The movement of railroad ties: Simulation and field validation

The railroad tie is an important component in track structure which provides lateral resistance, continuous support for rail and transfers the train load to ballast. The movement of the tie subject to train loading is usually considered as a vertical motion. However, it is believed that the real-world tie movement is not only translational but rotational due to moving load. In order to investigate the real movement of railroad ties, a train-track interaction computer program was used. The computer program includes a vehicle dynamics model and 3-D Finite Element (FE) track model. The wheel-rail contact forces were obtained from the vehicle dynamics model, and then input to FE track model to simulate the tie movement. Furthermore, the field validation was conducted at Northeast Corridor (NEC) in United States. The measuring units were mounted on the edge of ties to record the angle and acceleration change of the tie in three orthogonal directions. The data analysis showed that the fieldmeasured translational and rotational movement of ties have good agreement with the simulation results. It is concluded that the tie movement is not only up-anddown motion under moving train load, but also comprises rotation and lateral movements.