The Analysis On Dynamic Responses Of Highway Pier Due To Vehicle Impact

The impact of vehicles and piers is common,and the consequences are often more serious,so it is urgent to study the dynamic response of piers affected by vehicles.This paper mainly uses finite element technology to study the impact problem between vehicle and pier.Taking a bridge of Zhengzhou fourth Ring Line as the engineering background,the finite element model of the bridge is established by using ANSYS/LSDYNA software.The F800 biaxial truck,C2500 pickup truck and HGV heavy truck developed by the bridge are selected as the vehicle models to discuss the dynamic response of the pier to impact.The main work and conclusions are as follows:(1)On the basis of finite element technology,a simply supported beam bridge model is established by ANSYS/LS-DYNA,and the relevant modeling details of the vehicle-bridge coupling model are described to establish the finite element model corresponding to the drop hammer test in [1] literature.Thus,the rationality of material constitutive of vehicle-bridge coupling vibration analysis model is verified.The results show that the stress characteristics of concrete structure can be accurately simulated by selecting suitable material constitutive,collision contact algorithm and mesh size.(2)In order to compare the difference of the dynamic response of the pier after the impact of the vehicle when the pile-soil action is considered and not considered.The pile-soil models of 3 times,5 times and 8 times depth were established by equivalent embedded method,and two kinds of pile-soil models were established by equivalent spring method and finite-area soil method.In addition,the bottom of the pier is consolidated,that is,the consolidation model of the pier bottom without considering the action of pile and soil is established.The vehicle impact velocity is 60 km/h、80km/h and 100 km/h,respectively.The vehicle weight is 8t、10t and 12 t.The results show that the dynamic response of the pile-soil model and the consolidation model is quite different,and the calculation results are not conservative without considering the pile-soil action.At the same time,At the same time,there are some differences between the results of each pile-soil model.From the point of view of engineering design,it is recommended to use 8 times embedded model to calculate.In terms of calculation accuracy,finite domain soil model,equivalent spring model and 3 times embedded model are close.(3)A simplified single pier model is established,and the parameters are analyzed from two aspects: vehicle and pier.Vehicle parameters are: truck car cargo stiffness,impact eccentricity and vehicle type.The pier parameters are: pier diameter,pier height,pier section shape,longitudinal reinforcement ratio and stirrups spacing.The results show that :1)The local peak value of impact force caused by the stiffness of carriage cargo is affected by impact velocity.when the impact velocity is equal to 100 km/h,increasing the cargo stiffness does not cause a significant increase in the local peak.However,when the velocity increases to 120 km/h,the peak value of local impact force caused by the cargo becomes significant,and the increase of the vehicle weight becomes more significant.2)The impact effect of each vehicle eccentricity is very different,this is because the impact effect will be different under each eccentricity condition.3)C2500 impact effects of pickup trucks,F800 trucks and HGV heavy trucks are different,and this difference is more obvious with the increase of impact velocity.4)The diameter of the pier directly affects the bearing capacity of the pier,reducing the height of the pier,increasing the reinforcement ratio of the longitudinal reinforcement and reducing the spacing of the stirrups can improve the bearing capacity of the pier.In addition,the failure modes of square and circular section piers are similar after impact,and the shear failure is mainly in the collision position.