FEDERAL EMERGENCY MANAGEMENT AGENCY FEMA 273 / October 1997 NEHRP GUIDELINES FOR THE SEISMIC REHABILITATION OF BUILDINGS Issued by FEMA in furtherance of the Decade for Natural Disaster Reduction
The Building Seismic Safety Council (BSSC) was established in 1979 under the auspices of the National Institute ofBuilding Sciences as an entirely new type of instrument for dealing with the complex regulatory, technical, social, andeconomic issues involved in developing and promulgating building earthquake risk mitigation regulatory provisionsthat are national in scope. By bringing together in the BSSC all of the needed expertise and all relevant public andprivate interests, it was believed that issues related to the seismic safety of the built environment could be resolved andjurisdictional problems overcome through authoritative guidance and assistance backed by a broad consensus.The BSSC is an independent, voluntary membership body representing a wide variety of building community interests.Its fundamental purpose is to enhance public safety by providing a national forum that fosters improved seismic safetyprovisions for use by the building community in the planning, design, construction, regulation, and utilization ofbuildings.To fulfill its purpose, the BSSC: (1) promotes the development of seismic safety provisions suitable for use throughoutthe United States; (2) recommends, encourages, and promotes the adoption of appropriate seismic safety provisions involuntary standards and model codes; (3) assesses progress in the implementation of such provisions by federal, state,and local regulatory and construction agencies; (4) identifies opportunities for improving seismic safety regulationsand practices and encourages public and private organizations to effect such improvements; (5) promotes thedevelopment of training and educational courses and materials for use by design professionals, builders, buildingregulatory officials, elected officials, industry representatives, other members of the building community, and thegeneral public; (6) advises government bodies on their programs of research, development, and implementation; and(7) periodically reviews and evaluates research findings, practices, and experience and makes recommendations forincorporation into seismic design practices.BOARD OF DIRECTION: 1997Chairman Eugene Zeller, City of Long Beach, CaliforniaVice Chairman William W. Stewart, Stewart-Scholberg Architects, Clayton, Missouri (representing the American Institute of Architects)Secretary Mark B. Hogan, National Concrete Masonry Association, Herndon, VirginiaEx-Officio James E. Beavers, Beavers and Associates, Oak Ridge, TennesseeMembers Eugene Cole, Carmichael, California (representing the Structural Engineers Association of California); S. K. Ghosh, Portland Cement Association, Skokie, Illinois; Nestor Iwankiw, American Institute of Steel Construction, Chicago, Illinois; Gerald H. Jones, Kansas City, Missouri (representing the National Institute of Building Sciences); Joseph Nicoletti, URS/John A. Blume and Associates, San Francisco, California (representing the Earthquake Engineering Research Institute); John R. “Jack” Prosek, Turner Construction Company, San Francisco, California (representing the Associated General Contractors of America); W. Lee Shoemaker, Metal Building Manufacturers Association, Cleveland, Ohio; John C. Theiss, Theiss Engineers, Inc., St. Louis, Missouri (representing the American Society of Civil Engineers); Charles Thornton, Thornton-Tomasetti Engineers, New York, New York (representing the Applied Technology Council); David P. Tyree, American Forest and Paper Association, Colorado Springs, Colorado; David Wismer, Department of Licenses and Inspections, Philadelphia, Pennsylvania (representing the Building Officials and Code Administrators International); Richard Wright, National Institute of Standards and Technology, Gaithersburg, Maryland (representing the Interagency Committee for Seismic Safety in Construction)BSSC Staff James R. Smith, Executive Director; Thomas Hollenbach, Deputy Executive Director; Larry Anderson, Director, Special Projects; Claret M. Heider, Technical Writer-Editor; Mary Marshall, Administrative Assistant
BSSC Seismic Rehabilitation ProjectNEHRP GUIDELINES FOR THESEISMIC REHABILITATION OF BUILDINGS(FEMA Publication 273)Prepared for theBUILDING SEISMIC SAFETY COUNCILWashington, D.C.By theAPPLIED TECHNOLOGY COUNCIL (ATC-33 Project)Redwood City, CaliforniaWith funding byFEDERAL EMERGENCY MANAGEMENT AGENCYWashington, D.C. October 1997 Washington, D.C.
