Seismic Response And Simplified Mechanical Model Of Subway Station Complex Structure Covered With Buildings

With the development of urban underground space,urban rail transit has been developing rapidly,and the development mode of urban underground complex and overground buildings with subway stations as the core has gradually emerged.These kind of structures integrates transportation,business,office and other functions,and brings convenience to people.At the same time,its safety problems have also attracted attention,among which the seismic problem has become a research hotspot.At present,the seismic performance and failure mechanism of subway station complex structure considering the influence of superstructure are not clear,and there is a lack of simplified mechanical model for seismic calculation of this kind of structures.Firstly,a 3D numerical model of soil structure is established by using the finite element software Midas GTS NX,and the seismic response of the subway station complex structure affected by the superstructure is analyzed.Secondly,the finite element software ABAQUS is used to reproduce the seismic damage evolution process of the structural system.Finally,based on the basic principle of the traditional response displacement method,considering the influence of the upperstructure and the side wall opening,a simplified mechanical model is proposed for the seismic design of the subway station complex structure when the upper building is a single tower building.The main research contents and conclusions are as follows:(1)The seismic response differences of general large-scale subway stations,subway station structures with upper buildings,subway station structures adjacent to above ground buildings,and the seismic damage evolution process of subway station complex structures with upper buildings are analyzed.The results show that,compared with the general largescale subway station structure,the existence of buildings near the ground changes the stress field and displacement field of the lower soil,the horizontal displacement of the subway station structure decreases,and the amplitude of the bending moment of the center column of the subway station increases significantly.The existence of underground structure will significantly increase the horizontal deformation and acceleration of soil mass near the surface,while the acceleration of soil mass under the structure will decrease.(2)In order to study the seismic response law of the subway station complex structure with upper buildings,based on numerical simulation,the effects of input ground motion,the form of the upperstructures,the location of the upper cover double towers and the buried depth of the underground structure on the lower subway station structure are investigated.The results show that the seismic response law of the subway station complex structure with upper buildings under the excitation of artificial wave,Kobe wave and El-centro wave is relatively close,but the bending moment response of the subway station structure column end is greatly affected by the rich middle and low frequency seismic waves,and the displacement difference between the top and bottom plates under the action of Kobe wave and the structural acceleration at the most dangerous moment are larger.Under earthquake action,the frame shear wall structure of the upper building makes the roof and the top of the central column of the subway station produce large bending moments.Compared with the horizontal and vertical layout of the double tower structure,the oblique layout of the double tower structure makes the deformation of the subway station significantly increase under the earthquake action.As the underground structure is buried in the soil,the bottom of the upper cover building is constrained by the surrounding soil.With the increase of the buried depth of the underground structure,the bottom of the upper building is also buried in the soil.Under the earthquake,the bending moment of the central column along the longitudinal edge of the subway station increases sharply.(3)Based on the basic principle of the traditional response displacement method,considering the additional seismic load generated by the superstructure in the earthquake and the seismic calculation problem of the subway station with the side wall opening,the simplified mechanical model is reasonably improved,and finally an improved response displacement method suitable for the subway station structure considering the superstructure is proposed.Compared with the calculation results of time history analysis,the accuracy and applicability of the improved response displacement method are verified from six aspects:input ground motion,superstructure offset,superstructure form,structural stiffness,soil layer stiffness and side wall opening.The results show that the traditional response displacement method can not reflect the seismic response law of underground structures,and the calculation error is large when the subway station structure is covered with buildings;However,the calculation result of the improved response displacement method is slightly larger than that of the time history analysis,and the calculation accuracy is significantly improved,with the error less than 20%,meeting the needs of engineering design.