Dynamic Response And Probabilistic Safety Assessment Of Vehicle-Bridge System Under Correlated Wind-Wave Action

With the extension of railway network from inland to coastal areas,an increasing number of high-speed railway bridges have been built in sea-crossing environments.As the main environmental factors acting on the vehicle-bridge system,crosswind and waves will directly affect the vehicle safety and driving comfort of the vehicle-bridge system.On the one hand,the wind and wave fields are usually assumed to be independent,while the correlation between them is ignored.Meanwhile,the influence of the wind field boundary is often ignored in the aerodynamic studies for vehicle-bridge system.Few research has been conducted on the aerodynamic characteristics of vehicle-bridge under wind and wave action.In addition,due to the calculation efficiency of vehicle-bridge coupled vibration,it is difficult to conduct probabilistic safety assessment and give the safety threshold.Therefore,this paper mainly focuses on the aerodynamic characteristics of the vehicle-bridge under the marine environment,the correlation between wind and waves,the vehicle-bridge response under different return periods,the prediction model for the vehicle-bridge random respons,and the wind-wave threshold of safety driving.(1)Accroding to the stochastic process,the time history of fluctuating wind and track irregularity are simulated.Based on the characteristics of train bridge interaction and the integration theory of elastic body in multi-body system,the coupling of train bridge system is realized according to the deformation coordination conditions and force balance conditions of track and bridge,and the joint simulation calculation model is established.(2)Considering the test conditions and the parameter characteristics of the research object,the scale ratio of the vehicle-bridge model is determined.Aerodynamic tests under the influence of different wave parameters,clearance heights,vehicle positionand wind attack angle were carried out in the wind tunnel and wave flume joint laboratory.The force characteristics of vehicle-bridge system under the action of cross wind and wave surface are studied,and the influence laws of various environmental factors on the aerodynamic characteristics of vehicle-bridge system are analyzed.(3)Based on Copula theory and the measured data,three two-dimensional joint distribution models of wind speed and wave height is established,and the goodness of fit of the alternative models was evaluated.According to the characteristics of the two-dimensional distribution model,the wind speed and wave height combinations under different return periods were obtained.The crosswind load and wave force of vehicle-bridge system are calculated.The dynamic response of vehicle-bridge system under different return periods is studied.(4)By comparing the characteristics of the accept-reject method,M-H sampling method,and Gibbs sampling method,the Gibbs sampling method based on the MCMC method is used to obtain several samples as input parameters for the calculation of vehicle-bridge coupling response.By training and testing the samples through machine learning,the dynamic response computational efficiency of the vehicle-bridge system under wind and wave is significantly improved.The prediction model is used to predict and analyze the vehicle-bridge dynamic response,and the influence of wind and wave action is further studied.(5)According to the limit standard of vehicle-bridge response index,the critical state of safety driving under wind and wave are determined.Combined with the specific characteristics of the wind-wave bridge system,the "central domain" probability assessment method is proposed for the vehicle-bridge system.According to the safety driving probability surface,the driving safety of high-speed railway bridges is systematically evaluated and the threshold value for the safety driving is given.