NOTICE: This report was prepared under Cooperative Agreement EMW-91-K-3602 between theFederal Emergency Management Agency and the National Institute of Building Sciences.Any opinions, findings, conclusions, or recommendations expressed in this publication do notnecessarily reflect the views of the Applied Technology Council (ATC), the Building SeismicSafety Council (BSSC), or the Federal Emergency Management Agency (FEMA). Additionally,neither ATC, BSSC, FEMA, nor any of their employees makes any warranty, expressed or implied,nor assumes any legal liability or responsibility for the accuracy, completeness, or usefulness ofany information, product, or process included in this publication. Users of information from thispublication assume all liability arising from such use.For further information concerning this document or the activities of the BSSC, contact theExecutive Director, Building Seismic Safety Council, 1090 Vermont Ave., N.W., Suite 700,Washington, D.C. 20005; phone 202-289-7800; fax 202-289-1092; e-mail firstname.lastname@example.org.
PARTICIPANTS WOODPROJECT OVERSIGHT APPLIED TECHNOLOGY John M. Coil, Team LeaderCOMMITTEE COUNCIL Jeffery T. MillerEugene Zeller, Chairman Robin ShepherdThomas G. Atkinson, ATC PRINCIPAL INVESTIGATOR William B. VaughnGerald Jones, BSSC Christopher RojahnChristopher Rojahn, ATC NEW TECHNOLOGIESPaul Seaburg, ASCE PROJECT DIRECTOR Charles A. Kircher, Team LeaderAshvin Shah, ASCE Daniel Shapiro Michael C. ConstantinouJames R. Smith, BSSC Andrew S. Whittaker CO-PROJECT DIRECTOR Lawrence D. Reaveley NONSTRUCTURALBUILDING SEISMIC Christopher Arnold, Team LeaderSAFETY COUNCIL SENIOR TECHNICAL ADVISOR Richard L. Hess William T. Holmes Frank E. McClurePROJECT MANAGER Todd W. Perbix TECHNICAL ADVISORJames R. Smith SIMPLIFIED REHABILITATION Jack P. MoehleDEPUTY PROJECT MANAGER Chris D. Poland, Team Leader ATC BOARD Leo E. ArgirisThomas Hollenbach REPRESENTATIVE Thomas F. HeauslerTECHNICAL WRITER-EDITOR Thomas G. Atkinson Evan ReisClaret Heider Tony Tschanz GENERAL REQUIREMENTSSEISMIC REHABILITATION Ronald O. Hamburger, Team Leader QUALIFICATION OFADVISORY PANEL Sigmund A. Freeman IN-PLACE MATERIALSGerald Jones, Chairman Peter Gergely (deceased) Charles J. Hookham, Lead ConsultantDavid Allen Richard A. Parmelee Richard Atkinson (deceased)John Battles Allan R. Porush Ross EsfandiariDavid Breiholz MODELING AND ANALYSIS LANGUAGE & FORMATMichael Caldwell James R. HarrisGregory L. F. Chiu Mike Mehrain, Team LeaderTerry Dooley Ronald P. Gallagher Helmut Krawinkler REPORT PREPARATIONSusan Dowty Roger E. Scholl (deceased),Steven J. Eder Guy J. P. Nordenson Maurice S. Power Lead ConsultantS. K. Ghosh Robert K. ReithermanBarry J. Goodno Andrew S. Whittaker A. Gerald Brady, Copy EditorCharles G. Gutberlet GEOTECHNICAL & Patty Christofferson, CoordinatorWarner Howe Peter N. Mork, Illustrations FOUNDATIONSHoward KunreutherHarry W. Martin Jeffrey R. Keaton, Team LeaderRobert McCluer Craig D. Comartin AMERICAN SOCIETY OFMargaret Pepin-Donat Paul W. GrantWilliam Petak Geoffrey R. Martin CIVIL ENGINEERSHoward Simpson Maurice S. Power REHABILITATION STEERINGWilliam Stewart CONCRETEJames Thomas COMMITTEEL. Thomas Tobin Jack P. Moehle, Co-Team Leader Vitelmo V. Bertero Lawrence D. Reaveley, Co-Team Paul SeaburgPROJECT COMMITTEE Leader Roland L. SharpeWarner Howe, Chairman James E. Carpenter Jon S. TrawGerald H. Jones Jacob Grossman Clarkson W. PinkhamAllan R. Porush Paul A. Murray William J. HallF. Robert Preece Joseph P. NicolettiWilliam W. Stewart Kent B. Soelberg USERS WORKSHOPS James K. Wight Tom McLane, ManagerSOCIETAL ISSUES Debbie Smith, CoordinatorRobert A. Olson MASONRY Daniel P. Abrams, Team Leader RESEARCH SYNTHESIS Samy A. Adham James O. JirsaFEDERAL EMERGENCY Gregory R. KingsleyMANAGEMENT Onder Kustu SPECIAL ISSUES John C. Theiss Melvyn GreenAGENCY STEELPROJECT OFFICER Douglas A. Foutch, Team LeaderUgo Morelli Navin R. Amin James O. MalleyTECHNICAL ADVISOR Charles W. RoederDiana Todd Thomas Z. Scarangello
In MemoriamThe Building Seismic Safety Council, theApplied Technology Council, the AmericanSociety of Civil Engineers, and the FederalEmergency Management Agency wish toacknowledge the significant contribution to theGuidelines and to the overall field ofearthquake engineering of the participants inthe project who did not live to see this effortcompleted: Richard Atkinson Peter Gergely Roger SchollThe built environment has benefited greatlyfrom their work.
