Numerical Analysis On Track Slab Damage Of The CRTS Ⅲ Ballastless Track Under Temperature Loads And Vehicle Loads

With the increase of operation mileage and service time of China’s high-speed railways,various damage and fracture behaviors of ballastless track has appeared gradually on the operating high-speed rail.They can be classified to two problems: cracking of structure or components,interfacial failure of interlayer connections.As we known,the CRTS Ⅲ slab ballastless track is independently developed by CREC based on the application experience and extensive research of the other slab ballastless track,which has intellectual property rights.The CRTS Ⅲ track slab is made of reinforced concrete with different strength in tension and in compression,and the micro cracks easily occurs when it is acted by overall cooling or negative temperature gradient loads.Once the cracks appear in the track slab,the weathering in the air will lead to the exfoliation of the concrete cement.In addition,the infiltration of rain would increase stress level of the crack tip rapidly,which can speed up the deterioration of the track structure and then affect remarkably operation safety of high-speed railways.Aiming at the damage problem of track slab under temperature loads,a three-dimensional finite element model of CRTS Ⅲ slab ballastless track is established by the software ABAQUS,and the numerical analysis of the transient heat conduction is carried out.Then,the 24-hour daily temperature field data are input to the damaged plasticity model of the CRTS Ⅲ slab ballastless track.,and the damage behaviors of track slab under temperature loads are analyzed.Finally,damage behaviors and its evolution of the track slab under the vehicle loads and temperature loads together are simulated and analyzed comparatively.The simulated results show that the CRTS Ⅲ slab track will bend symmetrically along the track longitudinal center line under the temperature loads.In the cooling process,the tensile stress of the track slab exceeds the tensile strength of concrete materials,so the unrecoverable damage appears in the track slab.In the temperature-rise period,the stiffness of track slab gradually returns to the initial state,but the damage factor of track slab still remains the high level.When the vehicle passes through the damaged track slab,the stress of the track slab is still in elastic state,so the micro cracks are closed and opened alternately,the damage factor of track slab will not increase,and the stiffness of track slab restores partially and has tiny change.Comparing simulated results of the linear elastic damage model with that of damaged plasticity model,it can be found that the vertical displacement and stress amplitudes of the linear elastic model are greater than that of damaged plasticity model under the dynamic vehicle loads and the temperature loads.Because bearing capacity of the damaged track slab is weakened,the tensile stress amplitude of the track slab decreases.When the tensile stress of the track slab exceeds its tensile strength,the calculated results from the linear elastic model are slightly greater than that of damaged plasticity model,which means that the elastic damage model cannot reflect the softening behavior of track slab.In the other hand,when the stress of track slab is in the linear elastic stage,the calculated results of the linear elastic model are less than that of damaged plasticity model,it cannot represent the stiffness degradation behavior of the track slab.