Analysis Of The Seismic Response Of The Subway Station Structure By The Finite Element Method

With the increase of the number of underground structures and the frequently damage of underground structures, the underground seismic problems has attracted increasing attention to the seismic worker of the world. Especially in the Kobe earthquake in 1995, the Kobe subway station and tunnel was severely damaged, causing the attention of many scholars. However, the aspects of underground seismic research is lagging behind in our country, it stills have no perfect methods for seismic analysis of underground structures, there is also no independent seismic design of underground structures. For these reasons, this paper focuses on the subway station seismic performance with considering the soil- structure interaction, at the same time, conducted in-depth study and discussion for some difficulty that to be addressed during the seismic response finite element analysis process.(1) To use the APDL language of ANSYS, achieved the equivalent visco-elastic soil model successful. Example shows that: under the dynamic action, when using the equivalent visco-elastic model, the calculated results are much smaller than the linear-elastic model, because the equivalent visco-elastic model considers the damping effect of the soil fully.(2) Based on the of seismic wave synthesis theory, the article compose the synthetic procedures of seismic waves with FORTRAN language, so that the input seismic waves can meet local site conditions require. Using least square method, to amend the error for the process of seismic wave from the acceleration to the displacement, example shows that through amending, the acceleration and the Fourier spectrum has changed little, but it corrected the displacement drift. At the same time, based on one-dimensional wave theory, developed a seismic inversion process, and verify the correctness of the program by using examples.(3) Based on principles of artificial boundary, using APDL language to implement the applying method of variety of artificial boundaries. Example shows that the visco-elastic boundary is significantly superior to viscous boundary, because of visco-elastic boundary considered fully the restoring force of the foundation. In the transmission boundary, the visual velocity was determined by the influence of human factors, it may not converge in calculation when carrying out elastic-plastic seismic response analysis. In the seismic wave input mode, the displacement types are much better than the acceleration input.(4) Base on the dynamic finite element method, comparatively analyses and discussion the mechanical properties of the subway station under static, and the changes of displacement at various parts.(5) Comparative analysis the seismic response of the subway station with different input ground motion characteristics, different ground motion input modes and different artificial boundary conditions.(6) Analyzed the factors of the subway station seismic response, and study the differences of the seismic response between the surface structure and the underground structures; it also studied the seismic response of subway station under the factors of elastic modulus and Poisson's ratio, vertical ground motion, the peak of input ground motion and the thickness of cover soil, besides, it analyzed the dynamic response of the free field at the surface by the subway station.