Optimal index of earthquake intensity measures for seismic design of underground frame structure of shallow-buried subway station

The optimal index of earthquake intensity measures required in the probabilistic seismic demand model for seismic design of the underground frame structure of shallow-buried subway station is studied. Based on the ABAQUS/Standard platform, the two-dimension model for an underground frame structure is established. The seismic responses of three subway station cross-sections are obtained by using the nonlinear dynamic time-history analysis in term of 22 far-field earthquake records. The peaks of inter-story drift ratios are obtained and selected as the structural damage measure, and 15 candidate intensity measures (IMs) are examined based on the characteristics of efficiency, practicality, proficiency and sufficiency. The results show that PGA is an optimal IM for the probabilistic seismic demand model for the underground frame structure of shallow-buried subway station, whereas the PGV or the velocity response spectrum is an alternative IM. However, the PGD, root-square of displacement, root-mean-square of velocity and root-mean-square of displacement are failed in the tests on the sufficiency, in which they are not appropriate to the probabilistic seismic demand analysis for the underground frame structure of shallow-buried subway station. The findings may provide a helpful guide to the performance-based seismic design of underground structure and to the developing and improving of the determination method of optimal IMs of the existing probabilistic seismic demand model for shallow-buried underground structure.