Pushover Analysis of Daikai Subway Station During the Osaka-Kobe Earthquake in 1995

Abstract eng:
Pushover analysis method is a simple and effective method in seismic analysis and design of structures. Because of the restriction of the surrounding foundation, the deformation shapes of underground structures and super-structures are different. The deformation of the underground structure under horizontal seismic loads appears a shear shape mainly, however, the super-structure bears a combined action of moments, shear forces and torques. The foundation-underground structure system bears body forces mainly under seismic loads. Interaction exists between the foundation and the underground structure, so the restriction of the surrounding foundation can not be neglected, which is different from super-structures. Therefore so far, pushover analysis methods applied to super-structures can not be used in seismic analysis and design of underground structures. So it is necessary to develop a pushover analysis method applied to underground structures considering the restriction of surrounding foundation, and put forward seismic analysis and design method for underground structures based on displacement. Thus the disadvantages of present analysis methods based on bearing force can be improved, and accordingly, seismic analysis and design of underground structures will get easier and more reasonable. A pushover analysis method for seismic analysis and design of underground structures has been presented. Solution methods of distributions of equivalent horizontal inertial acceleration and target displacement are introduced together with the implementation procedure. Pushover analysis is carried out on Daikai subway station, which was greatly destroyed in Osaka-Kobe earthquake in 1995. A whole range seismic response of the structure members from elastic status to failure is performed and the capacity curves are given. Also included are the sequence and distribution of the plastic hinges and the failure mechanism of the structure is analyzed further. The results indicate the structure first fails at the columns in compressive bending under strong horizontal and vertical seismic loads. Ultimately it results in the failure of the integral structure and large subsidence of the super-road. Besides, the results obtained through the pushover analysis method are in good agreement with the real seismic damages, so the validity and applicability of the method are verified.

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