A structural reliability framework for collapse risk assessment incorporating ground motion duration and response spectral shape

Abstract

A structural reliability framework is developed to post-process the results of an incremental dynamic analysis (IDA) and compute a hazard-consistent collapse fragility curve. The ability to produce hazard-consistent collapse risk estimates eliminates a major drawback in the IDA procedure and brings its capabilities on par with multiple stripe analysis (MSA). The proposed framework uses two secondary ground motion intensity measures: SₐRatio which is used to quantify response spectral shape and 5- 75% significant duration (Ds₅₋₇₅). Both SₐRatio and Ds₅₋₇₅ are demonstrated to be efficient predictors of a ground motion’s collapse intensity, which is a measure of its potential to cause structural collapse. In the case of the ductile eight-story reinforced concrete moment frame building analyzed in this study, they are capable of explaining 81% of the variance in the ground motion collapse intensities. The collapse fragility curve estimated using this framework is found to compare well to the fragility curve obtained by conducting MSA using hazard-consistent ground motions. MSA is shown to represent a simulation-based approach to solve the same structural reliability problem. Finally, optimal ground motion selection strategies to produce accurate collapse risk estimates are proposed.