Research On Seismic Performance Of Large Column-free Metro Stations

Metro engineering is an important traffic lifeline and an important part of civil air defense preparations.After the Hanshin earthquake,its seismic performance has been paid more and more attention by the engineering community.Generally speaking,the permeability of pillared metro stations is poor.Therefore,the research and application of pillarless long-span metro stations have become a trend of development.Taking NahongJinqiao Passenger Station of Nanning Rail Transit Line 5 as the engineering background,this paper studies the main laws of the seismic performance of the structure of the largespan subway station without columns by means of shaking table test and finite element analysis of the structure model.The main research contents are as follows:(1)Based on the similarity theory,taking the structural form and geological conditions of Nahong-Jinqiao passenger station of Nanning Rail Transit Line 5 as the engineering background,using the modulus of elasticity as the main control indicator and referring to the existing research results,the mixture ratio design and preparation of particulate concrete are carried out,and a structural test model of subway station with a geometric similarity ratio of 1/50 is made.At the same time,the shear strength of Nanning soil is taken as the main control index.Taking shear wave velocity as the control index,the experimental soil was designed and prepared.Considering the influence of soilstructure interaction and boundary effect,the model box and the position and quantity of and sensor were optimized,and the corresponding shaking table test model of soilstructure interaction was prepared.(2)According to the site characteristics of Nahong-Jinqiao Passenger Station of Nanning Metro,three seismic waves are selected,of which two are natural seismic waves,named El Centro wave and Wenchuan Wudu wave,and one is artificial synthetic named Nanning artificial wave.Under the condition of seismic fortification intensity of 7 degrees,simulated earthquakes with Horizontal-vertical coupling effect under 7-degree frequent earthquakes,7-degree basic earthquakes and 7-degree rare earthquakes are carried out respectively.Shaking table tests are carried out to study the main laws of seismic response of model structures.The test results show that the boundary treatment method of the model box can effectively eliminate the influence of the box boundary.Under horizontal and horizontal-vertical coupling seismic action,the peak acceleration of each measuring point in the soil increases with the decrease of burial depth,while the earth pressure increases with the increase of soil depth.The soil pressure at the bottom of the structure is the largest.The peak acceleration response of the station model structure shows that the peak acceleration of the roof is largest,the mid-plate is the second while the floor is smallest,and there is little difference between the non-column section and the column section.Moreover,compared with the horizontal seismic action,the peak acceleration of the station structure model and the soil pressure between soil and structure with the horizontal-vertical coupling seismic action are increased.Taking the Nanning artificial wave action as an example,the peak acceleration of the soil increases by 20%-40%,and the peak acceleration of the station structure model increases by about 30%.,which shows that the increasing effect of the is obvious.(3)The three-dimensional finite element calculation model of the test model is established by using ABAQUS finite element analysis software,and the finite element simulation analysis of the model structure of the large-span metro station without columns under horizontal and horizontal-vertical coupling seismic action is carried out.The results of the finite element analysis are compared with the shaking table test results.The comparison between the two results shows that the finite element analysis established in this paper is in good agreement with the shaking table test results.The analytical model is effective and reliable.Then,the stress analysis of the model structure under various working conditions is carried out by using the finite element analysis model.The results show that the stress of the model structure in the bottom-side wall,the middle-side wall,the top-side wall and the floor is larger than that in the other parts of the structure,especially in the column section,and the stress of the lower column is larger than that of the upper column,and the stress of the two columns is the largest near the bottom of the column.In the column-free section,the average growth rate is about 40%,the maximum growth rate is 163.93%,and in the column section,the average growth rate is about 22%,and the maximum growth rate is 80.87%.It shows that under the action of horizontalvertical coupling seismic wave,the internal force of the structure is significantly enhanced,and the effect of the increase of the column-free section is significantly greater than that of the column section which should be emphatically considered in design.