Research On Track-Bridge Interaction Of A Railway Suspension Bridge Considering Bridge Expansion Structure Under Earthquake

Based on the engineering background of Wufengshan Yangtze River Bridge,the first kilometer level rail-cum-road suspension bridge in China.,the rail-bridge-pier-expansion structure integrated model is established by ANSYS.The influence of the bridge expansion structure and the traveling seismic wave effect on the bridge-track interaction of the bridge,as well as the analysis of the influencing factors on the expansion amount of the rail expansion joint were mainly explored.The main research contents and achievements of this thesis are as follows :1.In view of the particularity of the calculation of the continuous rail of suspension bridge in ANSYS,the longitudinal resistance curve of track bed selected in the specification is reconstructed to be suitable for the dynamic analysis of bridge-track interaction.The response spectrum of railway bridges suitable for short periods is modified according to the longperiod response spectrum of highway specifications to obtain the seismic response spectrum of long-period and long-span bridges.2.Based on the rail-bridge-pier-expansion structure integrated model,the influence of expansion structure on bridge-track interaction is studied.The results show that after the expansion structure is set at the joint between main bridge and approach bridge,the expansion,deflection,braking and seismic additional stress of the rail can be significantly reduced,without affecting the additional stress of the rail at other positions.The peak value of rail stress,the peak value of longitudinal horizontal force at the top of the fixed pier and the peak value of longitudinal shear and bending moment at the bottom of the pier and tower are increasing under four site conditions.The peak value of rail seismic stress decreases with the increase of the ultimate expansion resistance of the supporting beam of the expansion device,and the change at the joint between main bridge and approach bridge is the most obvious.3.The large mass method is selected as the seismic wave input mode and multi-support excitation model according to the large mass method is established in ANSYS.The calculation results show that the non-uniform excitation will increase the rail seismic additional stress and have different degrees of influence on the internal force and displacement of pier and tower.The rail seismic additional stress increases with the decrease of apparent wave velocity,and the rail stress change at the joint between approach bridge and foundation is particularly large.The shear and moment of the main tower show irregular changes with the apparent velocity,and the axial force increases slightly with the decrease of the apparent velocity.The low apparent velocity is beneficial to the fixed pier,and the internal force and displacement are close to the uniform excitation calculation results under the high apparent velocity.4.The effects of bridge structural system,viscous damper,seismic site type,traveling wave effect,and seismic peak acceleration on the expansion amount of the rail expansion joint(REJ)were investigated.The research results show that: semi-floating bridge structure system,viscous dampers with low velocity index,seismic waves whose predominant period is closer to the inherent period of the bridge,smaller apparent seismic velocity and larger peak seismic acceleration will all lead to larger REJ expansion amount.