Seismic response of subway station structure with concrete-filled-steel-tube middle columns

In order to improve the seismic performance of underground structures, the concrete-filled steel tube (CFST) middle column is usually used in the existing subway station structures. The influences of concrete middle columns type on the seismic response of subway station structures are considered. A comprehensive 2D finite element model for a two-story and three-span subway station, considering the nonlinear dynamic soil-subway station structure interaction, is established using the OpenSees in this study. By utilizing the ynthetic artificial seismic ground motion inputs and conducting the nonlinear time history analysis on the model, the seismic response patterns of subway station with CFST middle columns are investigated. The results indicate that the maximum inter-story drift ratios of the top-level columns of the CFST subway station decrease by 5% and 1% under both the frequent and design-basis seismic ground motions, respectively, compared to those of the reinforced concrete subway station. The maximum inter-story drift ratios of the bottom-level columns is reduced by only 24% and 8%. The CFST middle columns reduce the maximum inter-story drift ratio of the top and bottom levels of the subway station by 9% and 7% under the rare seismic ground motions, respectively. The maximum shear force at the bottom of the CFST middle columns increases by 7% at the maximum deformation moment. The subway station structures exhibit significant deformations under the extreme seismic ground motions. The CFST middle columns are not damaged at the moment of damage in the reinforced concrete middle columns. The CFST middle columns significantly enhance the seismic resistance of subway station structures.