Optimal earthquake intensity measure in probabilistic seismic demand models of underground subway station structure

This paper investigates the optimal intensity measure (IM) for underground structure in probabilistic seismic demand models. A two-dimensional finite element model that accounts for the soil-structure interaction for a subway station was established employing the program ABAQUS. Probabilistic seismic demand analysis was conducted based on the cloud method, which involved 248 non-linear dynamical analyses. The peaks of first and second inter-story drift ratios, peaks of slab acceleration, and the peaks of bending moments for key sections were recorded as the engineering demand parameters (EDP). Based on the conventional and updated metrics of efficiency, practically, proficiency, 16 candidate intensity measures were evaluated, and their sufficiency was verified through the p-value or relative sufficiency measure. The results demonstrate that the selection of EDPs has a minor influence on the study of optimal IMs; there were no significant differences in selecting the optimal IMs based on evaluation considering either conventional or updated metrics. The sufficiency test results indicated that the assessment of p-value method is opposite to that of the relative sufficiency measure method for some IMs, and that the sufficiency measure method could provide more IM sufficiency information. The main findings are that the IMs related to acceleration curves performed well in all metrics evaluation, and that the PGA is the most optimal IM for the probabilistic seismic demand models of underground frame structure.