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september-october 2000 vol. 45, no- 5

Editor-in-ChiefGeorge D. Nasser

Assistant EditorKaren Banasiak STREST

JOURNALSED CONCRETE INSTITUTE

DEPARTMENTS6 Coming Ahead

13 Chairmans MessageProposed PCI EducationFoundation

14 2000 PCI Design AwardsProgram The WinningEntries

128 Problems and Solutions Formwork Issues by

John E. Dobbs andB. A. (Skip) Plotnicki

130 Reviews of TechnicalPublications

131 Reference Cards

135 Industry NewsCNL Center

150 Calendar of Coming Events

151 Index to Advertisers

TABLE OF CONTENTSPrecast Concrete Panels Give Scale and Grandeur toLazarus Department StoreGar Muse and Anthony Di Giacomo

Presents the design-construction highlights of this multi-million dollardepartment store in Pittsburgh, Pennsylvania.

Central ArterylTunnel Project: PrecastlPrestressedStructures Span the Big DigKeith Donington, Paul Towell, and Vijay ChandraIn Part 3 of this multi-billion dollar project, the authors discuss the use ofprecast, prestressed concrete in two bridges and a marine pier.

Proposed Revisions to 1997 NEHRP RecommendedProvisions for Seismic Re9ulations for Precast ConcreteStructures: Part 2 Seismic-Force-Resisting SystemsNell Hawkins and S. K. Ghosh

In Part 2 of this series of articles, the authors discuss specificrecommendations for precast concrete that are intended to be partof the 2000 NEHRP Provisions.

Design Criteria for Headed Stud Groups in Shear:Part 1 Steel Capacity and Back Edge EffectsNell S. Anderson and Donald F. Meinheit

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30

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ON THE COVERPrecast concrete played a prominent role inthe construction of this prestigious Iuxuiydepartment store in Pittsburgh,Pennsylvania. For more details on thisproject, see p. 20.

In this PCI-funded research project on headed studs, the authors presentresults and conclusions from the first part of the investigation.

Influence of Flexure-Shear Cracking on StrandDevelopment Length in Prestressed Concrete MembersRobert J. Peterman, Julio A. Ramirez, and Jan OlekBased on a comprehensive test program, the authors recommend specificchanges to the AASHTO-ACI requirements for strand development length.

Strand Development and Transfer Length Tests on HighPerformance Concrete Box GirdersP. Benson Shing, Daniel E. Cooke, Dan M. Frangopol, Mark A. Leonard,Michael L. McMullen, and Werner HutterPresents the results of an investigation on strand transfer and developmentlength in high performance concrete prestressed box girders.

Transfer Length of CFRP/CFCC Strands for Double-T Girders

Nabll F. Grace

Presents the results of a study on variations in transfer length in two types ofcarbon fiber reinforced polymer (CFRP) prestressing strands.

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September-October 2000 5

COMING AHEAD PCI DIRECTORS, TAC & STAFF

Highlights of PCIs 46th AnnualConvention & Exhibition andPCI!FHWA/fib InternationalSymposium on High PerformanceConcrete

Design-Construction of TheTerraces at Riverfront Recapture

Design-Construction of CruiseTerminals for Port of Miami

Reliability of I8 in. Anchor StudWelds Subject to Tensile Loads

Evaluation of a High PerformanceConcrete Box Girder Bridge

Continuous CFRP PrestressedConcrete Bridges Under Static andRepeated Loadings

JOURNALPRECAST/PRESThESSED CONCRETE PNSTTUTE

EDITORIAL DATAThe PCI JOURNAL (ISSN 0887-9672)is published bimonthly by the Precast/Prestressed Concrete Institute,209 W. Jackson Boulevard, Ste. 500,Chicago, Illinois 60606, (312) 786-0300. Copyright 2000, Precast/Prestressed Concrete Institute.Original manuscripts and ReaderComments on published articlesaccepted on review by the PCITechnical Publications Review Board.No payment is offered. The Precast!Prestressed Concrete Institute is notresponsible for statements madeby authors of papers or claims madeby advertisers in the PCI JOURNAL.Advertising rates available on request.Direct all correspondence to:The Editor, PCI JOURNALPrecast/Prestressed Concrete Institute209 W. Jackson Boulevard, Ste. 500Chicago, Illinois 60606Tel.: (312) 786-0300Fax: (312) 786-0353e-mail: [email protected] Rates: United States$38.00 per year, 3-year rate $90.00.Foreign $53.00 per year, 3-year rate$131.00. Single copy $7.00.

BOARD OFDIRECTORS

Chairmanof the BoardWilliam E. Whitcher

Vice Chairmanof the BoardSaul Shenkman

Secretary-TreasurerRon Schlerf

DirectorsCharles B. BakerBrian J. ConwayThomas J. DArcyGerald E. GoettscheDegan G. HambacherMarvin F. HartsfieldFred W. Heldenfels, IVR. Wayne LyleRobert S. McCormackRichard L. MogelDavid N. NesiusMilo J. NimmerCharles P. OLearyMichael E. QuinlanChristopher N. QuinnH. W. ReinkingStanley J. RudenWilliam F. SimmonsC. Douglas SuttonScott M. WaldronRichard L. Wells

Ex-OfficloWilliam C. Richardson, Jr.William N. Avard

PCI JOURNAL STAFFEditor-in-ChiefGeorge D. Nasser

Assistant EditorKaren Banasiak

EditorIal AssistantSusan Bowden

Layout ArtistKaren Marie Rokos

Cover DesignLeader Graphic Design, Inc.

TECHNICAL ACTIVITIESCOMMITIEE (TAC)ChairmanC. Douglas Sutton

SecretaryPhillip J. IversonKenneth BaurNed M. ClelandThomas J. DArcyS. K. GhoshSimon HartonMichael W. LanierDonald R. LoganTodd G. McCoyGuillermo MecalcoFrank A. NadeauGeorge 0. NasserMichael G. OlivaAndrew E. OsbornChuck PrussackDonald C. RathsA. Fattah ShaikhClark Weber

Ex-OfficioFIB RepresentativeCharles W. Wilson

PCI STAFFPresidentThomas B. Battles

Technical DirectorPhillip J. Iverson

Information OfficerJohn A. Lishamer

Research DirectorL. S. (Paul) JohalArchitectural DirectorSidney Freedman

Administrationand Finance DirectorGary H. Munstermann

Marketing DirectorBrian Goodmiller

Structures DirectorJohn S. Dick

Plant Certification DirectorDavid S. Jablonski

POSTMASTER: Please send address changes to PCI JOURNAL, 209 West Jackson Boulevard, Suite 500, Chicago, Illinois 60606.Periodicals postage rates paid at Chicago and additional mailing office.

PCI JOURNAL

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his indispensable publication provides the designer with comprehensive andefficient procedures for the safe design of both architectural and structural precast and prestressed concrete products. The design information and recom

mendations contained in the Fifth Edition of the Handbook are based not only on thelatest research but also on a consensus of engineers in practice. The topics in theHandbook are illustrated with numerous design examples that are in conformancewith AC! 318-95.

Shipping InformationHandbook(s) will be shipped as soon aspossible Book Rate by U.S. PostalService unless otherwise requested.Shipping and handling charges are as follows (check one):

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The Fifth Edition also includes newdesign recommendations on:* Structural Integrity* Headed Stud Connection Design* Pocketed Spandrel Panels* Seismic Design* Slender Walls

PRE CAST/PRESTRES S EDCONCRETE INSTITUTE and much more!

209 W. Jackson BlvdChicago, IL 60606

Phone: 312/786-0300Fax: 312/786-0353http://wwwjpci.org

e-mail: [email protected]

Also available is the Background andDiscussion of the PCI Handbook, FifthEdition reprinted from the PCI JOURNAL. This valuable resource is available for just $7.00 ($14 for non-PCImembers.)!

$85.00 for PCI member, $95.00 for non-member Engineeri

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CHAIRMANS MES SAGE

William E. WhitcherExecutive Vice President and

General ManagerCoreslab Structures (Miami) Inc.

Medley, Florida

Proposed PCI Education Foundation

When I assumed the PCI chairmanship a year ago, Iexpressed both concern and hope that we couldaddress a major interest of mine, namely, reachingout today to Americas youth that will emich and enhance ourindustry tomorrow.

Earlier this year, as I outlined my goals for my tenure asChairman of PCI, I placed a special emphasis on our need tobring students into the mainstream of the precastlprestressedconcrete industry. We have now taken a significant step towardthe achievement of that goal in the planned establishment of thePCI Education Foundation.

Spurred on by our Associate Member Jim Voss of JVI, Inc.,the new foundation will focus on several goals, all aimed atmaking students become more aware of the advantages thatprecast/prestressed concrete offers in the design and construction of a wide variety of structures.

First, the foundation seeks to influence educators so that theycreate and promote courses in the curricula of their respectiveengineering schools emphasizing precast concrete. Far toooften, our industry gets only cursory attention from educators,many who have little or no knowledge of our products and instead focus their educational efforts on competing materials.

A second goal is to encourage and nurture student participation in our industry. Our hope is that this endeavor will leadthem to consider positions within the precast concrete industryafter they complete their schooling.

