air rights, but would

312


S e c t 4.51

[Chap. 4

~

.

~ ,

Fig. 4.161

,

.

Eic~.utiun;Cilicorp Ccntcr.

~

~

313

half of the tower gravity load down to the four base "legs," one centered on eoch side. The ..- svslem. - ,~ . because it rcoeals a n each face o f t h c tower. is also very cflicienl in resistiug wind lorcus, hoth shcar and ovcrlurning, slnce il forms a cumpieke brncsd lubc. A ncal rtructural touch rvar the omission of the corncr columns at Ihc floor just bduw lllc main a i a ~ o n a inlcrsection l uith thr corner cvrry. cichl - storics. This was to avoid accumulating gravity load in the corncr columns and gives unobstructed corncr views as a bonus. An 8.8-m (29-it)-deep perimeter truss on top of each of the legs carries the gravity lnadr ofthe lowest seven floors to the center lees. The wind shear is transferred through the tenth-floor diaphragm at the top chord level of this truss over lo the diagonally bnced elevator core, which carries it down to the foundation. Wind overturning forces continue from the superstructure mast columns through the legs to the foundation. The office floors arc framed with convendonal steel beams, with a light.. - tvoical ,, weight concrete slab on clcctrificd undcrfloor slcei deck (Fig. 4 162). Thc core has morns~~~-cunncctcd lr3mus in nrdcr lo provide a syrtsm to delivcr floor-by-noor wind lorccs lo the h r ~ c c dtube . pancl . poine occurrin~ -cvcry.lounh story. and lo allow $honer unbraced lengths ofthc main compression members.

allow no columns of the office tower to pass through its facilities, and it required that a new church building be designed and constructed in that comer with its own distinct identity. This last requirement led the architect to place the first office floor more than 46 m (150 fl) above the streeL The most direct and economical way lo achieve the 23-m (76-it) comer cantilevers on each face of the typical tower floor was to provide a steel-hmed braced tube with a system of columns and dingonnls in compression, channeling the building's gravity loads into a 1.5-m (5-ft)-wide "mast" column in the center of each tower face [Fie. u 4.161). The main dingonnls repeal in eight-story modules. The compression diagonals are restrained by horizontal tcnsion ties at four-story intervals. This system brings one-

~

Hybrid Systems

;

,

314


[Chap. 4

The wind tunnel study for the tower, conducted by the University of Western Ontario. Canada, indicated rhat persons on upper floors ofthe tower t ~ ~ o u experience ld uncomfortably high lateral sway accelcrations in wind storms. In order to reduce nccclcrations to acceptable levels there were only t\vo possible approaches: add a great den1 of mass and latcral stiffness withour increasing the natural vibralion period, or add to thc building's natural damping. The first approoch would lrave cost about 55 million. whcrsas the second approach \vould lhavc required increasing the building's damping from about 1 to 4% and designing and constructing the \r,orld's firs! tuned mass da~npcr (TbID) of anywhere near lhis size. Tllc second approach was adopled at a final cost of less than one-third of the first approach. The inilial step was to convince thc arcl~itect and owner; then the slruc1ur;ll cngincer hod to find a \\,a). to actually do it. Fortunately. LeMcssurier Associalcs u r r c able lo cnlisl the technical assislance of Prof. Alan Davenport of the University of Westcrn Ontario. Prof. David \Vnrnmley of M.I.T., and tllc firm of MTS Systems Corporation of Minncilpnlis. The lauer firm provided the detnilcd mechnnicsl. clectricnl. and cuntrol system design and also constructed the TMD systcm. with the assistance of HRH Conslruclion or New York. the general contractor. The TblD is located an a dcdicalcd floor at 242 m (793 it) above grade, near the top of the towcr. for maximum cff~crivcncss.The Citicarp tower was dcsigned from the beginning to have the ThlD system. The system used includes a moving 373-tonne (4 In-ion) concrete-mass block tl~atslider binxially in the norlh-south and cast-wcst directions nn pressurized oil hearings on polished stecl plates. Tlic m a r is conneclcd to the building structure ria long t c c l boom struts, prcssurircd oitmgcn springs, and hydraulic scrvrl aclualors. The lateral atiffncss of the spring elements makes thc systcln inlo 21 clasrical passive spring-mass rystcsi. \\'hich basically is tuned to the same frcqucncy as thc tower and acts as a vibration absorbcr lo effectively incre:~scthe building's energy absorption. or damping. The TAlD reduced accelcrations lrom wind-induced motion by 40 to 505b. 11 is designed solely to increase occupant comfort. The building is dcsigncd for and strength as if the ThlD were not there. The TMD syslcm has pcrformcd very well since its installation and has weathered many wind storms and cvcn a hurricane.

Sect. 4.51

Hybrid Systems

315

CenTrust Tower Miami, Florida, USA Architect Structural engineer Year of completion Heighr from rtreel to roo1 Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity Maximum lateral deflection Design fundamental period Design acccleralion Design damping Earthquakc loading Type of stmclurc Footing type Typical floor Story height Beam span Beam depth Slab Columns Size at ground floot Material Core Material

I. M. Pci and Partners CBM Engineers. Inc. 1985 178 m (585 it) 48 None Office Concrete 2.5 kPa (50 psf) 5 4 mlsec (120 mph) 508 mm (20 in.) 3.50,4.50 rec Not calculated 2% serviceability: 5% ultimatc Not applicable perimercr partial tube with interior shear walls 2.1- to 2.4-m (7- to 8-ft)-thick mat on precast piles 3.81 m (12.5 ft) 14.6 m (48 ft) max 508 mm (20 in.) with 813-mm (32-in.) haunching Concrete joists at 1.8-m (6-ft) centers and 114-mm (4.5-in.) slab 1600- to 1220-mm (63- to 48-in.) diameter at 3.57-m (15-ft) centers 48-MPa (7000-psi) concrete Shear wall, 610 mm (24 in.) thick maa 48-MPa (7000-psi) concrete

Ovedooking Biscayne Bay. the 48-story CenTmsl Tower adds a unique shape to the skyline of downtown Miami (Fig. 4.163). Thc building consists of a 37-story-tall office tower set on lop of a block square 11-story ~ a r l t i n ggaroge. A quarter-circle in plan, the office tower's arc steps back three times as it rises up.The 90° comer of the quarter-circle is chamfered to create an additional 25.9-111 (85-it)-wide face of the building. The garage also serves Miami's convention center and has a people mover station on its fourth floor. On top of the garage, the building carries a large landscaped area, including a refleclion pool

316


[Chap. 4

The building is conslructcd in reinforced concrete. Floor framing consists of 520mm (20.5-in.)-deep pan j0iSls. spanning up lo 10.7 m (35 11) and supporied on 11.6-m (48-it)-long haunchcd girders. Ocplh ofthc haunched girdcrs varies from 520 mm (20.5 in.) in the middle to 813 mm (32 in.] at tllc ends. Thc three 4.6-m (15-11) Slcp backs at the circular face of the building are locolcd at floors 20.31. and 46, as shown in Fig. 4.161. Con\,entional girders are used to transfer the columns at floor46, but at floors 20 and 31 an unusual one-floor-dccp brackcl is employed to transfer each column. A normal marc of transfer girders would have rcsulled

Sect. 4.51

Hybrid Systems

317

in a loss of lease space at both of thcse floors. The location of transfer columns and brackets at the twentieth floor is indicaled in Fig. 4.165, and a typical one-stded brackel from the perimeter column is shown in Fig. 4.166.The gravity column loads at the twentieth floor range between 13.300 and 17.800 irN (1550 and 2000 tons). UidSr column load the bracket requires lateral bracing, which is provided in the form of wall sltear panels between floors 1 9 and 20. Where a wall shear panel aligns with the bracket, compression and tension chord forccs are directly anchored in tllese wall pnnels. Such tension chords at floors 19 and 3 0 are prestressed with an effective force of

Tower axis is 45 degrees o f f garage axis. Because the columns of the curved wall describe an arc in the garage, their spacing is wider than those on the straight walls to accommodate the parking bays. Fig. 4.164

Pcrin!clcr column 1n)uuL; CcnTrurt Tsacr.

t, 318


IChap. 4

11.136 IiN (1250 tons). For the other brackets. these chord forces are transferred to the wall panels via floor plates acting as in-plane diaphragms. The floor slab over pan joislj is increased from 114-mm (4.5-in.) normal thickness to 190 mm (7.5 in.) at floors 19. 20.30. and 31 to provide required strength and stiffness for the in-plane diaphragm forces. A partial framed tube at the perimeter of the tower and minimal shear walls in the core are provided for the lateral load resistance, causing least interruption in the flow of traffic in the garage and a minimum loss of parking spaces. Shear walls are transferred

[

1.

