Report - PEER - University of California, Berkeley

Present performance-based seismic design practice for buildings in the UnitedStates is embodied in appendices to the Recommended Lateral Force Requirementsand Commentary (SEAOC, 1999) and the FEMA-356 (ASCE, 2002) nationalrehabilitation guidelines. These documents define a series of discrete performancelevels, ranging from states of little damage and earthquake impact (e.g., ImmediateOccupancy) to states of near complete damage and total loss (e.g., CollapsePrevention), and provide methods of relating these damage states to responsequantities predicted by structural analysis (e.g., interstory drift, individual memberforce demand). These methodologies have had substantial impact on U.S.engineering practice and have experienced widespread application, particularly for theevaluation and upgrade of existing buildings. Further, the basic performanceframework for these performance-based procedures has been adopted by modelbuilding codes in the U.S. and extended to other design conditions including wind,snow, fire and blast. Despite this success, it is clear that substantial improvementscan be made. Current procedures evaluate performance on the basis of local ratherthan global behavior, do not adequately characterize the performance of nonstructuralcomponents and systems, provide no guidance on how to proportion a structure, otherthan by iterative trial and error procedures, are of unknown reliability and are tied toperformance levels that do not directly address the needs of the decision makers whomust select the appropriate performance criteria for specific projects.In September 2001, the Federal Emergency Management Agency contracted withthe Applied Technology Council to develop next-generation performance-basedseismic design guidelines intended to address these shortcomings. The resultingATC-58 project, a broad program based on the FEMA-349 Action Plan (EERI, 2000),is intended to be implemented over a ten year period in partnership with the threenational earthquake engineering research centers, the United States Geologic Survey,the National Earthquake Engineering Simulation program as well as industryassociations and other interested parties. It will culminate with the publication ofnext-generation performance-based seismic design guidelines for buildings as well ascompanion publications intended to assist decision makers in using and takingadvantage of performance-based approaches. Though primarily intended to addressseismic design, substantial efforts are being made to ensure that the guidelines aredeveloped compatibly with parallel efforts to develop performance-based designcriteria for resistance to other extreme loads including fire and blast.Guidelines development is occurring in two phases. The first phase comprisesdevelopment of building performance assessment guidelines. In a major departurefrom prior performance-based approaches, rather than expressing performance interms of arbitrary performance levels, the next-generation procedures characterizeperformance directly in terms of the probable life loss, repair costs andoccupancy/functionality interruption times resulting from earthquake damage. Theevaluation procedures closely follow the framework for performance-basedearthquake engineering, developed by the Pacific Earthquake Engineering ResearchCenter, in which probable earthquake losses are calculated by integrating over the90