A pseudo local flexibility method for damage detection in hyperstatic beams

Abstract

Summary Vibration‐based damage detection methods make use of structural features extracted from vibration signals to perform damage diagnosis. The local flexibility method, which can determine local stiffness variations of beam structures by using measured modal parameters, is one of the more promising vibration‐based approaches. The local flexibility method is founded on ‘local’ virtual forces that cause nonzero stresses within a local part of the structure. In this study, this basic rule has been broken. The ‘pseudo‐local’ virtual forces that cause concentrated stresses in a local part and nonzero stresses in the other parts of a structure are employed. The theoretical basis of the proposed ‘pseudo local flexibility method’ (PLFM) is derived. The effects of the number of modes on the damage detection results are studied using both numerical and experimental hyperstatic beam models. The results show that significantly fewer modes are required for the PLFM to estimate the damage location and extent with acceptable accuracy. Therefore, the feasibility of the PLFM is higher because only a limited number of high‐quality modes can be identified in real world applications. Furthermore, it was also found that when damage occurs close to the support, the PLFM is more likely to detect it, which is credited to the smaller local region induced by the PLFM. Copyright © 2014 John Wiley & Sons, Ltd.

Mode shape-based damage detection in plate structure without baseline data

“…Several advantages and limitations of these methods were also pointed out. Many studies confirm that mode shapes and corresponding mode shape curvatures are highly sensitive to damage and can be used for detection and quantification of the damage. Maia et al in performed extensive numerical simulations on a beam structure to compare damage identification sensitivity within different methods, based on the changes of mode shape, mode shape slope, mode shape curvature and mode shape curvature square, respectively.…”

“…Results showed that sensitivity of changes in vibration characteristics was proportional to stiffness of a beam support; however, as damage severity increased, the respective change of nonlinearity did not follow the monotonic trend; therefore, it cannot be used for damage detection. Hsu et al suggested a local flexibility method built on a pseudo‐local virtual force action on the structure to identify local changes in stiffness in hyperstatic beams. Damage detection studies employed variation of a number of mode shapes.…”