Effect of ground motion characteristics on seismic fragility of subway station

Abstract

Seismic fragility analysis of structure is fundamental in performance-based seismic design. The ground motion record set used in the analysis may have a characteristic effect on the fragility curves of a subway station structure. In this paper, fragility data have been developed by conducting the incremental dynamic analysis of subway station structure subjected to far-field record set (FFRS), near-field record set (NFRS), and near-filed record set with a pulse (NFRS + P). The dynamic analysis was conducted employing 2-D finite element models that account for soil nonlinearity and structural plastic damage. The vulnerability curves were derived utilizing the inter-story drift ratio as the damage measure (DM) and the peaks of ground acceleration as the intensity measure (IM). The results show that the second story was more prone to damage than the first story. The fragility curves derived from the data of the second story exhibited widely varying features for three ground motion record sets. The subway station sustained higher damage conditional probability when subjected to NFRS compared to NFRS + P and FFRS ground motions. The difference in the free field response under the three ground motion records sets directly correlates to the difference in the structural seismic vulnerability analysis. These results add to the rapidly expanding field of subway station performance-based seismic design.