A third goal will be to support and subsidize selected areas inthe education arena to stimulate the study and enthusiastic acceptance of precast concrete as a material to be considered intheir future professional careers.

The new foundation will in no way conflict with present PCIeducational activities. We seek instead to enhance efforts that arealready in place and work within the Institute. It remains my sincere hope that the PCI Student Education Committee continues itshigh level of positive activity within the educational community.

Chairman Al Ericson, working with his Student EducationCommittee, has produced a new $25,000 Engineering Competition called the Big Beam Contest, co-sponsored by Sika Corporation. Student teams will be encouraged to work with local

precasters to build and test a prestressed concrete beam. OurRMDs will be involved and prizes will be awarded regionallyand nationally. In addition, Al has been working with our PCIMarketing Department in producing a Career Paths Brochurenow in the development stages. He and his committee are taking this initial draft design and are tweaking it to meet the needsof the student, the committee and PCI.

Professor Norm Lach, from Southern Illinois University, isstarting a PCI Student Chapter and the Board at their recent meeting voted to amend the PCI Bylaws to allow this membershipcategory. Other important education outreach programs includeeducational subsidies of free Design Handbooks, Hollow-CoreSlab, Bridge Design and Architectural manuals being disthbutedto students taking courses in architectural and prestressed concrete.

Currently, there is a joint education project with our Georgia/Carolina region where PCI is planning to hold a PCI Educator/Practitioner Conference next summer at the University ofNorth Carolina.

Also, Professor Eric Steinberg has a student team from OhioUniversity working with PCI staff to build an image bank, i.e.,a library of photos and other artwork taken from Ascent, thePCI JOURNAL and the PCI headquarters library for use by Regional Marketing directors and members.

Finally, our PCI Marketing and Student Education committees have created a business card-sized CD ROM. In this small30-meg. CD, a fully animated and musically scored presentation offers students an overview of the excitement of the precastJprestressed industry. It will be distributed nationwide alongwith the new Career Paths brochure.

It is gratifying to witness how the PCI committees and staffhave responded to our goal of reaching out to the youth ofAmerica that will enrich our industry. To all who have participated, I offer my sincere thanks and a hearty.. .WeIl Done!


2000 PCI Design Awards ProgramThe Winning Entries

Over 100 entries were judged forthe 2000 PCI Design AwardsProgram, held May 19 inChicago, Illinois. In the end, 17 entriesreceived top honors. Entrants neededto show how they creatively used precast, prestressed concrete, glass fiberreinforced concrete and/or architectural precast concrete in their structure. Structures must have been completed within the past three years to beeligible in the program and have beenbuilt in the United States, Canada andMexico.

There were five categories, eachwith several subcategories. TheCommercial Buildings Category included office buildings, retail stores,mixed-use structures, public buildings, institutional buildings, schoolsand hospitals.

Warehouses, manufacturing facilities, food processing facilities, distribution centers and special industrialstructures were included in the Industrial Structures Category.

The Housing Structures Categorycovered single-family homes, multifamily structures, hotels, motels, condominiums, retirement facilities, dormitories and assisted living centers.

The Specialized Structures Categoryincluded parking structures, stadiums,arenas, sports centers, tanks, justicefacilities, jails, prisons and correctional facilities.

The Transportation Structures Category is also divided into subcategories torecognize the diversity of design possible using precast and prestressed concrete. The eight subcategories of thiscategory are: soundwall projects, pilingprojects, rail depots, bridges with spansless than 65 ft (20 m); bridges with spanlengths between 65 to 135 ft (20 to41 m); bridges with span lengths greater

than 135 ft (41 m); rehabilitated bridges;and non-highway bridges.

As in the past, there are no firstplace winners. Instead, each winningproject is given equal recognition inorder to acknowledge the diversity ofdesign solutions used by architects andengineers.

In addition, two entries received theHarry H. Edwards Industry Advancement Award, which is given for thoseideas and concepts that hold the potential to move the industry to the nextgeneration of technology. A separatejury judged the projects considered forthis award.

PCI extends its gratitude to eachmember of the 2000 Jury of Awards.

Jury members for the CommercialBuildings, Industrial Structures,Housing Structures and SpecializedStructures categories were: (CoChairwoman) Donna Robertson,Dean of the College of Architecture,Illinois Institute of Technology; (CoChairman) Eliseo Temprano, Immediate Past President, RAIC; Degan G.liambacher, president, FDG, Inc.;and Chris Sullivan, editor-in-chief,Building Design & Construction.

Jury members for the Transportation Structures category were: (Chairman) David H. Densmore, Chief of

Bridge Division, Federal HighwayAdministration; Richard A. Miller,Associate Professor, University ofCincinnati; and William N. Nickas,State Structure Design Engineer,Florida Department of Transportation.

Jury members for the Harry H. Edwards Industry Advancement Awardwere: (Chairman) Harry A. Gleich,Vice President of Engineering,Metromont Prestress Co.; and GeraldE. Goettsche, President, The Consulting Engineers Group, Inc.

Award winners received a specialrecognition at PCIs 46th AnnualConvention & Exhibition in Orlando,Florida, during the Design AwardsDinner/Dance on Tuesday, September26. Summary descriptions of the win-fling projects appear in the Fall 2000issue of ASCENT Magazine. In addition, winning entries will receive extensive national publicity throughmajor industry and architectural publications. The PCI JOURNAL willfeature articles about some of the winning entries and other noteworthy entries throughout the year.

The credits for the winning projectsare listed on the following pages. PCIextends congratulations to all those involved with these exemplary projects.

The purpose of the Design Awards Program is to recognize designexcellence in the use ofprecast, prestressed concrete and/or architectural precast concrete. The annual program is open to all registeredarchitects and engineers practicing professionally or in governmentagencies in North America. Winners are chosen on the basis of exceptional achievement in aesthetic expression, function and economy, andingenuity in the use of materials, methods and equipment. Please visitour website at www.pci.org for more information.

PCI JOURNAL

2000 Design Awards Program Judges

- David H. Densmore

Donna Robertson

Gerald E. Goettsche

William N. Nickas

Degan G. Hambacher

Chris Sullivan

Harry A. Gleich Richard A. Miller


Winner Winner Winner

Correctional Facility (Low-Rise) Correctional Facility (High-Rise) Custom Solution

David L. Moss Criminal Federal Metropolitan The Terraces at RiverfrontJustice Center Detention Center RecaptureTulsa, Oklahoma Philadelphia, Pennsylvania Hartford, ConnecticutEntrant and Architect: Entrant, Engineer and Architect: Entrant and Engineer:BKL, Inc./HDR Architecture, Inc. Ewing Cole Cherry Brott Brecher Associates P.C.Tulsa, Oklahoma Philadelphia, Pennsylvania Philadelphia, PennsylvaniaEngineer: Precast Concrete Manufacturer: Architects:BKL, Inc. High Concrete Structures Carol R. Johnson AssociatesTulsa, Oklahoma Denver, Pennsylvania Cambridge, MassachusettsPrecast Concrete Manufacturer: General Contractor: Goddes Bicher Quails & Cunningham, Inc.Coreslab Structures (Oklahoma), Inc. Keating Building Corp. Philadelphia, PennsylvaniaOklahoma City, Oklahoma Bala Cynwyd, Pennsylvania Precast Concrete Manufacturer:

Owner: Blakeslee Prestress, Inc.General Contractor:Hensel Phelps Construction Co. U.S. Department of Justice Branford, ConnecticutCape Canaveral, Florida Federal Bureau of Prisons

Washington, D.C. General Contractor:Owner: 0 & G Industries, Inc.Tulsa County Criminal Justice Authority Torrington, ConnecticutTulsa, Oklahoma Project Manager:

Connecticut Department of TransportationNewington, ConnecticutOwner:Riverfront Recapture, Inc.Hartford, Connecticut


Hotel Office Building (Low-Rise) Office Building (High-Rise)

Hilton Boston-Logan Airport Merrill Lynch Facility IJL Financial CenterBoston, Massachusetts Englewood, Colorado Charlotte, North Carolina*Entrant and Architect: Entrant and Architect: Entrant and Architect:Cambridge Seven Associates, Inc. Thompson, Ventulett, Stainback & Smaliwood, Reynolds, Stewart,Cambridge, Massachusetts Associates Stewart & Associates, Inc.Engineer: Atlanta, Georgia Atlanta, GeorgiaWeidlinger Associates, Inc. Engineer: Engineer:Cambridge, Massachusetts W.P. Moore and Associates, Inc. Stanley D. Lindsey & Associates Ltd.Precast Concrete Manufacturers: Atlanta, Georgia Atlanta, GeorgiaBton Prfabriques Du Lac, Inc. Precast Concrete Manufacturer: Precast Concrete Manufacturer:Alma, Quebec, Canada Rocky Mountain Prestress, Inc. Metromont Prestress Co.Northeast Concrete Products LLC Denver, Colorado Greenville, South CarolinaPlainville, Massachusetts General Contractor: General Contractor:General Contractor: Huber, Hunt & Nichols, Inc. Beers Construction Co.Beacon Skanska Construction Co. Branch Burg, New Jersey Atlanta, GeorgiaEast Boston, Massachusetts Owner: Owner:Owner: Merrill Lynch Denver Holdings, Inc. Bank of AmericaHilton Hotels Corporation Plainsboro, New Jersey Charlotte, North CarolinaBeverly Hills, California *A detailed article on this project was

published in the May-June 2000PCI JOURNAL.

