3D Vehicle-Highway Bridge System Based On Cellular Automaton Traffic Flow Simulation

The vehicle-bridge system is different to the train-bridge system because: 1) many vehicles travelling on the roadway bridge will be randomly distributed on the bridge, while either one or two trains travelling on a railway bridge will be uniformly distributed, 2) the width of the roadway bridge is larger than that of a railway bridge, hence the mechanical characteristics of a roadway bridge will not be similar to those of a beam. The paper initially proposes an analysis method, which can be applied for vehicle-bridge coupling vibration analysis, providing guiding significance for the road-bridge design. In addition, this paper originates from the National Natural Science Foundation of China(51208125), and the proposed approach is important for reflecting the dynamic response of vehicle-bridge coupled system induced by traffic flow. The main content of this paper is as follows:Cellular automation(CA), a microscopic scale traffic flow simulation model, which is widely used in the transportation field, was introduced in the simulation of traffic flow. Drivers Driving Behavior(acceleration, deceleration, braking, lane changing, etc.)and road traffic safety norm(safety distance, vehicle speed limit, the minimum speed limit of the highway, etc.) were considered in the model. Traffic flows under various traffic occupancies were present. Comparing with the real traffic flow photo collected on a highway, the proposed method was verified.Based on the sinusoid superposition method, a approach to simulate 3D numerically stochastic signals excited by road irregularities was provided, proceeding from space road spectrum, based on 2D road surface spectrum model. The simulated road irregularities acted as an input to the bridge-vehicle model.The project initially proposed a numerical method, which was found very practical to analyze the vehicle-bridge coupling vibration. The FEM software ANSYS was utilized to model the vehicles and bridges. APDL program could effectively assist modelling the behavior of bridges traversed by stochastic traffic flow. In ANSYS model, vehicle model and bridge model were independent. A concrete continuous box girder bridge was took as an example. The effects of factors were studied. The paper systematically discussed factors that.influenced the vibration response of vehicle-bridge system, including road roughness, density, speed limit. The result of investigation demonstrates: comparing 2D vehicle-bridge system, the impact coefficient of the bridge was smaller in the 3D vehicle-bridge system; for higher traffic occupancies, the displacement of bridge was higher; for lower traffic occupancies, the displacement of bridge was lower.A general framework for investigating the variation of natural frequencies of a roadway bridge under stochastic traffic flow(the on-load frequencies of bridge) has been developed. The results showed that the on-load frequencies of the bridge were less than the corresponding natural frequencies of the bridge. In general, the natural frequencies decreased as the values of the traffic density increased.