Wavelet-based damage detection of multi-degree of-freedom structures

In this paper, a method is proposed to identify the time and the location of the damage from responses of multi-degree-of-freedom (MDOF) structure based on the wavelet transform, which has the capacity to detect singularities. First, propagation of discontinuities in the response is investigated qualitatively in order to explain how the structural responses are influenced by sudden changes in structural parameters. Next, the influence of changes of stiffness to the response is quantified. And a method is proposed to connect the wavelet transform to the location of the damage by the state space representation of the MDOF structures. Finally, a simple experiment is carried out to show that the proposed methods are valid in the laboratory-scale structural model reinforced by additional stiffness members. Results of the experiment are showed that the proposed method can identify the existence of small changes in stiffness, but the damage identification is influenced by the way of selections of a sampling frequency and a central frequency of a wavelet.