Hybrid Systems

Sect. 4.51

319

tu culun~ns11 the lcnth fluor 01 the fsr;ige lo iacilit3tc tr.lilic flos\,. 'The p~r~i;~l lr:!mud ~ u h cir c ~ r r l e dthrough thc giir~gci~nddesigncd lo resist the cntire 131~131loads in th~. carnac ;IS rrcll. The nnrual fran>:d t ~ h cconsirts of 1%" ~ I ~ ~ n n ~ I - rsrB i t l~np~(~lith .~~d rnlt~mn.;st ~ . . 4 6 - n 115'-ft) , centers linked bv frames alone - lhe circular arc and the chamfered face. with the columns spaced at 8.6 m (28 f t 3 in.). Columns in thc garage are 1067 by 1880 mm (42 by 74 in.) rectangular and 1372 to 1067 mm (54 to 42 in.) in diamctcr round. Columns in the totver vary from 1067-mm (42-in.) diamctcr at lower floors to 761-mm (30-in.) diameter at the top. Spandrel bcams nv. -. 016, ...... rnm 176 in the tower., but varv in dcoth at the -carace - floors from 1372 ,--in ....,1 decn ---r .~~ ~~~mm (54 in.) at the three stmight sides to 813 k m (3- in.) along the circular arc due to headroom requirements. Concrete strength in columns and spandrel bcams rnngcs from 49 lo 28 MPa (7000 lo 4000 p i ) , but is keptat 28 MPa(4000 psi) for the remaining floor framing. The lower is supponcd on a 2.1- to 2.44-111 (7- to 8-ft)-thick mat foundation bearing on 350-mm (14-in.) squore precast piles. G a n g c columns are founded on spread footings. b

-

~~~

.~ ~

~~

shear panel between liwrs 19-20 and 30-31

Unusual eccentric transfer brackets at the 19th and 30th floors transfer wind and gravity loads directly to the perimeter columns. Plan of 19th floor is shown here; 30th floor is similar.

I

Elevation

u

the floors act as diaphragms restrained between vertical shear elements. -

Fig.4.165 Trunrrcr flour phn; CenTrurl To\rer.

Ftg.4.166

Column trnnrrcr dclnil; CcnTrurt Toncr

320


[Chap. 4

Columbia Seafirst Center Seattle, Washington, USA

Architect Structural engineer Year ofcomplction Height from street to roof Number of stories Number of levels below ground Building use Framc material Typical floor live load Basic wind velocity Maximum lateral deflection Design fundamental period Dcsign acceleration Dcsign damping Earthquake loading Type of slruclurs

Typical floor Story height Slab Columns

Chester Lindsey and Associates Skilling \Yard Magnusson Barkshire. Inc. 1985 288 m (947 it) 76 6 Retail, commercial, parking, offices Structursl steel with composite stecl-conC ~ C I Ccolumns 2.5 kPa (50 psO 34 mlscc (75 mph) 483 rnm (19 in.). 100-yr rclurn 5.3 sec 20 m g peak. 10-yr rcturn 2.510 including dampers lor 10-yr rcturn; 2.0% ignoring dampcrs for 100-yr rcturn Z = 0.75. C = 0.03, K = 0.80 Braced steel corc incorpornting viscoclastic dumners: trianculnr corc is linked bv diagonal steel members at its corners to 3 lerge steel and high-strength concrete

Hybrid Systems

sect. 4.51

321

framing for the p l a n , arcade, and parking levels is a 114-mm (4.5-in.) concrcle slab o\,er 76-mm (3-in.) metal deck. Abot,e the plaza letel, the floor framing is 50-mm (2in.) concrete slab over 50-~nrn(?-in.) dcck. All stecl floor bcnms arccomposite with the concrete slabs. Th'e'skyscraper conlains 135,415 m2 (1,457.561 ft2) of office space and six belowp d e levels of parking for 536 cars with an area of 29,670 m' (319.368 fs). Public

-

3.5 m (I l ft 6 in.) 50-mm P i n . ) concrete on 50-mm (2-in.) steel deck 3 major columns. 2.44 by 3.66 m (8 by 12 it) at ground floor Concrete, 66 MPa (9500 psi) Braced-stcel rigid fmme with arches up to I I stories tall transferring load to composite columns

This innovative skyscraper has just 73.24 kplm' (14.97 psO of structural stccl and three c o m ~ o s i t ecolumns o l ultra-high-streneth concrete. It uses both materials in their most efficir.nl manner. TILL.btulding is cumplelelg 1r:lm:d i n strurlur~lrlucl. \\'lnd and ~.nrtIlqllak~.loi!d* arc r~..i(t:d h! it ~ t r t ~ c t u~rI ~C Cl I innnlcnt r~.slstinghnc~.di r ~ m c a, l u c l ~I., triangular in shape and locatcd in the interior core. Exterior windows are unobstructed. Compositestructural steel and concrete columns are located at the vcrticcs of the triangular core to carry a large portion of the vertical loads. reduce wind swny, and resist seismic forces. At thc base of the structure, tllcse composite concrete columns are 2.44 by 3.66 m (8 by 12 it) in dimension. The concrete strength is 66 MPa (9500 psi). The sway of the building is limited to Hl600. The floor

~ i g .4.167

Columbtn scufirrt Ccnler. seutfl~,~ a ~ l ~ i ~(Courier). ~ t o n olSkilliag. . IVord Afosnurron Bnrlrbire. Incl

.: 322


: I

[Chap. 4

arcas consist of a lobby levcl containing an area of 1825 m' (19,641 it2); four shopping levels with a total area of 13.948 m' (150.135 ft'). featuring retail and c o i mercial space; n multilevel shopping arcade which is open 24 hours a day; a multilevel landscaped plaza surrounding the entire office tower; as well as an underground pedes. trian tunnel connecting the building to another office building across the street. Columbia Center's excavation was the deepest ever undcrtakcn in Seattle. It reached 37 m (121 ft) below Fifth Avenue and 21 m (70 ft) below Fourth Avenue. Complicating the task was the requirement to protect an existing five-story office building at the Fourth and Columbia comer of the building. The shoring wall was constructed by drilling 12-11?(4-it) holcs at 4 m (13 ft) on ccnter to at leas14.3 m 114 the hn?,~ ft) ..,hplnw -tom ofthe excavation. These holes were fillcd with lean concrete and n pair of 350-mm (14-in.) wide-flange steel soldier pilcs. Tiebacks wcrc placed in the normal manner between the pair of vertical soldier piles. 150- and 200-mm (6- and 8-in.1 wood lanvinn was used lo support the earth bcrween the pair of soldiers piles spaced 4 h (13 it) a p a n The building structure design underwent thc scrutiny ofextcnsivc testing i n n wind tunnel at lhc University of Wcstern Ontario, Canada, for both static and aeroclostic loading. The acroelastic tests mcasured the twist, sway, base shear, and acceleration of the building. They showed that thc building performed very well in the wind. but revealed that the accelerndon o f t h c building in a major windstorm might bc felt by a portion of the occupants. Viscoelvstic dampers to absorb wind energy were added to thc moment resisting braced frame to eliminate this possibility of uncomfortable acccleration.

--.-

!

,

S e c t 4.51

Hybrid Systems

323

First Bank Place Minneapolis. Minnesota, USA

$

:

Architect Smctunl engineer

:

Year of completion

i

Height from street to roof Number of stories Number of levels below ground Building use F m e material Typical floor live load Basic wind velocity Maximum lateral deflection Design fundamental period Design acccleration Design damping Ennhqualie loading Type of structure

,: ,' :

:

Foundation conditions Footing type Typical floor Story height Benm span Beam depth Beam spacing Slab Columns Material Core

Pei Cobb Freed and Partners. lnc. CBM Engineers. Inc. 1992 236.5 m (776 ft) 56 3 Office Steel with concrete supercolumns 2.5 W a (50 psQ 36 d s e c (80 mph) 533 mm (21 in.) 6.48, 5.26 sec 24 mg peak. 10-yr return 1.25% serviceability; 1.5% ultimate Not applicable Spine structure, supercolumns, and braced frames with Vierendeel "bandages" Rock, 7.5- to 10-MPa (75- to 100-lon/ft2) capacity Unreinforccd rock footings 3.96 m (13 fl) 10.97 to 18.28 m (36 to 60 ft) 406 to 838 mm (16 to 33 in.) 3.05 m ( I 0 ft) 133-mm (5.25-in.) lightweight concrete on 50-mm (2-in.) metnl deck 2160 mm (84 in.) square at 23.24-m (76R) centers Concrete. 68 MPa (10,000 psi) Braced spine. A572 steel [350 MPa (50 ksi)]; column size 1067 by 914 mm (42 by 36 in.) to 914 by 610 mm (36 by 24 in.)

A 236-m (776-it)-tall 56-story chiseled rosrcr i, the t;illcst of il~rci.distinct-looking hul

intcgral buildings which form First Bonk P1:lcc (Fig. J I 6 8 ) . The laver is crowned w t h a 13.7-1" (45-ft)-lti~h ctrculnr grid of stscl uhich c~ntiluwra6 m (?U fl) out rrom a \.
Z!? i.

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.

:

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Hybrid Systems

sect. 4.51

its base. One-fourth of the pcrimetcr of this atrium is a glass wall supported by Vierendcel pipe trusses. Some 12 m (40 R ) above the atrium flooris centered an 18.6-m (61-it)diameter ring beam which supports the columns of the l c n e space Floors above the atrium. Filling up the remainder of the L-shaped site is an 18-story 84-m (776-ft)-la11 "park; building, which overlooks Hennepin County Government Center Park. Underneith"i~lkeperk building, atrium. and tower is a three-level 450-car basement parking garage. The First Bank Place complcx has 130.000 m' (1.4 million f$) of floor space (Fig. 1.1691. Thc backbone ofthc First Bank Place tower is n cruciform-shapcd spine anchored by steel and concrete composite supercolumns, which are linked to one another with a vcrtical shear membrane formed by steel bracing in the core of the building and o!tr!gger bcams beyond the core moment-connected into the supercolumns. Charactcr~stlcof spine structures. Ihcse supercolumns extend unintcrmpled the full height of the building. They vary in cross-sectional area along their length from 7 m' (75 ft') at thc base lo 4.6 m' (50 11') at the top. Torsional s~abilitylor the tower is provided at the perimeter ofthe building by a dun1 system 01unsymmetrical diagonal bracing and Viercndeel bandages. The single dingonal pcrimetcr braces extend from the third floor to the forty-fifth floor in six-stoq-high

(c) 27th lo 45th TIC. 4.169

Fig. 1.168 Firrl Bunk I'luee. >linnropuiin, hlinnanln.

(d) 45th lo 54th

Fluor [,Inn: First 1l;lnli I'lucc.

56th

326


I

[Chap. 4

sections. Spandrel beams moment-connected through these diagonals, along with the supercolumns, restrain the tendency of these unsymmetrical bmcings lo deflect horizontally under gravity loads. The three-story-deep Vierendeel girder bandages, which are provided at floors 1215.24-27. and 4215. restrain the wamine. -. which would othc w k e occur in the open scc;ion composed of the cruciform spine and pcrimcter bmccs. n t u i e bandagss t r i p l ~lbc lower's tori~onalstiffnuss and incrense i b lateral stiffness by 36%. In addition, the bnndaees are used to Vansfer gravity loads to supercolumns and comer columns. thus increasine - the efiiciencv of thebuildine's o v e m m i n e resistance. Other Vicrrndeslr u e lared in llrc building to cllminalc transfer girders and increisc the building's loreral stiffi~ess.A 12-story Vicrendccl spms along 3n crtcnor h c e of lhe building between a supercolumn and n comer column. transferring a column which supports 28 floors of load. Above the fortv-fifth floor of the tower there is a nine-slorv-tall circular Vlurendccl girder which frames inta supcrcolutnns. lhu curved ~ i c r s n d c c noi l only incrcxus the 1;ltcral and lorsionitl stiffness uf ihe lap of the building, bul olso ;!Ilotvs l l circular-shaped ~ ~ ponion o r the buildlng to sir alup rlte squsrc s h p c below \ri\bout extending additional columns down through the leas; space. The structural system was chosen over a ~ G m e t ebracid r fmme or a moment fmme to achicve a column-free exterior facade f& thc building. The presence of composite concrete columns cnhanced the ovenurning resistance of the building and achieved overall economy for the structure. A572 grade 5 0 steel was used for columns and beams that were controllcd bv 5trcngrh crllerii. 2nd A 3 6 3td:I s.;ts used for inlemller, c~lntrnllcdby .Itfincrs uritr.ri:t. Thc sl~pr.rcolumi~s ultl17.r.d69- and 55.XlPa (IU.UOO- :tnd hO(lU-PSI)iuncrclc 'The rlc:l col~lllnh3s~.pl%lesb u r on the lop of ihe concrctr. hassment girapc columns. !\l!~ch SUP. port the posttensioned flat-plate garage floors. Special analGis was performed to as=&lain the effects of restraint on the posttensioned slabs due lo the presence of large concrete columns supporting the lower loads and perimeter basement walls. All building columns sit on individual footings which bear on rock. Three-story-tall Vierendeel bandages were provided along line CC' and also along E'D' (Fig. 4.170). The strategically placed bandages not only provided essentially column-Free exterior spans along face CC, but also improved the torsional resistance of the building dramatically, with optimum use of the S ~ N C ~ U ~steel. I I ~ The perimeter circular Vicrcndeel above the forty-fifth floor provided both lateral and torsional resistance to the entire frame. T l ~ uloa.cr b>sclnr.nt floors a r r c Jcs~&ncd as poitisnrioncd cuncrute flst-plate floorr. The pu>ticnsimcd conslnc~iun\gas csrunti31 lu control cracking in nuur sli~bsbecause of the cold, snowy winters af Minneapolis. The building was analyzed in a three-dimensional finite-element computcr model lor tlic following loading condirions:

.

-

~

~

BRACE

I CRUClFORM SPINE

~

BRACE CIRCULAR VIERENDEEL ABOVE 45TH FLOOR

-

12 STORIES VIERENDEEL FRAME

1. Sequenlially applied dead load consistent with the consuuction sequence of ihc building 2. Live load 3. Three-directional (.T,,: and 0) wind loads dynamically determined from wind tunnel study with appropriate combinations 4. Creep and shrinkage of concrete columns 5. Temperature gradients and differential temperature on concrete columns During the design, the members were checked for 99 load combinations. In Ille ;onrlrllcuon I C ~ L C I I C ? . t h ~~. n t i l ~ ~ ~concr?le i i t e colu!~ln 1\15 xlLd\v~d10 (3g 12 lloorr hr.hinJ cr;clr.d rirl:tor~l rlcel ind six flours bshinJ 111~.concrtt~.dsl;!bs no nts13l

(4

(c)

Fis. 4.170 Fir9 Itunk Ptuce. ( a )Structural rystcm. ( b l Estcrnul hmcing. (c) \\'firping-rcstrui~~lrle perimutcr bundi~gcr.

328


[Chap. 4

deck. Because of h e presence of unsymmelrical exterior bracing, localized bandages, and the free-spanning Vierendeel above noor 45. the SlNclUre was analyzed to cstablish its performance during the erection process. Both lateral and vertical displncements along with strength were checked. The strategically placed perimeter warping-restraining bandages improved the torsional performance of the structure dramatically. This is evidenced by the comparison of the torsional rotation (Fig. 4.171) and the lateral displacement (Fig. 4.172) of the stracture due to wind in the x direction, with and without the bandages. The presence of the three-story-deep perimeter bandages created a localized horizontal shift in h e center of rigidity of the lateral resistance of the structure and thereby

Sect. 4.51

Hybrid Systems

329

produced internory in-plane diaphragm stresscs. The associated floor diaphragms were nnolyzed lor in-plane shear and reinforced accordingly. building wns dso analyzed for the reduction in column and diaphragm stiffnesses due to cncliing of the concrete and the uncenainty of the effective modulus of elasticity.

6x displacement (inch)

wind in X-direclion Fig. 4,172 Lnternl dtrplncemcnt; Firrl Bunk Plncc.


330

[Chap. 4

Two Union Square Seattle, Washington, USA

Architect Structural engineer Year o r completion Height rrom street to roor Number orslories Number of le\,cls bclor\, ground Building use Frante malcrial Typical floor livc load Basic wind vclocity hlaximum laleral deilcction Design fundamental pcriod Design ncccleralion Design damping

Earthquakc loading

NBBl Skilling Ward hl;~enussonBarkshire. Inc.

Sect. 4.51

Hybrid Systems

331

points, an extension of an important urban park, and a nciv network of pathways for [he adjoining neighborhoods. I& cxccplional design has won widespread architectural praise and public popularity and received the Grand Award Tor Engineering Exccllcnce from the American Consulting Engineers Council in 1990.

1990 220 m (720 11) 56 4

Office. rct;~il Steel a,itlt uumpositc c u l u n ~ n s 2.5 kPa (50 p s n 34 mlscc ( 7 5 mph) 312 mrn (12.3 in.). IOU-yr ruturn 6 scc ?U lnlg p ~ i l k .10-yr return ?.l"rllO-yr return including damping dcviccs: 2 . 0 ~ ~ 1 1 0 0 - yrcturn r ignoring dnrnping dc\iccs Z = 0.75. C = 0.03. K = 0.8

Two Union Square building proridrd the construction industry wilb many new concepts, materials, and techniques (Fig. 4.173). By locoling the c;!rthqu:~ke and wind resistinr elements in thc interior core walls. tllc architect lrad Trcedom that cuntributcd lu its design. Two Union Souarc rcorcscnts n union oT busincss and communitv. I[ corn-

-

level plaza with large opcn spaces, relail shops, and restaurants. The desirn team was raced with a number o r uniaue challenres bv this comnlca lic s ~ a c e ill s the base of rhc tower. Particularly challenoinp was tlte constrnint-filled site. which included existinr structures on two sides. an aciiviinterstale rrccwav. adiacent. a cily ;I,C?I oter I I ~ Ub;~se.ind UIIJ~.~ the tusicr. :,nd r c q . ~ i r u n ~ ~lor . n ~2 rconlp.c\ u ~ c irc lure !tit11 c ~ c L .~<:~tdri!ll. ~. 2nd 13rp~.h~111Jcrs 513ir .tupping thr.3u.h lhc pl:,,:~. Among thc many technical nccomplisltments that incrcascd pcrTorm:!ncc. shortened construction time. and reduced ~tructuralcosts from $28 to SIE million arc the most advanced application of a composite system, the lirst to utilize stccl pipes filled with a n,orld-record-brcaking lhigh-slrcngth 131-hlPe (19.000-psi) concrctc, the most efficient ~,iscoelasticdampers-to control building movcmcnt, and unequaled crtcrior column eoecinrs o r u o to I 4 m 146 Trl. niavidine s\\'eenino vic!vs o r the citv and Puret Sound.

.

and sited in a seismicufi\~a c t i w area (arismic zone 3), thc d e s i ~ n~ r o r i d c dnc\v techneeded parking Tor downtown shoppers. a respite i n n busy do\\,ntori,n nrca, scenic viem-

Fig. 4.173 Two Union Squnre. Sculllc, \\'arPingtun. lCor8nr.r~ofSkillirrg Il'nrd ,hire, i,,~.)

Alo~nirrrrrn~ ~ r l -

332


[Chap. 4

Sect. 4.51

First Interstate World Center Los Angeles, California, USA

..Architect

Structural engineer Year of complclion Height from street to roof Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity Maximum lateral deflection Design fundamental period Design acceleration Design damping Earthquake loading Type of structure Foundation conditions Footing type Typical floor Story height Beam span Beam depth Beam spacing Slab Columns Spacing

I. M. Pei and Parmcrs CBM Engineers. Inc. 1990 310.3 m(1018 rt) 75 2 Office Swclural steel 2.5 LPo (50 p r o 31 mlsec (70 mph) 584 mm (23 in.). 100-yr return 7.46. 6.91 sec 23 rng pcok, IO-yr remrn 1.25% serviceability; 1.5% ultimatc C = 0.03. K = 0.8 Perimeter ductile tube with chevron braced core Shale Spread footings

:.6-

,

Hybrid Systems

The structural system lor the toueeris an a11 steel dual system comprising an intcracfive braced core and a perimeter ductile moment frame. Thc braced core. ancllorcd at its corners by stccl box columns, is 23.5 m (73.8 11) square. Tllc box colurnns weighing U m : ~ r i m > nf ~ m6308 kalm (-1320 lblftl at !he base carry a maximum design gravity laed a f 100,QQP.kN ( I 1.000ionsl. TWO-st& chevron bracis free span each of four sides of the corc.ln'order to achieve an efficient lateral load resisting structural ireme. flours frcc ~ n : mun to 16.76 m (55 it). looding the interior corc and the perimeter framc columns.

...~~ ~

. .

resisting fremc. The slructure is dcsigncd to remain csscntially elastic lor an snticipnled masimsm crcdiblc cunhquakc of magnitude 8.3 on thc Richter scalc at the nearby Sari Andrcas

4.04 m 0 3 it 3 in.) 16.76 m (55 it) 610 mm (24 in.) 4 m ( 1 3 it) 133- or 159-mm (5.25- or 6.25-in.) lightweight concrete on metal deck 1067- by 610-mm (42- by Win.) W F section. g a d c 350 MPa (50 h i ) 6.1 lo 7.6 m (20 to 25 ft) Bnced steel; column size at ground floor 1230 mm (48 in.) square. 6308 kglm (4230 Iblft)

Called a signature building for the city of Lor Angeles, the granite clad, 75-story building with its scrrotcdfacadc(Fig.4.174)riscs 310.3 m(1018 it) above street level. It contains about 130.000 m') (1.4 million 11') of office space. At present. it is thc tallest building in seismic zone 4 or its equivalent in the \vorld. The base of the rower is embellished by Spanish steps \rpithwater runnels, fountains and landscaped areas. These steps arc seismically isolated from the tower structure and bridge ihe elevational difference of approximately I5 m (50 fi) in the surrounding nrea along the north to south axis ofthe taa,cr.

333

CORE BRhCI:IG ISOMETRIC

i 334


[Chap. 4

f a ~ l t.?.p;!rt from ;inal!.ling the struct.lre for a con!'?ntion31 5 pur;unt d ~ t n p c dr e h ~ n n > e spcctnml fur the n~sxinttlrncrcdihlc earthquake, 111s f ~ ~ l l o w i nspscial g analysis otld dr.. sign features usereintroduced. 1. Since two-story chevron bracing was used for the lirst time i n the seismic region, redundancy i n the gravity structural load path was examined for an accidenrsl buckling .of n diaeonal. ?. The atructtlral rncmbtrh, buth hr.s!nr and columrl~.n u r c ttc>tonly designed for the grnund ,110ticu1i!lun: t h ~ttgn . ortltugunal principal 3,es u f t l v strucutrs, but ; ~ l r u ncre chccked lur the dtrcctinnal m:trima due to umnidiruution31 s ~ . i s m ~ motion c 3. Time history analysis was conducted primarily to detcmine maximum interslory drift and the absolute maxima for the horizontal acceleration at floors. The maximum intcrstory drift was used i n the design ofthe curtain wall, whereas the acceleration data wns used for the dcsign of floor-mounted equipment such as clcvator machincs and \\,aler Lanks. Timc history anal\ssis wns nlso conducted for vsruc31 3 c c c I ~ . r ~ t i ~B?sidcs n. cr~.:lting o\~.r~urrlin"UII?ct~~ :!I 111st ~ i l n ~fl,,,,~.. r~.~ an :~ntplifiuatinno l ~ ~ . r t ~nccclcr:,tiur~ ull uuuld lund tu ;L plunying hilure in t h ~ . tr;lnsfer gird^.^;. ThC 2llalylib $135 ~<5ellli31 IU pcccl~dc\uch 3 ilil.~,~.mode. 4. I n order to establish a load deflection curve and global ductility limit.., a monotonically increasing symmctric nonlinear lateral load analysis !\,as conducted. ~ pc:~klhori,.0nt:11 :I;;cI. 5. 1hc critcriun fur !61ttd t~tutiuns.25 set :!I:trunnd 2 3 r i i fur eralloo during 3 otlce i n IU )cdrs N ind aturm. Tnc I:~tcr:ll n~o.lc<01 s thr:ltiun u ere ~ d j ~ a t ci nda ~ i ? not , unly to :tcltie\r. tI1c c~ccup.~lt uomlr,rt :I[ tllc t ~ l n,lc;unlud noor for the 10 year wind storm. but which r\;ould not incrcasc thc'latcrai rcsponse lo seismic motion.

-

Sixtccn critical ioints i n the braced frame were mcchanicallv stre.; rclie\,cd hv - - .~ . . itl;inn ttw L c u n ~ r dT110,npsun !ihratiag method o f rtrsrs cclief. Spe:iiil nclding L~ICI t~.stirlg cudurs, n c r c ust;lbl~jhr.dfor ;tll sruldcd connsctionr. The structure is ioullded on shale rock u,itlt :ln ;1llnn3blu load btxrisg rapJclt! o l 7?0 ~ P(7J5 tonslft?). Thc corr. u l the structure i s sopported on a 3.1 m (1 1 5 i t ) th,ck COIIUIL.IL. mat. and i! p~.riiiIcterrung fuoling is used fur th~.~ U Crr311te. ~IIU ~

!

i

Sect. 4.51

Hybrid Systems

335

Hongkong Bank Headquarters Hong Kong Architect Structural engineer

Foster Associates Ove A m p and Panners

Year o f completion Height from street to roof

1985 I 8 0 m (590 ft)

Number o f stories Number o f levels below ground

45 4

Building use

Office, banking Svuclural steel frame; composite stcel and concrete floors 5 kPa (104 psfJ with some local increases

Frame material Typical floor live load Basic wind velocity Design fundamental period Design acceleration

64 mlsec (144 mph). 50-yr return. 3-scc gust 4.4 sec 20 mg peak. IO-yr return period (typhoon cucnO

Design damping

I% serviceability

Earthquakc loading Typc of structure

Not applicable Steel mast joined by suspension trusses acting i n p o n d frame action

Foundation conditions

Loose fill over marine deposits and dccomposed granite bedrock: granite bedrock up to 40 m (131 ft) below ground Machine- and hand-dug caissons to rock

Footing type Typical floor Story height Beam span Beam depth Slab Columns Size at ground floor

3.9 m (12.8 ft) 11.1 m (36 ft) 900.406 m m (35.5. 16 in.) steel 100-mm (4 in.) reinforced concrete 1.2-m (4-ft)-diameter i n groups o f four

Spacing

8 groups i n total on grid of 38.4 by 16.2 m (126 by 53 A)

Material

Steel, grade 50

Core

None

The 20-m (65-ft)-deep basement o f the Hongkong Bank (Fig. 4.175) was constructed using a perimeter diaphragm wall and top-down construction techniques. The superstructure is constructed using structural steel and composite steel floors. Stability is provided by masts, linked at five levels by trusses, the complete system acting as a fi\'elevel unbraced sway frame. Each mast comprises four tubular steel columns linked by horizontnl bos-section beams to create a Vierendeel system (Figs. 4.176 and 4.177).

Lateral Load Resisting Sysferns

[Chap. 4

Hybrid Systems

Sect. 4.51

180m

Vierendeel mast

Hangers

Two n o r y deep suspension

-dl!#EHla 1

BANK

3

Fig.4.176

Sccli
338

Lateral Load Resisting S y s t e m s 16.8m

[Chap. 4

.4.6mL

1

i.

1.

Sect. 4.61

Condensed ReferencesIBibliography

339

4.6 CONDENSED REFERENCES/BIBLIOGRAPHY

10.8m

1

5 2

.

Fig. 4.177 Typlcnl noor plnn, Hongkong Dank Heodquorterr

AlSC 1983. Modern Sfeel Corisrnlcrion AlSC 1987. One Liberty Place-EBicirncy and Elegor!ce in file Cradle oJHirrary Architeclun: 1988. Exploring Colnposhe Stnicrzdrer Archilecture 1988. Tlso Union Squore Architeaurc 1990. High Sfrerrgfh Architccrure and Urbanism 1991. Two Union Squore ASCE 1986. Corrzplrrer 011s Tower Srecl ASCE 1990,Alrrrie Steel Aurtnlia Port Publ. 1988, Cltflej Sprrore on rhe Alo\,e Stnrclurer Building 1990. Do,,ble Srrcnpth Uuildisg Dctign 3nJ Cunrthction 1184. Outi,l8ng fkr,gr>anrl Cc,#.~ir..cr,'~.n Civil Encinccr 1187. Co,flcre,e Slrc,,~plbHerord Jurapr 3 V r . Concrclc Toddy 1989. A h ~ ~ Sorr8erhing o ~ ~ s Ne$u in Concrcle Conrtrnclion Specifier 1988. Innovative Comporire Conrrr~~rion Canrlruction Steel 1990, The A h y Facer of fhe Bond B,,ilding Drew 1990. Riulro Towers Prqiecz Seirniic Rcrpn,riu A,mlysir and E>,nlr,oriorl Engineering Ncwr Rccord 1988. S.vdncy Slycrnpcr Serr Soil Engineering News Record 1989. 19.000pri Enginecring Ncwa Record 1990, btnoi,ori!,cTecbm'qlte> Engineering Ncwr Rccord 1991. Sydnry Toa,er Tertr A~lrfrolior~r Gcorgc 1990. Ii'ullirrgron'r IYiiid~Slirrpedthe C~~pirol', Tollert Bm,ilding Gillcrpie 1990. Derign and Co,zsrncrion oJSrn.1 Fronted High-Rire Blriidirrgs Grorrmnn 1985, 780 Third Atrenae, Tile Fin, High-Rirc Diagortolly Broccd Corrcrelc Sln,cf!8rc Grorsmnn 1986. Beliovior. Analysir orrd Corzrrr#ccriar~ ",fa Braced-Tube Conrrele Slrrrclt,ru Giosrmon 1989. Slender Smacnwes-Tlze Nc!v Edgc (10 Grorrman 1990. Sloider Carrcrere Sm,cfr,rrr-T18r New Edge Howillcur 1992, Dedgn oJrbeNorionr Bonk Corporufe Crnfcr Horc 1990. Srnrcrrrrol Design for rlre Riolro Towerr lloh 1991. 1Vind Rerisranr Derign oJo Toll Bl,ildi#tg ivi~irm N l i p ~ ~ i d Crorr o l Seclion Journol o f Wind Engineering and lndurtriol Aerodynamics 1990. Oprinii.~afionoJToll Bltilding* Jor lVittd Loading Kunemc 1985. Deep Coirron Fo~~ndofianrJor OUB Cerrlre. Singnpore Kuneme 1990. The OUB Centre Tower Folfndoria,rr. Sirtgopore Meinhvrdt 1981. S~8perrrrucrureDc~ignJarllzc O\,rrreor U#iiorzBonk B,,iiditcg. Si,,gll~lore Mcinhurdt 1990. Tire 008 Cmrre-Qnolig Deil>,eqs Melbourne 1985. Aerorlostic hlodel Tenr ovld Tl~eirAppiicorion jor rile OUB Ccrifre.Si8tgnporc Plnllcn 1986. Porrrtiodurn Engineering Plotten 1988. h f o ~ r ~ r ~Plocr: ~ r ! ~ ~Sleel t l Solvcr Co#!!plr.cGeon!vfricr Tnrnnth 1988. Sfrircf8~rnl Anolyrir orld Dcrigr! qfToll Baildir~gs

5

-7...*

-

Special Topics

5.1 DESIGNING TO REDUCE PERCEPTIBLE WIND-INDUCED MOTIONS 'She 3 ~ r ~ ~ c ~>!stem\ u r ! l Sor la11 h.~il,Ii~~;,3rd murc d l c n cun~r~>llcd I>> 11,c need 10 r:.lriein sr ind nction ;)I ~ c r ~ i r u ~ h iIc>cI\ l ~ t y 111:,n the nsu.1 tn pr,nidr. r<\ial.lo:? :,I ..I-~~~~~ linulc lirnil-~1311:condilionr. This
.

1 Response and Excitation Mechanisms

.

-

.-winrl :tclinn can be cnnvenirntlv T h e rcspnnsc of tall buildings ln , seoaretcd inlo alonawind and cross-wind motion in relation to the two distincdy separale excitation mcchanisms. The total response is, otcourse. a response lo both lhcsc motions superimposcd on each other, which results in a random. and somelimes r o u-~ h.l velliptic. motion o f the top of the building. T h e along-wind responsc is made up oS a mean component and a fluctuating componenl. The addition of these two c o ~ n e n l ~ o r t p o " lo " nthe t detcrminntion ofulliml?lf limit-state loads, but it is o n l y component s+~l~ich ~ i v c srise lo accclcralions that affect occupancy comfort. For the cross-wind response, lhc meen componenl iEiZiXJy very small, with the fluctuating componenl dominaling the response. The fluctuating component of thc along-wind response is primarily driven by iluclualing prcssurcs on the upstream Pace. which are caused by the fluctuating wind speeds in the incident turbulent flow. Thesc pressure fluctuations are conrreried to along-wind response of lhc building through a combination o r quasi-steady response to low-rrcqucncy components and narrow-band resonant responsc, primarily in the first mode. The cross-wind fluctuating rcsponsc is primarily a narrow-band resonant response lo lllc fluctualin$ prcssures on the streemwisc s u r f ~ ~ cc:iused cs by the fluctuating vortices shed Into the a,akc. 11 is rcrerred to as \\sal;c crcilation where buildings sie conccrscd in order lo distinguisli il from the narrou.-band vortex excitation o f slender slructurcs such as cl~imneys.The ~~~~~

~

~~~

Special Topics

342

IChap. 5

mechanisms really are thc same. hut the broad-band nature of the cross-wind oressure fluctuations normilly associated with buildings is due to both the effects of fuibulence nnd the intermittent reattachment of the separated shear layers onto the streamwise faccs of the building. Typical along-wind and cross'wind response m c c s and spectra are given in Fir. 5.1. which illustnter the resmnsc characteristics described. L:ttr.r in rhts ;r.ctiun ;~n;~l)ticill mcthuds will be gi\cn to pcrmlt prediction o i the along-wind and cross-wind r~spnnscs.HouL.\.L.~. 10 permil soms further duscriptiun of titc fluctu:~tingcon~poncntsthat are in~portnntto ~un.~ceabili[y and olumnte limit-atatc considerations, it is helpful to refer to a diagrammatic reprcscntation of the along-wind and cross-wind forcinr soectra. as is nrcsented in Fie. 5.2. T2I1 huildtngs typically b3vc serr1ce3bility 2nd ullimate I1m1t.st3teoperating value, o1r;ducr.d r.~.louit)in ihc range o f ? to 10 Fnr ea3lnple. a 3UU-m (98.1-it)-high hullding with a u,idth b of 50 m (164 II) 2nd fir.[-mode f r c ~ . u e n.c s!I ui0.15 Hz tnicl~thave scrvicenbility and ultimotc limit-slate design mean wind speeds a1 the top o i t h e building

-.

b

Sect. 5.11

.

