Investigating the wheel–rail dynamic response of transition system of concrete slab and ballasted tracks through train–track interaction model

One of the inevitable places where the railway track stiffness suddenly changes is the junction points of the slab and ballasted tracks. In these junction areas, differences in the vertical stiffness of the track cause an increase in wheel–rail contact forces that lead to some crucial damages in railway tracks such as rail defects, hanging sleepers, permanent deformations, asymmetric settlements, and decreasing passenger comfort. So, the wheel–rail contact issue plays an important role in the dynamic behavior of the railway transition areas. Therefore, recognizing the wheel–rail forces variation along the railway slab-ballasted transition zone, which accounts for one of the main parameters in transition zone design, is investigated in the current study. For this purpose, a train–track interaction model is established to determine the wheel–rail contact forces on the slab-ballasted transition zone. In this model, the vehicle is considered as a moving car body with two-axle bogies and the railway track, including the slab and ballasted tracks, built based on the finite element method. Then, the influence of the step-by-step change in track stiffness along the slab-ballasted transition is investigated to improve the dynamic performance of the railway transition zone from the viewpoint of wheel–rail contact forces. The effect of gradual consistency in the track stiffness along the transition zone and the effect of the transition length in the wheel–rail dynamic behavior have been studied by performing different sensitivity analyses. The results show that the optimal number of track stiffness changing steps in the transition zone is 4-step and the transition zone with 20–25 m length concludes appropriative performance in terms of the dynamic responses.