16 PCI JOURNAL

Co-Winner Co-Winner WinnerParking Structure

MacArthur Center North andSouth Parking StructuresNorfolk, VirginiaEntrant and Architect:Hobbs & Black Associates, Inc.Ann Arbor, MichiganDesign Architect:BrownlMcDaniellBhandari, Inc.San Francisco, CaliforniaEngineer:E & S Mechanical ServicesPasadena, MarylandPrecast Concrete Manufacturers:Tindall Corporation Virginia DivisionPetersburg, VirginiaGate Concrete Products CompanyOxford, North CarolinaGeneral Contractor:Sordoni Skanska Construction Co.Parsippany, New JerseyOwners (Joint Venture):Taubman Realty GroupBloomfield Hills, MichiganThe Conroy Development CompanyGreenwich, Connecticut

Parking Structure

Sun Trust Plaza ParkingStructureWinter Park, FloridaEntrant and Architect:Rich & Associates, Inc.Southfield, MichiganDesign Architect:RTKL Associates, Inc.Baltimore, MarylandEngineer:Rich and Associates, Inc.Tampa, FloridaPrecast Concrete Manufacturer:Finfrock Industries, Inc.Orlando, FloridaGeneral Contractor:Jack Jennings & SonsOrlando, FloridaOwner:Rollins CollegeWinter Park, Florida

Public Building

Center of Science &Industry (COSI)Columbus, OhioEntrant and Lead Architect:NBBJ Architects, Inc.Columbus, OhioDesign Architect:Arata Isozaki & AssociatesTokyo, JapanEngineer:Korda-Nemeth Engineering, Inc.Columbus, OhioPrecast Concrete Manufacturers:Concrete Technology, Inc.Springboro, OhioMarietta Structures Corp.Marietta, OhioConstruction Manager:Ruscilli Construction Co.Columbus, OhioOwner:Center of Science & IndustryColumbus, Ohio

Retail Building

Lazarus Department StorePittsburgh, Pennsylvania*Entrant and Architect:Cooper CarryAtlanta, GeorgiaStructural Engineer:Structural Engineering Corp.Pittsburgh, PennsylvaniaPrecast Concrete Manufacturer:Modern Mosaic Ltd.Niagara Falls, Ontario, CanadaGeneral Contractor:Turner Construction Co.Pittsburgh, PennsylvaniaOwner:Federated Department StoresCincinnati, Ohio

Stadium

Princeton University StadiumPrinceton, New JerseyEntrant and Architect:Raphael Vifloly ArchitectsMinneapolis, MinnesotaEngineer:Thoruton-Tomasetti EngineersNew York, New YorkPrecast Concrete Manufacturer:Metromont Prestress Co.Greenville, South CarolinaGeneral Contractor:Turner Construction Co.Philadelphia, PennsylvaniaOwner:Princeton UniversityPrinceton, New Jersey

tFor more information on these projects,see articles in the September-October andMay-June 1999 issues of the PCI JOURNAL,respectively.

Warehouse

Park Fletcher Building #40Indianapolis, IndianaEntrant and Architect:Ratio Architects, Inc.Indianapolis, IndianaEngineer:Smith Roberts & AssociatesIndianapolis, IndianaPrecast Concrete Manufacturer:Spancrete Industries, Inc.Waukesha, WisconsinGeneral Contractor:Duke-Weeks Realty Corp.Indianapolis, IndianaOwner:Duke-Weeks Realty Corp.Indianapolis, Indiana


*Adetailed article on this project appearsin this issue of the PCI JOURNAL.


Winner Winner WinnerBridge Span

Less than 65 ft (20 m)Bridge Span

of 65 to 135 ft (20 to 41 m)Bridge Span

Greater than 135 ft (41 m)

U.S Route 3A over King Avenue over the H-3!Lower Halawa ValleyNewfound River Olentangy River Viaduct; Unit 1, Phase 1 BBristol, New Hampshire Columbus, Ohio Aiea, HawaiiEntrant and Engineer: Entrant and Engineer: Entrant and Engineer:New Hampshire Department of HNTB Corporation T.Y. Lin InternationalTransportation Kansas City, Missouri San Francisco, CaliforniaConcord, New Hampshire Engineer: Precast Concrete Manufacturer:Precast Concrete Manufacturer: Eriksson Engineering Con-Fab California Corp.Northeast Concrete Products LLC Columbus, Ohio Lathrop, CaliforniaPlainville, Massachusetts Precast Concrete Manufacturer: General Contractor:General Contractor: Tecspan Concrete Structures, Inc. Kiewit Pacific Co.R.S. Audley Construction Grove City, Ohio Vancouver, WashingtonBow, New Hampshire General Contractor: Owner:Owner: C.J. Mahan Construction Hawaii Department of TransportationNew Hampshire Department of Grove City, Ohio Honolulu, HawaiiTransportation Owner:Concord, New Hampshire Franklin County, Ohio

Columbus, Ohio

Winner Winner

Non-Highway Bridge

Metropolitan line B StationsMexico City, MexicoEntrant, Engineer and Architect:Rioboo, S.A. de C.V.Mexico City, MexicoPrecast Concrete Manufacturer:PretencretoMexico City, MexicoGeneral Contractor:Ingenieros Civiles Asociados (ICA)Mexico City, MexicoOwner:Secretaria de Obras de Distrito FederalMexico City, Mexico

Hotel

Route 7 Bridge over Route 50Fairfax County, VirginiaEntrant and Engineer:Wilbur Smith AssociatesFalls Church, VirginiaPrecast Concrete Manufacturer:Bayshore Concrete Products Corp.Cape Charles, VirginiaGeneral Contractor:Corman ConstructionAnnapolis, MarylandOwner:Virginia Department of TransportationFairfax, Virginia

PCI JOURNAL

Harry H. Edwards Industry AdvancementAward Winners

Public Building Stadium

Center of Science & Princeton University StadiumIndustry (COSI) Princeton, New Jersey*Columbus, OIiio* Entrant and Architect:Entrant and Lead Architect: Raphael Violy ArchitectsNBBJ Architects, Inc. Minneapolis, MinnesotaColumbus, Ohio Engineer:Design Architect: Thornton-Tomasetti EngineersArata Isozaki & Associates New York, New YorkTokyo, Japan Precast Concrete Manufacturer:Engineer: Metromont Prestress Co.Korda-Nemeth Engineering, Inc. Greenville, South CarolinaColumbus, Ohio General Contractor:Precast Concrete Manufacturer Turner Construction Co.Concrete Technology, Inc. Philadelphia, PennsylvaniaSpringboro, Ohio Owner:Marietta Structures Corp. Princeton UniversityMarietta, Ohio Princeton, New JerseyConstruction Manager:Ruscilli Construction Co.Columbus, OhioOwner:Center of Science & IndustryColumbus, Ohio

*For more information on these projects,see articles in September-October andMay-June 1999 PCI JOURNAL,respectively.


COVER FEATURE

Precast Concrete Panels GiveScale and Grandeur to LazarusDepartment Store

Gar Muse, MAPrincipalCooper Carry Inc.Atlanta, Georgia

Precast concrete played a prominent role in building the new multi-million dollar Lazarus Department Store in dowtown Pittsburgh,Pennsylvania. The glitzy department store is four stories high withan underground three-level parking structure. Highly articulatedprecast concrete panels with deep reveals give the building scaleand character, and also complement the nearby historic buildings.In addition, the use of granite at the base provides richness anddepth of color. These features enhance the faades verticality andcontemporary look. To speed construction, structural precastconcrete columns are used in the parking structure. This articlepresents the conceptual and architectural design features of thebuilding, design considerations, and erection highlights of the project.

Anthony Di GiacomoVice PresidentModern Mosaic Ltd.Niagara Falls, OntarioCanada

p ittsburghs downtown FifthAvenue shopping district isundergoing a major revitalization, spearheaded by the citysown development activities and thedeep involvement of a variety of retailers. A centerpiece in this renovation program is the Lazarus Department Store, a new four-story,247,000 sq ft (23000 m2) retail center and three-level undergroundparking facility. The new structureblends very well with the nearbyhistoric buildings while offering adistinctly contemporary feeling in

its character and tone (see Fig.1).To achieve that combination, the

design team took advantage of themany benefits offered by architectural precast concrete panels to cladthe structure and precast concretestructural columns to support theparking structure. The result of theirefforts was not only an impressiveand successful addition to the downtown area but the building won theaward for the Best Retail Facility inthe 2000 Design Awards Competition sponsored by the Precast/Prestressed Concrete Institute.

20 PCI JOURNAL

Fig. 1.TheLazarusDepartmentstore indowntownPittsburghfeatures athree-layerlook on itsfaade and astrongentrancetower alignedwith theintersection.

