Damage detection of buildings: numerical and experimental studies

Abstract

Identification of damage of structures has recently received considerable attention in the light of maintenance and retrofitting of existing structures under service loads and after natural disasters. In this respect, most of the previous system-identification studies considered structural models typically with not more than three degrees of freedom. Although many of these identification methods should work in principle, local damage detection of real structures remains an arduous task for reasons such as insensitivity of modal frequencies to local structural changes, oversimplification of the model, numerical difficulty in 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. Static condensation is employed to reduce the system size. Identification is executed recursively on a remedial model, finally yielding integrity indices for all storys. By numerical simulation studies of a 12-story building with various noise levels, this method is shown to be feasible and computationally efficient. The efficacy of the method is further substantiated experimentally by damage detection of a 6-story laboratory model subjected to hammer tests.