Damage identification from wavelet-based acceleration response sensitivity

Early detection of damage in engineering systems during their service life is receiving increasing attention from engineers in the last few decades. Though vibration-based damage detection has been developed for several decades and there are large literature existing, there are still many problems restricting its application. The main work presented in this dissertation is listed as following.; The wavelet packet energy and the wavelet coefficients of acceleration responses of the structure under general excitation are computed numerically and analytically and are directly applied to identify the location and the extent of the structural damage by model updating and sensitivity analysis. The wavelet coefficients of acceleration responses obtained from structure under support excitation are also studied for damage detection in order to perform on-line structural condition monitoring. The phenomenon that time series data with low sampling frequency still have the ability to identify damage successfully are studied.; In order to be independent of the external excitation, the impulsive response function are computed from the measured acceleration responses via wavelet transform and their wavelet coefficients are computed numerically and adopted to identify damage in the structure under general excitation and support excitation.; Covariance of acceleration responses of structures under ambient excitation is numerically computed and their wavelet packet energy are adopted to identify structural damage so that the damage detection can be done with the response-only measurement.; In order to solve the ill-conditioning problems in the damage identification equations, Tikhonov regularization techniques are improved in the inverse problem by adding the corresponding constraints to determine the regularization parameter.; Uncertainties in the system parameters, such as the structural parameters of the finite element model, the excitation force acting on the structure and the measured acceleration response from the perturbed state of the structure are analyzed and the analytical formula are given, and they are included in the study for the damage detection.; To demonstrate the procedure and the efficiency of the proposed methods and techniques, numerical studies and experimental verification are performed results prove their feasibility.