ForewordThe volume you are now holding in your hands, the Council (BSSC), overall manager of the project; theNEHRP Guidelines for the Seismic Rehabilitation of Applied Technology Council (ATC); and the AmericanBuildings, and its companion Commentary volume, are Society of Civil Engineers (ASCE). Hundreds morethe culminating manifestation of over 13 years of effort. donated their knowledge and time to the project byThey contain systematic guidance enabling design reviewing draft documents at various stages ofprofessionals to formulate effective and reliable development and providing comments, criticisms, andrehabilitation approaches that will limit the expected suggestions for improvements. Additional refinementsearthquake damage to a specified range for a specified and improvements resulted from the consensus reviewlevel of ground shaking. This kind of guidance of the Guidelines document and its companionapplicable to all types of existing buildings and in all Commentary through the balloting process of the BSSCparts of the country has never existed before. during the last year of the effort.Since 1984, when the Federal Emergency Management No one who worked on this project in any capacity,Agency (FEMA) first began a program to address the whether volunteer, paid consultant or staff, receivedrisk posed by seismically unsafe existing buildings, the monetary compensation commensurate with his or hercreation of these Guidelines has been the principal efforts. The dedication of all was truly outstanding. Ittarget of FEMA’s efforts. Prior preparatory steps, seemed that everyone involved recognized thehowever, were much needed, as was noted in the 1985 magnitude of the step forward that was being taken inAction Plan developed at FEMA’s request by the ABE the progress toward greater seismic safety of ourJoint Venture. These included the development of a communities, and gave his or her utmost. FEMA andstandard methodology for identifying at-risk buildings the FEMA Project Officer personally warmly andquickly or in depth, a compendium of effective sincerely thank everyone who participated in thisrehabilitation techniques, and an identification of endeavor. Simple thanks from FEMA in a Foreword,societal implications of rehabilitation. however, can never reward these individuals adequately. The fervent hope is that, perhaps, havingBy 1990, this technical platform had been essentially the Guidelines used extensively now and improved bycompleted, and work could begin on these Guidelines. future generations will be the reward that they so justlyThe $8 million, seven-year project required the varied and richly deserve.talents of over 100 engineers, researchers and writers,smoothly orchestrated by the Building Seismic Safety The Federal Emergency Management AgencyFEMA 273 Seismic Rehabilitation Guidelines vii
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PrefaceIn August 1991, the National Institute of Building project tasks is shared by the BSSC with ASCE andSciences (NIBS) entered into a cooperative agreement ATC. Specific BSSC tasks were completed under thewith the Federal Emergency Management Agency guidance of a BSSC Project Committee. To ensure(FEMA) for a comprehensive seven-year program project continuity and direction, a Project Oversightleading to the development of a set of nationally Committee (POC) was responsible to the BSSC Boardapplicable guidelines for the seismic rehabilitation of of Direction for accomplishment of the projectexisting buildings. Under this agreement, the Building objectives and the conduct of project tasks. Further, aSeismic Safety Council (BSSC) served as program Seismic Rehabilitation Advisory Panel reviewed projectmanager with the American Society of Civil Engineers products as they developed and advised the POC on the(ASCE) and the Applied Technology Council (ATC) approach being taken, problems arising or anticipated,working as subcontractors. Initially, FEMA provided and progress made.funding for a program definition activity designed togenerate the detailed work plan for the overall program. Three user workshops were held during the course ofThe work plan was completed in April 1992 and in the project to expose the project and various drafts ofSeptember FEMA contracted with NIBS for the the Guidelines documents to review by potential usersremainder of the effort. of the ultimate product. The two earlier workshops provided for review of the overall project structure andThe major objectives of the