Analysis On Wind-Vehicle-Bridge Interacted Vibration For Long-span Cable-stayed Bridge

Long span bridges exhibit special characteristics such as high flexibility and low structural damping, which are very susceptible to wind actions. This paper consists of the following four parts:Firstly, it retrospects the current development situation of the long-span cable-stayed bridge and introduces roughly the Anqing Yangtze River Railway Bridge. The paper also reviews briefly the research actualities of the coupling vibration of train-bridge system and vibrations of long span bridges caused by the wind and the action of the wind on vehicle as well as the current situation of coupling vibration of train-bridge system suffered from wind. It expounds the significance and necessity of analyzing and studying the interactive and coordinating coupling vibration system that unifies the wind, vehicle and the bridge.Secondly, it applies dynamics of the bridge, dynamics of the vehicle and the principle of interaction between wheel and track, adopts an inter-system iteration solution for vehicle-bridge coupling model. By applying a modal superposition technique, the dynamic mode of wind—train—bridge system is established and the coupled equations of motion are efficiently solved.Thirdly, based on the mechanism of the coupling interaction of the wind, the vehicle and the bridge, it uses a simplified method of founding three-dimensional fluctuating wind of long-span bridge by analyzing the properties of fluctuating wind. An efficient method, which is featured mainly by a combination of finite element approach and pseudo-excitation method in the frequency'domain, is proposed to simulate the wind velocity field for the bridge. The proposed method is developed specifically for generating the span—wise turbulent wind velocities at the locations equally distributed along the bridge deck at the same elevation. The inverse FFT is carried out to enhance further efficiency of computation.Finally, based on the engineering background of Anqing Yangtze River Railway Bridge, the paper simulates the whole course of the trains passing through the bridge under the action of fluctuating wind, calculates every dynamic responses of the bridge and vehicle, analyses comparatively the effects of wind speed, train speed on the system vibrations by multi-operating method and evaluates the vibration performance of the vehicles passing on the long-span bridge under the action of wind load. Moreover, it calculates impact of the lateral wind pressure acting on the moving car body on the bridge.Major conclusions can be drawn as follows:1) The fluctuating wind greatly affects on the bridge. The lateral displacement responses of the bridge are mainly controlled by wind load. The vertical displacement responses of the bridge are mainly controlled by the running trains. However, as the mean wind speed increases, this controlling force relatively decreases.2) The impact of the lateral wind pressure, which is acting on the train vehicles on the bridge structures, is very large. It is an important factor that causes the lateral displacement responses of the bridge.3) The wind forces have great influences on the dynamic responses of the running train vehicles. The security of the train is threatened as the mean wind velocity is over 20m/s.4) Generally, the response of the bridge and train vehicles increases with the mean wind speed.