Development of a finite element-based damage localization technique for concrete by applying coda wave interferometry

Coda wave interferometry is a structural health monitoring technique that allows the detection of cracks in concrete using diffuse ultrasound. This study develops a finite element-based methodology that computes a substitute model referred to as a sensitivity kernel. This kernel simulates the decorrelation development of two compared ultrasonic signals over the signals' length and allows to locate damage by solving an inverse problem. Results are compared to an established analytical approach. Two different solving techniques namely the LSMR method and one that respects upper and lower bounds on the variables called STIR are successfully applied in this study. The finite element-based methodology is validated with a reference simulation. In addition to the synthetic wave signals, the approach is tested on a real four-point bending test of a reinforced concrete specimen, where multiple cracks were successfully detected.