The project was designed and builtfollowing the requirements of twodistinct clients. The Pittsburgh Economic Industrial Development Corporatiori (PEIDC) owns the site andserved as the impetus for the construction. PEIDC in turn leased thebuilding to Federated DepartmentStores to operate a Lazarus retail center in the building. As a result, bothgroups provided input into the design, with the PEIDC focused primarily on the structure and the underground parking facility, and Lazarusworking with the team on the store

design. Figs. 2 and 3 show a plan, elevation and various sections of thebuilding.

The site selected by PEIDC iswithin the citys main downtownshopping district and required the demolition of eight existing buildings toclear the site for construction of thenew building. The availability of thissite convinced Federated DepartmentStores to agree to build a new downtown store; however, once site workbegan, demolition and foundationpreparation showed that a retainingwall was required before the new

construction could begin, causing anunforeseen delay that threatened toslow down the project substantially.

Timing was a critical issue for theretailer, as the project had to be completed before the Christmas holidayseason, when the company makes asignificant percentage of its annualsales and profit. Because the demolition and preparation work delayed thetime when the site could be turnedover to the general contractor tobegin construction, the contractorsuggested converting the underground parking structures structural


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can use either emulation procedures orprocedures that recognize the uniqueproperties of a structure composed ofinterconnected precast elements (nonemulative).

For structures assigned to SDC C,moment frames made from precast elements must utilize, as a minimum, TypeY connections. However, they may alsohave the tougher Type Z connections ifthe designer so chooses. Structuralwalls composed from precast elementscan be designed as ordinary structuralwalls per Chapters 1 through 18 of ACT318-99 with the requirements of Chapter 16 superseding those of Chapter 14and with Type Y connections, as a minimum, between elements.

SPECIAL MOMENT FRAMESFor precast and/or prestressed con

crete special moment frames, hinge locations (nonlinear action locations),must be selected so that there is a strongcolumn/weak beam deformation mechanism under seismic effects, regardlessof whether emulative or non-emulative

design procedures are used.

Emulative DesignRequirements for design of precast

and prestressed concrete special moment frames, utilizing procedures anddetails that result in a structure with abehavior under seismic loading emulating that of cast-in-place special momentframes, were first introduced into theNEHRP Provisions in the 1994 Edition.Two design alternatives were providedand those alternatives, with minorchanges, have been carried over into the2000 NEHRP Provisions.

One procedure allows elements to bejoined using ductile connections and theother allows elements to be joined usingstrong connections. A strong connectionis designed to remain elastic while inelastic action takes place away from theconnection. Because a strong connection must not yield or slip, its designstrength in both flexure and shear mustbe greater than the bending moment andshear force, respectively, correspondingto the development of probable flexural

or shear strengths at nonlinear action locations.

Ductile connections, on the otherhand, have adequate nonlinear response characteristics, making it unnecessary to ensure nonlinear actionlocations remote from connections.Typical connection configurations areshown in Fig. 2. Additional information on the behavior and design of precast concrete structures using emulative procedures is contained in Refs. 3through 6.

Ductile Connections Where elements are joined using ductile connections, the aggregate interlock that ispresent at hinge locations in monolithicconstruction is unlikely to exist for precast concrete construction. Therefore,to prevent shear slip when the momentacting at the hinge location is at itsmaximum probable value of Mpr, theco-existing shear must not exceed halfthe sum of the nominal shear strengths,

Connection of all the connections at thehinging section. The nominal shearstrength, V0, of the section where theconnection is made must also not be

Fig. 1. NEHRP 2000 requirements concerning precast concrete seismic systems.

36 PCI JOURNAL

Connection

(c) Beam-to-Beam

Connection7/

(b) Column-to-Beam

(d) Column-to-Column

Fig. 2.Typical precast connectionconfigurations.

less than the shear strengths of themembers immediately adjacent to theconnection.

Individual connections must satisfyType Z connection requirements.Those connections can be either wetor dry. A wet connection is definedas one that uses any of the splicingmethods (mechanical, welded or lap)specified in Chapter 21 of ACT 318-99to connect precast members or precastand cast-in-place members, and usescast-in-place concrete or grout to fillthe splicing closure. One type of ductilewet connection widely used in emulative design is the splice sleeve connection.78Other connections with simi

jar ductility capabilities have recentlybecome available or are under development.

Strong Connections Wherestrong connections are used, the nonlinear action location (center of the nonlinear action region) must be no closerto the near face of the strong connection than half the member depth. Thus,for a frame with strong connections atthe beam-to-column interface, reinforcement details must result in beamhinging no closer than half the beamdepth away from the column face (seeFig. 3). Any strong connection locatedoutside of the middle half of the span ofthe beam must be a wet connection un

less a dry connection can be justifiedby approved cyclic test results.

Non-Emulative DesignOver the last decade many advances

have been made in our understandingof the seismic behavior of precast! prestressed concrete frame structures, as aresult of the NIST,9 USPRESSS121314and JAPAN-PRESSS research programs. Those advances havemade possible the provisional standardization by ACT5 of acceptance criteriafor concrete special moment framesbased on validation testing. That provisional standard, together with the re

37

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(a) Beam-to-Column

Connecti7

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Connection

Connection

(d) Column-to-Footing

September-October 2000

search advances, has made possible thedevelopment of criteria for the designof frames constructed from interconnected precast elements.

While criteria for such frames haveexisted in the NEHRP Provisions since1994, the previous criteria were in anAppendix and contained penalties forthe use of precast concrete elements

compared to monolithic concrete elements. Those penalties are eliminatedin the 2000 Provisions and the possiblebehavioral benefits of using precastconstruction are recognized.

The complexity of structural systems, configurations and details possible with the use of precast elementsrequires:

1. The selection of functional andcompatible details for connections andmembers that are reliable and can bebuilt with acceptable tolerances.

2. Experimental and analytical verification of force-deformation relationships for critical connections ofthe proposed seismic-force-resistingsystem.

3. Design of the building usingthose force-deformation relationshipsand recognizing the loading effectslikely to be imposed by the anticipatedground motions.

Traditionally, designers have hadthe flexibility to widely vary connection details within prescribed code requirements. For non-emulative special moment frame design, thatflexibility is sharply curtailed because experience shows that smalldesign changes can have marked effects on the building response in anearthquake. Thus, ACI/ITG Ti. 1-99requires a prior development program, including both analytical andexperimental investigations of a proposed seismic-force-resisting system,before any validation testing of critical details of the generic frame is undertaken. That ACI Provisional Standard requires that:

1. A minimum of one module of

Fig. 4. Illustration of connection configuration.

NonlinearAction Location

Precast

Precast Column

Strong Connection

Nonlinear

h/2 \h,2Action Region

Fig. 3. Example showing nonlinear action region and location.

I

(a) Interior One-Way Joint (b) Exterior One-Way Joint (c) Corner Joint

38 PCI JOURNAL

each characteristic configuration of intersecting beams and columns in thegeneric moment frame be subject tovalidation testing (see Fig. 4).

2. That testing be conducted at ascale large enough to capture the fullcomplexities and behavior of the materials and load transfer mechanismsin the prototype frame. Test modulesmust be not less than one-third scale.

3. The first loading cycle applied tothe module be within the linear elasticresponse range of the module.

4. Test modules be subject to a sequence of displacement controlleddrift cycles of increasing magnitudethat are representative of the drift cycles expected under earthquake motions (see Fig. 5). Testing is to be continued until the drift ratio (see Fig. 6)equals or exceeds 0.035.

For acceptance of the generic frame,the nominal strength, E, must be developed before the drift raio exceedsthe allowable story drift limitation ofthe governing building code (Value Bin Fig. 7); and the characteristics ofthe third complete cycle for each testmodule, at a drift ratio not less than0.035, must satisfy the following criteria:

1. The peak force for a given loading direction must be not less than75 percent of the peak lateral loadfor the same loading direction(Value A in Fig. 7).

2. The relative energy dissipationratio, f3, must not be less than one-eighth. That ratio equals the areawithin the hysteretic loop divided bythe areas of the circumscribing paral

Fig. 6.Definition of driftratio.15

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0

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Fig. 5. Cyclic deformation history for validation testing.

(..

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Final Position

Drift Ratio 0 = Jh

VOL

HAL


lelograms defined by the initial stiffness for each loading direction duringthe first loading cycle and the peakresistance for that same direction during the third cycle to a drift ratio of0.035 (see Fig. 8).

3. The secant stiffness between driftlimits of -0.0035 and +0.0035 must benot less than 0.05 times the initialstiffness of the module for the firstloading cycle (see Fig. 9).

The studies that lead to the specification of a limiting drift ratio of 0.035are documented in the Commentary toACIIITG Ti .1-99. Conventional cast-in-place special moment frames conforming to Chapter 21 of ACT 318-99will have limiting drift ratios approaching 0.035 but they may be unable toachieve that limit on a consistent basisfor the range of properties found inpractice.11 Thus, precast/prestressedspecial moment frames in the 2000NEHRP Provisions are being held to astandard at least as high as that forcast-in-place special moment frames.

