STRUCTURAL DAMAGE DETECTION USING MEASURED FRF DATA

The underlying principle behind structural damage detection techniques is that vibration signature, e.g. modal properties or frequency respo nse function (FRF) data, is a sensitive indicator of structural physic al integrity and thus can be used to detect damage. Since indirectly-m easured modal data contain accumulative errors incurred in modal param eter extraction and provide much less information than FRF data, it is more reasonable and reliable to use directly-measured FRF data for st ructural damage detection. In this paper, a new damage detection algor ithm is formulated to utilize an original analytical model and FRF dat a measured prior and posterior to damage for structural damage detecti on. Based on nonlinear perturbation equations of FRF data, an algorith m has been derived which can be used to determine a damage vector indi cating both location and magnitude of damage from perturbation equatio ns of FRF data. An additional development with respect to the proposed technique is an effective technique introduced for weighting perturba tion equations of FRF data at selected locations and frequencies so as to reduce influence of measurement errors on accuracy of damage detec tion to the minimum. For extension of the proposed algorithm to cases of incomplete measurement in terms of coordinates, an iterative versio n of the proposed algorithm has been introduced. The validity and appl icability of the proposed damage detection algorithm have been demonst rated through numerical and experimental studies on a practical plane 3-bay frame structure, respectively.