A Stochastic Traffic Flow Model For Long-span Bridge And Associated Loading Effects Based On Refined Cellular Automaton

Serving as the critical live load of highway bridges,the vehicle load plays a significant role in the design,operation,and maintenance of the bridge.With the development of national economy,the traffic volume increases continously,which brings a couple of serious issues including the overrun of bridge displacement and fatigue damage of structural component.Moreover,as the carrying capacity of the vehicle continues to increase,significant vehiclebridge coupling vibrations can be induced when the vehicle with heavy weight passes the bridge,which makes these issues even severer.Therefore,an accurate evaluation of the vehicle load is crucial to ensure the functionality and reliability of the bridge in service.In this thesis,a refined cellular automaton(RCA)traffic model is proposed based on microscopic traffic simulation theories,which is further incorporated into the static traffic-bridge(TB)system and the coupled wind-traffic-bridge(WTB)system.The proposed RCA traffic model and the numerical TB and WTB framework are further applied to a prototype long-span suspension bridge to evaluate the corresponding static and dynamic responses.The major contributions of the present study are as follows:(1)A RCA traffic model,which could describe the vehicular dimension,speed,acceleration/deceleration capability,and motion with sufficient accuracy,is proposed to overcome the limitations of the traditional cellular automaton(CA)traffic model commonly used in the bridge analysis.The effectiveness and accuracy of the proposed RCA traffic model are validated through comparison with the trafictional CA model.Additionally,the running characteristics of traffic flow with three typical densities in the RCA and CA model are studied.(2)Throuth the combination of RCA traffic model and in-situ monitoring data,a sitespecific stochastic traffic load is simulated,which is further applied to the prototype suspension bridge to investigate the static response of the bridge and the corresponding statistical characteristics.Moreover,the effects of vehicle weight limit on bridge static responses are studied,in which the importance of the vehicle weight limit is demonstrated.(3)The numerical framework of the coupled WTB analysis by incorporating the RCA traffic model is porposed,which is used to systematically evaluate the dynamic performance of the prototype suspension bridge under combined actions from wind and traffic loads.Later on,the advantages of RCA traffic model in describing wind-vehicle interactions in coupled WTB analysis are revealed,and a convenient approach is developed and validated to determine the suitable time duration for the coupled WTB analysis under RCA traffic model.(4)Finally,the effects of vehicle inertia force on the dynamic performance of the coupled WTB system are investigated at the traffic level for the first time.The dynamic responses of the vehicle-bridge system under various traffic conditions with and without considering the vehicle inertia force are presented in details.