Seismic Control Of High-Speed Railway Continuous Beam Bridge Based On Composite Isolation System

For the high-speed railway bridge,the single isolation bearing can reduce the internal force of the bridge beam and increase the displacement of the main beam,which may have an adverse impact on the traffic safety of the train on the bridge.According to this,a composite isolation system is proposed in this paper,that is,by arranging isolation bearings and liquid viscous dampers at the same time to reduce the seismic input and control the displacement of the main beam,so as to control the vibration reduction of high-speed railway bridges.Taking a(45+70+45)m three span high-speed railway continuous beam bridge as the engineering background,considering the influence of rail restraints,the seismic control effect of composite isolation system based on lead rubber bearing and viscous damper,friction pendulum bearing and viscous damper is studied.The main research work is as follows:(1)Using Midas civil 2019 finite element software,the model of isolated continuous beam bridge with LRB and FPS is established.Discusses the isolation performance of high-speed railway continuous beam bridge when LRB and FPS is set alone.The results show that: LRB and FPS seismic isolation bearings can reduce the force of the pier,but at the same time will increase the displacement of the main beam,the increase is 75.4% and 68.2%.Moreover,the lateral damping effect of LRB and FPS is better than that of longitudinal bridge,and the fixed pier has better damping effect than the movable pier.(2)Considering the influence of orbit restrain,the influence of orbit restrain on the seismic response of LRB and FPS isolated continuous beam bridges is discussed.The results show that: After considering the orbit restrain,the overall seismic response along the bridge tends to decreaseand the transverse seismic response increases.Among them,The bending moment at the bottom of fixed pier is reduced by 78.22%,and the shear force at the bottom of fixed pier is increased by 99.67%.Transverse pier bottom shear the establishment of transverse pier bottom plays a decisive role in the seismic design scheme.Ignoring the orbit restrain will make the LRB isolation performance safer.It shows that the orbit restrain will increase the lateral seismic response of LRB Isolation continuous beam bridge and reduce the lateral damping effect of LRB isolation bearing.And the research on the LRB isolation performance needs to consider the influence of the rail constraints..After considering the orbit restrain,The seismic response of FPS isolated continuous girder bridge is reduced,and the maximum reduction is 98.22%.Due to the strengthening of beam track constraint,the longitudinal force of ballastless track consumes the seismic energy,which reduces the seismic response of piers,so the influence of track constraint cannot be ignored.(3)On this basis,The model of continuous beam bridge-track integration for high-speed railway with LRB and liquid viscous damper is established.The influence of the key parameters of the liquid viscous damper and LRB on the seismic response of the composite isolation system is analyzed and the optimal value is obtained.The results show that: Increasing the damping coefficient and velocity index of the liquid viscous damper can reduce the beam end displacement,the shear force of the fixed pier bottom and the bending moment of the movable pier.Increasingthe yield strength and initial stiffness of LRB can effectively reduce the displacement of the main beam and the longitudinal seismic response of the bridge pier,and increase the transverse seismic response of the bridge pier.However,increasing the yield ratio of LRB will gradually increase the beam displacement,and the seismic response of the bridge pier shows a downward trend,so the adverse effect of yield ratio on the beam displacement should be considered.For the research conditions in this paper,when the liquid viscous damper 3000～5000(/)dC k N m s?= ?,? =0.5～0.7,when the LRB yield strength is 400～500k N,the initial stiffness is 1000～1500MN/m,and the yield ratio is 6～15,the composite vibration isolation system has the best shock absorption control effect.(4)The model of continuous beam bridge-track integration for high-speed railway with FPS and liquid viscous damper is established.The influence of the key parameters of the liquid viscous damper and FPS on the seismic response of the composite isolation system is analyzed and the optimal value is obtained.The results show that: Increasing the damping coefficient and velocity index will reduce the displacement of the beam end and increase the bending moment at the bottom of the pier.However,increasing the yield stiffness of FPS will reduce the displacement of beam end and increase the displacement and internal force of bridge pier.The friction coefficient of FPS has a certain effect on the displacement of the beam end,the displacement of the pier,and the internal force of the pier.When the friction coefficient is a certain value,the displacement of the beam end,the displacement of the pier,and the internal force of the pier will suddenly change.Increasing the FPS curvature radius can improve the seismic capacity of the fixed pier.For the research conditions in this paper,when the liquid viscous damper 3000～5000(/)dC k N m s?= ?,? =0.5～0.7,when the yield stiffness of FPS is 500～1500MN/m,the friction coefficient is 0.12 and the curvature radius is 2～4m,the composite isolation system has the best damping control effect.