Influence of Track Support Stiffness of Ballasted Track on Dynamic Wheel-Rail Forces

Dynamic wheel-rail force can be limited to high-frequency components owing to imperfections in the wheel-rail contact surface ($P1$) and may also contain low-frequency components owing to coupled wheel-rail vibrations in phase on the ballast ($P2$). Previous studies on dynamic wheel-rail forces have focused on the quality index of surface roughness (QI) of only rail welds. In this study, the influences of rail surface roughness and track stiffness of a ballasted track on dynamic wheel-rail forces currently employed in high-speed lines were assessed by performing field measurements using actual vehicles running along the service lines. The theoretical dynamic wheel-rail force determined using a previous theory was compared with the dynamic wheel-rail force determined through field measurements. At a constant QI, an increase in the vertical track stiffness caused an increase in $P2$. Therefore, the vertical track stiffness affects $P2$ more strongly than $P1$. Hence, $P1$ is more affected by QI and train velocity than is $P2$. Further, it is inferred that the results of multiple regression analysis obtained using measured data such as QI, vertical track stiffness, and $P2$ can be used to predict the peak dynamic forces acting on ballasted tracks.