Analysis of Dynamic Support Conditions of CRTS III Ballastless Track Slab Based on FBG Sensor Strain Measurements

The slab ballastless track experiences warping under temperature gradients, leading to variations in its support conditions. This study developed a finite element model of the CRTSIII ballastless track to investigate the support conditions under different temperature-induced warping scenarios. The model was validated against strain measurements obtained from FBG sensors. The results reveal that under a temperature gradient of 90°C/m during train passage, the center camber exhibits significant deformation characteristics while maintaining structural integrity through adaptive stress redistribution between the slab and sub-ballast layer. Conversely, at −50°C/m, dynamic support transitions occur within localized zones along the slab's longitudinal profile, with the slab ends consistently exhibiting zero contact pressure throughout thermal cycling.