Some strength degradation at highcyclic-drift ratios is inevitable and thedegree of degradation that can be expected will increase with increase inthe limiting drift ratio. A strength

degradation of 25 percent is consistentwith analytical and experimental findings for a drift ratio of 0.035. For agiven earthquake motion, the maximum drift experienced by a structureincreases as its relative energy dissipation ratio decreases.

If the relative energy dissipationratio is less than one-eighth, oscillations may continue for a considerabletime after the earthquake and lowcycle fatigue effects can result. If thestiffness is very small around zerodrift ratio, the structure is prone tolarge displacements for small lateralforce changes following a major earthquake and is, therefore, vulnerable tolow cycle fatigue effects in aftershocks and moderate winds.

For precast/prestressed specialmoment frames, the 2000 NEHRPProvisions add three additional itemsto the ACI/ITG Tl.1-99 criteria asfollows:

1. The test modules must be shownto be able to continue to carry thegravity loads that act on them in thegeneric frame at a 0.05 drift ratio. Thisrequirement was considered necessaryto document that the precast/prestressed frame had a toughness equiv

alent to that anticipated for a cast-in-place concrete frame.

2. Unless there was substantial experimental evidence obtained in aprior development program, the validation tests of ACTJITG T1.i-99 mustbe conducted at full scale and be atleast two in number for each characteristic configuration of intersectingbeams and columns.

While the Commentary to T1.1-99implies that experimental evidenceshould be obtained in a prior development program, the Provisional Standard does not require it. Rather, Ti .1 -99 requires only that, prior to thevalidation testing, a design procedureshould have been developed for thegeneric frame, and that procedure usedto proportion the test modules.

In the NEHRP Provisions, the number of tests required in the prior development program is not specified.However, the results for the severaldifferent frame systems studied in thePRESSS (Precast Seismic StructuralSystems) program suggest that five ormore tests at one-quarter scale orgreater should be made in order toprovide the range of experimental information needed to develop a mathe

Fig. 7.Quantities used in

evaluating acceptancecriteria.

LATERAL FORCE OR MOMENT

DRIFT RATIO

DRIFT FOR LIMITINGSTIFFNESS OF BUILDING CODE

OO35

40 PCI JOURNAL

matical model sufficiently accurate forpurposes of analysis.

3. The special moment frame mustbe designed using the nonlinear response history analysis procedurespecified in Section 5.8 of the 2000NEHRP Provisions, using the force-deformation characteristics for thenonlinear action locations obtainedfrom the module tests.

The 2000 NEHRP Provisions requires designs to be carried out usingstructural analyses conforming to oneof six types. Those types are IndexForce Analysis, Equivalent LateralForce Analysis, Modal Response Analysis, Linear Response History Analysis, Nonlinear Static Analysis, andNonlinear Response History Analysis.

The type of analysis required depends on the SDC of the structure, itsheight and irregularity. The typicalcast-in-place special moment frame instructures with a limited degree of irregularity and not more than 17 or 18stories in height can be analyzed withany one of the foregoing six procedures except Index Force Analysis.

By contrast, a precast special moment frame can be designed using Nonlinear Response History Analysis only.

That method requires that a mathematical model be used for the structure thatdirectly accounts for the nonlinear hysteretic behavior of the components ofthe structure. That model is then usedto determine the response of the structure, through methods of numerical integration, to suites of ground motioncompatible with the design responsespectrum for the site of the structure.

Use of Nonlinear Response HistoryAnalysis is required for non-emulativeprecast concrete special momentframes. This is because none of theother four procedures permitted forcast-in-place frames can realisticallycapture the strength and deformationdemands placed on the structure bythe range of structural characteristicspermitted by T1.1-99.

SPECIALSTRUCTURAL WALLS

The studies that led to the development of the acceptance criteria ofT1.1-99 for special moment framesalso catalyzed studies that have resulted in the development of similaracceptance criteria for special structural walls.16 The validity of those cri

teria for walls have been demonstratedby the results of tests in the directionof the structural walls of the PRESSSfive-story building.4

The 2000 NEHRP Provisions require that the substantiating experimental evidence and analysis for special structural wall systems meetrequirements similar to those of Tl.1-99 for the design procedure used forthe test modules, the scale of the modules, the testing agency, the testmethod and the test report. The minimum test module must be a stack ofwall panels at least two stories high.

Based on the work described in Ref.16, the test module must perform satisfactorily under cyclic loading at alimiting drift ratio that is a function ofthe characteristics of the wall and isgiven by the criterion:

1.0 zi Ih (percent) =0.67 [h/l] + 0.5 3.0

where

(1)

height of entire modulelength of entire module

Criterion 1 was derived after an examination of results from tests on 178cast-in-place walls with aspect ratios

Fig. 8.Relative energy dissipationratio.53 = A, I (E + E2) (0, + 02)

Ah = Hatched Area

BI---

C

D=O,

G E, F

DRIFT RATIO


(h/1) between 0.25 and 3.53. Thoseresults clearly showed, as apparentfrom Fig. 10(a), that the limiting driftratio at the peak load varied linearlywith the aspect ratio and varied between about 0.67 and 3.0 percent. Forductile behavior, some post-peakdegradation must be expected, although the acceptable degree shouldbe less for walls than for frames because the limiting drift ratio is less forwalls.

Analysis showed the acceptabledegree of degradation should be limited to 20 percent for walls as compared to 25 percent for frames. Forthat condition, Criterion 1 combinesthe drift predictions for a simplemathematical model of a wall hinging at its base and the use of a maximum displacement ductility factor ofeight to assess the limiting drift. Therelationship derived between displacement ductility and limiting driftfor varying h/l values is comparedto the 0.035 limiting drift for framesin Fig. 10(b).

For the third cycle at a drift ratioequaling or exceeding the valuegiven by Criterion 1, the 2000

NEHRP Provisions requires that thetest module exhibit:

1. A degradation in post-peak capacity not exceeding 20 percent.

2. A relative energy dissipationratio, defined in the same manner asin ACT ITG/T1.l-99 (see Fig. 8) thatequals or exceeds 15 percent.

3. A stiffness around zero drift thatequals or exceeds that required by theacceptance criteria of ACT ITG/T1.1 -99 (see Fig. 9).

The basis for the slightly higherenergy dissipation ratio required forwalls than for frames is also documented in Ref. 16. In the five-storyPRESSS building tests, a pair ofvertically coupled precast panelstructural wall stacks were used,with each of the stacks having centrally located unbonded post-tensioned tendons.

The results of those PRESSS testsfor the shear wall direction and analytical studies of precast post-tensioned walls reported in Refs. 14 and16 validate the appropriateness of thecriteria specified in the 2000 NEHRPProvisions for structural walls constructed from precast panels.

CONNEC11ONSDry connections for seismic-force-

resisting systems are classified intotwo types, namely, Type Y and TypeZ. At nonlinear action locations, displacements both in the direction of action of the connection, and transverseto it, must be controlled. For example,if a sliding shear connection is to beprovided between two precast concretemembers, then there must also be a tiebetween the two members to preventthe sliding surfaces from separating.

Type Y connections must be able todevelop, for the flexure, shear, or axialload, or combinations of those quantities expected to act on the connection,a probable strength, S, determinedusing a value of unity, that is not lessthan 125 percent of the yield strengthof the connection. In essence, the connection must be able to strain harden.

Under cyclic loading the connectionmust be able to develop a displacement, at Spr, that is at least 4.0 timesits displacement at yield. The anchorage of the connection into the precastmember on either side of a joint mustbe designed to develop in tension 1.3

Fig. 9.Unacceptable hysteretic

behavior.15

-0.0035 I- 0.035

0.0035 0.035DRIFT RATIO

//

42 PCI JOURNAL

times Spr, and be connected directly bya Type 2 splice to the principal reinforcement of the precast or cast-in-place element.

For Type Z connections, Spr mustbe not less than 140 percent of theyield strength of the connection, andunder cyclic loading the connectionmust be able to develop a displacement at Spr that is at least eight timesits displacement at yield. The anchorage for the connection must also meet

in both tension and compression allthe requirements for Type Y connections. Equilibrium based plasticitymodels (strut-and-tie models), as described in 18.13.5 of ACT 3 18-99, areto be used for the design of the connection region.

Confinement reinforcement in theform of closed hoops or spirals with ayield force not less than 0.05 times thecompressive force and with a spacingnot greater than 3 in. (76 mm) must be

provided around the anchorage wherethe local compressive stress at Sj,,,. exceeds 0.7 f. The connection region isdefined in the same manner as anchorage zone in Section 2.1 of ACI318-99.

The testing of connections and theevaluation of results must be made inaccordance with the principles ofACT TTG/Tl.l-99. Appropriate procedures for testing connections willbe described in more detail in thenext issue of the PCI JOURNAL inthe discussion of the design provisions for untopped diaphragms contained in the Appendix to Chapter 9of the 2000 NEHRP Provisions. Connections at nonlinear action locationsin modules of frames and structuralwalls used for validation testing aredeemed to satisfy the provisions forconnections if the results for the testmodule satisfy the acceptance criteria for frames or structural walls, asappropriate.

