Numerical analysis of interface damage in ballastless track on simply supported bridge due to thermal and vehicle dynamic load

Abstract

The stiffness, mass and damping matrix of 17 degree of freedom (DOF) vehicle model are derived on the basis of Lagrange equation. The bilinear discrete cohesive zone model (DCZM) is utilized to simulate the bonding performance of the interface between the track slab and the CA mortar layer. The ballastless track-bridge element model is proposed by the direct stiffness method, and the vehicle-ballastless track-simply supported bridge vertical-longitudinal coupled model with consideration of interface damage is established. In addition, based on the ballastless track-bridge element model, the ballastless track continuous welded rail (CWR) model on multi-span simply supported bridge is proposed. The ballastless track CWR model is employed to obtain the initial longitudinal relative displacement of track slab-CA mortar layer interface under bridge thermal load. The displacement response of ballastless track-bridge structure is taken as the initial displacement field of vehicle-track-bridge coupled dynamic model. The vehicle-track-bridge coupled model is adopted to obtain the interface damage of ballastless track under the action of bridge thermal load and vehicle dynamic load. Then, the effects of bridge temperature and longitudinal stiffness of the DCZM on the longitudinal relative displacement of ballastless track-bridge structure are investigated in detail. The mechanism and distribution law of interface damage of ballastless track under different running speeds, CA mortar layer gap length and DCZM parameters are discussed. The conclusions obtained in this paper could provide a technical guide for the formulation of maintenance standards for interface damage of ballastless track on simply supported bridge. Then, some parametric studies are presented based on the model in this paper. The analysis indicates that the longitudinal relative displacement of the track slab-CA mortar layer becomes large at both ends and small in the middle within the range of a simply supported bridge. When there is CA mortar layer void, the ballastless track interface is in the stress state of tension + shear mixed mode. The recommended threshold of void length of CA mortar layer is 0.65 m. More attention shall be paid to the construction quality of interface between the track slab and the CA mortar layer.