DETECTION OF STRUCTURAL FAULTS BY MODAL DATA, LOWER BOUNDS AND SHADOWSITES

Different algorithms have recently been developed for the diagnosis of many types of civil and mechanical structures using modal data, such as natural frequencies and mode shapes. Although many solutions have b een proposed, some important questions seem to be absent in the techni cal literature. If changes in a structure's modal parameters are able to reflect structural faults, it is important to know what is the smal lest detectable physical change in that structure. It is suggested tha t damage detection by means of modal data can be useful for macro-dama ge rather than for micro-damage. This resulted from numerical and expe rimental tests using a simple correlation between measurement noise an d sensitivity of modal data, with respect to structural changes in dif ferent parts of a system. An automatic sensitivity approach is present ed to obtain the lower bound of structural faults for the particular s tructure under study. The same automatic procedure is able to detect p ossible shadow sites within the frequency range analyzed. (C) 1998 Aca demic Press Limited.