Analysis of the Three-dimensional Seismic Performance of Underground

In order to analyze the seismic performance of the underground station structure under oblique incidence of ground motion,a 3-D finite element model of Xinghai subway station which is a double layer underground structure located in Suzhou was established. Based on the model,the seismic responses of soil and structure under different angles of incidence were researched. Then the space effect of underground structures ' seismic responses and the irrecoverable deformation were analyzed systematically. It is found that irrecoverable deformation generates in the soil subject to earthquake,which appears as the settlement of the ground surface. And the irrecoverable deformation is significantly affected by the incidence angle of ground motion. Moreover,significant space effect can be found in the seismic response of the underground structure,i. e.,the side columns have larger deformation in the longitudinal direction,whereas,the inner lateral columns have larger deformation than the outside lateral columns in the lateral direction. Furthermore, the middle-columns are the weak link due to the longitudinal discontinuity and lack of constraints of the surrounding soils. The articulated middle-columns are recommended in the design of underground structure,because such middle-columns only bear the vertical loading rather than the horizontal shear loading.