Seismic Response Analysis Of Turnout Girder Bridge In High Speed Railway

In recent years,the construction of high-speed railway network in China is advancing rapidly.subject to the limitations of complex terrain conditions and the influence of existing lines,a large number of turnouts need to be laid on bridges to form turnout bridges(turnout girder bridges and adjacent bridges).The bridge in the turnout area as the hub of the rail transit network,if the earthquake damage occurs,it will not only cause serious economic losses,but also affect the smooth flow of the whole railway traffic network,resulting in post-earthquake rescue is extremely difficult.Compared with the adjacent bridge span,the turnout beam bridge has both irregular structural layout similar to skew bridge and plane irregularity similar to curved bridge.Under seismic excitation,the structural dynamic response is more complex.At present,few scholars have studied the dynamic characteristics of turnout girder bridges,and the seismic response characteristics of turnout girder bridges have not been fully demonstrated.In this thesis,taking a high-speed railway turnout beam bridge as an example,the seismic response law of this kind of bridge is studied.The main research work is as follows:(1)In this thesis,the formation reasons and design requirements of bridges in turnout area are introduced,the main factors causing the complex seismic response of turnout girder bridges are analyzed,and the deficiency of seismic response analysis of turnout girder bridges in the existing research is found.The seismic response characteristics of similar bridges and the harm of velocity pulse effect of near-field earthquake to bridge structure are summarized,and the influence of track constraint on bridge seismic response is summarized.On this basis,combined with the structural characteristics of turnout girder bridge,the research idea of seismic response analysis of high-speed railway turnout girder bridge is clarified.(2)Taking a 4-span high-speed railway turnout beam bridge as the research object,a spatial finite element model is constructed to analyze the dynamic characteristics.Through the study of structural natural frequency and corresponding vibration mode,it is clear that the turnout beam bridge is prone to beam and pier torsion.Combined with the structural characteristics of turnout beam bridge,the influence of dynamic characteristic parameters of turnout beam bridge is further studied,and the effects of different structural parameters on the dynamic characteristics of turnout beam bridge are compared.the study shows that its dynamic characteristics are sensitive to the skew angle of beam.(3)Based on the above model,different types of seismic waves are selected to analyze the seismic response of turnout girder bridge,and the significant destructive effect of near-field pulse earthquake is clarified by comparing the difference of seismic response of turnout girder bridge under all kinds of seismic waves.Combined with the variation law of dynamic characteristics of turnout girder bridge,the influence of seismic response parameters of turnout girder bridge is further analyzed,and the effects of ground motion parameters and structural parameters on the seismic response of turnout girder bridge are compared.the seismic wave input angle has a great influence on the seismic response of turnout girder bridge.(4)Considering the constraint effect of track-turnout system between adjacent bridges,the influence of track constraint effect on the dynamic characteristics and seismic response of turnout girder bridge is analyzed,and the differences of natural frequency and structural vibration modes of the two models are compared.it is found that considering the track constraint effect will aggravate the torsion of the turnout girder bridge.On this basis,the influence of seismic response parameters of turnout girder bridge considering track constraints is further studied,and the relevant research conclusions can provide support and reference for engineering design.