CONCLUDINGREMARKS

The 2000 NEHRP Provisions areexpected to include expanded seismicdesign provisions for precast, prestressed concrete lateral-force-resisting systems. Emulative design, whereparity with the seismic performance ofcast-in-place reinforced concretestructures is sought, and non-emulative design, where the unique properties of precast concrete constructionare sought to be taken advantage of,are both permitted to be used. Emulative design procedures are prescribedfor special moments frames as well asfor special structural walls (suitablefor use in Seismic Design CategoriesD,EandF).

Under the special moment frameprovisions, designers may utilizestrong connections which remainelastic as inelastic action takes placeaway from those connections, orthey may utilize ductile connectionsin which seismic energy dissipationis allowed. Only the ductile connection option is available under thespecial structural wall provisions.Non-emulative design proceduresare also prescribed for special moment frames as well as for specialstructural walls.

6

5

Q30

2

0

7

6

.5C

I:0

3

2

0

ASPECT RATIO (hJ)

(a) Limiting Drift - Aspect Ratio Relationshipfor Test Wall Database

DISPLACEMENT DUCTILITY

(b) Drift-Displacement Ductility Relationship forCantileaver Model of Wall

Fig. 10. Basis for Criterion 1 for special structural walls.


ACKNOWLEDGMENT

The original proposal leading to the reported changes from the 1997 to the 2000Edition of the NEHRP Provisions was prepared by a PCI Fast Team consisting ofNed Cleland, Thomas DArcy, Robert Fleischman, S.K. Ghosh, Neil Hawkins,Phillip Iverson, Michael Oliva and Richard Sause. The contribution of the membersof this team is gratefully acknowledged.

REFERENCES

1. Federal Emergency ManagementAgency, NEHRP Recommended Provisions for Seismic Regulations forNew Buildings and Other Structures,1997 Edition, FEMA 302, February1998; and Commentary, FEMA 303,Washington D.C., February 1998.

2. ACT Committee 318, Building CodeRequirements for Structural Concrete(318-99) and Commentary (3l8R-99), American Concrete Institute,Farmington Hills, MI, June 1999.

3. Restrepo, J. I., Park, R., andBuchanan, A. H., Tests on Connections of Earthquake Resisting PrecastReinforced Concrete Perimeter Framesof Buildings, PCI JOURNAL, V. 40,No. 4, July-August 1995, pp. 44-61.

4. Restrepo, J. I., Park, R., andBuchanan, A. H., Design of Connections of Earthquake Resisting PrecastReinforced Concrete PerimeterFrames, PCI JOURNAL , V. 40, No.5, September-October 1995, pp.68-77.

5. Yoshioka, K., and Sekine, M., Experimental Study of Prefabricated Beam-Column Subassemblages, ACT SP123, Design of Beam-Column Jointsfor Seismic Resistance, AmericanConcrete Institute, Detroit, MI, 1991,pp. 465-492.

6. Kurose, Y., Nagami, K., and Saito, Y.,Beam-Column Joints in Precast Concrete Construction in Japan, ACT SP123, Design of Beam-Column Jointsfor Seismic Resistance, AmericanConcrete Institute, Detroit, MI, 1991,pp. 493-5 14.

7. Yee, A. A., Design Considerationsfor Precast Prestressed ConcreteBuilding Structures in Seismic Areas,PCI JOURNAL, V. 36, No. 3, May-June 1991, pp. 40-55.

8. Warnes, C. E., Precast Concrete Connection Details for All SeismicZones, Concrete International, V. 14,No. 11, November 1992, pp. 36-44.

9. Cheok, G. S., and Lew, H. S., Performance of Precast Concrete Beam-to-Column Connections Subject to CyclicLoading, PCI JOURNAL, V. 36,No.4, July-August 1991, pp. 56-67.

10. Cheok, G. S., Stone, W. C., and Kunnath, S. K., Seismic Response of Precast Concrete Frames with HybridConnections, ACI Structural Journal,V. 95, No. 5, May 1998, pp. 527-539.

11. Stanton, J. F., Stone, W. C., andCheok, G. S., A Hybrid ReinforcedPrecast Frame for Seismic Regions,PCI JOURNAL, V. 42, No. 2, March-April1997, pp. 20-32.

12. Priestley, M. J. N., Overview ofPRESSS Research Program, PCIJOURNAL, V. 36, No. 4, July-August1991, pp. 50-57.

13. Priestley, M. J. N., The PRESSS Program Current Status and ProposedPlans for Phase III, PCI JOURNAL,V. 41, No. 2, March-April 1996, pp.22-40.

14. Priestley, M. J. N., Sritharan, S., Conley, J. R., and Pampanin, S., Preliminary Results and Conclusions from thePRESSS Five-Story Precast ConcreteTest Building, PCI JOURNAL, V.44, No. 6, November-December 1999,pp. 42-67.

15. ACT Innovation Task Group 1 andCollaborators, Acceptance Criteriafor Moment Frames Based on Structural Testing, American Concrete Institute, Farmington Hills, MI, 1999.

16. Seo, S-Y., Lee, L-H., and Hawkins,N. M., The Limiting Drift and Energy Dissipation Ratio for ShearWalls Based on Structural Testing,Journal of the Korean Concrete Institute, V. 10, No. 6, December 1998,pp. 273-311.

44 PCI JOURNAL

ARCHITECTURALPRECAST CONCRETE

Color and Texture Selection GuideFor the first time, a visual guide is available to assist architects in the initialselection of color and texture for architectural precast concrete. The Guideis an extension of the information included in the architect-orientedArchitectural Precast Concrete Manual, published in 1989.

Architectural Precast Concrete Color and Texture Selection Guideillustrates more than 430 colors and textures for enhancing the aesthetics ofprecast concrete panels. There are 236 6i x 11 in. color plates, with themajority of the plates having two finishes on the same sample. Thephotographs are numbered and arranged from light to dark colors. Inaddition, there are six photographs of buildings that illustrate brick, tile,terra cotta, granite, limestone and marble veneer-faced precast concretepanel applications.

The variables considered in developing the color plates were cements.pigments, coarse and fine aggregates, and texture or surface finish withvarious depths of exposure. Since aggregates were collected from all partsof the United States and Canada, designers are able to determine theavailable aggregate colors. Identification of materials used to produce thesamples is included in the back of the Guide.

Who should have a copy? U ArchitectsU Producers

Payable in U.S. Dollars, drawn on a U.S. bank, or useyour Visa or MasterCaid. Payment must accompanyyour order. For addresses outside the United States,add $25.00 per copy for airmail delivery.Amount Enclosed: $

______-_______

Visa/MasterCard #

Cardholders Name

Expiration Date -

CTG-92, First Edition,260 pp., 8%xll in.

address p.o. box, also give Street address)

city

state zip code

country

Precast!Prestressed Concrete Institute209 W. Jackson Blvd.Chicago, Illinois 60606Phone: 312-786-0300 Fax: 312-786-0353

U Specifiers of precast concreteU Owner/developers

SEND FOR YOUR COPIES TODAY!

yes, please send me custom 3-ring binder copies ofArchitectural Precast Concrete Color and Texture Selection Guide (CTG-92).I understand the price is $40.00 per copy. (Illinois residents add 8.75% sales tax)name

company

Mail to: D

PCI-SPONSORED RESEARCH STUDY

Design Criteria for HeadedStud Groups in Shear:Part 1

Steel Capacity andBack Edge Effects

The Precast/Prestressed Concrete institute sponsored a cornprehensive research program to assess the shear capacity of headed studgroup anchorages. This program was initiated in response to newprovisions introduced into the 2002 AC! 318 Building Code. Theproposed AC! provisions are based on extensive data dominatedby post-installed anchor tests. Tests of headed stud anchorages, asused in precast construction, are not prevalent in the literature.The test program, conducted by Wiss, Janney, Elstner Associates,Inc. (WJE), examined headed stud connections loaded toward afree edge, a free edge near a corner, parallel to one free edge, parallel to two free edges, away from a free edge, and in-the-field of amember, such that edge distance was not a factor. The informationreported herein addresses the steel capacity failure mode. Test datawere obtained when the shear force was directed away from a freeedge, in-the-field testing, and from other edge distance tests wheresteel failure governed the capacity.

Neal S. Anderson, P.E., S.E.ConsultantWiss, Janney, Elstner Associates, Inc.Northbrook, Illinois

Donald F. Meinheit, Ph.D.,P.E., S.E.Senior ConsultantWiss, Janney, Elstner Associates, Inc.Northbrook, Illinois

H eaded stud anchorages areused extensively in the concrete industry in both cast-in-place and precast construction. Welding studs to steel plates provides aneasy and economical means of embedding and providing a ready tocomplete structural connection. Sucha connection has substantial versatility by allowing large variations inconstruction dimensions.

Headed stud anchorages in precastconcrete members can be found in column corbels, spandrel beams, dappedend members, wall panels, tee beams,and other components. Commonly,studs in precast members are 3 to 8 in.(76 to 203 mm) long and form multi-stud group connections. The load capacities of these connections are generallyaffected by stud spacings, edge distances, and member depth or thickness.

