Identification of structural damage

The relationship of the changes in the natural frequencies to the localized reductions in the stiffness of a structure is approximated by a set of simultaneous linear equations. These equations can be solved for the magnitude of localized damage if measurements of the changes in the natural frequencies are available. However, since only a small number of the natural frequencies can be measured, the equations are underdetermined and a unique solution can be obtained only with the introduction of an optimality criterion. An optimality criterion that is based on measurements of the Markov parameters of the system is proposed herein to estimate the location and magnitude of the structural damage. The resulting algorithm is used to identify the damage in a 90 d.o.f. frame. Light to severe damage is induced in the structure in the form of 10 to 50% reduction of the stiffness of several elements. Both the location and the severity of the damage were identified successfully.