343

Designing to Reducs Perceptible Wind-Induced Motions

height of 26 and 45 mlsec (85.3 and 147.6 fdsec), respectively, which gives, for Serviceabilily.

and for the ultimate limit state,

With reference to Fig. 5.2 it can be seen that buildings operating in the low reducedvelocity range arc not likely to have occupancy comfort problems. At higher operattng

along-wind

Fig.5.1 Dirploccmcnt IrurcsulUwlop ulnnncruclnsticmodcl olorquorc toner: hm = 7.

Fig. 5.2

Along-wind and crurr-wind force rp~ctrnlor model squurc inner: I d

=

7: I'h/nlr

= 10.

346

Special Topics

[Chap. 5

Plots of the acceleration criterion are given ns a function of frequency in Fig. 5.3 for a period of 10 min of maximum wind in a return period of R years. The period of I 0 min has been used both to fit in with the original curves of lrwin and of I S 0 6897, and because it is typical of n period of maximum response in areas dominated by thunderstorm activity and where mean design wind speeds tend to be worked backward artificially from peak wind-speed data. For regions where the maximum response may occur through longer periods, such as I hour, the maximum hourly mean wind speed will he less than the maximum 10-min mean wind speed, and the value of T i n Eqs. 5.5 and 5.8 would increase to 3600 sec.

At the design stage estimates of the response of a building are required to determine serviceability nccelcration levels, equivalent static uitimale limil-slate base moments, and momcnt and shear force distributions. These estimales may be obtained analytically, from wind tunnel measurements, or from a combination oflhe two. The wind tunnel derivation of lhesc design data will be givcn elsewhere in this Monograph series. For this

347

section, a dcscriplion of ihc snalyticsi approaches will be givcn, aibcit heavily cmpirically supported in places. r ta p p m ~ c ~l ~~O I I L . : I L0) . ~ D ~ V S I I ~(19611 O T I and ;llnnp-IIT,,d R r p o n r c . 'I.he ~ ~laclur Vickcr). (1966. 1969) prosides tlle simpl~.slmc:tns of esiintalin: tllc llunf-wind resoonrc o i $: buildins sod the tqoivalcni riatic i o ~ dlo pruducd illc pe3k rslponrc. V?rsions of this approach have been developed in a number of the \vorld's wind-loading codes. In particular, the Australian code AS1 170.2-1989 has a version in which nll tile parameters arc given in equation form. As ihe gust factor approach is in such gcncral use, there is no need to develop it here. nnrticuiarlv as it rcleies io the determination of ullimate limit-state design data. However. so that comparisons may be m a d ~bmwcen along-wind and cross-wind serviccability acccleralions, it will bc of help lo develop the along-wind equations here. The evaluation of i i ~ ealong-wind response is divided into background and resonant response components. The background, or qunsi-stcady, response is at random and rclaiivciy low frcqnencics. It is !he narrow-band rcsonanl response component. which generates the majority of the ulo?g-wind acceleration at thc lop of s building. Using ihe gust factor npproach, ihc peak acceleraiion at the top o f a building for rcsonnncc in a fundamental beading modcmay be obtained from ~~

3 Determination of Response

Designing to Reduce Perceptible Wind-induced Motions

Sect 5.11

~-

wherc GtC,= gusl laclor for resonanl component; = g?(u,j@,, M = mean base orsertu_ming momcnt: for a square building, it can be approximated by 0.6'11 bh2 ill, = inenial base bending moment for unii displacement at top of building: for constant density and linear mode shape. = '4 p bdlt' (2lIr1,)' g = peak factor; for normally distributed process, = rt." = first-bendine-mode natural frequency; can be approximated by 46lh, where 11 is hCighl in meters (u,/iil,, = longitudinal lurbulence intensity at height h T = oeriod under consideration, scc; usually 600 scc for accelcrniion criteria Ir = 'height of building b = width of building d = depth of building = hourly mean wind spced at height - It S = size factor; = i1[(1 + 3.5rr,ltll'h)(l + -1,1~bl?,)1 E = longitudinal turbulence spcczum; = 0.47Nl(2iN')"' N = reduced frequency; = I~L,/V, L. = measure of turbulence length scnlc; = 1000 (hliO)"lr = air density p, = building density 5 = critical damping ratio

p?z

forO.06cncl.O

01

ix

.-C 0

O.~
-_.. - ...-. . ....-...-. .. -. ... .. ....

return period 10 year

. . 1

-rn lo 0,

(U

D 0

m

-

.

5

.-N

I S 0 6897 (1984) Curve 1, - standard deviation

r

.horizontal acceleration

criteria lor 1 0 minutes in 5 year return period - for a building (1.e. approximately normally distributed response). 0 , 2

.

0.5

5 year

a,. exp (-3.65- 0 . 4 1 Ln n)

I

1

0.05

0.5 I

0.1

,,*,I 1.0

frequency n

, Hz

Fig. 5.3 Horizonlol ucrulcrntion criiorin for occu~oncycomfort in buildings.

.

I:, p

Cmss-IVi,ld Response. One of the simplcsi ways of evaluating the cross-wind response, involving all ihe important parametcis in the process of resonant response lo wake excitation, is to use a mode-generalized force spectrum approach proposed by

Special Topics

348

[Chap. 5

Suunders and Melbourne (1975). Tltc mclhod makes usc nf mcasurcd cross-wind dirplacement spectra to g i v e n mode-gcnemlizcd forcc rpcctrum (for the firs1 mode) n l

Sect. 5.11

Designing t o Reduce Perceptible Wind-Induced Motions

349

Holmes (1987). where k is lhe mode-sltape posver crponent from Lllc rcprescntalion o r the lundamcnlal modc shape by $,!, = ( ~ l h ) ~ . , .,

't: *:

4 Parameter Sensitivity Tlicre arc sevcrnl steps lo csn~niningparamcler sensitivity. First it is important to demonstntc that along-svind response is n relatively ntinor problem compared lo crosswind response. Second it has to be shown that mode shape is important and that it is here that tlte slructural systcm can piny a significant part. Third !he real problem of crosswind rcsponsc lias to be demonstrated along with its attendant parameter sensitivity.

where $(,I) = spectrum of cross-wind displaccmcnt a1 lop o i building I!,, = first-mode frequency nr = mod;il mass H'(ri) = mechanical admiliancc: = 111I I - (rll,,,,)']'+4<'(riIr,,,)?] i = critical damping ratio For n lincar mode. and if crcit:~tion by low ircquencic is sntall and ihc structural damping low so lhat tlteescitation bandwidth is large compared wilh the rcsonanl handamidth. thc stondz~rddeviation o i displeccment at the top 01thc building m;,y bc s p p r u irnated by

and the t a n d : ~ r ddc\,iation oioccclcr:~lionis g i w n by

square seclion, chamlered or rounded corners

The lorce spectrum may be espiciscd in coclficicnt lorm by ll,,S,.~ll) 'r.~ = (k4pT;61,)2

15.13)

where b = building beieht 6 = buiiding width normal to wind direction ?r, = mcon wind speed al top 01building

rough circular section, octagonal, hexagonal.

Then in terms 01this forcc spectrum coefficient the standard devintion of acceleration becomes p7$7/z Ti=-

.I,,,

-

-

(5.14)

For an w e r a g e building densily p, and a lincvr modc. &hemodal mass is

and thc pcak acceleration at the top o f t h e building due to cross-wind rcsponsc is given by

-

Typical values of mode-ecncmlized cross-wind force socclmm cncffirirntr fmr n .. lundnmental mode 01vibrntion that hns a linear modc are gjven in Fig. 5.4. Extension of llicsc data tu nonlineer modc slinpcs may be made conservativclv. bv. multi~ivinr!bv a nlode-shape correciion factor Tor accelcmtion of (0.76 i0.24k). as discussed in ~~~

.. - .

350

Special Topics

[Chap. 5

Il'orI.cdExo,nplc. The simplest way lo introduce a study or the relative significance of the response t)'pe and the \'arious parameters is by means o f a worked example. For this purpose considcr a lall building for a rclurn pcrind of I year lor rvhicl~ Ir = 300 m

Sect. 5.11

Designing to Reduce Perceptible Wind-Induced Motions

2. Cmsr-~vindl.e.rl?ol!se.

C,, = 0.00 15

Y

= --

(0.76 i0.25I.)

4 pf' = 0.14 mlsec'

p, = 200 kglm'

(r,/ l'),,

From Fig. 5.4.

Peak accelcrntion at the top of the building due to cross-wind resonant response for a cantilever mode shape. u,ltcre I. = 1.5,

b=rl=50m l',= , 26 mlscc

-

351

= 0.I?

= 14.3 m g

i= 0.01 (at scrviccability lcr,els)

and for a linear mode. I. = 1.0,

and frctlucnuy st the lirrt mndu. rr,, =

rcduccd velocity.

46

= 0.15 Hz I, -

1'" =

pcc~hfactor ( I 0 oiin).

6 I'

= 3.47

It is noted h a t the acceleration criterion for occupancy comfort for the l-ycar rculrn period and iirst-mode frequency o f 0 . 1 5 l - 1 ~for I 0 min is ublained from

-

s = V'l In 60Uu,, = 3.0 I. 1

1

iI

Gust

~ J C ~ Ofor I

resonant co~iiponcnt.

klean bnse-o\,crturning moment.

-

I 4 = 0.6 - plf,:bh' 2 = 1.095 X 10'' N-m

Inertial basr-hending moment lor a linear mode for unit displacement at the top,

I (?nrr,,)' 3 = 13.32 X lo9 N-m

dl, = - p$rll!'

Peak nccclcrotion at the top of the building due to along-wind resonant response for a linear rnodc.

Forthis worked example tltc along-wind acceleration is \$-ell inside this criterion, but the cross-wind accclcration, even with a lincnr mode, is abo\,c this criterion.

I. Along ivind i,erst,r cro.ss wind. In Fig. 5.2 it $$,asshown diagrammalically why the cross-wind dominate the oroblem or occuoancv. comfort, but thc ~ ~ ~~ nccelcrations \\,orked example sho\vs tltot even for a reduced velocity of 3.17 the along-wind acc c l e n d o n is about 3 0 % of the cross-wind acceleration (3.9 versus 11.8 ms). 2. ,+lode shnpe. Adjustments of the mode shape in order to get nearer a linear mode shape, by using structural systems such as k bracing at Zome levels to gel facade columns to contribute morc to resisting motion, can make n signilicant difference. In the worked example, going from a cantilever mode shnpe. I. = 1.5, to a linear mods shnpe, I. = 1.0, redrrccd the peak accelerntion by 10% (from 14.3 to 12.8 mg). For - a buildine on a reducina core or tube svstem. onlv with I. = 2.0, for example, tlx p?n:!lty rslat!vc to ii I i n c ; ~~ ~ m d\II:L~LO c i 3 ;trutu~J5'i. 3. Duntpi,ty. Thr. urors-bind a:cclur~tion !s apprd\lm3tcl! III\L.~\L.I! JC~L.II.IIIII c)n the snu;lrc roul u l thc d ~ n .t l l -i n I~t .is 3ppruxiut31~. ~U;:IU,C th~.rl:is 2 d ~ n ~ p i uc- ~. n l r i .. bution from nerodvnamic damoinc. - which is normallv ~ o s i l i v eand which then rcJuzc, the r ~ r u r i ~d;lnlpinn r~l Jcp~'aduo;c In this nurLr.d ? \ ~ m p l e .if tllu huild~ng Ih;id <; rutninrcr.d rullircw ,truut.~r;il *!rtim :lnd d:lml>inpii~*~.~riceahiltl: I-.!.r.ls 111 = 0.015. the urtlrr-wind pcak : . C C C ~ C ~ ~ I L Uf .I1I ~2 1111::.r fnllldc 1s~111l.l~ L . L . U I I I - .

.

~

-

.

..

Special Topics

352

[Chap. 5

which would bring the acceleration lo willtin the occupancy comfort criterion of 11.8 mg. 4. Frcqeency, . . 6ttildirrx de!>sirv, beizhr and esidrb, and .olrrrtfonr~rlmne. The dcocndr.ncc u l cm.s-wind .1ccclur3lic1nun p;lramstcrh a h ~ c bdlr.cl ircqucr~cy:~tldmodal m x s is quit: c n m p l c ~and has bcen ~liacusredand er3luatr.d in somu dutail h) \!elb n ~ r n c2nd Ch~.ung(19881 Thc cun~pliu:lliunis mxinlv c n u c d hv !he i3c1 thxt C.. is very sensitive to planlorm shape and reduced velociiy, as shown i n Fig. 5.4, anla anything which impacts on frequency similarly allecls rcduccd velocity on C,, Examples orthc sensitivity 01cross-wind acceleration lo building height, sspcct ratio, and planform shapc wcrc given i n Melbourne and Cheung (1988) and arc rcproduced here as Fig. 5.5. From this study the overall conclusions with respect to parameter sensitivity errccts on cross-wind nccclcrations wcre as lollows: o. The accelcr;llion is not, ss onc might inluilivcly think, dcpcndcn~dircclly on height or aspect ratio hld, but rather on buildinc- .platform size. lndirecllv, hciaht is imnlscd hecausc the wind rl>:?d is 3 (UIICI~OII 111It~.igbt.HCIIUCrcI;t!\~.Iy .IL.~dcr lhuildings will h3vc Itifher 3cculerslirnr III~I SC,U>I hllilcl:ny\, h u tllu ~ importan1 p.ranlr.l:rr bcrc 51Lt2plilr"rm >iruand 3 r c r ~ gd-n\it).-ill ~. olller srurdr, ms*-

.

-

Fire Protection of Structural Elements

Sect 5.21

353

b. Accrlcration is proporlional to lltc square root 01the lorcc spectrum coellicicnt C,, and this is where paramclcr dependence bccomcs cnmplicaled. With relercnce to Fig. 5.1 it can bc noted lllat CFS,l o r a_fii.cn building gcamclry, is cx, ;pressed as a lunction nrreduccd velncily 1'" = V,lr,,b and that C ,, increases wilh

y>

V, up to a peak tltis range covers most applications. This implies an additional direct -~~ dcoendcnce on wind soeed. which makes thc accclcralion dcpendcnl on somethink approaclling 10 over this region. Also thc increased size dcscribcd by building width 6 reduces V.. nnd llence C,:,, which also works to reduce acceleration nddilinn to the n;bssivcncss clfict. Howcvcr, this size increase also moves to reduce frequency and hence increases V", and also C, and accelcration. c. hlodest rounding or chnmlcring orcurners (10% 01widdt) docs no1significantly rcducc serviceability accclcralion lcvels, although a significant reduction in ultimate lirnil-state momcnls cun be achicvcd. More significant comer roundinc or chamlcr-

.

in

relative to that Tor a square, sharp-corncred building is rcasonsbly ochicvnble. O v c n l l the eliccts o r irequcncy, building density. l t c i g l ~and l \vidth, and planlorm shape are so inrerrclalcd that it is nnly by the typc arcvaluation shown i n Fig. 5.5 that an appreciation or lhese aspects can bc uhtaincd.

a

t

1-

I

square building, sharp corners

-----

--

square building, chamfered corners (-0.1 b) rough circular, oclagonal or tapered building

5 Conclusions The excitation mechanisms \\,lliclt csusc the most pcrccplible motions i n tall buildings havc bccn dcscribcd. nnd il has bcen shown tIt;i~ thc cross-wind rcsponsc i s (he domin:mt cnusc o f motion ocrccotion nroblclns

a pirameler scnsiliaity discussion, wilh worked examples, has been presented to give a desiener some indication 01how lo avoid lhinh " acccleration levels i n loll buildings, and so avoid the need for auxiliary dnmping systems. In particular il was shown that very tall buildings arc not necessarily the most sensiliue i n terms of occupancy comfort, but that souareTsham-cornered. hieh-aspccl-ratio tall buildincs are likely to have accclera- . tion p;oblems an.d that thcsc can be avoidcd by using p l a k r m shapes with cul corners approaching n circular shape. tapering with height. increased mass, and structural systems which straighten up the first-mode shapc. b

+=recommended

I

criterion

-

5.2 FIRE PROTECTION OF STRUCTURAL ELEMENTS The slruclunl system adopted for a building. including lhc choice of construction materials, is ohcn strongly influenced by ihc fire resislencc requircmenls o f building rc€ulations and codes. Although building code requirements with respect to lire vary between countries, it is gcncrally accepted that buildings should bc designed for the limit svatc 01fire to achieve tllc follor\,ing objectives: building height, m Fig.55 hlasimum shndord dcriulion urcclcmllll_nfar I0 lnin In 5-scar rtlurn period for nrrluu rsnogumtiunr; 5 = 11.111; ps = I60 kg/m'; V,,= 12 (hNOOl"J'; n = 4611,.

1. Providc an nccepl.able level o f safety l o r ihc building occupants and limfighters. 2. The adjvccnt propcrty is not dnmugcd.

354

Special Topics

[Chap. 5

The level of safety offered to the occupants of a building in the cvent of a fire is a complex function of numerous factors, including: I. The likely chnmctcristics of the fire 2. Thc likely behavior o f t h e occupants (whcthcr they are alert or asleep, their reactions) 3. T h e likely pcrformnnce ofcompartmcntation with respect to rcsvicting the movcmcnt of smoke and flames 4. The likely pcrformonce of early \\wning systems (if any) in notifying the occupants 5. The performance o f t h e sprinkler system ond smokc control systems (if any) 6. The response of thc firc brigade All o i thcsc factors arc probabilistic by naturc and functions of time. Time is of the utmost imporlancc in designing buildings for firc safcty-it being important thnt succcssful egress be achic\,cd bciorc conditions become untcneble in the fire compartment. A systematic approach to dcsigning buildings for fire mfety needs lo take into account all ofthcse factors from a probabilistic approach and lo recognize the importance oftime. In contmst to such an approach, tllc regulatory rcquircmcnts with respect to fire safcty that have evol\~edin many countries gcncrnlly represent an ad hoc and unsyslcmatic approach to designing buildings for fire safcty. Buildings arc rcquircd to be dcsigned such that the structural mcmbrrs possess a ccrlain fire rcsistancc as dctcrmincd in accordance with the standard fire test-a test that generally bcnrs littlc relationship to real fires and takes no account o f t h e time for fire dc\,elopmcnt :!nd sprcnd. But it is a useful tcst in that it allows the fire rcsistancc of clcmcnts of construction to be n t c d on n relative basis. Littlc account is taken of the types ofacti\,itics taking place within the building, and generally little provision is made for the reduction of fire resistance requircmcnts due to the presence of other components of the fire safety system such as sprinklers, smokc detectors, and more cflicicnt egress provisions. However, it is likely that in msny silustions the application of a systematic approach to assessing the fire saiety of buildings will allow a substantial reduction in the level of the fire resistance required for membcrs-without resulting in any decrease in fire saiety. T h e purpose of this section is lo consider how the structural form of buildings may be influenced by the need to design for fire safety. For a thorough consideration of 19921. fire snictv in tall buildinrs. scc Fire Sofen, , . irr Trill Btrildin~s ,. (CTBUH. . r11 the outist i t nr.r.d. to hc $l:,ted t l ~ ct o ~ i c r ? I ~ - i r ; t ~buildings ll~d src. rc13tiv~Iy111121f ? c t ~ . by d r:qt#irr.m~.nlsfor
-

.. .

It ii the requircnrcn~iTor r~rucluiislfire prolcction (and corrosion protection) that ha\,c inhibited !he usc of crprcsscd or visible cxlcrnrl rteclu,ork with lvll buildings. Cladding and curlrin \\,all ryslcmr llrvc evoivcd and h1iv.e been urcd la camoullvgc (he fire-protected steel. As the need for taller buildings 1 ~ 1grown, s i t hidr became more important lo utilirc thc

Sect. 5.21


355

cilcrior ollhc hulldings ior lntcral lo3d reriatoncc. Utrlqus $1slcnrr rurh nr ihc brncrd lube of the John Hanmck Center. Chirqo. the framed tube o i the \\'orld Tnde Ccnlcr. New York, nnd ihc bundled l ~ b ryslrmuf r the S c ~ r rTowur.Chic3go. hmceval\ud. Y c l ~ n111 df there clrcr ihc c r l r r n ~ membcrr l hld lo he fircpmoied nud clld cvcn iho~glnromc stnlrturd reprrren!urion on iltc focsdcr hlr been ochicvcd. In the following, det,elop,nsnts nri5ing from the n w d to design buildings for firc wlety cconumically and ihc cffcct n i t h i s on the chuice oistructurnl aystsm and iortn o i member consuuclion are reviewed. These developments vnry from innovative ways for desienine steel members to achieve the snecified levels of standard fire resistance as given in the building regulations, to designing mcmbcrs Tor "real" fire rcennrios, t o a ntional engineering approach to designing for fire safely which lakes into account all components of the firc safety system

- -

1 Design of Building Structures to Satisfy Building Code Requirements Over the years various innovative approaches have been developed in an nttempt to reduce o r eliminate the need for conventional fire-protective coatings for steel members, while at the same time satisfying the (usually high) lcvcls of standard fire resistance required by the rclcvant building code.

ll'oter-Filled Alember~. Around 4 0 buildings (IISI. 1993) have been constructed with tubular columns filled with walcr and with an appropriately designed circulation system to ensure that local overheating of the column does not occur and thnt there is a sufficient supply of water to absorb the energy nssociatcd with the required level of fire resismncc. A detailed design method has been available for many years (Bond. 19751. The 64-storv U.S. Steel Cornomtion headauarters in Pittsbureh incornorales watcr-filled extcnorcolumos and is onc of thc tollcst buildings in rhc world uhcrc this ryitum lhns been oscd fur providing the requircd fire rcslstancc for the columns. \\';it
-

Firc-Resistant Steels.

