Transverse seismic vulnerability analysis of tunnels based on modified IDA method

Vulnerability analysis is a crucial method to study the seismic performance of tunnels. Two benchmark cross-sections of tunnels, namely circular and rectangular cross-sections, are selected as the research object to investigate the transverse seismic property of tunnels. A finite element model is established by SAP2000 software, and the influences of various site types, depths of burial of the tunnel, and cross-section sizes on the transverse seismic capacity of a tunnel are discussed. The probabilistic seismic demand model of ground motion intensity measures and the engineering demand parameters are determined by utilizing a modified incremental dynamic analysis (IDA) method, and the reasonable ground motion intensity measures are specified by analyzing four evaluation criteria. The failure probability of the structure under each earthquake intensity and the seismic vulnerability curve of the construction are calculated to evaluate the transverse seismic performance of the tunnel by combining the probabilistic seismic demand model with the limits on the engineering demand parameters. The numerical results indicate that PGA is the ground motion intensity measure suitable for the transverse seismic performance of the tunnels. The site type has the most significant influence on the structural damage, and site type IV is the most dangerous under an earthquake. The tunnel has better seismic resistance in the elastoplastic stage, and a tunnel with a large depth of burial is more hazardous than the one with a small depth of burial. A tunnel with a large cross-section has a higher probability of damage than the one with a small cross-section.