Study On Seismic Performance Threshold Value Of Story Drift Angle Of Rectangular Underground Stations

There are a large number of urban rail transit structures are being constructed in China.However,it’s difficult to take underground stations far from active faults because of the functional limitation of urban rail transit and the laggard of detecting active faults in our relevant specification are difficult to take underground stations far from active faults.The seismic records of underground structures showed that the underground structures may be severely damaged under strong earthquake.In addition,it will bring more direct and indirect serious losses if damage occurs to cost.Therefore,it is of great economic and social significance to ensure the seismic safety of underground stations.Seismic performance threshold values of story drift angle of rectangular underground stations are studied based on a large number of finite element calculation and statistical analysis of test data.The main research contents are as follows:(1)Modified Incremental Dynamic AnalysisBased on the incremental dynamic analysis,a modified incremental dynamic analysis method is proposed,of which analysis is divided into two steps.Firstly,one-dimensional soil free field analysis is carried out adopting equivalent linearization,and then nonlinear analysis of structure is carried out adopting the reaction acceleration method.In order to obtain the incremental dynamic analysis curve of story drift angle,25 conditions is set,which include 5 factors,namely,structure type,site type,seismic wave,thickness of soil layer and depth of structure.(2)Data Statistics and AnalysisThe experimental data,which come from American Peer database and domestic test data in recent years,are analyzed from the concrete intensity,axial compression ratio,shear span ratio and steel content distribution.The experimental data are analyzed by mathematical statistics method,namely,the average value of each test data reduced 1 times the standard deviation(guaranteed rate of 84.13%).(3)The relationship of story drift angle between the frame and column is obtained,according to the rule of elastic and plastic deformation of reinforced concrete frame.Furthermore,collecting all test data,and getting story drift angle of the yield point,the maximum load point and the ultimate displacement angle.(4)Based on the results of the comprehensive calculation of Modified Incremental Dynamic Analysis method and the statistical analysis results of the test data,the limit of the inter-layer displacement angle of each performance point is obtained by referring to the principle of determining the performance points of the ground.(5)An engineering example analysisUsing E1(Frequent Earthquake),E2(Moderate Earthquake)and E3(Rare Earthquake)seismic wave,the underground station of Shanghai rail transit subway section is carried out the bending,shear and deformation check,and evaluated of the seismic performance of each performance point.Finally,the problems requiring further studies are discussed.