Alternative "fire-resislant" stccls hove been developed (Maruoka c t a]., 1992: Assefpour-Derfuly e l al.. 1990; CTBUH. 1992) and promoted by

356

Special Topics

[Chap. 5

Sect. 5.21


various steel companies, particularly rrom Japan. These slecls give somewhat superior mechanical properties under elevsred ternpenlure conditions compared with convcntional steels, although use of these steels w i l l not rcmorc the necessity Tor a firc-protective coating-a lesser thiclkness or fire protection w i l l need lo bc applied and ihc steels are generally more cxpcnsivc than conventional steels.

2 D e s i g n o f Building S t r u c t u r e s for "Real" F i r e Scenarios

"Reol" Fires ~,crrrrsSlnndord Fires.

The previous section has dealt with the design of buildings where the members are required to have levels of fire rcsismncc as determined i n accordance with the standard fire test (ISO, 1985). The time-temperature curve associntcd with lhc stnnd;~rdlire test varies markedly compared with those associntcd with real fires (Fig. 5.8). Thir ntatter -'ill not be considered in detail hcrc exccpl to notc that this has bccn demonstrated by firc tests that hare bccn conductcd i n various-size compartments having dirierent surrace linings, various qunnlitics o i rucl (nonnelly rcpresented by timber and plastic cribs), and varying degrccs or \.cnlilation (Pcucrsson el al.. 19761. Othcr fire tests have been conducted with real furniture i n small and, more recently. i n large firc comporlmcnts (Thomas el nl.. 1992a). Based on compnrtmcnt tests conducted in room-size enclosures \vith thc firc load rcprcscnted by cribs. various cngineering models haw bccn dcvclopcd to prcdicl the temperature (and timc-tempcralure)

reinforcement

(8) Square Sleel Tubs wilh Concrete Filling

(b) Circular Slssl Tube with Concrele Fillhg

Fig. 5.7

(c) I-Section with Concrele

Bstween Fiangss (Arbed Column)

(d) I-Section Encased in Concrsts

Furrst Ccntrc. Pcrllr, Aurlruli:~

357

Special Topics

358

[Chap. 5

Sect. 5.21


condttions given n certain lr\,el of \'entilation and fire load (Pcttcrsson el al.. 1976). Through .uch testing it has been recognized that under cenain conditions, it is pos~ible lo reducc (or cvcn cli~ninnte)tile lcvrl of firc protsction rcquirud for slructural members. It has been shown C a w and O'Brien. 1981: Kr.~pp;l, 1981) thdt the locntion of sleelwork beyond or at the facode of the building. or such that it is p m l y bhiuldcd from flames which ma). come frnm thc uindows i l l tltc event of a fire. will under certain ventilation conditions result in temperatures that are not sufficientlv hieh to reouire fire ~rotectionof the steelwork. ~em~oeratures cxncri~.nucd31 (or hcyond) the facade are generally considerably lower than those within the fire cotnpanmrnt. This fact has bccn dcmonstr~tcdby muanr of fire tcsu in compnnmenu where h e fire load has been generally represented by wood cribs and thc fire compartments have various degrees of vcntilntion. This aooroach has rcSulted in the use of unorotected external steelwork in numcrous bu!ldings such 3s Bush Lunc Houac. Lundun (lZig.5.9) (Brorzstti r.1 nl.. 1983). uhurc thc S I L . L . I ~ O forming ~~ the external lit tic^. is of relat!vcly s r n ~ lcross l sr.ctiun 2nd cuulud by water. The Hotel de Ins Anes tower in Bnrcclona. Spain (Fig. 5.101, is a very recent example of the use of unprotected external stcelwok (lycngar, 1992). In this cnse the outer columns and the lateral bracing system arc located outside the building facade. Calculations were perlormed using the mcthod given by Law and O'Bricn (1981). assuming n git~cnlire load in a hotel compartment and a reprcscntalivc Icvcl of ventilation. The calculated temperatures for the external steelwork wcre confirmed by mcnns of a lire Blriidinrs o~ tviflt External Steelwork ~~~

.

-

..

Fig. 5.9

I

0

20

I

4

I

I

40

60

80

Time (min)

Exompic of use o f rratcr-fillcd tuba; nusln 1.usc

14eu.c. Landan. U.li.

Special Topics

Sect. 5.21


361

lesL 11 is clear that In this case the regulatory authorities were prcparcd to acccpt t l ~ i sap. proach in licu of all members having to achieve the higher level o f l i r c rcsislancc re. q u k d by [he regulations. Similar calculalions havc bccn uscd in Japan (Sakumoto e t al., 1992) lor high-rise buildings to permit the use of unprolecled "fire-resistnnt" steel al lhc lacsde. Pnrki11i,,6 Gnrnges. The firc load and vcntilalion conditions associated with parking garages are well known. Opcn-deck parking garages ore generally dclined a s buildings that havc at least two onnosite sides onen lo nt least 50%. Firc lesls involvinc cars in nrovidcd the structurul members are at least o l a ccrtein size-snd this size is n ~ c wilh l prlctical scctions uscd in parking gers~ger-lhc temperatures achieved will not lead to off-loading of lhc ~ l ~ c l u r members. ol Thus mullislory st~.ul parking gacrges wilhuut firc protccliun cladding arc pcrmiltcd in muny countries o r ihc world. Tcsts have bccn conduclcd on closcd ourkin:- -rarancs - nnd thnsc ryhich arc waniallv open but do not comply \t*ith thc prcccding delinition ol' opcn dc~.k(Bennclts ct al.. 1989). Thc lcsts sho~vcdt l ~ a lhe t fire tcmpcrelurcs in partially open parking geragcs can bc equivalent to those lhst would be expcricnccd in a clrrscd gsiregc. which in turn arc l ~ i e l ~th;m e r those lhar a,ill he acliiet,ed in onen-deck romars. In Auslralia. Ibr r;lr:trcs

- ing g : ~ r u g ~ w ~ i usprolcctcd tlh slruclurai slecl. dfixircd-Occrrpnng. flrrildi~~gs. The n l a t l o ~ l~mircd-ncuupuncy hsildings i h no\$,considcrcd. hlullislory buildings oltcn incorporate stories \ahich under ihu huilding rcgol;~.

l i o n arc rer~uiredto 11:lvc a more fire-resistanl l\,nc of utlnstructiun or

il

hichcr lcvui of

stories. For eramplc, in many countries where isolalcd open-deck parking psrnge!, are nermittcd to hc constructed in unnrotected slecl. Ibis \vould not be ncrmittcd i f t h e onenwhere numerous buildings havc now bccn permitted Lo hc constructed with unproteclrd steel parking levels below srlorics ofofficcr and shops. Figures 5.11 and 5. I? shogr, osc such crumple, where {our le\,els of open-deck parking garage constructed from nnntireprooled stcclr\.ork sre locatcd below I?, stories of office accon~rnudation. E.s.vcnlir?l nrrd A'or~csso~liol~llcmbers. Buildin. codes usunllv rcuuirc

:ill

members

been succrsfully argued in o number of situations. For csample. the building shnwn in Fig. 5.13 is a high-rise building incorporating large-dian~cler cuncrctc-lillcd l u h e . conlpositc concrete floors. and a reinforced concrclc scrricc s113f1. Exlcrn:tl trusrcr spanning hctwccn thc calumns \\,ere provided to ensure adcrluntc lalcral load rchist:lnc~ under design ultimnlc wind forccs and adrquate lelcral stiffness endcr scrvicc wind loads. The architecl required the estcrnztl b r ; ~ c i nlo~ hc o f c r n o s e d stcclivork. yet u~rdcr

Fig. 5.10 Hnlul dc Ins Artcs. Uorcelunn.Sguin.

argued on thc basis that in thc cslrcmc cvcnt ol' fire. thc prc*cncc ol'thc br;wing \vus not

364

Special Topics

IChap. 5

Sect. 5.21


365

A... n illustration of the benefits that mav be achiewd by the approach described is if. lu$trated try a relsarch program undcrt3ken to in\.esIip;llc nplior~sar5o:i;lted N 11h111~'rciurbi*t!!nc6tt uf n . I i - $ l u ~building. . Thc building. shown in Fig. 5.14. incorpural+ :r braced str.ci cors and ciosuly r l ~ x c dcxterior s1:r.l column* uhich cnmbinl: tvith stecl spandrel beams to form an cirekor tube structure. The K-braced core is connected to the exleribr tube by means of transfer trusses at the lop and midheight of the building. Bell rrusscs extending around the perimeter of the building are located at the top, midhcighl. and bottom of thc building. All of these steel members are fire protected by means of concrete encasement, which in the case of the exterior columns, is further encapsulaled ~

Fig. 5.13 I'n,poarll llmcc building, Sydncg, Austruliix.

~

~

~

366

Special Topics

[Chap. 5

by 51ur.l plxe. In addition. thr. corc is sep~r:tt~.dfrom tile re51 of thc ares ofr.;ich $lor?. b! mjsunry
.

-

.

..

5.3 CONDENSED REFERENCES/BIBLIOGRAPHY Arrcfpour-Drrfuly 1990. Fire Rcsirrottl High Srrcngri, LLIII,Alloy Slrcls Beck 1991, Fire Sufeir S?rrerr?s Drrign Urittg Risk Arsrr.vrsenr A I o r i ~ l r - D e ~ ~ c l o p ~in~AIII~e~~i~ I~ii" Benneru 1985. Open-Deck Carpork Fire Turrr Benncus 1989. Firc 6, Carpork., Bond 1975. Fire artd Sic.el Co,~rm,crion:Il'nrcr Coolcd Holloa Colrrrrnis British Stcrl 1992. Derigr~Alo~l,rolfor Conrrcre Fiilcd Coiirrruir

Sect. 5.31

Condensed Referencee/Bibliography

367

Brolctti 1983. Fire Prolerrio,~rfSlcci S!n,cnirer-ErornpIcr of Applicorionr Chen 1973, Hurnon Purccptio,~Tltrtrhoidr lo Horizonral hlorioll CTBUH Group CL 1980. Toil Building Cn'rerio ond Looding CTBUH Cornmillee 8A 1992. Fire Sofsi). in Tnii Bzriidirrgs Ducnport 1967. Gtrir Looding Focrorr ECCS 1988. Coicuiarion of rhe Fire Rcrirrosce of Curtrrolly Loodcd Corr!posire Srrei-Cancrere Col~mirzrfiposcd ro rite S~orrdardFire Holrnei 1987. Mode Sltope Carrecrior~rfor Dyeo,riic Rerpor!rc lo tl'in~d llSl 1993. Fire Errgincerir~gDesign forsteel Srrucnrrer: Store ofrhe Arr Irwin 1986, Aloriorz in Toll Buildirlgr IS0 1985. Firc-Rcrirloncc Test$-Eiemrnrr of Br#ilding Corolnrcliol? lyengvr 1992. Holei de lor Ancr To$l.rr. Borceiona, Sl~airl Kruppv 1981. Fire-Rrrizroece oJExien~oiSreei Coit,asls Krunnv 1990. Srriccrt~ralFire Design Law 1981. Fire SaJcry of Errenrol Srerin'ork Mnmoku 1992. De$,eion,nrnr orxd Terr Rertritr ofSAl51OB-NFR Fire Rcsirnl,>rSleul for Procrer rG . Gorrllle For ~ o r r 18,;. Jopon Heodq?mnerr Baiidirig McBcan 1990. Tize AIYER Cunrre. Adcioidc-A Core Snady hlelbournc 1977. Probubilir). Dirrribtrrior~rArrocio~cdwirh rhc I\'i,'i,ld Loodiug of Slrilclsres hklboume I 980, hrorernr,dReco,z~rne,~dorionran Accrlerolio,l Crileria for Occ~lpuncyCarrforl in Toll Slntcl,,r.ur hlclboumc 1988. Designing forScn~icc~1hIe Acederorio,zr in Toll Buiidirtgr hlelbournc 1991. Acccieroziortr and Carrfirl Crircriolor Dtriidi#igr O'Mcaehcr 1993. Bc1,osiosr of Co,,zporilc Colurr!nrin Firc Petlenson 1976. Fire E,lginrrring Design of Sled Slnncrllrer Rccd 1971. I\'i!'i,ld htdr,ced Alolion mid Heaiatt Coaforl Sakumolo 1992. ilppiicorion offire-Resirronr Stcrl to o High-Rirc Building Saunderr 1975, Toil Rccro,8puiar Building Rmponre ro Crorr-ll'ind Gcilorion Thornus 1989, Fire in Mircd Occztponc). B~ildirlgs Thomas 1992n. Fire Tesrx of ritc 1.10 IViiiio,n Srreel Oflcc Buildblg Thomnr 1992b. T l ~ eEfccr ofFire on 140 IVilliom Srrcrr-A Risk Asrcrrrrlenr Vickcry 1966. 011rlie Arsesrmenr of Wind Efecrr on Elonic Slri,crllrer Vickery 1969. Or, rhe Reliobiliq ofG,,rr LLIadi,zg Focrors Watson 1990, Tt,br,lar Contporhe C a l u m , ~ortd ~ Tircir Deurloprnrnr in Atrsrroiio Wyctt 1987. Sirilcrrrroi Fire Etrginccrittg in Building Design-A Core S r ~ d y

