Dynamic Response And Impact Factor Analysis Of Variable-section Continuous Box Girder Bridge Under Vehicular Loading

In recent years,our country has seen rapid economic development and significant improvements in people’s quality of life,and the traffic infrastructure has improved significantly.However,with the increase of highway traffic density and vehicle load,the bridge deck pavement and bridge structure will be gradually damaged under the long-term impact of vehicle loads,which will greatly reduce the safety of the bridge in use,especially when the vehicle load is overloaded and speed conditions,vehicle and pavement and bridge coupling vibration damage effect is more obvious,but also produce resonance phenomenon,which further This will further exacerbate the dynamic response of the pavement and bridge,causing damage or destruction of the bridge deck pavement,and in severe cases even lead to bridge collapse,causing a major impact on traffic safety.This thesis focuses on a continuous box girder bridge with varying cross-sections spanning three spans from Beijing to Qinhuangdao.The vibration characteristics of the bridge structure were analyzed by establishing a three-dimensional finite element model.Additionally,the vehicle was modeled using UM software,and the bridge model from ANSYS was imported into UM to construct a coupled dynamic model of vehicle-pavement-bridge.The dynamic characteristics of the bridge deck pavement and the bridge structure under vehicle loads were studied and analyzed.The specific research content is as follows:(1)A three-span variable section continuous box girder is the subject of research,and a three-dimensional model including the bridge deck slab and bridge superstructure is constructed in ANSYS according to the actual design drawings,and a comprehensive fixed-modality analysis is carried out to determine the bridge’s self-vibration characteristics.(2)A coupled vehicle-bridge pavement dynamics model was established in UM software and the effects of different vehicle speeds,different loads,and different travel positions on the dynamic response of the bridge deck pavement under a single vehicle load,with bridge deck unevenness as the excitation,were analysed.(3)In addition,a fleet load model and a vehicle braking model were created in the multi-rigid body dynamics software to analyse the influence of the number of transverse lanes,the number of longitudinal vehicles,the distance between longitudinal vehicles and the initial braking speed,bridge deck irregularity,braking position and braking deceleration on the bridge on the fleet load.The effects of braking speed,deck irregularity,braking position and braking deceleration on the dynamic response of the bridge were analysed.(4)The vehicle jump model was created by incorporating the impact effect of the vehicle jump.Study the variation law of bridge dynamic response and impact coefficient for different jump height,jump speed and jump position.The study shows that the dynamic response of the bridge deck pavement increases significantly with increasing vehicle load under the influence of the vehicle-pavement-bridge coupling dynamics.In addition,the longitudinal,transverse and shear stresses in the deck pavement tend to increase with increasing vehicle load and tyre stiffness.The shear stresses in each layer of the pavement are much greater when the vehicle is travelling off-load than when the vehicle is travelling centrally.Under fleet loading,the greater the number of transverse loading lanes,the greater the dynamic impact coefficient,the greater the number of vehicles in the longitudinal direction of the fleet,the smaller the dynamic impact coefficient,and the greater the longitudinal spacing of the vehicles,the smaller the dynamic impact coefficient.The power response of the bridge in the braking state is significantly greater than that of the vehicle at constant speed,and the power impact coefficient is greater when the vehicle is braking in the first half of the bridge mid-span than in the second half of the bridge;the power response and impact coefficient of the bridge mid-span section increase significantly when the vehicle is under the effect of jumping impact,and the bridge power impact coefficient is the largest when the vehicle is jumping in the mid-span.