Seismic Fragility Functions via Nonlinear Response History Analysis

The estimation of building fragility, i.e., the probability function of seismic demand exceeding a certain limit state capacity given the seismic intensity, is a common process inherent in any seismic assessment study. Despite this prolific nature, the theory and practice underlying the various approaches for fragility evaluation may be opaque to their users, especially regarding the handling of demand and capacity uncertainty, or the generation of a single fragility curve for multiple failure conditions, using either an intensity measure or engineering demand parameter basis. Hence, this paper provides a comprehensive guide that compiles all necessary information for generating fragility curves of single structures based on the results of nonlinear dynamic analysis. Although various analysis methods are discussed, incremental dynamic analysis is invoked to clearly outline different methodologies that rely either on response parameter or intensity measure ordinates. Step-by-step examples are presented for each case, under both a deterministic and an uncertain limit state capacity framework, using limit states that range from simple structural damage to the global collapse of the structure.