Experimental Study on CRTS III Ballastless Track Based on Quasi-distributed Fiber Bragg Grating Monitoring

In order to investigate the damage process caused by the seismic pseudo-static load, quasi-distributed fiber bragg grating (FBG) sensors were placed in CRTS III ballastless track specimens. Low-cyclic reversed load experiments were then carried out. We studied the strain conditions at various points along the ballastless track under cyclic loading as well as the damage modes, strain curves, residual strains, and cross-sectional stresses of the self-compacting concrete layer and foundation slab. The damage process may be broken down into three stages: First, fractures show up at the base plate anchors; second, the shear reinforcement deforms; and third, the concrete layer is lifted until it is crushed. The CRTS III ballastless slab's maximum transverse tensile strain is greater than its maximum longitudinal tensile strain. Premature cracking of the self-compacting concrete layer will result from greater strain at the edge and corner of the groove and from a lack of reinforcing. It is tough to monitor the deformation of the groove area at simultaneously, which is not possible with more conventional monitoring methods like strain gauge sensors. Quasi-distributed FBG sensing can effectively observe the detailed strain development of the groove and its surrounding areas.