Study On Pounding Effect Of Long-span Rigid Frame Bridge With High Piers And Multiple Approach Bridges Under Earthquake

With the intensification of China’s infrastructure construction,more highways and railways have been extended to the western region.Long-span rigid frame bridge with high piers have been widely used in western highway construction due to their unique advantages of crossing high mountains and deep valleys.However,the frequent occurrence of earthquakes in the western region has also brought many difficulties and challenges to the design of high-pier long-span bridges.Combined with previous earthquake damage,it is shown that high-pier long-span continuous rigid frame bridges are prone to collision damage between adjacent beams.Collision is a highly non-linear behavior,and there are many influencing factors accompanying in the simulation process.Therefore,in combination with the existing research foundation,this paper takes the typical long-span rigid frame bridge with high piers in southwest China as the research object,considers the collision effect between beams,analyzes the impact of collision behavior on the bridge structure,and summarizes the general Sexuality.The main research contents are as follows:(1)Summarize the current status of seismic research on long-span rigid frame bridge with high piers at home and abroad,and focus on the study of the impact of beams between expansion joints,and consider the effect of water on the structure during numerical simulation,and summarize the dynamic water pressure.The results will lay the foundation for further research.(2)Using a typical long-span rigid frame bridge with high piers in southwest China as the engineering background,use Open Sees to establish a finite element analysis model of the whole bridge;input seismic waves,and consider the main bridge pier and both sides of the main bridge Fluid-solid coupling effect of transition pier and nonlinearity of pier column.The results show that considering the effect of water on the structure,the seismic response is obvious.Especially under the condition that there is water inside and outside the hollow pier,the fluid-solid coupling effect is more obvious.(3)Considering the collision effect between beams,a collision element is set at the expansion joint to analyze the collision seismic response of the whole bridge model.The results show that considering the collision effect at the expansion joint is beneficial to the main bridge pier.Couclusions as below: the bending moment and shear force of the main pier on both top and bottom are reduced accordingly;the bending moment and shear force of the transition pier on both top and bottom changed not significantly;collision will have a greater impact on the bearing displacement at each transition pier and increase the possibility of falling beams at the transition pier of the approach bridge.(4)Based on the results of the collision analysis,select the stiffness of the collision and the initial clearance for parameter analysis,and analyze the law of changing the response of these parameters to the earthquake.The results show that the change in collision stiffness will significantly change the collision force at each expansion joint,and the peak value of the collision force increases with the increase of stiffness;the change of stiffness has a small effect on the force of the main bridge pier;the increase of stiffness will significantly increase the forward displacement of the support,especially the transition pier support of the right approach bridge and the right abutment support,which will increase the risk of falling beams.The change of the initial gap will affect the collision force at each expansion joint,and the peak of the collision force will decrease with the increase of the initial gap;the change of the initial gap will have a smaller effect on the force of the main bridge pier;narrow gap will be significant increasing the forward displacement of the support in the forward direction of the bridge,especially the positive displacement of each transition pier support of the right approach bridge and the right abutment support.Finally,some suggestions are provided for the design values of the collision stiffness and initial clearance according to the obtained laws.