Improved pushover method for seismic analysis of shallow buried underground rectangular frame structure.

Simplified methods are widely used in the seismic design of underground structures, but they generally ignore the influence of vertical ground motion. This can result in unreliable design because seismic earth pressure induced by vertical ground motion can have a significant adverse effect on their seismic performance. Therefore, this paper proposes an improved pushover analysis method (I-PAM) that applies distributed horizontal and vertical inertial forces to simulate the mechanical behavior of underground structures under both horizontal and vertical ground motions. The profile of load distribution and target displacement is calculated from corresponding site response analysis. A rigorous time-history dynamic analysis method (TDAM) based on the finite element numerical analysis was employed in three case studies to evaluate the performance of the developed I-PAM. The results showed that the I-PAM can accurately predict the structure's peak axial force, bending moment and displacement under the combined action of horizontal and vertical ground motions, especially for lower ground motion intensity. It was also found that the responses of the center column and middle slap were calculated with higher accuracy compared to that of the components in direct contact with soil including sidewalls and top and bottom slabs. The developed I-PAM offers a framework for further development and enhancement of simplified analysis methods for seismic design of underground structures. • The effect of vertical ground motion on daikai subway station is conducted in present study. • The mechanical model of improved pushover analysis method considering vertical ground motion is developed. • The reliability of the improved pushover analysis method is verified by comparison with the dynamic method. [ABSTRACT FROM AUTHOR]