Thermal response of the bridge supported longitudinal CRTS II slab track subject to diurnal temperature variation

•Two 1:4 geometrical scaled models with fixed and free boundary conditions under a cyclic temperature test were conducted.•The heat transfer under the fixed boundary condition could be accelerated from the track slab to the CAM layer.•The heat transfer models of two scaled models are verified by the temperature and stress results of cyclic temperature tests.•The positive and negative cyclic temperature zone could produce a larger interlaminar displacement between track slab and CAM.•The large cyclic temperature amplitude in slab strack leads to larger internal temperatures, stresses and vertical displacement. As a kind of multi-layer concrete structure, thermal responses China Railway Track System type II (CRTS II) slab track subject to diurnal temperature variation could significantly affect its long-term structural performance of slab track, and ultimately the safety of the high-speed train. However, the thermal responses of the bridge supported longitudinal CRTS II slab track have not been fully understood due to the complex of the structural system. The purpose of this study is to systematically investigate the thermal responses of the bridge supported CRTS II slab track system by conducting experimental testing on the scaled models with different boundary conditions in conjunction with theoretical modelling. The results show that the boundary conditions of the CRTS II slab track haveasignificantinfluenceon thermal responses of the slab track. For example, the heat transfer from the track slab to the cement asphalt mortar (CAM) layer could be accelerated under fixed boundary condition. In addition, the longitudinal thermal stress within the CRTS II slab track under the fixed boundary condition is higher that under free boundary condition. Importantly, it indicates that the vertical thermal gradient in the CRTS II slab track induced by the diurnal temperature variation could lead to the damage of the interface between the track slab and CAM.