Two-stage identification of interlayer contact loss for CRTS III prefabricated slab track based on multi-index fusion

To accurately identify the potential contact loss of the China railway track system (CRTS) III prefabricated slab track, a finite element model with contact loss of self-compacting concrete (SCC) under transient impact was established. Then the vertical accelerations near impact points on the track slab surface were extracted to obtain damage-sensitive indices in the time and frequency domains. The indices were initially normalized to obtain independent items of evidence before the Dempster-Shafer (D-S) evidence theory was used to fuse these into one. Finally, a two-stage identification was performed to identify the damaged SCC area, comprising a rough identification (Stage I) and a precise identification (Stage II). The research results show that the damage indices extracted based on the transient impact response change abruptly at the damage location, and that can be used for damage identification. However, the use of a single index to determine the damage of the impact point may be misjudged. In Stage I, five damage indices of acceleration were fused to magnify the difference between the damaged point and undamaged point, thereby improving the accuracy of finding damage. In Stage II, in the area where more impact points were added, a fusion of three indices of acceleration response, that is, the absolute mean of the time domain, the maximum amplitude of the frequency domain, and the power density ratio, further narrowed down the area where damage exists. As a result, when the contact loss of SCC is greater than 50% along the thickness direction, the identification accuracy can be as high as 70% to 80%. The two-stage identification method proposed in this study can greatly improve the efficiency of interlayer damage detection of slab tracks and is expected to provide effective technical support for damage identification of track structures in the future.