Seismic performance and failure mechanism of a subway station based on nonlinear finite element analysis

Abstract

A nonlinear three-dimensional finite element model is employed to investigate the seismic performance and failure mechanism of a subway station. The interaction between subway station and surrounding soil is considered and the nonlinear behavior of the station structure is taken into account. Structural concrete and steel bars are simulated separately. The results demonstrated that the carrying capacities of structural middle columns and wall-to-roof slab connections are vital in underground structure’s seismic design. During an earthquake, the structure’s plastic damage first appears at beam-to-roof slab connections; but the damage at beam-to-roof slab connections does not develop significantly as seismic going. The heaviest damage parts is columns’ bottom, and then is columns’ top. The damage of wall-to-slab connections can, firstly, let the load transfer to columns and, secondly, reduce the restraint to the roof slab. The relative displacement between the roof slab and bottom slab leads to additional moment on structural middle columns. Besides, the damage at the connections of walls-to-diagonal bracings and slabs-to-diagonal bracings is remarkable. The structure is failure as an italic “M” shape. The results are consistent with the phenomena observed in the collapse of Daikai subway station during 1995 Great Hanshin Earthquake.