Baseline-free multidamage identification in plate-like structures by using multiscale approach and low-rank modelling

Damage localisation based on structural characteristic deflection shapes (CDSs) or their spatial derivatives has been widely investigated due to their high sensitivity to local damage. Despite substantial advances in this kind of methods, several key problems must be addressed to boost their practical applications. This paper deals with three vital issues: their susceptibility to measurement noise, absence of baseline data on pristine structures, and their low effectiveness in identification of multiple damage. To tackle these problems, a statistical baseline-free multidamage identification method is proposed for plate-type structures. In this method, a Laplacian of Gaussian (LoG) filter is adopted to enhance the noise-robustness of the estimated curvatures of CDSs. Without the baseline data on pristine structures, a robust principal component analysis (PCA) is proposed to extract the damage-induced local features by using only the CDS curvatures of the damaged structure. Moreover, a robust multidamage index is defined, which has the capability of integrating the damage information of several CDSs. Finally, the feasibility and the effectiveness of LoG filter, robust PCA, and the proposed multidamage index are validated by using both numerical and experimental studies of plates with two damage zones. It is found that the two damage zones with only 10% thickness reduction can be accurately detected and localised by using the proposed multidamage identification method.