Fatigue Life Prediction Of Steel Bridge Considering Vehicle-bridge Interaction And Stochastic Traffice Load

Vehicle load is the main factor that causes the fatigue damage of bridge structures.Combined with stochastic traffic load based on the measured traffic data,the accurate prediction of the fatigue life of highway steel bridges considering vehicle dynamics,bridge dynamics and the deterioration of pavement roughness is a valuable research issue at present.In order to quantify the impact of these two factors on the performance of steel bridges,the following research work is carried out:(1)The research background of highway steel bridges' fatigue problem is briefly introduced.The research content of vehicle-bridge interaction problems and its current research results are summarized and analyzed.Besides the development history of study on fatigue problems is reviewed.Finally,several common evaluation methods of fatigue performance are briefly introduced.(2)The common vehicles in highway bridges are classified based on the data of traffic load survey.The corresponding vehicle dynamics analysis models is established.According to the generalized principle of virtual work,the mass matrix,damping matrix,stiffness matrix in the dynamic equations of each vehicle model are theoretically derived.(3)To solve the vehicle-bridge coupling vibration problem,the analysis model of vehiclebridge interaction is established by contact force method.After determining relevant parameters,the corresponding finite element models of vehicle in dynamic analysis is established.The influence of road roughness deteriorating with time is introduced into the analysis model.With contrastive analysis of two time-domain integral methods for solving dynamic problems,the more suitable method of solving the vehicle-bridge coupling vibration problem in this thesis are selected.(4)The fatigue detail of the highway steel bridge studied in the thesis is confirmed.The corresponding multiscale finite element model with beam element,shell element and solid element is built.In order to improve the consistency between the finite element model and the actual engineering structure,the finite element model is updated with the natural vibration frequency as the structural response and the elastic modulus of the finite element model as the design parameters,combined with the response surface method and genetic algorithm.The natural frequency of the updated finite element model is more consistent with the measured data.(5)The distribution characteristics of traffic flow variables are analyzed,and the stochastic traffic flow loads in the whole life cycle of the truss bridge are generated using the Monte-Carlo method.The fatigue life of steel bridge structure is predicted by considering the deterioration of pavement roughness and stochastic traffic load in its whole life cycle.The coupling vibration effect of vehicle-bridge,the deterioration of road roughness and the effect of stochastic traffic load on the fatigue performance of the structure are compared and analyzed.