Report - PEER - University of California, Berkeley

CONTRASTING PERFORMANCE-BASED DESIGN WITHPERFORMANCE ASSESSMENTHelmut KRAWINKLER 1 , Farzin ZAREIAN 1 , Ricardo A. MEDINA 2 , and LuisIBARRA 3ABSTRACTPerformance assessment implies that the structural, nonstructural, and content systems aregiven and that decision variables, DVs, (e.g., expected annual losses, mean annual frequency ofcollapse) are computed and compared to specified performance targets. Performance-baseddesign (PBD) is different by virtue of the fact that the building and its components and systemsfirst have to be created. Good designs are based on concepts that incorporate performancetargets up front in the conceptual design process, so that subsequent performance assessmentbecomes more of a verification process of an efficient design rather than a design improvementprocess that may require radical changes of the initial design concept. In short, the designapproach could consist of (a) specifying desired performance targets (e.g., tolerable probabilityof collapse, acceptable dollar losses) and associated seismic hazards, and (b) inverting theperformance assessment process, i.e., deriving parameters for design decisions, given theseismic hazard and targeted values of DVs (rather than computing DVs, given the seismichazard and a designed structure). This paper illustrates basic concepts on which PBD can bebased and contrasts PBD with performance assessment.Keywords: Performance-based design; Conceptual design; Performance assessment;Collapse; Losses.1. INTRODUCTIONPerformance assessment, as developed in recent PEER research, implies that for agiven system so called decision variables, DVs, are determined whose values shouldfulfill specified performance targets (Cornell 2000, Krawinkler 2004, Deierlein 2004).For life safety/collapse performance, the process of determining DVs is illustrated inthe left half of Figure 1, with the information flowing from right to left, as indicatedby the light horizontal arrow lines and as summarized here: intensity measures, IMs,(e.g., spectral acceleration at the first mode period, S a (T 1 )), are determined fromhazard analysis; relevant engineering demand parameters, EDPs, (e.g., story drifts)1Dept. of Civil and Environmental Engineering, Stanford University, Stanford, CA, 94305-4020, USA2 Dept. of Civil and Environmental Engineering, University of Maryland, College Park, MD 20742, USA3 Southwest Research Institute, CNWRA, San Antonio, TX 78238, USA505