Research On Seismic Response And Seismic Isolation Analysis Of Small Radius Curved Beam Bridges

Small radius curved beam bridges are irregular bridge structures with extremely complex forces in plane and space.They have the characteristics of beautiful linearity,strong crossing ability,and strong adaptability,and often appear in urban viaducts and mountain highways.The biggest characteristic of this type of bridge is that the bending and torsion coupling effect is very obvious under strong earthquake action,resulting in extremely complex stress in plane and space,and it is easy to generate serious earthquake damage.Therefore,it is particularly important to study its seismic response under strong earthquake action,seismic mitigation and isolation analysis,and optimization of seismic measures.This paper takes a three span curved beam bridge with small radius in Chongqing as the research object,and uses Midas Civil finite element software to analyze its seismic response parameters and optimize seismic mitigation and isolation measures.The key work and conclusions are as follows:(1)Midas Civil bridge analysis software is used to analyze the dynamic characteristics of a small radius curved beam bridge.The effects of pile-soil structure interaction,curvature radius and pier on natural vibration frequency,natural vibration mode and mass participation coefficient of the structure are analyzed.It is found that when pile-soil interaction is considered,the low-order natural vibration frequency of the structure decreases obviously,while the high-order natural vibration frequency increases obviously.With the increase of curvature radius,the change of natural vibration frequency is obvious but nonlinear.The smaller the radius,the faster the increase of high order natural vibration frequency.With the increase of pier height,the natural vibration frequency of the structure shows a nonlinear change trend,and the natural vibration mode changes obviously.The lower the pier height is,the faster the natural vibration frequency increases,and the higher the pier height is,the slower the natural vibration frequency increases.(2)Using the time history analysis method,explore the seismic response of different seismic waves and input angles to key parts of the structure,and obtain the most unfavorable input angle of seismic waves.From this perspective,the effects of three factors,namely,pile soil structure interaction,radius of curvature,and pier height,on the seismic response of the structure are analyzed.It is found that the radius of curvature has a significant impact on the seismic response of the structure.The tangential internal forces of the structure are greater than the radial internal forces.The displacement of the pier top decreases with the decrease of the radius of curvature,and the displacement under the same radius of curvature decreases first and then increases;Considering the pile soil structure interaction,the displacement at the top of each pier increases significantly,and the variation of the internal force in each direction is more obvious than that of the displacement;The higher the pier is,the lower the internal force is,and the higher the pier top displacement is.(3)Explore the comparison of seismic reduction and isolation effects on small radius curved beam bridges after optimizing the parameters of different seismic reduction and isolation devices.As a result,it was found that a viscous damper with a damping index of 0.7 and a damping coefficient of 4000 k N-s/m is the structure that provides optimum seismic attenuation during strong earthquakes.When the lead core yield force of the lead rubber bearing is 384 k N,the structure can achieve the optimal vibration reduction effect under strong earthquake action.Through the comparison of seismic effects,it is found that both devices can achieve better seismic reduction and isolation effects.Overall,the effectiveness of viscous dampers is better than that of lead rubber bearings.(4)Explore the impact of the initial clearance of the stopper on the seismic reduction and isolation effect under the combined action of lead rubber bearings and anti falling beam devices.The results indicate that the joint analysis of the anti falling beam device using lead core rubber bearings combined with the initial clearance of the block is 0.08 m,which not only has better seismic performance in terms of internal force than the single use of viscous dampers,but also has a relatively significant impact on displacement.At the same time,it also reduces the engineering cost,providing a new idea for seismic measures of such bridges.