Based On The Response Of Soil - Structure Interaction Subway Station Seismic Dynamic Finite Element Analysis

Recently, with the expanding of underground structure construction, anti-seismic design of the underground structure as well as its security assessment become an topic that is attracting more and more concern, thus making soil and underground structure dynamic interaction an important part of such a design. Under the framework of soil-underground structure dynamic interaction theories, this paper has established a finite element model of soil-underground structure interaction with the help of ANSYS software, and has made the following achievements:1 Time-history response analysis has been conducted on free field and soil-underground structure dynamic interaction respectively under the effect of horizontal seism, vertical seism and the coupling of horizontal-vertical seism.2 According to current specifications, a static analysis has been carried out on the basic combinations of various loads for a subway station in Shanghai. And the analysis shows that under static condition, the central pillar of the subway station is bearing mainly the axial force, and is under small bending moment and shearing force, the maximal force of the latter occurs at the joint of the station floor and the flank walls. The result is compared with internal force that the structure produces during seismic process.3 Analysis on the seismic free field for the geological environment of the subway station shows that, when EI-Centro wave, Qian'an region wave and kobe wave are input along the horizontal direction of bed rocks, though the peak values of surface acceleration are the same, the acceleration peak values of the base and the surface displacement peak values are different. This proves that displacement response is not only related with the peak value of seismic wave that is input, but also with the combination of frequencies.4 Horizontal seismic wave response analysis and horizontal-vertical coupling seismic wave response analysis on the subway station are conducted respectively, and the result shows that coupling has increased the maximum response of the system. Therefore, when doing seismic response analysis, considering only horizontal shear failure will not ensure anti-seismic security of project, and coupling seismic function shall be taken into full consideration.5 In the underground structure dynamic response analysis, central part of the roof is under great force and has a large degree of distortion, so do the corners of the flank walls for the high concentration of forces. Therefore, aforementioned parts shall be given special attention to in design and construction.6 Increasing density and rigidity of station body structure has little influence on changes of natural frequency of vibration of the soil-structure system as well as structure displacement under anti-seismic effect, but structure stress grows a lot. Natural frequency of vibration of the soil-structure system is mainly determined by structure surrounding soils, and displacement and stress of the structure under seismic effect dwindle markedly with the increase of the elastic modulus of the soils.