project were to develop a for detailed review of the 50-percent-complete draft.set of technically sound, nationally applicable The last workshop was held in December 1995 whenguidelines (with commentary) for the seismic the Guidelines documents were 75 percent complete.rehabilitation of buildings; develop building community Participants in this workshop also had the opportunityconsensus regarding the guidelines; and develop the to attend a tutorial on application of the guidelines andbasis of a plan for stimulating widespread acceptance to comment on all project work done to date.and application of the guidelines. The guidelinesdocuments produced as a result of this project are Following the third user workshop, written and oralexpected to serve as a primary resource on the seismic comments on the 75-percent-complete draft of therehabilitation of buildings for the use of design documents received from the workshop participants andprofessionals, educators, model code and standards other reviewers were addressed by the authors andorganizations, and state and local building regulatory incorporated into a pre-ballot draft of the Guidelinespersonnel. and Commentary. POC members were sent a review copy of the 100-percent-complete draft in August 1996As noted above, the project work involved the ASCE and met to formulate a recommendation to the BSSCand ATC as subcontractors as well as groups of Board of Direction concerning balloting of thevolunteer experts and paid consultants. It was structured documents. Essentially, the POC recommended that theto ensure that the technical guidelines writing effort Board accept the documents for consensus balloting bybenefited from a broad section of considerations: the the BSSC member organization. The Board, havingresults of completed and ongoing technical efforts and received this recommendation in late August, votedresearch activities; societal issues; public policy unanimously to proceed with the balloting.concerns; the recommendations presented in an earlierFEMA-funded report on issues identification and The balloting of the Guidelines and Commentaryresolution; cost data on application of rehabilitation occurred between October 15 and December 20, 1996,procedures; reactions of potential users; and consensus and a ballot symposium for the voting representatives ofreview by a broad spectrum of building community BSSC member organizations was held in Novemberinterests. A special effort also was made to use the during the ballot period. Member organization votingresults of the latest relevant research. representatives were asked to vote on each major subsection of the Guidelines document and on eachWhile overall management has been the responsibility chapter of the Commentary. As required by BSSCof the BSSC, responsibility for conduct of the specific procedures, the ballot provided for four responses:FEMA 273 Seismic Rehabilitation Guidelines ix
“yes,” “yes with reservations,” “no,” and “abstain.” All development of seismic rehabilitation designs for at“yes with reservations” and “no” votes were to be least 40 federal buildings selected from an inventory ofaccompanied by an explanation of the reasons for the buildings determined to be seismically deficient undervote and the “no” votes were to be accompanied by the implementation program of Executive Order 12941specific suggestions for change if those changes would and determined to be considered “typical of existingchange the negative vote to an affirmative. structures located throughout the nation.” The case studies project is structured to:Although all sections of the Guidelines andCommentary documents were approved in the balloting, • Test the usability of the NEHRP Guidelines for thethe comments and explanations received with “yes with Seismic Rehabilitation of Buildings in authenticreservations” and “no” votes were compiled by the applications in order to determine the extent toBSSC for delivery to ATC for review and resolution. which practicing design engineers and architectsThe ATC Senior Technical Committee reviewed these find the Guidelines documents themselves and thecomments in detail and commissioned members of the structural analysis procedures and acceptancetechnical teams to develop detailed responses and to criteria included to be presented in understandableformulate any needed proposals for change reflecting language and in a clear, logical fashion that permitsthe comments. This effort resulted in 48 