Study On Seismic Response Characteristics Of Large Underground Station Structure

As an important part of modern rail transit,underground station structure provides great convenience for urban residents to travel.Several underground transportation hubs have been built in our country,as one of the countries which suffer from most frequent earthquakes in the world,our country put forward higher requirement for the seismic resistance of underground structures,especially the seismic design of complex large underground structures in the area with high intensity pay more attention.In this paper,a large complex underground station structure in Xiongan New Area is taken as the research background,Midas GTS finite element software is used to analyze the seismic response characteristics of the large underground station structure by response displacement method and time history analysis method.The internal force distribution and deformation rule of the large underground station structure under earthquake action are studied,and the applicability of response displacement method in the complex large metro station structure is discussed.The main conclusions are as follows:(1)Based on practical engineering and relevant parameters,the equivalent linear analysis of soil mass is carried out to obtain the shear modulus of soil layer when it converges and the acceleration,displacement and shear force of the site at the most unfavorable moment under the earthquake action,which provides the calculation basis for the subsequent response displacement method calculation.(2)Based on the static finite element method,the sensitivity analysis of six calculation parameters of the foundation spring stiffness is carried out.The influence of each calculation parameter on the spring stiffness is that the soil spring stiffness increases linearly with the increase of the soil elastic modulus,and the influence of the soil Poisson’s ratio on the spring stiffness can be ignored.The change of the structure width only affects the spring stiffness of the top and bottom,and the change of the structure height only affects the spring stiffness of the side wall.As the depth of the structure increases or the distance from the floor to the bedrock becomes closer,the spring stiffness value will also increase.(3)The results of the Response displacement method and the time history analysis method show that,under the conditions of basic earthquake,basic earthquake and rare earthquake,the axial forces of different layers show a change law of large down and small up.The maximum shear force and bending moment appear at the bottom of the side wall,and the law of the Response displacement method is more obvious in numerical value.The horizontal relative displacements obtained by the two analysis methods are large in the upper part and small in the lower part,with the roof being the maximum and the floor being the minimum.The limit value of the displacement Angle between floors is less than 1/250,which meets the relevant regulations and has good horizontal seismic performance.(4)Compared with the time-history analysis method,the Response displacement method has the same internal force variation law,and the numerical calculation results of the Response displacement method are slightly larger than the time-history analysis method,and the maximum axial force,shear force and bending moment difference is 26%,22% and 22%.In terms of horizontal displacement deformation,the maximum displacement Angle of Response displacement method is(1/433),which is larger than that of time history analysis method(1/768),so it can be used as conservative design in seismic calculation of underground structure.