Influence of 3D spatial effect of underground structure on the nonlinear seismic response of subway station based on the comparison of 2D and 3D models

This paper takes an actual station of Nanjing Metro Line 2 as the research object and establishes the corresponding 2D and 3D overall time-domain nonlinear finite element models, respectively. By analyzing the results of the two models, the influence of the 3D spatial effects of the underground structure on the seismic response of the structure is studied. The results show that the 2D model cannot correctly reflect the deformation characteristics of the 3D station structure at the middle of the longitudinal length. The results obtained from the 2D model are roughly equivalent to the results at 1/4 of the longitudinal length of the 3D station structure. The overall longitudinal bending deflection of the station's top and middle slabs in their own plane can well reflect the 3D cooperative work degree of the station. Based on this, the conversion coefficient of the maximum interstory displacement angle proposed in this paper can better convert the 2D model results. The minimum error between the converted 2D model results and the 3D model results is only 0.78%, and the maximum error is only about 10%. The maximum inter-story displacement angle conversion coefficient with 95% probability guarantee finally given is 1.447. Through the statistical analysis of the internal force ratio of the 3D model and the 2D model at the key cross-sections, this paper also gives the conversion coefficients with 95% probability guarantee for the bending moment, the axial force and the shear force of the key cross-sections, which are 0.696, 0.773, and 0.785, respectively.