Experimental Validation of a Damage Identification procedure based on the Analytical Signal

For civil engineering structures it becomes of primary importance to detect and quantify damage at the early stage, much before structural collapse. One of the greatest difficulties in damage detection lays in the low damage sensitivity of structural response. When a very low level of damage occurs, for instance a little variation in structural stiffness, this phenomenon cannot be detected either in time domain or in frequency domain. Different structural response characteristics can be used for this purpose including modal data curvature measures3,4, frequency response functions and strain energy. A robust technique should be able to detect damage at very low level. Recently it has been developed a damage identification procedure very useful to detect low variation of structural stiffness. This procedure is based on applying Hilbert Transform, to obtain the analytical representation of the system response to an impulse. In fact, by considering some characteristics of the analytical signal, such as the phase, it has been possible to develop a damage identification procedure based on an objective function between the characteristics of the analytical theoretical and measured signal. So far this investigation has been performed only by means of numerical tests, now the aim of this paper is just to validate the damage identification procedure through experimental tests on a two-degrees-of-freedom shear-type model.