Aseismic Performance Analysis And Damper Parameters Optimization Research Of Longspan Railway Steel Truss And Flexible Arch Bridge

Long-span continuous steel truss flexible and arch bridge with large span capacity and bearing capacity,novel structure and beautiful shape,is one of the common bridge types of long-span railway Bridges.Long-span railway bridge is a throat project with high cost and long construction period.If it suffers serious damage and destruction in earthquake,it will have a negative impact on regional economy and rescue&relief work.In this thesis,the long-span railway steel truss and flexible arch bridge with two main spans of 360m is taken as the research background.Midas/Civil 2020 is used to establish a spatial beam element model considering pile-soil interaction,and the natural vibration characteristics of the bridge are analyzed.It is found that the first-order natural vibration frequency of the bridge is 0.304Hz,and the first-order vibration mode is antisymmetric transverse bending of the arch ribs and main truss.The vibration mode is relatively concentrated and compact.Response spectrum method is used to analyze the linear elastic dynamic response of the bridge under 8 design earthquake conditions and 4 rare earthquake conditions when the longitudinal and transverse support are not fused.The results show that the seismic response of the bridge achieves the aseismic fortification target under the action of design earthquake.Under the action of rare earthquake,the tensile stress of the pier bottom is too large,the longitudinal and transverse counter-force of the support is too large,and the aseismic fortification target cannot be achieved.Based on response spectrum analysis results,the nonlinear time-history analysis of uniform excitation under the action of rare earthquake is carried out to study the aseismic performance of the bridge when the longitudinal and transverse support respectively fused and block limited.The results show that the stress of the longitudinal beam and transverse beam is too large and enters the plastic stage,and the limiting block’s reaction force is too large,prone to failure,the bridge cannot meet the aseismic fortification target.LMM method is used to study the influence of traveling wave effect on the seismic response of the bridge in the range of 500～5000m/s.It is found that the influence of traveling wave effect on the seismic response of the bridge is significant when the wave velocity is low,and the seismic response considering the traveling wave effect is more unfavorable.Based on the results of nonlinear time-history analysis,the nonlinear time-history response of the bridge under uniform excitation under different parameter combinations of longitudinal viscous damper and transverse E-shape steel damper is studied.When the damping coefficient C of longitudinal viscous dampers is3000k N/(m/s)~αand the damping indexαis 0.5,the yield force Fy of transverse E-shape steel dampers is 2000k N and the initial elastic stiffness K is 80000k N/m,the bridge under the action of rare earthquake can obtain a better damping effect,achieve the aseismic fortification target.