Report - PEER - University of California, Berkeley

46.4 58 58 58 58 58 58 58 58 58 58 58 58 46.412.30(a)(c)5.054.70(b)8-mode IRSA1-mode IRSA(d)(e)(f)Figure 3. (a) Viaduct side view, (b) cross-section, (c) modal capacity diagrams,(d) deck transverse displacements, (e) pier drift ratios, (f) plastic hinge rotations.4. CONCLUSIONSIncremental Response Spectrum Analysis (IRSA) is a recently introduced procedureattempting to replace the intuitive approach governing the current applications ofsingle-mode and multi-mode pushover analyses with a rigorous one. The essentialrequirement of practicality in engineering applications dictates that pushover analysisincluding multi-mode effects should be simple enough without involving any timehistoryanalysis. It means that seismic input is to be defined through a smoothedresponse spectrum and the analysis procedure should incorporate a modalcombination technique based on peak modal response quantities. In fact IRSA isdesigned to satisfy all such requirements through an incremental application of theconventional Response Spectrum Analysis (RSA) procedure combined with anefficient use of the well-known equal displacement rule. As demonstrated throughtypical examples presented in this paper, IRSA can be readily applied to any 3-Dstructure including plan-asymmetric multi-story buildings and irregular bridgesinvolving multi-mode response at each piecewise linear pushover step.355