The objective of this study is development of a method for evaluation of performance ofmoment resisting steel frames under seismic loads. The emphasis is on modeling and quantificationof the large uncertainties associated with the excitation, details in designaccording to current code specifications (UBC) , and the nonlinear inelastic response behaviorof the structure. A site-specific seismic hazard.analysis is carried out to identifyand quantify the uncertainties associated with· the source, the path and the site condition.Future earthquakes are treated as either characteristic (major event along a well-identifiedmajor fault segment) on non-characteristic (local events). Ground motions are modeled asnonstationary random processes with time varying amplitude and frequency content, whoseparameters depend on the source, path and site conditions. A strong column - weak beammodel is developed for the structural frame and with which response can be obtained withgood accuracy and computational efficiency. The response statistics are obtained by methodof random vibration based on an equivalent linearization solution procedure and a smoothdifferential equation model for the hysteretic restoring force. The accuracy of thismethod is verified by comparison with simulations. A fast integration technique is thenused to evaluate the probability of limit state (interstory drift limit being exceeded)considering the uncertainties in the excitation parameters. The robustness of the proposedmethod is demonstrated in the numerical examples throughout this study. The methodcan be used in assessing the risk implied in current earthquake resistant design, and in developing reliability-based code procedures.
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