Pounding Effects And Buffer Measures Of Superstructure Segments In Isolated Multi-coupling Bridges During Earthquakes

In the thesis,the nonlinear seismic response of isolated multi-coupling bridges in high-intensity earthquake area is evaluated,considering the pounding of superstructure segments by contacting elements.Comparing no pounding?bilateral pounding with unilateral,The influence of adjacent pounding effect on seismic response of isolated multi-coupling bridges is invested.With the ordinary bearings instead of isolation bearings,the effects of bearings on pounding are studied.In addition,the effects of different influence parameters of pounding:initial gap,pounding stiffness and damping on pounding between adjacent beams are analyzed.Finally,the buffer measures are set up between adjacent beams,including rubber cushion,limiting devices and shock absorbers.Comparing the effects of different buffer devices,the seismic performance of the structures are optimized.The results indicate:1.Strong longitudinal earthquakes can lead to large displacements and relative displacements of girders,causing pounding of adjacent girders at the movement joints due to the using of High-Damping Rubber Bearings(HDR)and Friction Pendulum Bearings(FPB).Pounding can reduce relative displacements of girders.Compared with the bilateral pounding,the unilateral pounding is more harmful to the bridges.The pounding is not harmful to the bridge piers,and the isolation bearings can play a good role in the pounding of the adjacent beams.2.The isolation bearings does not obvious increase the maximum pounding force between adjacent beams,but will significantly increase the number of pounding between adjacent beams.Using ordinary bearings,pounding effects will transfer to the piers,the bridges shows high independence and integrity,separated by expansion joint;Using the isolation bearings,pounding effect of main girders will not transfer to piers of substructure,superstructure and substructure has strong independence.3.For the initial gap,increasing initial gap of adjacent girders can effectively reduce the number of pounding,but may increase the maximum pounding force,pounding frequency and the maximum pounding force of adjacent expansion joints;will increase the relative displacement of main girders.increasing the pounding stiffness will not change the number of pounding,but will significantly increase the pounding force;without affecting of adjacent expansion joints pounding frequency and maximum pounding force.For the pounding damping,the pounding damping is not sensitive to the number of pounding and the displacement of the main girders.When the damping is small,the effects of pounding damping on the maximum pounding force and the relative displacement of the main girders are not obvious.When the damping is large,them will increase monotonically with the pounding damping.4.The rubber pad increases the number of pounding,but can significantly reduce the pounding force,and effectively buffer the pounding,can not significantly reduce the displacement and relative displacement of the main girders.By installing a buffer rubber pad,the combination of larger clearance and large rubber pad stiffness should be adopted.In addition,a smaller clearance with a smaller rubber pad stiffness can be used.The installation of the limiting to reduce the number of collisions increases the number of pounding,but do not change the maximum pounding force.The limiter can not significantly reduce the displacement of the main girders,but can significantly reduce the relative displacement.The installation of the damping device increases the number of pounding,but can significantly reduce the pounding force,and the decrease amplitude is much larger than the installation of rubber pad;displacement of the main girders can be significantly reduced,more significantly reduce the relative displacement than the limiting measures.In addition,the seismic response of the first bridge piers are significantly reduced.