Pushover analysis of underground structures: Method and application

Pushover analysis is common because of its conceptual simplicity and computational attractiveness in computing seismic demand. Considering that traditional pushover analysis is restricted in underground structures due to the stark differences in the seismic response characteristics of surface structures, this paper proposes a pushover analysis method for underground structures and its application in seismic damage assessment. First, three types of force distribution are presented based on ground response analysis. Next, the target displacements and analysis models are established according to force-based and performance-based design. Then, the pushover analysis procedure for underground structures is described. Next, the applicability of pushover analysis to underground structures is verified by comparing the responses of a Chongwenmen subway station determined by the proposed procedure and by nonlinear response history analysis. In addition, two other points are made: that the inverted triangular distribution of effective earthquake acceleration is more practical than the other two distributions, and that performance-based design is more effective than force-based design. Finally, a cyclic reversal loading pattern based on one cycle of reversal loads as an earthquake event is presented and applied to the seismic damage assessment of underground structures. The results show that the proposed pushover analysis can be effectively applied to the seismic design and damage assessment of underground structures.