Analytical Seismic Fragility Analysis of Bridges Excited By Near-Fault Pulse-Like Ground Motions

Abstract eng:
In this paper, based on the framework of the next generation performance-based earthquake engineering proposed by PEER, a method of simplified seismic fragility estimation has been developed for an illustrated bridge under near-fault earthquakes. First, the double-side pulse-like ground motion records are selected from the PEER NGA strong ground motion database based on the perk point method (PPM), and the far-field records are also selected following the opposite rules for comparison. To consider the characteristics of near-fault pulse-like ground motions, the spectral acceleration (S a ), the peak ground acceleration (PGA) and the peak ground velocity (PGV) are chosen as the intensity measures (IMs). With the aim at comprehensive investigation of multiple performance objectives, four engineering demand parameters (EDPs) for bridge components are defined, including the drift ratios of the middle pier and the side pier, the deformations of sliding bearings and fixed bearings. Based on a series of nonlinear dynamic time-history analysis of the case-study bridge using the OpenSees software, the probabilistic seismic demand models for each EDP and IM couples are established through regression analysis. Finally, the seismic fragility curves for bridge components and system are developed for different damage states. The numerical results highlight that the seismic demands of near-fault pulse-like ground motions are much larger than those of far-field ground motions, and that the middle pier is more fragile than side piers, and the failure probability of the system is larger than bridge components.

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