46 PCI JOURNAL

In the past, the design of stud anchorages usually followed proceduresset forth in the PCI Design Handbookor the nuclear structures code, developed by ACT Committee 3492 Untilnow, stud anchorage design has notbeen codified within the widely accepted Building Code Requirementsfor Structural Concrete,3 as preparedby ACT Committee 318. However, anapproach for the design of anchoragesto concrete has been approved as Appendix D4 of the upcoming ACI 318-02 Building Code. The ACI 318 Appendix D method is based on theConcrete Capacity Design (CCD)model proposed by Fuchs, Eligenhausen, and Breen.5

The ACT design approach necessarily must consider all types of cast-in-place and post-installed anchors. Thedesign procedure in ACT 318-02 Appendix D is calibrated using adatabase heavily dominated by post-installed anchors. Anchorages used inprecast concrete construction fall intoa relatively narrow range of those considered in ACI 318-02 Appendix D.

For headed stud anchorages, theACT design approach shows significantly different capacity under certainconditions than the approach used inthe current PCI design model. Theconcrete break-out capacity calculatedwith the proposed ACT approach istypically lower than that predicted byPCI design procedures, particularlywhen edge and spacing distance effects on stud groups are considered.

The differences in capacity promptedthe PCT to undertake a research program with the ultimate objective of improving design criteria for headed studanchorage groups, a connection typecommonly used by the precast concreteindustry. The research project includedan experimental program to provide thebackground information for modifyingthe ACT or PCI design approaches or tojustify and refine the PCI design approach as currently published in thePCI Design Handbook.

This paper represents Part 1 of fourparts included in this research program. The work reported herein presents findings on two of the six primary variables evaluated in this shearcapacity study. The variables in theshear testing program included condi

tions that loaded the headed studgroups:

1. Toward a free edge (de3).2. Toward a free edge at a corner

(de3 and del simultaneously).3. Parallel to one free edge (del).4. Parallel to two free edges (del

and de2 simultaneously)5. Away from a free edge (de4).6. In-the-field of the member such

that edge distance was not a factor in the failure.

Schematic representations of thedel, de2, de3, and de4 edge distancesare provided in Fig. 1.

Stud anchorage behavior when theconnection is loaded away from a freeedge and in-the-field is discussedherein. These two conditions cause the

capacity to consistently be one of steelfailure.

This paper provides background information for the steel capacity equations in ACI 3 18-02 Appendix D. Theremaining components of this shearresearch program including the frontedge effects, side edge effects, andcombined front and side edge effectsor corner influences will be reportedin future issues of the PCI JOURNAL.

OVERVIEW OFRESEARCH PROGRAM

In mid-1996, PCI selected Wiss,Janney, Elstner Associates, Inc. (WJE)of Northbrook, Illinois, an engineeringconsulting firm, to undertake this re

-1

PLAN

hI

hf

,.

,. dh -

SECTION THRU SLAB

Fig. 1. Member geometry and edge distance notation after PCI definitions.


search program under the direction ofPCIs Research and DevelopmentCommittee. An advisory panel wasappointed to closely monitor the project and consult on the testing scope.The advisory panel includes individuals from academia, consulting engineering, and precast concrete producermembers.

Program DevelopmentThis research work6 focused on an

chorages and geometric conditionstypically used in the precast/prestressed concrete industry. The research concentrated on diameter, embedment depth, and number of weldedheaded studs on a connection plate inconfigurations commonly used in precast concrete applications; the studyexcluded post-installed anchors.

The first task of the research program was to review existing data on

headed studs embedded in structuralconcrete loaded in shear. Some experimental data on headed studs subjectedto tension, shear, and combined tension and shear loadings have beenpublished. However, the database forheaded stud anchors is limited especially when compared to the databaseexisting for post-installed anchors.Additionally, cast-in-place anchorageshaving head geometries similar to thatof headed studs were included in thisreview, as applicable; for example,some cast-in-place anchor bolts fall inthis category.

A literature search and analysis ofexisting data were used to formulate alaboratory test program. The sheartesting program, conducted in theWJE laboratory, had the followingobjectives: Verify that a well-developed stud

connection, that is, studs long

34 concrete slab specimens cast(12)5 x 5 ft x 6 in.(4) 4xlOftxl6in.(3) 4x4ftxI6in.(I5)Sx5ftx 16 in.

enough to preclude a concrete pry-out failure, located away from edgeinfluences will develop a capacitydictated by characteristics of thestud steel properties.Evaluate group behavior near theside (del), front (de3), and back(de4) free edges considering as variables: distance from an edge, spacingin the x- and y-directions, number ofanchors in the group, embedmentdepth, and anchor diameter.

Review or refine the concrete breakout model with respect to the del,de3, and de4 edge distances.

Determine the influence of the slabthickness effect for shear-loadedconnections.

Evaluate anchor group behavior at acorner, where the del and de3 edgedistances meet.

Evaluate anchor group behaviorwhen simultaneous del and de2edge conditions exist, such as in acolumn.

Testing Program DescriptionThe WJE experimental program in

cluded 312 plate configurations inshear and 16 push-off type specimens,as summarized in Table I. The testswere typically conducted in slabs measuring4x lOftor5 x5ft(l.2x3.Omor 1.5 x 1.5 m) with either a 6 or 16 in.(152 and 406 mm) thickness. The 16push-off specimen tests were conducted to simulate the shear loadingconditions when an embedded anchorgroup is adjacent to two longitudinaledges simultaneously.

In the shear testing program, a totalof 14 different plate designationswere evaluated, which included different combinations of plate size, studspacing, stud embedment depth, andstud diameter. A conscience decisionwas made that plate thickness andconcrete compressive strength wouldnot be variables in the test program.Headed stud diameters of /2 and/8 in. (12.7 and 15.9 mm) were testedin this program.

The test program evaluated the capacity of single and group connectionconfigurations in several geometricconditions. Referring to Fig. 1, anchorages were tested toward the freeedge (de3), at a corner, adjacent orparallel to a free edge (del), and away

Table 1. Summary of the WJE/PCI test program.Tests completed 328 shear tests performed

Test specimens

16 push-off specimens utilizing a steel wideflange section

Fabrication Six separate concrete castings made40.5 cu yd of concrete used for an average of

6.5 cu yd per casting

Supporting tests Concrete compressive and tensile strengthConcrete modulus of elasticity

. Tensile strength of all headed stud sizes used

..

(23 tests total)Double shear strength of all headed stud sizes

.

.

used (18 tests total)

Stud sizes /2 x 3/s in. h,1= 5.38dJ, /2 4 x 55/ in. hf= 9.84d

5/s4x43/ioin. h,15.93d

AnchoragesL --

14 anchorage plate layouts -1, 2, 3, 4 and 6 stud combinations evaluated

Concrete strength J 5000 to 6000 psi (typical of precast concrete)Test locations Front edge (de3) 102 tests

Side edge (del) 94 testsBack edge (de4) 23 testsFront corner (del-de3) 67 testsIn-the-field 26 testsPush-offs 16 tests

Note: I in. = 25.4 mm; I ft= 0.3048 m; 1 lb = 4.448 N; 1 kip = 4.448 N; I psi = 6.895 kPa; 1 ksi = 6.895 MPacu yd = 0.7646 m2.

48 PCI JOURNAL

from a free or back edge (de4). Additional testing was directed to evaluateconnection capacity when it was positioned far away from the influence ofan edge, or the so-called in-the-fieldtests. The in-the-field tests were anticipated to produce a better understanding of connection capacity when thestud steel governs the failure mode.Several test series were repeated inboth 6 and 16 in. (150 and 400 mm)thick specimens to evaluate the effectsof member thickness.

The test findings reported in thispaper represent one part of an overallcomprehensive report on the shear behavior of headed stud anchoragesloaded in shear. Results reported hereare limited to defining the capacity ofthe stud steel in shear.

LITERATURE REVIEWThe welded headed stud gained con

siderable research attention in the late1950s and through the 1960s. Theearly research work on welded headedstuds was focused on applications inthe concrete slab-steel beam composite member. The headed stud wasviewed to be an efficient and effective

shear transfer device, replacing channels, angles, or fabricated spirals attached to the top flange of a steelbeam. The headed stud arc weldingprocess represented a labor and material cost savings over manual arcwelding the aforementioned shapes toa steel beam.

Push-Off TestsTesting to evaluate composite beam

behavior typically utilized a push-offspecimen to study shear transferthrough the headed studs. The push-offtest specimen commonly used a wideflange beam section sandwiched between two concrete slabs. Headed studswere welded to both flanges in someprescribed pattern or spacing and embedded into a thin concrete slab representing the composite deck slab. Theconcrete slab was usually reinforced tosimulate a bridge deck. As shown inFig. 2, the steel beam was held aboveboth the top and bottom elevation ofthe slabs. Both the beam and two slabswere oriented vertically fitting conveniently into a universal testing machine.

Early composite beam research,using the push-off specimen, was con-

ducted by Viest at the University ofIllinois,7 Slutter, Fisher and others atLehigh University,89Baldwin, Dallum, and others at the University ofMissouri-Columbia,2Goble atCase Western Reserve University,3Chinn at the University of Colorado,14and Hawkins at the University of Sydney.5 These early test programs produced a significant amount of sheardata on headed stud behavior with aparticular emphasis on groups. Severalof the push-off test failure loads weredue to stud steel shear, which is relevant to this paper.