..

~~~~

5-c

Systems for the Future

A look at the future not only concludes this study of slate-of-the-an sWctures but also

-.

ooens the door for another monoeranh in this series. The subiect of unbuilt ~ . r o.i c c t sand futurs syslcms. a rich mix of \isiunary project* from around lhc norld, hls fascinsung poluntl=l for furthcr chplorallon and prcscntation in 2 rcpir;tle volume. Thls fi1131 chapt~.rsill semc as 3 brief summap o f u hcrl: !;!I1 build~ng,)slcms sccm to bc headed in the near. rather than distant. futurk. Several oroicct dcs&intions are appendud 10 chis sccuon, which illuilr=tc aamc nf thcrc principd icndcoc~si.The projculs dcmonslralc lhc rich divcrrity ol ayalcms now an\ail:,hlc lo d:signcrs. They irL. ;!I1 recently designed unbuilt projects, utilizing systems discussed in earlier chapters,

. .

Core and ostriggers)~srems: Miglin-Bcitler Tower. Chicago and Dearborn Ccntcr. Chicago Trussed rube q 1 s r e m : Shimizu Super High Rise, Tokyo Hybrid qsrems: Bank of the Southwest Tower, Houston

The rcasuns ll1111these building> rtnl;iin unhuilt range from chxnglng cconnmic condition,. as in thc c;tss ofthe Hank of ihc SoutBu,esi, lo pro~cctsihdt au,ail h m c i n y in a slow m;lrkcl. such as the Sllimizu Suncr Hiah Rise. In addition lo lhcir unbuilt ht3tUs. the", also share some features that i~lubuatcl&dencics in tall buildioc desien. These includr ;~rchilectur;tl,slrucluml. as ucll 3s othur lcodcncies lhai point to ihc fulure. Before discussing lhe fcatures nflhcsl: tutvsrs. 11 is uorlh munlioning une \isionnry projccl, of ihe type that might appear in a future monograph, as suggested. It has some feamres common la the other schemes presented in this chapter, extrapolated to a height significantly taller. Willinm LeMessurier has proposed a half-mile-high tower [850 m (2789 R)]. the Erewhon Center (Fig. 6.1) (Architectural Record, 1985). With a floor plan approximately the size of the Sears Tower or the World Trade Center it has usable floorarcas proven in existing tall buildings. The structunl systems for this tall building have more in common with the unbuilt projects of this chapter than the current record holders. The use of massive high-strength concrete columns on the exterior, cast composite with the structural steel frame, utilize the cost-effective strength and stiffness of concrete in compression. Bracing is employed both as a lateral resistance system and 3s a rravitv load transfer system to allow all load-bcarjne columns to pnrticipalc in the lateml rcs(s11ncL. f o r n p l i i u m cfIiciency.Thc result Is a;ury rigid 1oir.r nil11 3 10-acc P C riod uf\lhr.~lion,ulilizing convcn~ion;tluonrtructlun i:chniq.te~. ~

~~

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ki ii

Sect. 6.21

37 1

Structural Tendencies

6.1 ARCHITECTURAL TENDENCIES And so what nre some of the current tendenc~esin tall buildine dcsien that can be expcctcd to continuc in the lite twcntirth ccntury and inlo thc n e u ? n l & u is no sinflc architectural trend, as in the 1960s and 1970s. char damirlarrs the design of 1311 bujldings. There are, of course, buildings that utilize structure as part of the architectural expression. in the tmdition oioroiecls such as Chicaeo's John Hancock Tower. whereas other building slructurcs, primmly f r o r rhc 1980s. defer to the architcctur.4 massing choscn mare in con,idcrntion of urb3n design issucs. Grcatcr use of mixcd s)slr.ms, alung with architectural wends toward utilizing the structural syslems as a form generator (along with urban desien). are blurrinr these earlier distinctions and creatine mnnv outions for the 1990s and beyond. The Bank of the Southwest Tower exhibits the potential for the massing and nrchitectural expression to accent and reveal the structural rystcm. The massive composite columns rcduce in size with height, and the architect lakes advantage of the column locations and dimensions to shane the tower in n more dvnamic and soarine, - exuression . thdn n aimplc prismatic form. The hliglin-Buitler Touer :!nd the De3rborn Ccntcr, utilizing a core 2nd outriggcr system. x h i s v e similar form;, but with difiercnt slenderness proportions and tops. Thc Shimizu Suoer Hieh Rise is a tmsscd tube with some other similarities with Chicago's Hancock. They are both mixcd-use buildings, with officesbelow and residcntin1 floors ahove.This requires smaller flour plates in upper floors.The Hancock achic\.es this with a constantly slouine exterior truss~tube.whereas Sllimiru rotates the tube, rewltina in smaller flo~rol&;with each rotation. These two nroiects illustrate the oonor, . ~unltyprcsr.ntcd hy ;tn exterior truss guomctry 3, the print3ry 5ourrr: of ;trchitsctur;~lcaprcssion, uhilc 31 tltc s3me time adhering to an clficlcnt and rigid slructur;~li!rtcm. ~

~

.

-

.

-

- -.

~

~

.

.

6.2 STRUCTURAL TENDENCIES The systems for the tall buildings presented here all take full advantage of the mass. widih. and uotential efficiencies of the towers. The similarities among.these building system, illustntr., by rxxmplc, d o i g n idcas that work in nt;ln! dilfcrcnt cuild~tiuns.Thc follu~ringlid sumrnnrtacs the\e common features: Composite elements Use of high-strength concrcte for supercolumns Bracing or core walls for lnteral stiffness Use of active and passive damping systems Use of better analytical 1001s and testing facilities ' h e r s is a grsaler lsndency to mix systeslr 2nd mattrials t o d ~ y purti;ularly . uanci2le 3nd steel Cnmpnsllc ncel 2nd cuncretc floor ryitem, =re utili2uJ i n sll of tlw projcclr ~h;!tlullon. in additinn to elficir.nt urr. uf mxcri31*, tht scltlshuril~p":!turd .,I th2 r!ia m lends itself to the reouiremcnts for fast construction. The improvement of highextcnsibn, bending stiffness

372

Systems forthe Future


[Chap. 6


The use of braced frames or shear walls, in lieu of moment resistant frames, is also evident. Thcsc systems are inherently more stiff, and therefore more economical in achieving drift and acceleration limits. Bracing and walls sre locally more limiting than framed tubes, particularly when bracinapcnemtes the insrior volume. But bracinn and .. core ivallc also upun up other opportunities for flexibility An e ~ a m p l uof this is the e r . tsrior wall oihraccd lor\r.rs. $rhcrc column* nn). be njuch sn~allr.rb a n llte massive sections required for framed tubes ;\nuther 3d\,anccmunt in the pcrlormsncc nltnll buildings is thc usc ofdamping ,),Itmi. Activc dilmping r)alums u,er: lir.4 uscd in llte rulrolil of Boston's klancock building. 35 llcll :IS i l l orifinil design fc3lure in Sen York'r Cilicom Ccnlcr. Thc World Trade Center was one ofthe first to use pnssi\,e damping systems..~heuse of these systems is becoming more common now, and indeed the Shimizu tower proposes an active damping system (HMD). The improvement in analyticsl tools, namely, more powerful computers at affordable prices, has made some of these aduancements possible. And i m p r ~ \ ~ c m e nint stesting facilities, both shaking tables and wind tunnels, have also aided the undcrslanding and usefulness of these systcms. Base isolation systems for earthquake motion, as well as tuned mass dalnpcrs for the control of wind nloucmcnts, arc now common dcsign consideretions. Other systems, such as active control of building structures with advanced microprocessors, are also being tested, and increasing use could be anticipated in the future.

Typical floor liuc load Basic wind velocity

6.3 OTHER TENDENCIES

Maximum lateral deflection

Finally therc is mo\,cmcnt toward greater inlegration in thc design and construction process through information systems. Consideration of construction methods and syrterns, including prefabrication, modulnr construction. and robotics. is cllanging the traditional project delivery systems. Information systems for monitoring quality assurance during construction as well ns monitoring the long-term performance of buildings are also on the horizon, with the integration of mechanical. wnical lransportation and maintenance systems.

Design fundamental period Design acceleration Design damping Earthquake loading Type of structure

-

373

Miglin-Beitler Tower Chicago, :?. Illinois, USA

Architect Svuctural engineer Year of completion Height from strcct to rool Number of storics Number of levels below ground Building use Frame material

Foundation conditions Footing type Typical floor Story height Beam span Beam depth Beam spacing Material Slab Columns Size at ground floor Spacing Material

Cesar Pclli Associates Inc. with HKS Inc. Thornlon-Tomasetti Engineers Future 610 m (2000 ft) 141 I Orlice Concrete core, major columns, outrigger walls, steel floor beams, Vicrcndcel trusses 2.5 kPa (50 psf) 33 mlsec (73 mph) at 10 m (33 ft); 1 6 mlscc (I03 mph) at 610 m (2000 ft), 50-yr return 71 1 mm (28 in.) at l loth floor, 50-yr return 9 scc 23 mg peak. 10-yr return 1.5 to 2% serviceability ZC = 0.0012: horizontal force factor 1.33 Consrctc cur< linked hy concrete b-am5 to cight major perimcler concrcte columns 30-m (100-ft) silty and sand clay over dolomitic limestone bedrock 17.4-m (90-ft) deep. 2.1-to 3-m (6- 1010h)-diametcr caissons sockeled into rock 3.96 m (13 ft) 10.67 m (35 ft) 460 mm (18 in.) 3.05 m (10 rt) Steel 69-mm (3.5-in.) normal-weight concrctc on 76-mm (3-in.) melal deck

I I by 2 m (36 by 6.5 ft) 18.6 m (61 it) 100-MPa (14.000-psi) concrete


374

Core

[Chap. 6

Concrca. 100 lo 7 0 MPa (14.000 to 10.000 psi) 914.460 mm (36. 18 in.)

Thickness at ground floor

The ~tructuralsystem for the proposed 141-story 610-m (2000-Ft)-high Miglin-Beitler office building has been designed by the structural engineering firm ThorntonTomasetti Engineers of New York City (Fig. 6.2). A simple and elegant integration of building form and function has emerged from close cooperation of architectural, stmcmml, and development team mcmbers. The resulting cruciform tube scheme offers structural effieiency, superior dynamic behavior, ease of construction, and minimal intrusion at leased office floors (Fie. . - 6.31. . hlnjor objucti\cs ofthc structural design were to ~ c h i e v cspeed and cconnmy uf conslruclion 2nd arold inlerior colutit~isin urdcr to intaximizc net rentable nrcl. This \ras achieved through a structuml concept bared on a C ~ c i f o r m(crosslike) tube which, in ulun, is similnrin anocarance to a ticLtac-toe board. The simulidtv . . . ofthis structurel erid allous 5 t r u c l ~ r tlcmcnts ~l for the rlendcr t
.

I. A 19- by 19-m (62.5- by 62.5-11) concrete core with walls of varying thickness. Theintcriorcross walls of the corc arc gencmlly not penetrated with openings. This contributes significantly to the lateral stiffness. 2. Eight cascin-place concrctc fin columns located on the faces of the building, which extend up to 6 m (20 it) beyond the42.6- by 42.6-m (110- by 140-it) lonar footprint. 3. Eielit link beams canncctinc the four corners of the core lo the eieht fin columns u 31 e\c.ry llonr. 'These reinforced concrclc b:nm< arc hxunchud at both ends for incrcn,ed s t i f f r l : ~:~nd ~ rr..l.l;r.d in dcpth 31 m i d r p ~ nto allow fctr p35b3fc 01 mcchnnacill ~ L I C I S . Linking.the fin columns and cure cnoblur thc full uidtli uf thc h ~ l l d i -n etu act i n r e r w ine lsteral forces. In addition to link benms at each floor. sets of two-stam-dcco outriegcr walls 3rc lucntud at Ievcls Ib, 56. m d 91. Thtac outrigger aallr the m>tin-place concrete elements. 5 . Exterior steel Vierendeel trusses consisting of the horizontal spandrels and two vertical columns at each of the 18.6-m (61-it)-wide faces on the four sides of the building between the fin columns. To eliminate stresses produced by creep and shrinkage hlrains in the concrete fin columns, theverticals in 1heVirrendeel arc provided with vertical slip connections. This has the added benefit of channeling all of the gravity loads on each of thc building faces out lo the fin columns to help eliminate uplift forces on the foundations. Exterior steel Vicrendecl trusses are used to pick up each of thc four cantilevered corners of thc buildinn. Corner columns are eliminated. n r o v i d i n ~for comer offices \%itllondisturh:d tisa,s. Coone:tlon* herncen the stc:l Visrendeel iru*.us 2nd 1111: r u n ;r:w fin c o l ~ , n n \:!re typi:311! itmple shr.:~rc
.

~~

~

.

b

376


[Chap. 6

A cruciform tube structure provides a safe, elegant, efficient, and consmctible solution to h e challenge of designing the world's tallest building, the Miglin-Beitler Tower. The proposed s w c t u n l solution combines the erection speed of concrete construction, the flexibility for future change and the efficiency for horizontal spans of a steel floor system, and the superior dynamic acceleration response of a composite latenl load resisting slluctunl system.


Dearborn Center Chicago, Illinois, USA '

Ar$$ilect Stnicturul engineer Year of completion Height from smeel to roof Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity Maximum lnternl deflection Design fundamenlnl period Design nccelenlion Design damping Earthquake loading Type of smcture Foundation conditions Fooling type Typical floor Story height Beam span Beam depth Beam spacing Material Slab Columns Size at ground floor Spacing Material Core

Fig. 6 3 Ploor Iruming plnn; hliglin-BeitlcrToner.

Skidmore Owings and Memll Skidmore Owings and Merrill Proposal only 346 m (1 135 ft) 85 3 Office Concrete core, steel perimeter frame, steel outrigger trusses 2.5 kPa (50 psf) 34 d s e c (75 mph) H/500, 100-yr return period 7.9 sec 22 mg, 10.~1return period 1.75% serviceability Not applicable Concrete core, steel perimeter frames, steel outrigger and bell trusses 24.4 m (80 ft) of clay over bedrock Concrete caissons with steel liner 3.96 m (13 fl) 13.7 m (45 fl) 762 mm (30 in.) 3.05 m (10 ft) Steel, gnde 250 MPa (36 ksi) 63-mm (2.5-in.) lightweight concrete on 76-mm (3-in.) metal deck 914 by 610 mm (36 by 24 in.) 9.14 m (30 it) Steel. grade 350 MPa (50 ksi) Concrete shear walls. 760 mm (30 in.) thick at ground floor: slrenglh 49 MPa (7000 psi)

The project will consist of an equivalent 85-story oflicc tower with a total overall gross enclosed area of approximately 246,000 m' (2.6 million ftz) of which approximately 227,000 mz (2.4 million ft') is above gnde (Fig. 6.4). The first five floors will cover an area approximately equivalent lo the site and will contain approximately 9270 mz (98,000 ft') of retail syucc on the ground floor. con-

378


[Chap. 6


379

course level, and second floor (Fig. 6.5). The omce lower will be located at the west end of the site. Figure 6.6 shows the outrigger tmss system used. There will be three below-grade levels. The concourse level contains relail rcntnl space plus mecbanicnl, clcctrical, and building services arcas. The second and third lower lcvels will bc devoted primarily lo parking for 237 cars. but will also contain the main incoming electric and telephone services, employee facilities, and tenant areas. A multilevel relail galleria will extend from thc concourse lcvcl up through the second floor and will interconnect with the Dearbom Street and State Street subway slalions at the concourse level. The retail levels will be linked by cscalalors within a slcylighted, stepped atrium space. Two additional pairs of escalators will connect the first. second, and fourth floors at the clcvalor core. Offices spaces on the third, founh, and fifih floors !+-ill open into the atrium.

Fig. 6.4 Dcnrl~ornCcnlcr, CBicugo, Illinsis. (Pliorn il).Hcdriclz-Blcrring.)

380



[Chap. 6

381

Bank of the Southwest Tower Houston, Texas, USA

Architect

..;Structurdl engineer

iagonal lo bottom chord connections shall lev loose for approximately 360 days

Year of completion Hcighl from street lo roof Number of slories Number 01levels below ground Building use Frame rnalerinl Typical floor live load Basic wind velocity Maximum lateral deflection Design fundamcnral period Design ncceleration Design damping

Shear wall

Earthquake loading Type of structure Foundation condilions Fooling type

++ Fig. 6.6 Outrigger truss; Dcnrborn Ccnler.

Typical floor S l o q height Beam span Beam depth Beam spacing hlatcrial Slab Columns

MurphyIJahn with Lloyd Jones Brewer Associates LcMessurier Consultan& with Walter P. Moore and Associates Never built 372 m (1222 ft) 82 4 Office and retail. Steel with concrete supercolumns 2.5 kPa (50 psO 47 mlscc (105 mph). 100-yr return 1167 mm (3.83 it). 100-yrrelurn 7. 6.75 scc horizontal: 7 scc torsion 22 mg pcak wilh T M D 40 mg without 1 to 1.2% scrviceebility: 3.5% with TMD: 1.5% ultimate Not applicable 9-sloq-high A-frame trusses spanning building between concrcle supercolumns At lenst 76 m (250 ft) of very skirr clay 75-m (245-it)-wide octagonal mat. 4 to 1.8m (13 to 6 ft) thick. 17 m (56 11) below gnde 3.96 m (13 ft) 14.2, 13.4, 11.6 m (46.75.43.92, 37.92 ft) 530.460.410 mm (21, 18. 16 in.) 3.05 rn ( I 0 11) S a e l . grade 350 MPa (50 ksi) 63-mm (2.5-in.) lightweight concretc on 50-mm (?-in.) metal deck 8 columns. 2.9 by 6 m (9.5 by 19.7 11). mpered to 1.37 by 1.6 m (1.5 by 5.27 it) al roof: 70-MPa (10.000-psi) concrete at base Stccl. grsdc 250 nnd 350 MPn (36 and 50 ksi) supported on A-frame trusses

The tapered form of titis mixed-construction 372-m (1222-11)-high towcr. its pcakcd sculptured crown, and the slender spire to top it of1 recall the dramatic upward-reaching

Systems forthe Future

382


[Chap. 6

skyscrapers of rhc 1930s (Fig. 6.7). The architects were chosen as a rcsull of a design competilion l ~ r l dby the dcvclopcr. Unforlunately the Texas oil-based recession made it necessary to cancel the project after completion of the design developmenL Thc towcr contained an area of over 204.400 m' (2.2 million ft').At ground level and below there were and oarkine in addition lo a erand lobby. mace. -.-.retail soace . The towcr was set diagonally an its downtown Houston site. The tower was square wit11 sllnped corners to provide more officcs with comer windows. and tapered from 5 5 to 46 m (180 to 150 ft) square at lhc cighliclh noor. It rcsled on only cigh; large concrete columns, which diminished in cross &ion from the lop of the hmmdatinn mat to floor 80 (Fin. 6.8). ~... .. The overall slruclural slenderness mlio oftllc tower was 8.0. based on 390 ml48.7 m (1279 ftl160 ft), the ratio of t l ~ clo\ver ltcigllt above the lop of the mat to the horizontal dimension center to center of the columns at that level. The severe Houston wind climotc. the liieh slenderness ratio orlhc tou,cr. and its nar~~~

~

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. -

.

and stiffness, with the lenst cost premium over that rcquircd for gravity loads nnd minimal interference with architectural lavoul. Thc main structural frames were four stccl s u p c r ~ r ~ s ta.n c ~ . in c3cil ilir~ction.ahicll a m ? (tic c n t h~ilding ~ luxd n ~ tot tbc concr?I~.coIun~n\.The ,.lp:rlruuc\ h:,d Ji:lcon;!ls III :. cl,c\ron P : I I I ~ T I I 21 n i l t ~ - * ~ oi,>tcrry tnls, uith 11~r;ront;lltlr., n t 1 l 1 ~lo.trtll ~ n rliuth d >tory ufe3ch. TIIL.d i : ~ n o n ~~l sn l y;I"pcnred outsidc the central service corc fur four stories out of each nine-story modu.lc (Fig. 6.9). The entire nonrspncc outside the corc was olher\r,ise column-free, with conventional composite stcel beates spanning from the corc to a pcrin~ctcrstccl girder. The 24.4-m (SO-ill-wide core w a s bridccd bv a eair of Vierendcel trusses. Thc cieht high-strennth cause of vortex shedding, thc tower would have excessive wind forces nnd lateral accelerations unless its vibration ncriod \r,as limited lo above 7 sec. a lour value for so kill 3 i1ru;tJrc Esun .d tltot pcrtod. ths tuner nccup:~ntsaoulJ L'\p?rlcnc: t n l~r s q ~ c n dir. t conlfurl ir.m uin,l-iod~ur.dnl.,tlun .A sp~'c!alsh#d\ N : I ~ madr: to assera the :.ntount u l ndditiunnl d;lmpinfi 1h3t illr. i . ~ o ~ ~ d : ~ t ~ o n - m i~nt~- e~rn: i~It l oSIOUIJ n provld? (i,pproxi. .. matelv 0.3%). In order LO reduce accelcralions to acceotable levels. a tuned mass damner $!,tern. of 3 lype vmil:lr lo t11a1iltrt311
