Seismic fragility analysis of two-story and three-span metro station structures based on IDA method

Based on the non-linear soil-structure interaction model for a two-storey and three-span metro station in a typical underground engineering site, an IDA (incremental dynamic analysis)-based structural seismic fragility analysis method is introduced for underground metro station structures. The earthquake intensity measure IM suitable for the underground structures is proposed, and the change of their seismic response with the increase of earthquake amplitude is preliminarily discussed. The seismic fragility curves of shallow-buried metro station structures are established, and the failure probability of structures under different seismic intensity levels is obtained. The results show that PGA is an appropriate IM under non-free field, and comparison of the numerical results with the fragility curve of other scholars shows that the proposed fragility analysis method is feasible, and can quantitatively give the failure probability of structures at different performance levels, and provide reference for seismic design of underground structures.