2-D seismic fragility analysis and structural type effect of a multi-span subway station

This paper focuses on seismic damage mechanism analysis of a multi-span subway station. A practical method, the response displacement method, is presented to evaluate the aseismic capacity of the subway station. In analysis, seismic design loads for underground structures are characterized by the deformations and strains imposed on the structure by the surrounding ground. The development of appropriate ground motion parameters is briefly described, including the stiffness of soil spring and the amplitude of free-field displacement response which is induced by shear wave. Then elastoplastic analyses are conducted on the multi-span subway station under ground motions with different seismic peak accelerations, using the response displacement method combined with the finite element method. A clear expansion process of plastic zone in the underground structure is tracing according to the result. Finally a comparison of the multi-span subway station with a single-span and a two-span one is made. And the effect of different structural types is evaluated. It is found that damage mechanism of the multi-span subway station is related to peak ground acceleration based on the magnitude of the affected earthquake. It is also found that the increase in span aggravated the danger of the subway station against earthquake, due to the larger moment of components induced by multi-span.