Fig. 1.7

U:lnk sr the Soutliwust Tosrcr.

llourton. Tcus.

Composite col (typ)

'

(Side vierendeel truss (4 per floor)

Corner vierendeel truss (8 per floor)

1

Fig. 6.9 Elrvntion; Bnnk orthe Southwest Towcr.

386


[Chap. 6

Shimizu Super High Rise lSSHl Tokyo, Japan

Architect Structural engineer Year or carnplclion Height from street to roof Numbcr of stories Numbcr of levels bclow fruund Building use Frame ~natcrial Typical floor lit'c load Basic wind velocity Maximum lateral dcflcction Design fundamental period Dcsifn accslrration Design datnping E;irthquake loslding Typ? of rtructurc Fuundation conditions Footing type

Typical floor Stury height Bcnm span Bcom depth Beam spacing hlatcrial Slab Columns Size ot ground floot Spacing hlatcrinl

Sllimizu Corporation Shimizu Corporation Proposal 550 rn (1804 11) 121 6 Hotel, officcs, retail shops. balls. parking Stccl reinforced cnncrctc 1.8. 3 kPu (36. 60 psf) 45.5 mlscc (I02 mph) Hi300 (Ievcl I loading; Hi200 (Icvcl 2 loading) 6.0 scc 5 rng peak. I-yr return 0.6% ser\,iccability: 2% ultimolc Sciscnic rcrpansc rztctor (1.05 Trussud tube nlegastructurc 160 m (525 rt) a f send Combination ofcontinuous \r,:!lls and pretensioned high-strength concrctr (PHC) piles


367

The SSH building is 550 rn (1801 it) tall with 121 stories above ground and six stories underground (Fig. 6.10). This design project was intended to confirm the feasibility of consmcting such a tall building in the earthquake- and typhoon-prone counvy of Japan by the end of this century based on the technologies available today ot Shimizu. The SSH building rvns designed as a complex consisting of hotels, offices, and shops. The building areais 44.000 m ' (474,000 f?) for a plot area of 90.000 m' (969.000 ft2). The total space of the SSH building is 754,000 m' (8.1 16,800 it2) and is divided into three zones along the height. A zone was designed to be squeezed through the top and

3.25 m (10 ft 8 in.) hotel; 4.3 m (14 ft I in.) office 27.4, 15.8 m (73 f t 6 in.. 51 it 10 in.) 1.2, 0.9 m (-17, 35 in.) 12.8.10.0 m (42 rt, 65 f t 7 in.) Steel U-type steel deck ilightweight concrete, 155 mm (6 in.) thick 4.0 by 2.4 m (13 by 8 ft) 26.0. 12.8 m (85. 4 1 Ti) Stcel and concrete; HT60. F = 60 hlPa (8500 psi) Braced frame Sleel, NT6O I.? m (17 in.) , Fig. 6.10 Sitlmizu Supcr High Rise ISSII), T o k ~ oJnpnn

388



[Chap. 6

rotated by 45' against the lower zone. The bottom zone, zone 1, consisls of 43 stories with an average floor space of about 6200 m' (66,700 ft'). The middle zone. zone 2. consists of 37 stories with an average floor space o f 4 8 0 0 rn' (51.700 it2). The top zone. zone 3. consists of 36 stories with an nveroee floor space of 2000 m'(21.500 it2). Zones 2 2nd 3 h a w qky lobb~esat thetr lowesl levcls. n t e sky lobbies are tlte lohhirs for shuttle clesnmrr. They arc also dc\ignrd tin mucl the rcqlliremunt for cvacu~lionarea, in thc evcnt of fire. The critical desien loads for the SSH buildine were the seismic and wind loads. The rdsponsc apectra lor far-field eanhqitakes u.it11 largc magniludes sxpscltd in tlic Tokyu area appenr lo hare clsar p s x k around 8 a c c Considering !hew spcctrsl peaks. 3 m q a structke svstem with a truss-tube mechanism was employcd lo i c e p the SSH buildinr stiff enoudh to have a fundamental natural oeriod o f a b o u i 6 sec. Thi; s h o r t ~ e r i o dhelor -~~~~ avoid a lock-in vibrall?n resulting from the \'onex shedding in serer* uindr. The sltore o f T o k ) o Bay co~nprisessort suil srmlo. To ovcrcolne the roft soil conditions, special attention hasbccn paid to the foundation ryslem. The proposed foundvtion svstem consists of a circular cvlindrical wall of a diameter of 162 m 1531 it) with oiler ind diaphragm rvalls inside. T'he thickness of the cylindrical outer will is 4.'0 m (1'3 ft) in the upper portion. It reaches e depth of74.5 m (244 ft). This unique foundation system a ~ ~ dthis i s supcrtall building t o be built on such soft soil

-

Srnrctttrol Sjrron. A! tile sliu on the shore o l tht Tok)n Rny nrea. apeutral compoocnls of ohnut8 scc m3) hc pronouni~dill ths rcsponsL. spcctrn f o r i ~ r - f i e l ?2nltq~:ihci d uilh large n~agnitudcs.Thcrciorc IIIC n;itural period o i 8 iec shduld bc a\oldsd for the SSH lhuildir~g.Hosrever. B ~ I I I :ft~ndilmtntnln:lturnl psrind is hct lo be lnngur than R w c . ;I lock-in tihriltion due lo strong wind may bccoms a big issuc. Two strategies werc eslablished to overcome these problems. The first strategy was to achieve a fundamental natural ~ e r i o dofsienificantlv less than 8 sec. The tareet natural period was set at 6 sec. The second strategy was to select the configurntion of the building to minimize the wind loads, especially for the purpose of avoiding a lock-in vibration. For the first strategy. the structural system selected is a megastructure with a truss tube with steel columns filled with hieh-sueneth concrete. This svsrem achieves enoueh = sliffn~.s, for tile SSH hullding to have n first n;itural period olappro.\i~nately6 scc. For the second str3tcgy. the optimum configurntion for the SSH building was suught u a i n ~wind lunnul c\ocri~nr.nts.Tllrce rvsolutioos r\.ers a.p.~ l ~ lo u dthe bulldinc. Th: first resoiution was to cui the corners off the building so that the floor plan wouid become closer lo a round shape. The second was to reduce the plan wea in the upper zones. The third was to rotate each building zone by 15" with respect to the zone below. This combination effectively broadened the power spectra of wind loads so that lock-in vibration should bc unlikely to occur (Fig. 6.1 1). A perspective of the strnclural frame is shown in Fie. - 6.12. Thc soil 21 tile hullding silt i, urpdci3lly suft. To 3rsurs muugh c3pxity undsr Illis snil uundition. ;I spcci:ll ioendation syatum has hcen ~~mplo)cd.'I'lic unique asp
D e s i ~ nCrirerio. The design criteria for the SSH building against enrthquake and wind loads are as follows: 1. Under leilel I loods. The stresses of the slructural main frames should be smaller than the allowable stress. In principle, no uplift is allowed Tor the foundation. 9 2. Under level 2 loads. The stresses of the smctural main frames should be below the level thnt can be considered to be elastic as a wholc. In addition, no harmful residual deformation due to the foundation movement should be allowed. Level 1 loads are those that are likely to be experienced by the building during the service pcriod. Level 2 loads are those that can be considered to be the maximum credible loads at the building site.

3rd Zone (hotel) typical-floor plan

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389

-

2nd Zone (oMce) typical-floor plan

~

" 1st Zone (olflce) typical-lloor plan

Fig. 6.11 Tgplcul nsnr plunr; SSH buildint!.

Sect. 6.41

Condensed References/Bibliography

391

I n addition to these design criteria, the discomfort of the tiuilding's occupants due lo

the vibration was assessed for wind and earihauake loads ex~ecledl o occur once evew w a r . F n ~ r11)hrid mnss dampers , l i h l D ~ )$
6.4 CONDENSED REFERENCES/BISLIOGRAPHY AlSC 1991. Tljr ll'nrld's To11r~tDeilding-Tlre hliglbzdcirlrr Tower Architculurdl Record 1985. Il'illio,n LcAlern,rirr'r Super-Tall Srrircrurcr ASCE 1991. Bz,ildi,~gAbnr to Dr ll'orld's Tollert ot 1.999f1 Engineered Concrclc StrucLurer 1990. TI,< lVorldZ 7bllcrr Bui;di,rg-Cl,icogn's Afiglin-Dcirlcr )irt~.cr

Mia" 1993. Soil-Sintottre lrrrrracriou Eljrc!.~on rkc 121-Siog. SSH Blrilrlbig \Vmabc 1993u. Sln,cn,ral Dcrigrt atldA8?ol?.~i:rir ofrlrr 121-Slory SSH Duildirrg \Vvtebc 1993b. Onurgbzg Needsfor Dnr,,ping ,lnga!orri,zg Sj.rlun,r Applicable lo Super Toll Btnildingr

Fig. 6.12

Eluvutlss: SSH I~uildlng.

Current Questions, Problems, and Research Needs

I . What are the structural systems and building data Tor other significant high-rise buildings in Europe. South America, and Africa? 2. What is the appropriate way to classify tall building laternl load resisting syslaced within the classification tems? How are innovative and evolvine- systems . schun,s stlch lhnl cataloging and data cullcctiott oTstructur3l syslcnls can be continuously upd3tcd ;lnd oT urc to the pr~crlcinrcnginctr! 3. How are structural schemes tailorcd to local geographic condilions to produce economical desirns? I. Should lhcrc be a proiu.wun;~lc o n s e t ~ s rufardii~g ~s the auccpt;~h~l~t) df lall huilding structures wit11 rcspcct to wniccnbilit) iswe? such as later:ll drllt. nnru vibration, occupant cornfori, and noor levelness? 5. What oossible structural forms for extra buildine suauorl auvcd . towcrs . . such as . arc possible for ultra-1211 high-rise buildings'! Whnt arc tllc sociulugical, pl;lnning. and inlnintcnmcc implicatinnr lor soch buildings'! Whal h)slellls are unvisioned for the nert gcncmtion of tall buildings over 600 m (2000 TI) i n hcigllt'! 6. What unique problems are enconnlered when exposing lall building slructural Trnmes on the building perimeter? What are the solutions? 7. What are the structural systems Tor the future in arcas of high seismicity?

-

Nomenclature

GLOSSARY A36.

Structurul rleel with yield strength of 250 MPP (36.000 pri). per ASTM svmdrrd.

A572 grade 50. dard. Acceleration.

Strucarol steel with yield rtrength of 350 hlPo (50.000 psi). per ASTM stunRate of chongc i n vclocity

us u building su%~ys due to wind or crnhquakr foiccs.

Allowable stress design or w o r k i n g stress design. hfcthod o f proportioning stiuclurcs such that the computed elastic rtrerr does no1 cncecd Ispccificd limiting strcrr. Band beams. Widc, shullow bcrmr used to achirrc minimum rtructur8l floor dcpth. A typical size would be 350 mm (13.8 in.) deep by 1500 m m (59 in.) wide. Basic w i n d velocity. Wind rpced uicd for design before adjusting for rhiclding. height, ctc. (urually the vrlocily 10 m (32.8 11) above ground i n smooth. lcrel terrain withoul significanl ahrtruclionr). Window projecting from the wall between columns or buuierrcr.

Bay window. Beam link.

Bcam scgmcnl bctwccn bmccs.

or bclu'een a brace ond u column.

Bent. Plant frnmcworli of bcnm or truss members that support a floor or roof ilnd llle columns that support there members. Braced frame. Usually u fnme which derives is rtnbilily primarily from 1NSS raian. h l o i t elcrncnu hove pinned ends and do no^ dcvelop bcnding resistance. (Thcsc f n m e i usually develop minor bcnding farces.) Building standard.

Documcnt defining minimum standards for design.

irlnwd luhcs "re >n;o?r.d or lrt.:~.tled loBundled lube. Slruclural s)slem in nhicn rira;hlr.l ~ e ~ l l rn u r t h sorilmnn ~ ~ u.all$ U -IIIIII~LIO.IT I ! ~ h ?:re i C U I I I O : ~ C ~ $!!to 18ngle \\:II1. IIICTC~! f~ri8ng cnmnr~zbll#!r . I n :t h,nJI;.I I.,h:. ~ndi\~J~:rl - - r~~ . ~ ~ tnf rtrc\\es 31 ihc inleridsc uf \a:h c o n l i n ~ ~ utuhc,. tube elemenlr may be ierminutcd a1 any nppropriste lcvcl ~~

-

2

Castellated beam. Bcvm fubricoted by culling Lhrough the web a f the hcsm with a profile burning machine, reporating (he two halves, moving one half along the other until the "tceth" o f the cu.tellationr and lack weldinr'the two hal$,cstoecthcr. Deeo "enelration Wcldinr is then ~ ~coincide. ~ urcd to wcld both sidcs o f the \s,eb.

..

Center length. lar members.

-

Distance along one member bctx,ecn intersections of ccnlcrlinrs o f perpendicu-

Central business district.

Key commcrciol iarso inridc most modem U.S. cilics.

Central-services core. Zone o f a high-rise building. often located cenlriilly in plan. where elcmtars. svairs, toilets, and ien.iccs shofts arc loc~lcd.Core may be cnclascd by co,lcrcle m r l l i or eiecl framer with lightwcighl cladding.

396

Glossary

Nomenclature In!,cned V i n appearance.

Chevron.

Code. Building code, o legal document providing design crilerin far buildings in a paniculvr jurisdiction. coefficient of variation. Rolio o f the rtvndard drvindon to the meno of n n n d o m variable. Concentrically braced frame. Frome i n which rcsislvnce l o lilteral load or frame instability ia provided by diagonal K o r other auxiliary system ofbncing. Core. Ponion o i n building lhvl includes elevaton, sloin, mrchvnical rhafl, and toilets, oflcn centmlly located.

Creep. Slow limc-depcndcnl change in dimcnrionr of concrete undcr il sustained loiid, primarily i n thc dirccdon i n whicl> !he load iicL5: u dimcnsionlesr qurntity having u n i u o f strain. Dirsiporion o f energy for dynamic lauding.

Damping.

Dapped girders. Girders (or bcbms) h w i n g u notch ul one or both ends in the underside to accommodate u corbel support within the girder depth or to crcrle additional rpnce for air ducts m d h e like.

Doubler.

Difiercnce or change between two vulucs.

Plate welded to or p i l r ~ l l eto l a web or nilngc to add strength.

Ductility.

Ahility o f il mnterb~lto ahsorb energy through defornlidtion without hilurc.

Eccentrically braced frame. Fiiamc i n which the ccntcriinc\ o f bracer air offset lrom !he paints ofintrrscctinn o f l h r crnturlinrs of bcami and columns. Environmental loads. Facade.

Lozids on a i t r u c u r r due to wind, mow, canhquakr, or tcnlpcraturc.

..

Load combinations.

Loads likely to nct rimuiwneourly.

Load effects.

Momcntr, shcuis, and vxiul forcer i n u membcr dce l o loads or other actions.

Load factors.

Fuctors applied to o load to cxpresr probability of no1being excccded; safety factors.

Longitudinal.

Direction of the longer plan dimension.

M a x i m u m l o a d lultimate load). Plvsric limit load 'or rlability limit load. ur defincd: also manimum load-currying capocity of u rmcture under test.

Medium-rise building. mngc of 10 to ZO stories.

Shear wall following m i r r r g u l x line i n plan. (No1 u rectilinear asMultistory building ncithcr punicularly high nor low: usuillly i n the

Modulartubas. Condguoua framed tubular struaurnl aysremr which % togcthcr to form u complete bundlcd tube structure. M o m e n t resisting frame. lnlcgivted syslcm o f r m c t u m l elemcnu porrrrring cantinuily and hence capable o f resisting bending forcer. (Thcse fnmcr uruuily develop minor u i o l forcer.)

Puce, espcciillly thc piincipul elrvdtion. o f u building.

Factor o f safety.

Limit-state derign. Design process thal involver identification of all potential modes olfailure (limit rtnter) and mainlnining an nccepxable level of safety ogvinst their occurrence. Thc safely level is usually erlubiished on n probabilistic bnsir. .* , i o a d end resistance factor design. Design method i n which, a1 n chosen l i m i t swte, loo* effeels and resistances are sepnntcly multipiicd by factors ihal uccount for h c inherent uncenainlies i n the determinudon o f these quuntilier.

Meandering shear wall. semblage o f wnlli.)

L i l t r n l displaccmcnt due to laterill force.

Drift.

ir urunlly rcluted to there typcs of limit slntc), and (2) rrn~iceobilir). l i m i t slotcr, related to the criteria governing normal use of h e structure.

M e a n recurrence interval IMRII. A v c n g r time betu,rcn occurrences o f n random rvriablc thnt exceed its M R I value. The probability ihat h e MRI value w i l l be exceeded i n any occurrence is l/MRI.

A c ~ u i i weight l o f rlrucluml clumcna. (This is a gmrity lodd.1

Dead load. Differential.

397

Rulio o f ,Ire u l ~ i m a l rrrrrngxh (or yield point) a i 3 malcriol to ihc working

alrers i l i u m e d i n derign (stress foctor orrarcty): or ratio ofthc ultimntc loud, momcnl. or slrcvr o f a structur;,l mrmbcr to thc ss'orking loild. moment, or shcar, respectively, assumed in design (load fuccor o f rarely).

Mullion. Horizontill or vcnicul membcr of n window-wall orcunnin-wall system hrl is normally attached l o h e floor slab or benmr nnd ruppons thc glusr and/or elements o f a window widll. ..

Failure. Condition where o limit itute is reached. This mzy or may not i n ~ o i r ecollupsc ar other cvtvrtraphic occurrences.

Neoprene. Synthetic rubber boring physical prapenier closely resembling those o f n a r u n l rubbcr bur not requiring sulfur for vulcmizution. I t is made by polymerizing chloroprcncs. and the Intter is produced f i o m vcctylene and hydrogen chloride.

Fin.

Node.

Plate projecting from u member.

Flange m o m e n t connection. o f the column.

hlonlent connection in which the bcdm is connected to thc flange

Floor area ratio IFARI. Spccilicd ratio o f permissible floor space l o lot arc*. in which the inducemenl l o reduce lot coverage is sn impoiiant componml. Thc bidsic ratio is frequently inodilicd by providing "bonus" or "prcn~ium" floor npiacc for rucl, aspects as ilrcadcs. \rlb;icks. und plrziiq. Also called ldor mr;,~. Framed tube.

Pciimetcr ccluiwlent tube consisling o f closcly rpacrd columns ilnd rpiindrclr.

Fundamental period. i ' r r m . l i > i i l ~ ufir\t 111c,.lu8ll%#hr:ll#.ln .i.l tl~l8l.ln;. .Tlw 1111,: n ~ . ~ l d ~l.) s <.<. ..! l i u i ~.i\ l PCIIII:~~~I I III:~\IIIII.~II ~ J C I ~ L ' C ~on ~ Uoilr ~ - 8 1 1 ~ 111 ihc \:111;.11 ,,Id#" "cfl~:,,~~,, ,112 .%,,,CC .,\I< ..,,.I Ih.8.L 1.8 11,: fir., ;,g:,,n

*##,

H a t truss.

lbli.18 111 11*

iw

1111.

-

Stiff structural irusswork exlending from cure to pcrirnelei a top o i building.

Hybrid building frame. F u m e conslruction uomposcd ofdificrent structural building matrriitlr. such us concrete and itccl. L i m i t states. Condition in which i! structure or a part ll%creofcelrcs l o fullill one o f i o funcriunr or to satisfy the cc~ndilionrfur a.lticl~it 1v;s dcsigncd. Limit stales uiln br clasrilicd in t a n categaiics: iI ) ttliirr~rrirlimit sttt~es,ur,rrcsponding to the inad-c:lrrying c ~ p l c i l )oflhc rtructurc (safely

Point a1 which subsidiary puns originate or cenler.

N o m i n a l l o a d effect. Calculated using a nominal load. The nominnl load frequently is defined with rcierence to u probability level; for cxnmplc, 50-gmr mean rccunence intcwal wind speed ured i n cnlculuting wind load. Nominal resistance. Calculated using nominal material and crass-iectionul propcnies nnd u mtionnlly developed f o m u l n b a e d an on unalydc~landlor expcrimcntnl model o f limit-swte behavior. Outrigger. Stifirtructurul m r r work extending from core to perimeter or any point to distribute column loads betwccn them. Outstanding. P-delta effect. members.

Projecting fiom main plunc.

Secondary effect o f column arid loads and latcral deflection on momenu i n

Probabilistic design. checking procrrr.

Design m c h o d that explicitly utilizer probability theory i n thc safety

Probability distribution. Marhematical law UIm describes the prohubility that a random vrriable w i l l vssumeccmin valuer: either ilcumulotivedistribudon function (cdfl or aprobability dcnrity iuncdon ir used. Probability o f failure.

