Vibration Theory And Numerical Study On A Railway Simply Supported Bridge Under Moving Loads

With continuous increase of train speed and vehicle load, the dynamic interaction between railway bridges and moving trains is paid more and more attentions. However, the establishment of a complicated vehicle-bridge model needs a lot of parameters of real train vehicles, rails, and tracks. Besides, high theoretical quality of analysts is also needed to apply the theories of structural dynamics, vehicle dynamics, finite element methods in modeling and programming, which are not easy to be accepted by engineers, thus limiting the application of the complicated vehicle-bridge model.This paper establishes a simple vehicle-bridge model to study a railway simply supported beam under moving vehicles. The bridge is modeled by the modal superposition technique, while the vehicle is simulated by a moving distributed mass with stiffness. The dynamic equilibrium equation of the bridge under moving vehicle is deduced, and compared with that of under a moving wheel and sprung mass, and under a complicated vehicle with a multi-degrees-of-freedom system composed of rigid-bodies connected with spring-and-dashpot suspensions.Taking a simply supported bridge with the span length of32m located in the Beijing-Tianjin high-speed railway as the engineering background. A3-D FE model is established with the help of ANSYS firstly. Then the three above-mentioned vehicle models are used to simulate the whole history of the German ICE-3high-speed train passing through the bridge. Dynamic responses of the bridge are computed and compared. The serviceability and feasibility of the simple vehicle-bridge model established in this paper are studied by changing the train speed, the ratio of the mass of the vehicle and bridge, and the ratio of stiffness of the vehicle and bridge. Numerical results indicate:(1) As the train speed increases, the fluctuation of the bridge vertical displacement amplitude is not significant, while the vertical acceleration amplitude has an increasing trend.(2) With the ratio of stiffness of the vehicle and bridge increases, the bridge vertical displacement amplitude decreases slightly, while the bridge vertical acceleration amplitude increases as the stiffness of vehicle increases.(3) With the ratio of mass of the vehicle and bridge increases, both the bridge vertical displacement and acceleration increase significantly.(4) The amplitudes of the dynamic responses of the bridge, including the vertical displacement and acceleration, are very close to each other by using the three vehicle models, indicating that the numerical method proposed in this paper can be used to predict very efficiently the dynamic behavior of coupled train-bridge systems with reasonable computational effort.