Seismic Vulnerability Analysis in the Longitudinal Direction of a Tunnel
To examine the longitudinal seismic resilience of tunnels,the seismic response of the tunnel in the longi-tudinal direction is calculated using an improved nonlinear beam-spring model,where the PQ-fiber beam model is employed to simulate the nonlinear behavior in the longitudinal direction of the tunnel,and the torsional moment is considered to account for the tangential interaction between the tunnel and the soil.Subsequently,the Incremental Dynamic Analysis(IDA)method for seismic vulnerability analysis is applied to tunnel structures,and the suitable seismic intensity measure(IM)for tunnel structures is studied.Twelve near-field seismic motion records are selected for IDA analysis of the seismic performance level of the tunnel's longitudinal direction.The probability seismic de-mand models are combined with engineering demand parameters to establish the seismic vulnerability curves for the structure.The results indicate that Peak Ground Velocity(PGV)is a suitable seismic intensity measure for the lon-gitudinal seismic performance of tunnels.The impact of site type has the most profound effect on the extent of dam-age in the tunnel's longitudinal direction,with Type I sites showing the highest probability of damage under seismic action.Furthermore,a comparison analysis is conducted between the calculated vulnerability curves and existing empirical vulnerability curves and numerical vulnerability curves,demonstrating the feasibility of the results and providing valuable insights for seismic design of tunnel structures.
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