A method for the estimation of structural damages based on the measured data of the natural frequencies and the natural mode shapes at a limited numbers of structural nodes is presented. The structural damages are modelled by using the local (element) damage parameters. The damage parameters are evaluated solving the modal perturbation equation by an optimal fashion. Example analyses are carried out for several cases of stick models and a truss type structure. The numerical results indicate that the present method can detect the localized structural damages reasonably, particularly for the cases where the number of possible damaged structural members can be restricted beforehand.
