Damage detection and assessment of structural systems from measured response

A new damage detection algorithm is developed based on a system identification method. The algorithm can be used as a non-destructive diagnostic technique to aid in decisions of repair and rehabilitation of existing structures. The developed algorithm is able to detect and assess damage in a structure when the measured data are sparse and polluted with noise.Damage is defined as the reduction in estimated parameters between two time separated inferences. Damage is localized by updating parameter groups hierarchically and assessed by perturbing measured data. Parameter groups are continuously subdivided until all the existing damaged parts in a structural system are completely localized. The measured data are perturbed to examine the sensitivity of each parameter with respect to the measured data, and to thereby provide a statistical basis for assessing damage. The bias of the mean estimate from the baseline value and this bias divided by the standard deviation of the Monte Carlo perturbation sample are calculated as damage indices. The upper limit values for both damage indices are determined from the simulation study for the undamaged baseline structure and are used to determine damage in the existing structure.The algorithm assumes that the baseline values of the parameters of the presumably undamaged structure and the amplitude of noise in the measured data are known. The stiffness of a member cannot increase from a previous investigation of the baseline properties. In the present work, we assume that the mass matrix is known. We also assume that a suitably refined finite element model of the structure exists. The current algorithm can accept static and modal responses as the measured data in identifying the given structural system.To examine the damage assessment algorithm, case studies are performed on a planar bowstring truss structure and a cantilever beam structure. Simulated static responses are used to identify damaged planar bowstring truss structures. Real measured modal responses from a laboratory experiment are used to identify the cracked cantilever structural system.U of I OnlyETDs are only available to UIUC Users without author permissio