Analysis Of Train-Metro Viaduct Coupling Vibration Under Seismic Excitations

Urban rail transit has developed rapidly in recent years,with the characteristics of fast speed,large traffic volume,and small area occupation.The proportion of viaduct lines have been increasing of urban rail transit.China is a seismic-prone country.When a seismic occurs,the bridge structure generates strong vibration due to the impact of the seismic load,which affects the safety of the trains running on it and the safety of the bridge.As one of the most common ways of urban rail transit,the subway system differs from the traditional railway bridges,highway bridges,and light rail viaducts in the aspects of loadings and design principles.Existing studies have mainly focused on traditional railway bridges and high-speed railway bridges,and few analyses on metro train-bridge coupling vibration under seismic excitations.In this thesis,a typical continuous-beam structure of the subway viaduct is studied to analyze the dynamic response of the bridge under seismic excitations and subway train.The main research work and conclusions are:(1)Based on the secondary development platform APDL of ANSYS finite element analysis software,a train-bridge coupled vibration analysis model with the fixed pier was established.Eight carriages of subway train move on the bridge with considering seismic excitations and track irregularity excitation.The comparative analysis is conducted for the three cases: only seismic excitation,only train load,both the seismic and train loads.Studies have shown that,compared with the dynamic response of the bridge under the load of only the train,the seismic action has a greater influence on the internal force of the pier structure.Compared with the separate action of seismic and train load,the simultaneous action of seismic and subway train load has a greater influence on the lateral displacement of the bridge.(2)Two simulation methods,"equiavalent spring on cap" and "pile-soil interaction",are used to consider the effect of soil on the pile,and a train-bridge coupling vibration analysis model considering the pile-soil interaction is established,and the influence of seismic excitations and track irregularity excitation were considered.The pile fixed model without considering pile-soil interaction is compared.The calculation found that the pile-soil interaction has a greater impact on the dynamic performance of the structure.The main dynamic response errors of the "equiavalent spring on cap" model and the "pile-soil interaction" model are both within 16%,and the “equiavalent spring on cap” model calculation higher efficiency.(3)Based on the train-bridge coupling vibration analysis model considering pile-soil interaction and considering the influence of seismic excitations and track irregularity excitation,eight carriages are exerted on the bridge to calculate the dynamic response of the bridge when the train runs on a single line and double lines.After analysis,it is found that when the train runs on both lines simultaneously,the vertical displacement of the bridge is close to the algebraic sum of the response of the bridge of the two single-line cases;the lateral displacement is close to the horizontal displacement of the bridge caused by one single line;the maximum value of the bending moment of the girder is greater than the sum of the internal force of the bridge section when the two single lines are driven alone;and the maximum value of the internal force of the pier’s bottom section is less than the sum of the internal force of the two single-line cases.The response of the critical section of the bridge is increased for both double lines and single line cases if the seismic force is considered.