Seismic fragility analysis of underground structures subjected to bi-directional ground motions based on the damage weight coefficients of components

Abstract

The seismic resilience of underground structures is generally based on the results of the seismic fragility analysis and the damage of all the structural components comprehensively. Whereas, the seismic behavior of underground structures is greatly influenced by the vertical ground motions. Therefore, this paper proposed a new method to study the seismic fragility of underground structures subjected to both horizontal and vertical ground motions, and by considering the damage weight coefficients of the structural components to the overall structure. Pushover/pseudo-gravity analyses were conducted to determine the demand measures and seismic performance levels of all the structural components. Then the intensity measures of earthquakes were determined and the seismic fragility curves of structural components were built by combining the seismic performance levels of structural components and the 3D incremental dynamic analyses on the underground structures. Meanwhile, according to the damage probability of each structural component, the damage weight coefficients of components to the damage of the overall structures were calculated. After that, the seismic fragility surfaces of the underground structures were built and the seismic fragility of the structures was discussed. The method developed in this study could not only be used to evaluate the damage probability of underground structures caused by the vertical ground motions, but also to evaluate the damage probability and post-earthquake repairability of the components.