Review of the push-off test resultsprovides good comparative data forheaded studs loaded in pure shear. Asstated earlier, previous testing on theheaded stud connections used in precast concrete attachments is limited,especially when groups are considered. To evaluate group stud connections, with an emphasis on steel failure, there are no known published testresults.

Most of the non-push-off testingprograms were conducted by loadingthe connection toward a free edge withthe intent of studying anchoragesloaded in shear and failing in a con-

Fig. 2. Typica push-off test specimen (from Oflgaard, Slutter and Fisher).9


crete breakout mode. Therefore, published behavioral results on headedstud groups loaded in pure shear without the influence of any edge effectsand failing the steel is entirely contained in the aforementioned referenced push-off tests.

It should be noted that the design ofthe push-off test specimen has characteristics that limit its full applicabilityto emulating a precast concrete anchorage. Most of the thin concreteslabs used in push-off tests containednominal reinforcement, more representative of bridge deck construction.The reinforcement had no influence onthe first cracking load, but it islikely that the reinforcement in theconcrete slab held the slab together toallow for additional displacement andductility.

The early researchers were particularly concerned with load-slip characteristics of the connections. Unreinforced concrete specimens, reported inthe literature, oftentimes produced atransverse splitting failure in the concrete slab, a failure mode unlikely tooccur in actual bridge deck construction because of the presence of transverse reinforcement.

Another limitation of the push-offspecimen relates to the mechanism toapply load to the embedded studs.Load transfer from the steel columnthrough the headed studs into the twoconcrete slabs results in the best conditions to place the studs in pure shear.However, the external applied loadcauses a reaction against the ends ofthe two concrete slabs, placing them incompression. This condition is viewedto be analogous to a headed stud anchorage located in-the-field of a member; that is, a significant amount ofconcrete slab is located in front of theanchorage to preclude any front edgeinfluences.

The favorable concrete compressionstress developed in front of the studsdoes not affect tests having one transverse row (or one y-row) of studs. Onthe contrary, when stud groups withmultiple longitudinal rows were testedusing the push-off specimen, the testresults become more difficult to interpret. Each longitudinal row in thegroup is subjected to a different levelof compressive confinement stress.

4 6 8 10Embedment Depth Ratio (li.1 Id)

1.4

1.2

D 1.0

c.

0.8

0.6

0.

0.4

0.2

0.0

(a) Concrete and steel failures.

6.0

5.0

U

4.0

3.0

U

2.0

1.0

0.00

(b) Shallow embedment capacity predictions.

2 3 4Embedment Depth Ratio (h., / d)

3.0

-. 2.5

2.0

1.5

U1.0

0.5

0.0

PCI Ply-Out Equation Llghw.Ight ConcreteSteel Equation (AoFut)

.

.

:: $

2

0 2 4 6Embedment Depth Ratio (h, Id)

(c) Concrete and steel failures in push-off tests with lightweightconcrete using PCI pryout capacity equation.

Fig. 3. Test-to-predicted capacity ratio as a function of embedment depth.

50 PCI JOURNAL

Likewise, multiple longitudinal (or y)rows which are spaced at large distances reduce the efficiency of the anchor group due to shear lag effects.

A push-off specimen with multiplelongitudinal rows of studs is similar toa long bolted connection whose efficiency is reduced in proportion to

/ L (where . is the distance between the shear plane of the connectedparts and the centroid of the connectedcomponent) in accordance with steeltension member design.

Our review of the available push-offdata shows the overall connectionlength, L, may be a significant variable in determining the capacity thatcan be achieved by the stud because ofshear lag. For further discussion ofshear lag, see the book by Kulak,Fisher, and Struiki6

Keeping the above limitations of thepush-off test in perspective, somevaluable data were applicable to thepresent study. Relevant informationfrom these early tests is discussedbelow.

Embedment Depth In 1955,

Viest7 performed 12 push-off tests atthe University of Illinois as part of research into composite beam behavior.Stud diameters ranged from 1/2 to 11/4in. (12.7 to 31.8 mm), with a reasonably constant effective embedmentdepth (hej) between 3 and 3/2 in. (76.2to 88.9 mm). All studs were placed inone row with an approximate 4 in.(101.6 mm) x-spacing for 10 of the 12tests. Two tests had four, 3/4 in. (19.1mm) diameter studs in one y-row withan approximate 2 in. (50.8 mm) center-to-center spacing. To ensure thestuds were the only shear transfermechanism, the steel I-beams werecoated with grease to minimize anyfrictional transfer of the shear loadalong the flange width.

As reported in the work by Viest,the two-stud tests having ratios of effective depth to stud diameter (held)of 4.53, 5.5, and 7.0 failed in studshear (steel failure). The four testswith two studs having diameters of 1and 1/4in. (25.5 and 31.5 mm)experienced concrete failure. These fourtests had average held ratios of 3.22and 2.51, respectively.

In the original Viest work, becausethe stud height was relatively con-

stant, two prediction equations werepresented for stud diameters less than1 in. (25.4 mm) and greater than orequal to I in. (25.4 mm). In a subsequent research summary paper,Viest7 described testing ten additional push-off specimens and modifying the equations for the 1957AASHO Specifications. Instead ofmaking the design equation a functionof diameter only, the critical parameter became held.

Another observation from the Viesttest data is the apparent good correlation of steel shear capacity using aprediction of 1.0 A5F, when held4.53. In this equation, A5 is the cross-sectional area of the stud shank andF, is the ultimate tensile strength ofthe stud steel.

This predicted steel shear failureload corresponds quite well to testdata when ultimate tensile strength ofthe steel is used, instead of a value reduced for tensile yield (F = 0.9 F,),where F is the offset tensile yield

stress for the stud steel. Likewise, it isa better predictor than the shear yield(F = O.58F, that is, 1/ J), whereF5 is the shear yield stress accordingto the Huber-von Mises-Hencky yieldcriterion.8

WJE compiled push-off test datafrom a number of the referenced research studies to evaluate concrete andsteel failures. To eliminate having thedata influenced by shear lag, onlypush-off specimens with one longitudinal (y) row of studs were evaluated.Fig. 3(a) shows a graph of the test-to-predicted ratio for steel failure plottedagainst embedment depth ratio (held),where the predicted capacity is basedon 1.0A5F,.

The trend of the data indicates that1.0 A5F, is a good predictor for a steelfailure when the embedment depth(held) exceeds about 4.5. This is justslightly greater than the value of 4.2identified by Driscoll and Slutter5 andincorporated into the 1961 AASHOSpecifications.

Table 2. Review of PCI Design Handbook requirements for stud strengthgoverned by steel.

PCI Handbook Parameters Steel strengthedition phi (ci) Steel equation

1 (1971) none f=60ksi V=0.75Aj;

---

2(1978) 0.85 f. = 60 ksi =(shear-friction concept) = 45.0 Ab

(where u= 1.0)---+-----

3 (1985) 1.0 f. = 60 ksi = (0.75) A,.L= 45.0 A5

4(1992) 1.0 J=60ksi 4Vci(O.75)fA5n= 45 0 A, n

5 (1999) 0.90 = 50 ksi = ci(0.9)fA,,nI I =40.5A,,,z

Note: = A,, = cross-sectional area of the stud shank (sq in.); n = number of studs in the connection;f, = ultimate tensile strength (ksi);f = yield strength (ksi).

Table 3. Minimum mechanical property requirements for headed studsadapted from AWS Dl .1 2000.31

Property Type A Type B

Tensile strength (mm.) 61.000 psi (420 MPa) 65.000 psi (450 MPa)Yield strength (0.2 percent offset) 49.000 psi (340 MPa) 51,000 psi (350 MPa)

Elongation (mm. percent 2 in.) 17 percent 20 percent

Reduction of area (mm.) 50 percent 50 percent


For some tests conducted in normalweight concrete, steel stud shear failure occurred at embedment depth ratios (held) less than 4.5. The tests withshorter stud embedment depths generally have predicted steel shear capacities (using 1.0 ASFUF) greater than theactual test results, even though the reported failure mode was that of studfailure. The steel failure mode mayhave, in fact, been a secondary failureafter considerable concrete crushing orstud deformation had occurred.

Work performed by Ollgaard, Slutter, and Fisher9 at Lehigh Universitywas an extensive study using studswith an effective embedment depth(held) of 3.26 and different types oflightweight and normal weight concrete. Failures were noted in both studsteel shear or by a concrete mechanism. Results of this work produced aprediction equation, independent offailure mode, basing individual studstrength on stud area, concrete compressive strength, and elastic modulusof the concrete. Their final predictionequation was:

where

= (1)

Q = nominal strength of a shearstud connector embedded in asolid concrete slab (kips)

A5 = effective cross-sectional areaof a stud anchor (sq in.)

f = specified compressive strengthof concrete (ksi)

= modulus of elasticity of concrete (ksi)

This equation is applicable to bothnormal and lightweight aggregate concrete. Unlike earlier prediction equations from the push-off test, this equation did

pci journal sept-oct 2000 vol. 45 no. 5.pdf

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