Structural damage detection based on wavelet transform

Several continuous wavelet transform (CWT) based damage indices are developed to detect the damage of structures suffering from sudden damage and linear time-varying damage. The damage indices are calculated from structural impulse responses and can be classified into two types: one type of damage indices is obtained from the shape of scalogram of an impulse response at each time instant. The other type of damage indices is related to the ratios of the scalograms of impulse responses at different locations of the structure and at the scale relevant to the frequency of a certain mode. It is illustrated that the proposed damage indices can be used as indicators of the damage time instant as well as indices of the global damage of the whole structure. Numerical examples, including sudden damage and linear time-varying damage cases, are given to show the effectiveness of the proposed damage indices. The influences of measurement noise on damage detection results are also investigated.