DAMAGE DETECTION OF BUILDINGS - NUMERICAL AND EXPERIMENTAL STUDIES

Identification of damage of structures has recently received considera ble attention in the light of maintenance and retrofitting of existing structures under service loads and after natural disasters. In this r espect, most of the previous system-identification studies considered structural models typically with not more than three degrees of freedo m. Although many of these identification methods should work in princi ple, local damage detection of real structures remains an arduous task for reasons such as insensitivity of modal frequencies to local struc tural changes, oversimplification of the model, numerical difficulty i n convergence, and inherent measurement noise. This paper presents an ''improved condensation'' method for identification of local damage of multistory frame buildings in terms of change in story stiffness. Sta tic condensation is employed to reduce the system size. Identification is executed recursively on a remedial model, finally yielding integri ty indices for all storys. By numerical simulation studies of a 12-sto ry building with various noise levels, this method is shown to be feas ible and computationally efficient. The efficacy of the method is furt her substantiated experimentally by damage detection of a 6-story labo ratory model subjected to hammer tests.