Study On Influence Of Nonlinearity Of Bridge And Vehicle Models In Vehicle-Bridge Coupling Analysis

The safety and comfort of vehicles running on long-span bridges has always been a hot spot in the field of bridge dynamics research.In the past,vehicle-bridge coupling analysis generally used linear vehicle models and bridge models,and carried out dynamic solutions based on the step-by-step integration method of linear systems.In fact,both the vehicle subsystem and the bridge subsystem contain various nonlinear factors,which affect the dynamic response of the vehicle-bridge coupling.In order to correctly evaluate the influence of various nonlinear factors of the vehicle and the bridge on its dynamic response in the vehicle-bridge coupling analysis,the following research work is carried out in this thesis:The safety and comfort of vehicles running on long-span bridges has always been a hot spot in the field of bridge dynamics research.In the past,vehicle-bridge coupling analysis generally used linear vehicle models and bridge models,and carried out dynamic solutions based on the step-by-step integration method of linear systems.In fact,both the vehicle subsystem and the bridge subsystem contain various nonlinear factors,which affect the dynamic response of the vehicle-bridge coupling.In order to correctly evaluate the influence of various nonlinear factors of the vehicle and the bridge on its dynamic response in the vehicle-bridge coupling analysis,the following research work is carried out in this paper:(1)The nonlinear problems existing in the vehicle subsystem and bridge subsystem in the vehicle-bridge coupling analysis are described;for vehicle nonlinearity,three vehicle models are established: linear vehicle,geometric nonlinear vehicle,and suspension nonlinear vehicle;for bridge nonlinear Linearity,established a bridge dynamics analysis model,a bridge dynamics analysis model considering geometric nonlinearity and large displacement nonlinearity;Numerical iteration method for the problem—Newton-Raphson iteration method.(2)Based on the MATLAB platform,the vehicle-bridge coupled dynamics analysis program VBIP is developed.This program has the functions of static analysis,modal analysis,and transient analysis,and has two modules: linear vibration solution and nonlinear vibration solution of vehicle-bridge coupling.Then,through many examples,the effectiveness of VBIP for vehicle nonlinear analysis and bridge nonlinear analysis is verified.(3)Research on the influence of vehicle nonlinearity on vehicle-bridge coupling analysis based on VBIP: with the help of three vehicle models: linear vehicle,geometric nonlinear vehicle,and suspension nonlinear vehicle,the vehicle-simply supported beam bridge under the excitation of road surface roughness is carried out.Coupled vibration analysis,coupled vibration analysis of vehicle-simply supported beam bridge under impact force of vehicle jump,coupled vibration analysis of vehicle-cable-stayed bridge under impact force of vehicle jump,bridge dynamic response,vehicle dynamic response,vehicle Running comfort was analyzed.The research results show that the nonlinearity of the vehicle should be regarded as an important factor affecting the results of the vehicle-bridge coupling analysis,especially when the vehicle jumps,the impact of its nonlinear characteristics on the vehicle-bridge coupling vibration will become more significant.In the coupled vibration analysis of the vehicle-simply supported girder bridge,considering the nonlinear characteristics of the vehicle suspension system,the maximum vertical displacement of the bridge mid-span increased by 111.48%,and the maximum vertical acceleration of the vehicle body increased by 20.35%.Such non-linear effects significantly reduce the driving comfort of the vehicle.(4)Based on VBIP,the influence of bridge nonlinearity on vehicle-bridge coupling analysis is studied.In this study,under the excitation conditions of different vehicle models,vehicle speeds and road surface roughness,the influence of bridge nonlinearity on the analysis of vehicle-bridge coupled vibration is analyzed,and the comfort index of the vehicle is evaluated.The results show that the influence range of the nonlinearity of the bridge on the maximum vertical displacement of the bridge mid-span is between-2%and 3%,and the influence on the vehicle comfort is very small.When considering the nonlinear factors of the bridge,the 1/3 octave band acceleration was used to evaluate the vehicle comfort,and the vertical acceleration of the vehicle body did not exceed the comfort reduction limit under each working condition.(5)The effects of vehicle nonlinearity and bridge nonlinearity on bridge dynamic response,vehicle dynamic response,and vehicle operating comfort are summarized.It also summarizes the limitations of this study and the key issues that need to be solved urgently.