A Seismic Analysis For Single-Tower Self-Anchored Suspension Bridge By Considering The Interaction Between Soil And Abutment

Large-span single-tower self-anchored suspension bridge is a soft structure because of its only tower.Under the action of earthquake,the displacements of the two ends of the beam tend to be large,and the two ends of the beam usually collide with the abutments.Many seismic disasters also show that the bridge abutments are seriously damaged during the collision with the beam.So the pounding effects of the bridge structure can be regarded as a constraint in the dynamic response,and it is bound to affect the bridge's natural vibration characteristics because the stiffness of the bridge will be larger.So the pounding effects will enlarge the internal force of the bridge structure and the girders will easily fall from the pier or abutment and the bridges can easily collapse.Abutments are the coupling member between beam and subgrade.Therefore,it is very necessary to study the interaction among beam-abutment-subgrade under earthquake.The engineering background is taken from a highway.Two finite element analysis softwares were used to analyze the seismic response of this bridge.The influence of the interaction of beam-abutment-subgrade on seismic response of the bridge under longitudinal,transverse and vertical directions is studied.First of all,based on the ANSYS software,the 3D solid model of abutment-subgrade nonlinear analysis model is established.The static force nonlinear analysis method(Pushover)is used to simulate the horizontal force-displacement relationship of the abutment under the horizontal impact of the beam.The above-mentioned force-displacement relationship is input to MIDAS software as boundary conditions for linear stiffness of the beam.The finite element analysis model of the bridge is established.The gap element is used to simulate the collision between the abutment and the beam.The response spectrum analysis method and nonlinear time history analysis method are used to get the influences of the abutment-soil interaction on the dynamic characteristics and the seismic response of the bridges.The results have been shown that considering the abutment-soil interaction will increase the fundamental frequency of the bridge,and which will enlarge the overall stiffness of the bridge and will be also unfavorable for the bridge's force state under earthquake.Finally,two seimic methods are compared.Therefore,it is necessary to consider the impact effect of two ends of the beam when seismic analysis of long-span bridges is carried out.In the seismic design,the conclusions in this paper have a certain reference value for the same type of bridges and the nonlinear time history analysis method is a better way for seismic analysis of the bridges.