Statistical strain-based surface interpolation method for crack localization in distributed-fiber-optic-monitored concrete slab structures

Early-stage damage in concrete slabs can evolve into crack propagation and eventual structural failure if not detected and repaired in a timely manner, posing a significant threat to structural integrity and safety. Early detection and accurate localization of cracks are therefore critical for maintaining the long-term performance of slab structures. Vibration-based damage identification methods offer a promising solution but are generally constrained by sparse sensor deployment and susceptibility to environmental noise. This study proposes and validates a statistical strain-based surface interpolation method (S ³ IM), which extends the surface interpolation method (SIM) to concrete slab structures using distributed fiber-optic strain measurements for crack localization. Concrete pavement slabs supported by an elastic foundation were selected as the representative structural system. Finite element simulations were performed to systematically assess the feasibility of the interpolation-based methodology and investigate the effects of damage severity, measurement noise, and load-to-damage distance on localization performance. Experimental validation was conducted on six 1.5 × 1.5 m concrete slabs instrumented with distributed optical fibers. Localized damage was simulated by introducing saw-cut cracks on the surface of slabs, and controlled excitations were applied to generate continuous vibration data. Strain-based operational response shapes were constructed from strain-rate transmissibility functions, and a statistical damage indicator with adaptive thresholding was used to localize abnormalities. Comparative analysis demonstrated that the proposed statistical strain-based SIM increased F1-score from 0.2 to 0.8 compared to the deterministic method and reduced false alarms and missed alarms by 75% (both from 4 to 1). Overall, the findings highlight the potential of S ³ IM for strain-based crack localization in concrete slab structures.