Probability h a t thc limit slate is exceeded or violated.

Abbreviations

Nomenclature

398

Probability of survival.

One minus the probability of failure.

Rack. To deform o rrclangle in shcvrby dispiilcingonc sidc latcmlly relalive to theopposite ride. Rmistance. Maximum loud-c~nyingcapacity ns defined by a limit nille. Resistance factor. Panial safety factor ro nccount far the probability ofunderrtrength of mulerials or arucruml mrmbcrs. Seismic. Penvining to cunhquukes. Shearstud. Short mild-steel rod with flattened head, wcldcd to a steel mcmbcr. to tmnsfcrsheor force brtu,cen steel and runounding concrete. Skewed. Not parallel or perpcndiculur. Slab-typs high-rise building. Building in theshvpc ofo vcnicvl slnbsrvnding on the ground on i u ahon dimcniion. Spandrel. Bcnm spanning between columns on the erlerior of u building. Spandrel beam. Floor-lcucl berm in thc face of a building, urunlly iupponing the edges of the floor slabs. Staggered truss system. S l n c l ~ i a lr)rlecr, for .l b~ildingn ~ l hu!tbrir:d fr3mcr in "nu ulrcc. lion and fr.ui8cr bnced ill the other direr!inu hy s\c u i stor).-duep in,...:, rucgcrco in lar3tinn 31 lltcrnjtc fnrnrr on C\L.TY ~ l h ~nnor . r of 1 1 8 ~b.!ilding. Stocky. Hcuvy and thick, compored of clemcnls u'ith low width-lo-thickncrs ratios. Stressed skin. Masriul used for strength and stiifnerr in its own dune, as in u membnnc Stub girder. Vicrendcel floor girder comprising the concrete floor as thc top chord, u wideflange beam or column section os lhe bottom chord, with the chords connected by the floor bevmr end shon lengxhs of the floor beam (stubs1 fired in line with the bottom chord. Table forms. Prefubricated beam and slab fonwork complete with venical props.

399

b

= width of building normal to wind direction

C,

= force spectrum coemcient

d E

G

= depth of building = longitudinal turbulence spectrum; = 0.47Nl(2+fl)"6 = peak factor; for normally disvibuted process. = = gust factor for resonant component. = g 2 ( r r ~ f i ~ e

h

= height of building

6

H2(n) = mechnnical admittance; = Lh

I [ I - (nln,)']'

+ 4(2(nln,)'

= measure of turbulence length scale; = 1000 (hll0)'"

-

M

= modal mass = mean base overturning moment; for a square building, can be upproxi-

M,

= inertial bnse bending moment for unit displacement nt top of building; for

n

= frequency of oscilladon with an approximately nnrmnl disvibution =, reduced frequency: = nLhlV, = first-bending-mode natural frequency; can b e approximated by 46/b, where h is height in meters = return period, years

nt

mated by 0.6 (112)~T'bh'

constant density and linear mode shape. = (l/3)pbdlt'(2irn0)'

N "0

R

Tiebacks. Mechanical devices for rupponing sheeting, consisting of porttenrioncd rods ertmding to anchor points in the soil surrounding the cxcnvution or to rack. Transverse. Direction of b e rhoncr plan dimenrion.

1

= size factor; =

(1

+ 3.5n,hlVh)(l + 4n,bl&)

= specmmm of cross-wind displacement at t a p of building = longitudinal turbulence intensity at height h

Trussed tube system. Tubular system for tall buildings in which larernl iorces are resirled by tmBs uclion.

= period under consideration, seconds: usually 600 sec for acceleration criteria = hourly mean wind speed a t height h

Tubs. Struclure with continuous perimeter fmme designed to act in a manner similar lo lhut of o hollow cylinder. Tune. Adjurtcorefully.

Unclad. Not covered by facade. Vierendeel action. Using n planar rccmngulnr giid of members working in flcrurc to act ui a lrurs for longer spans far loads in lhnt plonc. W14.

Nominally 356-mm (I-l-in.)-deep steel scction n'irh wide nungc or wide I shapc.

Web moment connection. Moment connection in which beam is connected to web of column.

SYMBOLS

L

= critical damping ralio

ABBREVIATIONS ACI AISC

American Concrete Institute American Institute of Steel Construction

ASCE ASTM

American Society of Civil Engineers American Society for Testing and Materials

CBF

Concentric braced frame

CCD

Chicago City datum

CTBUH

Council on Tall Buildings and Urban Habitat

P p,

= air density = building density

EBF

Eccentric braced frame

ECCS

European Convention for Constructional Steelwork

uL

= standard deviation of ncceleration in horizontal plane

Nomenclature

Abbreviations for Units Bm -C cm' cm "F

h S gal hp hr Imp 8".

1

K kg kgf kip km

kN a

k

British thcmnl unil degree Celsiur (ccntigmds) cubic centimeten centimeter degrec F~hrenhelr foal ~"m gallon horrepowcr hour British lmpsriol inch joule kelvin liilogrvm kilogmm-force 1000 pound force kilometer kilonewlo" kilopascal kips per square inch

kW Ib Ibf I MI MPn m mi ml mm MN N OL

Po psf psi 'R rcc

slug \V yd

kilowan pound pound force pound mars meg&jojoule megnpurcvl mcler mile milliliter millimelcr meganewton ncwlon ounce pnscvl pounds per square foot pounds per squnrc inch degree Rankine second 14.594 kg WBll yard

AISC. 1983 MODERN STEEL CONSTRUCTION. Americidn lnrtilurc of Stccl Conslmclion. Chicago. Ill.. 2d Q u o n ~ r AISC. 1987 ONE LIBERTY PLACE-EFFICIENCY AND ELEGANCE IN THE CRADLE OF HISTORY. blodent Slecl Co!8rrrucrion, no. 2. pp. 9-14. AISC. 1991 THE WORLD'S TALLEST BUILDING-THE MIGLIN-BEITLER TOWER, blodern Steel Cnnrrrncrion.. Aururr. Archiiecarul Record. 1985 WILLIAM LEMESSURIER'S SUPER-TALL STRUCTURES. Arcl~irecrr,rrtl Rcrord. JunuurylFcbruary. Archltec1ure. 1988 EXPLORING COMPOSITE STRUCTURES. Arcbiruclirre, March Archilcclure. 1988 TWO UNION SQUARE, ilrcl~ilccivrc,hlsrch Architeclurr, 1990 HlGH STRENGTH. Arcltirrcn,rc. October, Architec~ureand Urbanirm. 1991 TWO UNION SOUARE. Arcbiiecn,re and Urbanirnr. Fcbruarv, ASCE, 1986 COMPUTER CUTS TOWER STEEL. Ciuil Engbzreriag, March ASCE. 1990 AUSSIE STEEL. Civil Enri,rcerinr. ". Dcccmber. ASCE. 1991 BUILDING AIMS TO BE WORLD'S TALLEST AT 1.999 FT..Ci!,il Er~ginrering,March. Asrefpour-Dezfuly, M.. Huguor, 8. A.. and Browrigg. A.. 1990 FIRE RESISTANT HlGH STRENGTH LOW ALLOY STEELS, bloreriolr Sciertcr o,rd Tecltn o l o ~ svol. , 6. December. AurlrnlioPorl Publ.. 1988 CHIFLEY SQUARE ON THE MOVE STRUCTURES. no. VBP 88 I0 Beck. V.. 1991 FIRE SAFETY SYSTEMS DESIGN USING RISK ASSESShlENT MODELS-DEVELOPMENTS lh'AUSTRALIA. Fire Sojrr). Scinice, Proceedings of ihc 3d lnternnlionul Symposium. Elsevier. Bennclu.1. D.. Almand. K. H..TBomas. 1. R.. Pioe. 0.1.. and Lewins. R. R.. 1989 FIRE IN CARPARKS. BHP Melbourne Rcscarch Labomtorier. Auslralia. Repun MRLIPS691851005. Aueurr. * Bcnnelts, I. D.. Proe. D. I.. Lewlns. R. R.. andThomas, I. R.. 1985 OPEN-DECK CARPARK FIRETESTS. BHPMelbournc Rcscarrh Luboratarier. Australi:l. Repon hIRUPS691851001. Bond. G. V. L.. 1975 FIRE AND STEEL CONSTRUCTION: WATER COOLED HOLLO\V COLUMNS. Cortrrroilo.

-

".

British Steel. 1992 DESIGN MANUAL FOR CONCRETE FILLED COLUMNS-PART 1: STRUCTURAL DESlGNlPART 1:FIRE-RESISTANT DESIGN. Brorcui. I., Law. M.. Petlmron. 0..nnd Willeveen. 1.. 1983 FIRE PROTECTION O F STEEL STRUCTURES-EXAMPLES OF APPLICATIONS. 1ABSE Periodical 1.May. Building. 1990 DOUBLE STRENGTH. B~ildirtg,July. Building Derign nnd Conitruction. 1984 BUILDING DESIGN AND CONSTRUCTION. Cnhncrr Publirhine. -. Junc. Chen. P. W.. and Robenran. ti. E.. 1973 HUMAN PERCEPTION THRESHOLDS TO HORIZONTAL MOTION. Journoi of ri8e Sintcnlrol Divirion. ASCE. vol. 98, .pp. . 1681-1695, Civil Enpincer. 1987 CONCRETE STRENGTH RECORD JUhiPS 36%. Ci~,iiEtlgineer. Oclabcr. Concrete Today. 1989 ALWAYS SOMETHING NEW IN CONCRETE. Concrcrc Todqv. Spring. Conswclion Specifier. 1988 INNOVATIVE COMPOSITE CONSTRUCTION. Canrrr,~crionSpecifier. April. Conrtruclion Strcl. 1990 THE MANY FACES OFTHE BOND BUILDING. Consrn!ciio,i Srcul, February. CTBUH. Group CL. 1980 FIRE, cllilpter CL-4, Toll Bl#ildb,g Critcrio orld Loodirrg. 1.01. CL of hIo,!ogr,,pi~ (11: PIo,rt~inp und Dcrigri ofToll Bi,ildi,~gs.ASCE. New Yark. CTBUH. Group SC. 1980 TALL BUILDING SYSTEMS AND CONCEPTS. vol. SC of hto,~ogropicu,r Plon,,ing and Design of Tali B,,ildings. ASCE. New York. CTBUH, Committee 8.4. 1991 FIRE SAFETY IN TALL BUILDINGS. hlc0nw-Hill. New York. Dirmpon, A. 0.. 1967 ~ Divirion, ASCE, vol. 93. no. ST3. GUST LOADWG FACTORS. Jozrnial of l h Srn,cr!nrai Drew. R. I.. and SL Claire Johnson. C.. 1990 RIALTO TO\VERS PROJECT SEISMIC RESPONSE ANALYSIS A N 0 EVALUATION. vols. I . 1.3, ond4. Junc. E r. r. s . 19RR . ... . CALCULATION OF THE FIKE IlESISTAh'CE OF CESTRALLY LOADED COSii'OSI'lE STEEL-CONCRETECOLtihlNSTOTHEST:\NUARD IlRE.Tcchsic~lNutcno. 5 5 . Eu. rdprln Commllnn ior Cunxruaion~lSlccluoil. Bru5relr. B~lpjunl. Engineered Concrete Structures. 1990 THE WORLD'S TALLEST BUILDING-CHICAGO'S MIGLIN-BEITLER TO\VER, rol. 3, no. 3. December. Engineering Ncwr Record. 1988 SYDNEY SKYSCRAPER SETS SAIL. Engineeri,8g Are~~.rReccrrd. August I I . Engineering Ncu's Record. 1989 19.000 PSI. E,wincerit8c NcwsRecnrd. Frbmurv. Engineering Ncws Record. 1990 INNOVATIVE TECHNIQUES. Errg8nrering News Record. April Enpinccring News Record. 1991 SYDNEY TOWER TESTS AUSTRALIANS.. Errcinceri,~~ Arc\w Record. Junc ... 17 " Falconer. D.. and Beedlr. L. S.. 1984 CLASSiRCATION OF TALL BUILDING SYSTEMS. Council Repon no. 142.3.Councii on Tall Buildings nnd Urban Habitat. Brthlrhrm. Pa.

George. S. F.. 1990 WELLINGTON'S WINDS SHAPED THE CAPITAL'S TALLEST BUILDING. NCII'Zeuiond Engincerlng. Sepkmbcr. Gillerpic. B. I.. Nuirn. S.. and St. Claire Johnson. C.. 1990 :'"DESIGN AND CONSTRUCTION OF STEEL FRAMED HiGHRISE BUILDINGS. Prnccedingr of Seminnr on Steel Slructurer. Singopore. Grossman. J. S.. 1985 780 THIRD AVENUE. THE FIRST HIGH-RISE DIAGONALLY BRACED CONCRETE STRUCTURE. Concrete inlernarlonoi, Derign and Consmtcrlon, vol. 7. no. 2. February. pp. 53-56. Gmsrmnn. J. S.. 1989 SLENDER STRUCTURES-THE NEW EDGE (n).Proceedings of the lntemvlionnl Conference on Toll Buildings nnd Cily Development. Brisbanc. Aurtmlia. October, pp. 93-99, Grossman. J. S.. 1990 SLENDER CONCRETE STRUCTURES-THE no. I. Jonuury-February. pp. 39-52.

NEW EDGE. ACi Slntcr!tral Jounral, vol. 87,

Grosrman. J. S.. Cruvellier. M. R.. and Stnffard-Smith. 8.. 1986 BEHAVIOR. ANALYSIS AND CONSTRUCTlON O F A BRACED-TUBE CONCRETE STRUCTURE. Concrete it8rernoriono1, Derign or~dConstrunion, vol. 8, no. 9. Scptcmber. pp. 3 2 1 2 . Holmcr. J. D.. 1987 h4ODESHAPECORRECTlONS FOR DYNAMIC RESPONSETO WIND. Etlgblccring Slntcrurer. vol. 9. pp. 210-212. Horviiieur. J.F.. 1992 DESIGN O F THE NATIONS BANK CORPORATE CENTER, The Stn,crlrroi Design of Tali Buildings. Vol. 1. pp. 75-1 19. Hare. R. M.. 1990 STRUCNRAL DESIGN FOR THE RIALTO TOWERS. Melbourne. IISI. 1993 FIRE ENGINEEIlING DESIGN FOR STEEL STI
FIRE-RESISTANCETESTS-ELEMENTSOF BUILDING CONSTRUCTION, AS 1530. Pan 4. lntcrnadonnl Standards Organiration. Geneva. Ituh. 51.. 1991 \\'IND RESISTANT DESIGN 01; ,\ TALL BLIILUlSG \\'ITH AN ELLII'SOIDAL CllOSS SECTlOh'. Prorcedlngr of inc 2d Cnnfcrenru on l ~ l Ballding$ l ln Srl$!nlc K?glon.. Lus ,\nvclrr T ~ l Rtuldinrr l Slrurlur-l D c w n Cn~nclliind Council un Tall UuilJinc< ;!nd L'rlyengnr. H.. 1992 HOTEL UE LAS ARTES TO\VER, BARCELONA. SPAIN. Stntcnrrol Engineering birrnorioaoi, vol. 2. no. 3. August. J u u m ~uf l \Vtsd Esg~sc:nng and l$nla
Ki1mirter.M. 8.. 1983 DESIGN AND CONSTRUCTION OFTHE LUTH HEADQUARTERS BUILDING. KUALA LUMPUR. Proceedings ofthe Biennial Confrrrnce of the Concrerc lniritutr of Aurtnliu. June. Kruppn. J.. 1981 FIRE-RESISTANCE OF EXTERNAL STEEL COLUMNS. Find Rcpon. Technicul Stccl Research. Commirrion of the European Communilier. Kruppo.J.. Schaumann. P..Schieich. J. 8:. and Twilt. L.. 1990 STRUCTURAL FIRE DESIGN. Pun 10, draft Euiocode 4. Commirrion of thc European Cammunitier. April. Kurrrme.M.. Hose. R. M.. and Ndsis~.5.. 1990 THE OUB CENTRETO\VER FOUNDATIONS. SINGAI'DRE. Proceedings ofthc Conference on Deeo Foundalion Piuctice. Sinrunorc. K~rzeme,XI., "8% Ku51b, 31 C., 19&5 DEEP Cr\lSSOS FOUSD,\TiOSS FOR OCU CLVTRI:. SlSG.\POIlE. l'rll;ccJin-\ oillli. d l o Sn.th E..l A v : ~C c . ~ ~ u c o nCnni:cr.srr., ~c~I Kudl. L..nrpur. Law, hl.. and 0'Bricn.T.. 1981 FlRE SAFETY OF EXTERNAL STEEL\VORK. Co,,rrmdn. L'lndlistrio ltnlihna dcl CemCnto. 1987 THE LUTH BUlLDlNO IN KUALA LUhlPUR 1hIALAYSIAI. L'lnriri.v!rin lrrrli2,m 0 ~ 4 Ce,rlhi!n. no. 613.luly-August, pp. 472185. Marlin. 0.. und Puyton. J.. 1989 WIND DESIGN OF FOUR BUILDINGS UP TO 3UO nl TALL. Kc~iri/lrrrrrlC ~ a r r c r cDiscr!, lilimh. Muruoliu, Y., Tsubaki. H.. and Hisa~aku.T.. 1992 DEVELOPMENT AND TEST RESULTS O F SM520B-NFR FlRE RESIST.4NT STEEL FOR PROCTER G; GAMBLE FAR EAST. INC. JAPAN HEADQUARTERS BUILDING. Proceedings of the Pacific Stiuctur;xl Steel Confcrrncc. Tokyo. McBern. P. C.. 1990 THE MYER CENTRE. ADELAIDE-A CASE STUDY. Proceedings of the Struclural Engineering Conference. Adelaide. The Institution of Engineen. Austr;llia. Meinhardt. W. L..und Narim. S.. 1990 THE OUB CENTRE-QUALITY DELIVERY. Prorccdings af Zero Delcets Construction lael90 .~ Ouoiilv Deliver\,. . Sineuoorc. Mcinl~ardt.W.L.. andNisbet. R. D.. 1984 SUPERSTRUCTURE DESIGN FOR THE OVERSEAS UNiON BANK BUILDING. SINGAPORE. Proceedings af the lntemadonal Cunfcrrncr on Tali Buildines. Sinmoore. -. Mclbourne. W. H.. 1977 PROBABlLiTY DISTRIBUTIONS ASSOCIATED WITH THE \\'IN0 LOADING O F STRUCTURES. Civil Ertginerrir~pTrtrarnninrzr The institution of Engineers. Austnlia. uol. CE19, no. I . pp. 58-67. Mclhnurnc. \V. H 19R0

-.

~

~

-.

-

5l~lbourn:. \\' II. ~ n Cr,:l.rlg. d J C. K , l5Sh IIESIGKISC FOR SEIl\'ICE,\BLI! :\CCI!I.I:RI\TIOSS IS T.1I.I. IlCILu1sGS. I'~.~:!cJIII$. .lf 1 1 r -111, I ~ ~ ~ ~ . r n . l lCJIII:ICI):L. ~ ~ r # . i l .#I> T L I BJ IJcnil. IIIIII! Kim: .lnJ SI~:.nph~l, ~pl~. 14S-Ij5. hlrlbouinc. \V. H.. and Niabet. R. D.. 1985 AEROPLASTICMODEL TESTS AND THEIR AI'PLICATION FOR THE OUB CENTRE. SINGAPORE. Piocecdingr ufthc lnlcrnntiunvl Confrrrncc an Testinz and lnstrun~enrillion in Building nnd Conrtructioo. Singupore.

Melbourns. W. H.. nnd Palmer. T. R.. 1992 ACCELERATIONS AND COMFORT CRITERIA FOR BLIILDINOS UNDERGOIN0 COMPLEX MOTIONS, Journnl of lVind Engineering and lndustriol Arrodynamics, vol. 41, pp. 105-1 16. Mitn. A,. and Fuchimoro. M.. 1993 SOIL-STRUCTURE INTERACTION EFFECTS ON THE 121-STORY SSH BUILDING. Proceedings of lhc Inlernntionnl Conference on Tail Buildings. Rio dc Jnneiro. Brazil. May 17-19. O'Mcaghrr. A I.. Bmnelts. I. D.. Stmcnr. L. K.. 2nd llulchinron. G. L . 1993 BEHAVIOR OFCO'VIPOSITE COLU\INS IN FIRE. BHP Mclbuumc Research Lahorolunes. Aunrdllo. Rcpon BllPNPPAiW93.001lSG3C. Plntten. D. A.. 1986 POSTMODERN ENGINEERING. Civil Engineering. June Plauen. D. A.. 1988 MOMENTUM PLACE: STEEL SOLVES COMPLEX GEOMETRIES, hiadern Sfeel Connruclion. Fcb.. No. 2. Pcuerrron. 0..Mngnurron. S. E.. nnd Thor. 1.. 1976 FIRE ENGINEERING DESIGN OF STEEL STRUCTURES. Publicndon no. 50. Swedish Inrtilute of Steel Consmction. Reed. 1. W.. 1971 WIND INDUCED MOTION AND HUMAN COh
ceedings of the 4th International Conference on Wind Effecl London. Cambridge University Prcrr. pp. 369-380. Tnmnnth. B. S.. 1988 STRUCTURAL ANALYSIS AND DESiON OFTALL BUILDINGS. McGmw-Hill. Ncw York. Thomor. I. R.. Almnnd. K. H.. Bsnnetu. I. D., Proc. D. 1.. and Lewinr. R. R.. 1989 FIRE IN MIXED OCCUPANCY BUILDINGS. BHP Melbourne R e r e w h Labomlorier. Aurtralio. Rcpon MRUPS69/89/W4. August. Thomnr. 1. R.. Benncle. I. D., Proe. D. I.. nnd Lcwinr. R R.. 1992n FIRE TESTS O F THE 140 WILLIAM STREET OFFICE BUILDINGS. BHP Mclbourns Research Lnborntorier. Aurmlin. Repon BHPWENG/W92!043/SO2C. Jonuury. Thomnr. I. R.. Bennetu. I. D., Proe. 0.1.. and Lewinr, R. R.. 1992b THE EFFECT OF FIRE ON 140 WILLIAM STREET-A RISK ASSESSMENT. BHP Melbourne Research Laborntories. Aurtrnlin, Repon BHPRENGiN9?10MiSG2C. January. Vickcry. 8.1.. 1966 ON THE ASSESSMENT O F WIND EFFECTS ON ELASTIC STRUCTURES. Civil Engineering 7ianrocrionr. The Inrdlution of Engineers. Auslmlio, pp. 183-192. Vickery. B. 1.. 1969 ON THE RELiABILlTY OF GUST LOADING FACTORS. U.S. Depvnment of Commerce. Nvtionnl Bureau of Standards Building Science rer. 30. \Vnlobe. M.. and Mila, A,. 19938 STRUCTURAL DESIGN AND ANALYSIS OFTHE 121-STORY SSH BUILDINO, Proceediner of the lnlernotionnl Conference on Toll Buildings, Rio deluneiro. Brazil. May 17-19. Wntnbc. M.. and Mitu. A.. 1993h EMERGING NEEDS FOR DAMPING AUGMENTING SYSTEMS APPLICABLE TO SUPER TALL BUILDINGS, Proceedings of the intemndonol Wokrhop on Structurvl Control. Honolulu. Hownii. Augurt 5-7,

Wnuon. K B.. nnd O'Brien. L. 1.. 1990 TUBULAR COMPOSITE COLUMNS AND THEIR DEVELOPMENT IN AUSTRALIA. Proceedings of lhc SVvcturnl Engineering Conference. Adclnide. The Institution ofEnginecrs. Aucmtin. Wystt. G. W., and Bcnnclu. L D.. 1987 STRUCTURALFIRE ENGINEERING IN BUILDING DESIGN-A CASE STUDY. Pmceedings of the First Notional Smcturnl Engineering Conference. The lnrtitution of Engineers, Auslmlia.

Contributors .1~, ,

The following is n lisl of those who have contributed their time and effort to mnke this volume possible. The names, affiliations, cities, and countries of each contributor are given. Inn D. Bennelts, BHP Melbourne Laboratories, hlelhournc. Ausrralia Joseph Burns, LeMessuncr Consultants. Inc., Chicago. Ili!nois. USA Brian Cnvill. VSL Prcstrcssin~(Aust) Pt). Ltd.. Sydncy, Austmlia Joseuh . ~ n e i i e e r s .~ o u i t o n~. e n n sUSA . - - - - = - ~P. ~- o l a c o CBM Henry J. ~ o w a n , ' ~ n i v e r s i i osydney, f syd"ey. ~ " s t r a l i n P. H. Dnyawansa BHP Melbourne Laboratories. Melbourne, Australia James G. Forbes, Irwin Johnston and Partners. Sydney. Ausmiia Eiji Fukuzawa, Kajima Design. Tokyo, Japan Max B. Kilmister, Connell Wagner Consulting Engineers. Brisbane. Australia R y s n r d M. Kownlczyk, Department of Civil Engineering. University of Beira Interior. Covilha. Porngal (former: Bialyslok University of Technology, Biaiyslak, Poland) Owen Martin, Connell Wagner Rnnkine and Hill. Sydney. Australin William Melbourne, Department of Mechanical Engineering, Monash University. Melbourne, Australia Seiichi Murnmatsu, Kajima Design, Tokyo, Japan T. Okoshi, Nihon Sekkei, Tokyo. Jnpnn Ahmad Rahimian, The Office of hwin G. Cantor, New York, New York, USA Thomas Scarangello, Thomton-Tomasetti Engineers, New York, New York. USA Robert Sinn, Skidmore Owings and Menill, Chicago. Illinois. USA Richard Tomasetti, Thornton-Tomasetti Engineers. New York. New York. USA A. Ynmaki, Nihon Sekkei, Tokyo, Jnpnn ~

~

Buildina Index

Pictures of the buildings uppevr on the itnlicized pilges. Atlantn. Georciu. United Stater: Gcoria -~~ -. Pacific. ~ 214.215.216.217-219.3W . . . .. Allnnlic City. New lesey. Uniled Shtes: Tnj Mnhnl Hotel. 17.94.95. g6,97.98

B8rcelonn. Spain: Hatcl de 13s Aner. 276.277. 278. 279. 358. 360 Boston. Mnrachurenr. United States: Dewey SquvreTower. 3 5 , 2 3 6 , 2 3 7 lohn Huncock Building. 372 Brirbane. Auruulia: Ccnuvl One P l m . 47.48.19.50

Charlotte. Nonh Cumlino. Uniled Slates: Nations Bank Corporate Center, 241.242.243 Chicogo, Illinois. United Smtes: Amoco Buildine. 203,204,205

John HuncockCenter. 268.Z69.270.355.370

NBCTowcr. 3 I81 \Vest hlvdison Streel. 206.207.208.209 OneNonh Franklin. 15 Onterir Ccnter, 265.266.267 Quukcr Onls Tower. 2 Sears Tower. 202,280,181,182-284,355, 369 77 West Wacker Drive, 124,125, 126

-

Chicuco. Illinois, United Stotcr (Conr): 10 South LoSdle Sweet. 208 Three R n t National PI-. II 3 11 South Wncker Tower. 213 31 1 Wcrt Wuckcr Drive. 15.213 Two Prudential Plucc. 182.183. 184. 185 Water Tower Plocc. 113 ~

~