proposals for valid engineering determinations to be made, and tochange to be submitted to the BSSC member evaluate the ease of transition from currentorganizations for a second ballot. In April 1997, the engineering practices to the new concepts presentedATC presented its recommendations to the Project in the Guidelines.Oversight Committee, which approved them forforwarding to the BSSC Board. The BSSC Board • Assess the technical adequacy of the Guidelinessubsequently gave tentative approval to the reballoting design and analysis procedures. Determine ifpending a mail vote on the entire second ballot package. application of the procedures results (in theThis was done and the reballoting was officially judgment of the designer) in rational designs ofapproved by the Board. The second ballot package was building components for corrective rehabilitationmailed to BSSC member organizations on June 10 with measures. Assess whether these designs adequatelycompleted ballots due by July 28. meet the selected performance levels when compared to existing procedures and in light of theAll the second ballot proposals passed the ballot; knowledge and experience of the designer. Evaluatehowever, as with the first ballot results, comments whether the Guidelines methods provide a bettersubmitted with ballots were compiled by the BSSC for fundamental understanding of expected seismicreview by the ATC Senior Technical Committee. This performance than do existing procedures.effort resulted in a number of editorial changes and sixadditional technical changes being proposed by the • Assess whether the Guidelines acceptance criteriaATC. On September 3, the ATC presented its are properly calibrated to result in componentrecommendations for change to the Project Oversight designs that provide permissible values of such keyCommittee that, after considerable discussion, deemed factors as drift, component strength demand, andthe proposed changes to be either editorial or of inelastic deformation at selected performance levels.insufficient substance to warrant another ballot.Meeting on September 4, the BSSC Board received the • Develop empirical data on the costs of rehabilitationrecommendations of the POC, accepted them, and design and construction to meet the Guidelinesapproved preparation of the final documents for “basic safety objective” as well as the highertransmittal to the Federal Emergency Management performance levels included. Assess whether theAgency. This was done on September 30, 1997. anticipated higher costs of advanced engineering analysis result in worthwhile savings compared toIt should be noted by those using this document that the cost of constructing more conservative designrecommendations resulting from the concept work of solutions necessary with a less systematicthe BSSC Project Committee have resulted in initiation engineering effort.of a case studies project that will involve thex Seismic Rehabilitation Guidelines FEMA 273
• Compare the acceptance criteria of the Guidelines Commentary can be obtained by phone from the FEMA with the prevailing seismic design requirements for Distribution Facility at 1-800-480-2520. new buildings in the building location to determine whether requirements for achieving the Guidelines The BSSC Board of Direction gratefully acknowledges “basic safety objective” are equivalent to or more or the contribution of all the ATC and ASCE participants less stringent than those expected of new buildings. in the Guidelines development project as well as those of the BSSC Seismic Rehabilitation Advisory Panel, theFeedback from those using the Guidelines outside this BSSC Project Committee, and the User Workshopcase studies project is strongly encouraged. Further, participants. The Board also wishes to thank Ugothe curriculum for a series of education/training Morelli, FEMA Project Officer, and Diana Todd,seminars on the Guidelines is being developed and a FEMA Technical Advisor, for their valuable input andnumber of seminars are scheduled for conduct in early support.1998. Those who wish to provide feedback or with adesire for information concerning the seminars should Eugene Zellerdirect their correspondence to: BSSC, 1090 Vermont Chairman, BSSC Board of DirectionAvenue, N.W., Suite 700, Washington, D.C. 20005;phone 202-289-7800; fax 202-289-1092; email@example.com. Copies of the Guidelines andFEMA 273 Seismic Rehabilitation Guidelines xi
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