Effects of Contact Loss underneath Concrete Roadbed on Dynamic Performances of Slab Track-Subgrade System

ANSYS/LS-DYNA, a large general finite element software, was used to establish a vertical vibration model for vehicle-track-subgrade coupling system, and the dynamic responses of a vehicle-track system caused by contact loss underneath concrete roadbed were analyzed. The research results show that contact loss length less than 3.125 m (corresponding to a contact loss area of 10 m2) has a negligible effect on the dynamic responses of a vehicle-track system. The dynamic responses of the vertical displacement of rail and vertical accelerations of bogie and car body will increase significantly when the contact loss is longer than 3.125 m, being unfavorable to the ride comfort and safety, so contact loss length underneath concrete roadbed should be less than 3.125 m.