CT imaging method with stress wave for interfacial debonding defects in mesoscale RSCCS

Interfacial debonding defects in rectangular steel–concrete composite structures (RSCCS) can significantly diminish the confinement effect of the steel on the concrete core and reduce load transfer efficiency, potentially impacting the overall performance of the structure. Detection of these defects in RSCCS is therefore considered critical. This study investigates the complexities of stress wave propagation in heterogeneous media, focusing on detecting and tomographically imaging interfacial debonding defects in RSCCS cross-sections with mesoscale concrete structures. An efficient polygonal aggregate modeling method is proposed to enhance the efficiency of collision detection, and an improved first arrival time algorithm (FATA) based on the Akaike information criterion (AIC) is developed to improve the accuracy of extracting the first arrival time of stress waves. Additionally, a random walk algorithm (RWA) based onSnell law is introduced to address accuracy issues related to the theoretical shortest ray path of stress waves. A finite element model of an RSCCS containing interfacial debonding defects and various aggregate distributions was constructed. By simulating the stress wave field in mesoscale models and their corresponding RSCCS model with homogeneous concrete, the study validated the feasibility of stress wave measurements and confirmed the significant influence of interfacial debonding defects. The FATA method was then applied to analyze the first wave arrival times, and the internal linkage mechanisms of the first peak amplitude of stress wave and wavelet packet energy were thoroughly explored. Using the simultaneous iterative reconstruction technique (SIRT) algorithm, the initial velocity model was iteratively optimized by comparing the extracted stress wave first arrival times with theoretical shortest ray path propagation times. Numerical simulations and experimental results demonstrate that the proposed method can accurately identify the location and depth of interfacial debonding defects within heterogeneous concrete core at the mesoscale, providing an effective non-destructive testing and evaluation technique for RSCCS.