Research on guided-wave damage imaging and identification of load-bearing structures based on the improved RAPID algorithm

Load-bearing structures are critical components in buildings, however, during service, they are susceptible to damage due to various factors. If such damage cannot be detected and addressed in a timely manner, it may lead to serious consequences. Therefore, this paper proposes a damage imaging and identification method in cylindrical structures based on a fused damage index formulated in the cylindrical coordinate system, taking cylindrical concrete structures as the research object. In this method, the direct waves of guided wave response signals before and after structural damage are utilised to construct a fused damage index. Furthermore, a GE-RAPID (Geometrically Extended RAPID) algorithm is proposed, which extends the planar elliptical path principle of the traditional RAPID algorithm to the cylindrical coordinate system, thereby enabling three-dimensional damage identification and imaging of cylindrical structures. Numerical simulations and experimental validations demonstrate that the proposed method can effectively achieve the identification and imaging of single, multiple, and different types of damage in cylindrical structures. The results indicate that the proposed approach exhibits satisfactory damage identification performance, providing an important reference for research on damage detection in cylindrical structures.