Dullu$. Texas. United Swtrs: Bank Onc Centcr. 24-1.1-15.246 Fint lntcmational Building. 260.261. 262-261 Intefint Plaza. 301

Hvmamulsu City, Japan: ACT Towcr. 68.69.70-72 Hong Kong: Bank of Chino Towcr. 199

337.338

Bcnkofthe SoulhwestTower.369.371.381. 382,383,384,385 Four Allen Cunter. 166,167.168. 169 Two Shell Plau. 197

Kamogawa, lapan: Kvmogvwt GnndTowcr. 104,105. 106. 107

ng Index

Kobe. Jupm: Kobe Commerce, Industry 8. Tnde Center. 85.86.87-89 Kobe Ponopiu Hotel. 73. 71.75.76 Kunlu Lumpur. Malaysia: Luth Building. 17.32.33.34-37

London. Englmd: Bush h e House. 358.359 Lor Angeles. California United Stoles: Figucroa nt Wilrhire. 162. !63. 16-4. 165 First Interrule World Center. 313,333,334

Mclhournc. Aurtmlin: Bourkc Place. 19.23.24.U. 45.46. 109 Cassulden Place. 117.128. 129.300 Mclboume Ccnlnl. 27.28.29-31. 109 140 William Succt. 365 Rialto Building. 285.286. 287-289 624 Bouike Slrect. 362, 363 Telecom Coiporute Building. 137.138. 139 Miami, Florida. United Stotei:

New Yok. New York. United Stuter (Cotzr.1: World Tnde Ceacr. 194.196.355.369.372

06aynma. lupun: Sumitomo L ~ r eInrumcc Building. 230, 231. 232-234 Osaka. Japan: Lcvin21. 130.131. 132 Nunkoi Soulh Tower Hotel. 77. 78.79. 80 Tokyo Mnnne Building. 99.100, 101-103 World Trddc Center. 81.82.83.81

Perth. Auruulia: Fonert Ccmc.357 Philadelphia. Pennrylvmio. United Slates: hlcllon Bunk. 225.226.217-229 One Libeny Place. 140. 154.155. 5.56, 157 1650 Market Street. 143

CenTruslTomer.315.316.317-319

hlinneopolir.Minncsoto. United Stutes: First Bank Place. 3W. 323.321.325-329

New York. New YoiL United Sutcs: Camegie Hvll Tower. 293.2%. 295,296 CamegieMusic Hull. 293 Citicaip Center. 310.311.312-314.372 City Spire Building. 109. 145.146. 147-149, 296 Concordis Hotel. 296 Embassy Suites Hotel. 116.117, 118 450 Lexington Avenue. 220. 221-22.1 Gmnd Central Station. 220 Mvrriott hlvquis Ha~el.17.90.91.92.93 Metiapolitan Towcr, I1 1.112. 113-1 15. 145. 296 PvliiceTheatie. 116, 118 Russian Tea Room. 793 780Third Avenue. 267.271.272.273-275 17 Stale SmcL 158, 139.160. 161 Trump Tower. 170-172

Name lndex

-.

Ovenear Union Bunk Ccnier. 300,302,303. 3M-309 Rvrncs Place. 30.1 SingopareTm?ury Building. 119.120, 121-123 Sydney. Au~uuIrd: Bond Building. 142 Chiflcy Tower. 150.151, 152. 153 proposed office building. 361

Tokyo. lapw: N6E Building. 290,291. 292 Shimizu Super High Rise. 369,371,386,387, 388-390

\Vellington, New Zealand: hlnjestic Building. 133. 134. 135. 136 (undetermined): Ereahon Center (proposed). 369.370

American Concrete Inrtimle. 147 Americnn Conrulting Engineers' Council. 169.

Asrclpour-Derfuly ct ul. 119901, 355 ASTM. I I Auslnlim code AS1 170.2 (19891.347 Aurlnlivn Consuuction Senicea. I27

Butc. Smun & McCuchean. 27 Bcllurchi. Piew. Inc.. 235 Bcnnetu et nl. (1985). 361 Bennets a ol. (1989). 361 Bofill. Ricnrdo. 124. 126 Bond (1975). 355 Bomhont and Ward Pry. Ltd.. 173 Boundary Lvyer Wind Tunnel. 254 Bnnncn. June. Associates inc.. 235 Brennm..Becr.. Goman Associates. 293 British Steel (1992). 355 Brouctti et al. (1983). 358 Buildinr Center Firc Snlew and Protection Committee. 103 Burgee. John. ArchitecE with Philip Johnson. 244

-

Comeran Chisholm and Nicol (Qld.) Ply. Ltd.. m . .Cantor. Irwin G..Office o t 170.220. 225 CBM Engineers. Inc.. 162, 163. 182. 183.315. 316.323.332 CrrmuMPetcrka. 157 Chen and Robcmon (1973). 341-346 City Center Theatre. 147 Cohcn-Burreto-Mmhcnrr. Inc.. 124.206 Connell \\'ngncr. 27.43. 127. 129. 137

Consulting Engtnccja Cn~nciloiTeh'rrur. 169.262 Council [on Tall Bu~ldinps].5. 6 Council on Tall B.lildingr (19ROJ. 363 Council onToll Building;. Gmup SC (19801. 1.6 Council on Toll Buildings (195'2). 354.355

DnemIhloore Panncnhip. The. 244 Dilvenpon (1967). 347 D~r,mpon.Alan. 254.314 de Prru. Grmrd. 285 DcSimone. Cbnplin. and Dobiyn. 116.158 DeStelono nnd Goctuch. 124 DeSafano and Ponncrs. 126 Dumont. Francis Xovier. 94

ECCS (1988). 355 Ellisor and Tanner Inc.. 166.260

Falconer and Beedle (19841.6.7 Fenucsr. C. W.. and Arrocivter P. C.. 186 Flnck nnd K u m Auslnlio. 150 Faster Associnter. 335 Fox and Fowle Arshitecu. I1 6

Horrell Archiacrs. 127 Hedrich-Blcrsing. 21 1.239.298.378 Hellmuth Obatr m d Korsabuum. inc.. 260 HI(S Inc.. 373 Holmes (1987). 349 HRH Construction. 314

Name lndex

Name Index

National Society of Prohrrionnl Enginccrr. 169 Notions Bonk, 242 NBBJ. 330 Nihon Sekkei Inc.. 68.290 Nikken Sekkei Ltd.. M). 73.77.81.85. 130.?30

Stone. Edward Durrell. 203 Svuctunl Engineen Associalion of Illinois, 240 Srubbinr. Hugh and Associates. 119. I20.310. 311 Swnnkc Hnyden Conncll. 170

O'Msaghcr ct ol. (1993). 355 O'Neill. 135

Tmge. Kenzo. 302 Thomas ct ol. (1989). 361 Thornor ct nl. (1992n). 356.358.366 Thornor a o1. (1992b). 363 Thompson. Leonard. 334 Thornton-Tomare6 Engineen. 150,154,373,374 Tokyo Marine. 99 Travis Pmncn. 150

U.S. Slcsl. 95.355 University of Western Ontario. 254,314,322. 382 UneclSAA Pmnenhip. 302

Vickery (1966. 1969). 347 Jucoby. Edward. 31 1

Kujimo Corpontion. 104 Kajimn Dcrign. 99. IM Kasturi, liijjas. As~ociales.32 Khan (1966). 5 Khan. Fuzlur. 192 Kohn. Pedenm. Fox. 150.225 Kruppv(1981),358 Kfuppa et nl. (1990). 355 Kurokau'a, Kiiho. 27.47

Law ilnd O'Bricn (1981). 358 Lchlersuricr. William. 369 LeMesrurier Canrultunu. 119.310 Levy. Jcnnifcr. 91 Lindsey. Cbcrter. and Arrociatcr. 320 L l q J Joser Br:rr.r A~~ucistcr. 166. 381 I.r,ehc Schla<$n,xo2nd I l ~ c l l .I82

McBcan (1990). 355 Mackboii~eiDenrnaflVcdigcr, I I I Man. Nu Chun. and Arsociater. 247 Mvncini Duffy Asrocintea. 81 M'lnning and Associates. 133 Mmin. Albcn C.. 162 M~ruokael 21. (1992). 355 Massachusctu Institute ofTechnology. 95. Maunsell Prv. Lld.. 47

Melbourne (1988). 345.316 Melbourne nnd Chcung (1988). 352 Melbourne ilnd Palmer (1992). 344 Milsubishi Estate. 68 Moore. Widllcr P.. and Arraciuter. lnc.. 241 MTS Syslemr Corporation. 311 Murphy J h n . 145. 151.381

Paulur Sokolowrki and Sonar. Inc.. 94 Pel. I. M.. ond P m e n . 315.332 Pel Cobb Freed and Pamen. lnc.. 323 Prlli. Ccror, and Associates, 206.209.241.293, 373 Perbnr and Will Pnmecrhip. The. 203.238 Perrort Lyan Malhirron Pty. Ltd.. 137.285 Petlcrsson et ol. (1976). 356 Ponman. John. ArrociaBs. 90 Panopin Hotel Daign Office. 73

Ranhill Bcrsckutu. 32 Reed 119711.341-346 Roarn$on. Lellle E.. ondArrucijlc$, 196. 199 Ko:co Design P0nr.n. I h8 Rorenthnl. Steve. 236 Roienwusser. RobeR Asrocintes P. C.. I 11. 112.145.116.271.272.293 Roth. Emery. nod Sons. 158,310 Rudeman. J m r r . Office of, 310

Sukumoto etnl. (1992). 361 Snunders and Melbourne (1975). 348 Schumun. Lichtenstrin. Clnrnnn and Efron, I I I Sean. Rocbuck and Compnny. 280 Seidler. H w . and Asrociaer. 39 Sevrud Arrociler, 186 Shidw and Asrociuter, 206. 209 Shimiru Carpontian. 386.387 Skidmore. Owingr &Memill. 2.3. 197.210,214. 220.265.268,271.276.279-281.297.377 Skillins Ward Mngnurion Barkshirr, Inc., 320, 321,330,331 Smith. Jcsr. 204 Squire Pholognphicr. 44. 138

415

Wmr Buller and Arrociom. 133.135 Watson nnd O'Bn'en (19901.355 Wcidlinger Asrocinter. 90.214.215.235 Womlcy. David. 314 Wu. Gordon, and Asrocinter. 256 Wyctt and Bennctu (1987). 355

Subject Index '

8

A-fmmc rmsrer. 381 accelrntian. 353 cn'lcrie 311-346.351.353 ncmlastic tesls. 322 oirn'ghh.311 ollsoncrele scheme. 243 along-wind force rpecug 343 along-wind response. 49.341.342.345.347. 350.351 mchonges. 19 arch. tied. 323 mbitecturnl exprcrrion. 279 architecruml tendencia. 371 nrmwhcod desicn. 186.187

bnlcony weight, 79 b u d beams, 138 h m s o l u m n join4 194 beam joint. 37 benmz.eomporile. 9 belled Enissons. 212.213 bolted joints. high-strength. 2M hx-1vm SVUEIUR.109 boredrhenr wall rynemr. llO braced core spine. 162 braced fnme. 4.51.52.68. 73. 87.89.90.372 connections. 52 braced oerimeter tube..310 bncedrteel core. 154.3W. 320 wilh ouuiggcs. 150. 166 brnced steel frame. 3W braced rleel SlrucNrC. 94 building code. 245. 353 building density. 352.353 building drib 157

..

~

building mponw. 346

build in^ awnv. 95 hundicd bm;d cart tuber. 158 bundled lmmed tuber. 280 h~ndlcdtube. 198. 2W. 290.299 behavior, 202

cnntilever efficiency. 198 canlilcverryswms. 195 cmtilevcd bny windows. 175 cnntile"cdC0~.49 cmtilevcd noor. 126122 cmtilcvcred ring barn. 139 cnntilcvcred rhcnr wall. I09 cnntilcved tube. 192.194 cmtilevered venicnl rmrrcr. 51 cmtilevering wind benm system. 177 cast on rilecanmete. 104 chevmn bracing. 332,334 chevmn portem, 382 chord memben. 14 circulnr concrete core. 92 sirculnr face. 152.316 circular shaped buildings. 32.256259 cladding. 61. 147.209, 212,237,298,354 clasrilicntion of systems. 2.5-7 column nonunifomity. 296 column m r f e n , 243.317.319 cohm: composite concnc-filled steel-lube. 127 gravity-designed. 58 high-strength conmele. 320 pilotis. 101 d i n g . 191 combined fnme. 77 comporlte action. 9 composite benmr. I2 design. I I

418

Subject Index

Subject I n d e x

composite column sections. 356 composite floor, 13.208 comporite me~oldeck. 212 computer molysir. 3 W computer flooring. 150 computer modeling. lhree-dimensionul. 267 concenuic hnccd frdmc;. 51 cancenuicnlly bnced core. 164

crou,n. 34. 162.206.241.381 crucifow-rhnped spine. 32.5 cruciform tube. 374.376 cunain wall. 27. 120.354 curvilinmr-rhapcd building. 330 cylindrical tower. 119

concme:

dnmped rtructurcs. 1. 115,3W damper plater. 106 dnmperr. viscoclarlic. 330 damping. 1l5.227.296.314.322.341.351.382 capabilities. 3 W ryrtcm. 69.372 drpprd girdrrr. I 2 dead loud. 157 d e ~ o n ~ u u ~ lstyle. i v i ~ tI dcflrctionr 274.275 design: onowhead. 186. I87 competition, 382 criteria. 389 laad deflection. 179 problcmr. 147 diagonal bncing: core. 85.297 exterior tube. 271 fnmcr. I tube. 276 displnccment tnccs, 342 double tube design. 296 ductile moment f m c . 333 dynumicstiffnesr, 103

choiceof, 113 core. 373.377 with outriggers. 186. I88 care tube. 206 encaTcments. 227 stcel fnmes. 230 high-smngh. 44,285.330.371 high-suenglh columns. 320 perimeter fnmcs. 285 porttenrioned. 19 precast pretensioncd. 17 schcmc. 251 ahcvrcorc. 124. 170 slab. 10 rpvndrcl beams. 97 tube. 272.293 (See also reinforced concrete) connections. 57.110.282 dewilr. 54.55 typcr. 58 conrtruction: cycle. 275 time. 137.256.330 continuous walls. 386 core: diagonally bnced. 85.297 fnmc. 95.98 K-bnccd. 365 m d outrigger systems. 14G144.369 and perimeter fnmr. 133 umsverscly bnced. 81 trinngulw. 320 (Sce olro shcw care) core-alone system, 143 carmrion pmtection. 279,351 costs. 330 coupled shear walls. III c m h wollr. 223 creep. 147.287.304 crosr-wind force specuu. 313,348,349 crosi-wind responic. 49.311.342.345.347. 319.351

eunhquohe. 131. 165.330.333.388 londr. 109 resistonce. 104 resisting cnpocity. 85 rerpanre. 107 wares. 69 eccentric braced fnmc. 51.53 ccccnuic K bncing swaure. 60.65 economy. 369.374 electrified floor system. 262 elecwrlvg u,eldine. 282 ulc%lt$un.IUh. 249, 305. 312. 385. 390 cnc~wd-
excitation mechanirmr. 341 cxteriortube: concrete-fnmed. 210 diagonally bnced. 271

facade: onhitecture. 196 dingonulimdon. 198 geomelrier;. 152 snwtoolh. 219 fin walk. 90 finite elcmen, nndyrir. 50 fire. 353.354 fire compmments. 356.358.361 fire pmtmtion. 4. 103.279.353-367 pmteclivc coatings. 355 fire mgulnlory requirements. 354 fire rcsirwnce. 354.355 fire safety design, 362 fire tests. 358.366 firepmafed rtructunl rtecl. 212 firer. time-tempcnture curve. 358 noor diaphngmr. 329 floor fnminr. 7. 1l plan. 168.208.299.376 floor plans (drawings), ?9.36.41,45.63.73. 75.79.83.88.107.121.132.148. 149.

quarter-circle. 158 floor plae. I ? floar wction. 36 floor slab. 9.318 floorryrlems, 2. 304 composite, 9 p m m r e d and porttenrioned, 15-26 ~OOE:

circulx. 32 long-spm. 16 open-web. 13 plank 93 footing plan.35 formwockrynemr. 1 10 foundation. 82.304.319.388 rynem. 141 f m e - t m r r intcncling syrtems. 57.59 f m c d tubesystem. 192 fnmcr: conccnuic bnced. 51

419

fnmes (Con!.): deformolion. 55 diagonally bmced. 1 ductile moment, 333 cccenuic bmccd. 51.53 elevntion. 71.72 perimeter diagonally bmced. 265 perimeter moment. 158. 160 perimeter rigid moment, 130 perimeter steel. 124. I 8 6 rigid. 60.61.74.77.81.90 rigid perimeter. 94 X-bnccd. 279 fnmcu,ork. M. 76.80.84.87.98. 233.278 rnming plan. 123.218.224.227.264.273.283. 305.379 frequency. 352.353 rriction tests, I81 furniture. 356 luture systems. 369-372

gallcriu. 379 geotcchnicnl conrultanl. 34 gnrity-designed columns. 58 g n r i t y load. 5.56. 122, 200.270.312. 333 gust factor. 347

hnnging gwdenr. 92 high-ruenglh concrete. 1.44. 110. 127. 172. Z55.3W. 330.371 high-suenglh bolted joints. 204 hollow corr plank;. 134 honeycomb dnmper plate. 108 honeycomb dnmper wall. 104.106.107 hurricane. 314 hybrid perimeter tube.214 hybrid steel. I hybrid immure. 116.271.272.307.308 hybrid systems. 4.3W302.369

infarmodon systems. 372 inlemntionnl style. 1

jerk. 344 joist girdcrr. 13. 14 jump-form system. 137

Subject Index

420

loleml deflection. 237 lotcrdl load momcnu, 243 lateral load resistunce. 5-7.355 resirdngsystem. 101.215 lateral loads, 4 lnteml stiffness. 314 lvteml n,ind-resisting system. 168 live-laad deflection. 122 long-span floan. 16

massing. 371 mart. 335 marlcolumn. 312 materinlr. 5 meandering shear wall. 113. 1I 4 mcchvnical ducu. I 2 mega ponvl fnmcs. 276 mc~xolumn Eyslcm. 221.222 mcgustructurc. 223.296 megumrres. 301 mctul deck. 9. 10 mixed conswction. 119 mixed-use. 265.268 made-generalized forcc sprcwm. 348.349 mode shape. 349.351 modemist style. I modes o f vibration. 103 moment frame. 73 moment-resisting frame. 4,5.51.53.55-58.99.

I01 moving farmwork ryrlemr. lI 0 mulliure complex. 276

neohistoricvl style. I

occupancy comfon. 95.341.341-346.351.353. 391 open views. 152 open-wch noor. 13 optimiution. 56. 140. 157 ourriggcrs: beams. 172.300 and belt w n c s . 377 benefiu. 141-143 drawbuck. 143. 144 hutmsr. 158. 160

ourriggen (Canr.): rupenlingonds. 156-157 systems. 1.4. 146144. 186.188. 369 mires, 297.380 wollr. 374 ovenuming moment, 140. 142

p m e t e r w n s i t i v i t y . 349 parking ganger. fire conditions. 361 ponial fnmed lube. 319 peak occelcntion. 345,348,350,351 pedmrrian bridge, I 6 6 pcdesrrion tunnel. 166 perceived motion. 113 pcmrptible motions. 353 perimeter h d a g c r . 327 pcrimetcr column loyout, 317 pcrimeler concrete columnr. 373 ~crimeterdiveonullv bmced frame. 265

perimeler moment frame. 158. I6U pcrimear punid lube. 315 pcrimcler rigid momenl framer. 130 perimeterring mrr. I 2 1 perimcterrleel fmmcr. 124. 186 perimesrrube. 170.223.225.235.241.244 wilh b n m d core. 220 nnd core. 247 and inlemvl core. 256 piles. hi&-strenglh concrete. 386 pilotir column$. 101 planform rhapc. 352.353 p l a l k f l w n . 93 p l m . 43. 102.173.299.321 pony w r r . 323 porunodem style. I posttensionedbeam. 22 porttensioned cancme. 326 n 0 0 ~15 . pornensioned flot deb. 20 pornensioned systems. common. 17 possenrioninp, rconomicr of. 2&25 Pnn uurr. I 4 precost concrete ponel. 66.67 precart pretenrioncd concrete. 17 prerhoring method. 115 preruerred floors. 15 presmessed tendons, cultinp, 2+26

Subject Index pmject descriptions, 27-50.66108 302-338 fnmed lubes. 203-259 lrusscd Nber 266299

.

111-139.

nilmod b a c k . 220.238 nilwoyrmtion. 78 nliingcalumnr. 191 reclnimcd nren. 82.247 reinforced concrete: comtruction. 192 cam. I41 fmmc;. 57 rmctuml system. 285 reinforcement dewilr. 31 residentid buildings. 17. I W rigid box. 192. 198. rigid fnme. 60.61.74.77.81.90 rigid perimeter fmme, 94 ring bcom. 139 risk ;rrscssmenl. 363.366

suwloolh facade. 219 scismicmn. 69 seismic load. 333,388,389 reirmic zone. 134.330. 332 ienritivity studies. 274 servicwbility requiremenu. 6.341 setback. 215 shenr core: with ouoigg~rbenmr. I 8 2 with o u r r i ~ e n 173 . (See o l ~ core) o sheor f m e deformations. 192 shcnrlng. 196. 198 cfiecf I94 shear ounels.. 267 s h r u wall rystemr.4. 109. 110,309 open tube. 147 shear wallr. 77. 110. 116.230.318.1 172 with ourriggcn, 145 shrinkage. 109. 147.287 skeleton. 307 sky lobbies. 388 slender aspect rdtio. 271 slender buildings. 352 slenderswcture. 113. 145.296 slendrmerr mdo. 53.382 slip-formed concrete core. 43.92 slipjoint. I80

.

'

sloped colu4n ryrtem. 229 slopingsiIe. 256 spandrel beam dcmil. 97 spandrel uniu. 216 specin1moment misting h e s , 57 spine suncurer. I.1M. 165.323 spire. 381 s p r i d e n . 366 aquare be. 198 IWCNre. 230 staggered uuer ryrtem. 95 st*]: cantilevered floor bcnmr. 119 dcck 3 M fire-reriiwnf 355 framed mrr rmcture. 223 haming. 156 f m i n g r y r t e m . 129 higb-yield rwctuml. 301.308 mast. 335 open webjoirn. 13.14 perimeter fmmcd tubc. 166 perimeter frdmes. 150, 377 perimelerrube. 206,210 rteclwoik, crtemal. 358 alep buck. 162 stepped beam soffit. 24 stiffness. 12.109,296.3W, 341 ~tresling.42 rvucrunl andyris, high-temperature. 279 r m c t u d plan. 70.292 r m d v r a l ~ k efll ~ r f n m i n e .122 structural stecl scheme. 250 s W F Ntendencies. ~ ~ 371 rmIItie mr. 178 rtubgirdersyatem. 12. 262 stud rhcorconnecton. 95 subsystems. 7 rupeicolumns. 116.3W.323.325. 326.371 supilrurr. 229 suspension mrres. 335 sway o f building. 82. 113

tall building, definition. 5 Wllc5t building. 280.376 wndem elevntan. 260 tapered girders. 12 tcndons. 21. 139 thin-wnlled concrete-filled tubes. 129 three-dimeniionol ncxion. 287 three-dimrruionul computer model. 153

.

-

. Subject I n d e x

422 time h k ~ r unolysis, y 334.

. top-down canrtruction. 188.335

torsional louding. 109 ; loaionol mhlti?n. 328 : toniond stability. 325 m r f c r f l b o r p i n h 318m r h r rwmu&. 240, m r v e n e l y bmced corc. 81 me elemenu. 194 ., me-type construction. 299 w r . 203 .. . vinngulvrcom. 320 vinnguiar rhupc. 39 triongulnr rile. 186 Irinngulnr lower, 111.30-1 vinngulur lube. 198 m r r e d abe. 196.260.371 . systems. 197.369 ~ l l c s215.30-1.313 , comporilefloor. 14. 15. 16 pony. 323 P m t ~14 lube: concrete. 293 concrete-filled rlcel. 300 divgannnly brdced. 171.276 double lube design. 296 exterior. 210 pnniul rmmed. 319 perimeter fmmed. 47.85,203.238.268,297 perimeter pnniul. 315 side-by-ride. 293 ruucture. 168 surpenrion. 335 triangular. 198 venicol. 52 Vierendeel pipe, 3% Warren. 14 water-filled. 355,359 obr-in-tube. 27.32,39.-13.85. 137 tubulorconcepr. 304 lubularefticiency. ?0i hlbulursyslemr. 1.4.5.143, 192-202 tuned morr dompcr. 153.314 tunnels. 129 . typhoon wind ciimae. 254 :

3

'

.1 ;

r @bmced lube, 274

vnlue engineering. 245 vmicill conliirver. 192, 194,282 vcnicsl trurrm. 52 vibrations. 13 modcr of, 103 Vierendeel bandages. 313,325 girder bundogrr. 326 Vicrendeel benm. 192 Vierendeel fnmer. 93.239 Vierendeel mort. 337 Vierendeel panel. 14.95 Vierendeel system. 335 Vierendeel truss. 223.2-16.262.374 pipe trusrcs. 325 vircoelvrtic dnmpen. 330 voncx shedding. 113. 119.226.382

wuming syrterns. 354 warping-restmining bandugcr. 328 Warren Irurr. 14 wcb diagonals. I 4 wclded girder srubr. 236 welding. tillel. 237 wind. 6. 109 wind beam joinl. 181 wind heumr. 179 wind bracing. 263 wind engineering. 330 wind forces, 313 wind induced motions. 4,311,382 windload.49.82.121.131.249.273.287.388. 389 wind motion. 334 wind ovenuming forces. 313 wind reairloncc. 29 eiemenu. 330 syrlem. 157 wind response. 349 wind rhenr. 254.313 wind-shedding farm 299 wind sway. 57 wind tunnel less. 49.68.75, 103. 113. 131, 133.146. 157.160. 166. 175,?26,217. 254.273.274.287.314.322. 388

X-bmccd frumer. 279 X-bmcing. 51,260,270

Structural System for Tall Buildings

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