Identification of stiffness degradation in structures using wavelet analysis

An approach for structural health monitoring (SHM) and damage detection using a wavelet based time-frequency technique is presented here. The characteristics of dynamic responses of structures are studied by wavelet analysis. Inferences are drawn from the wavelet coefficients obtained. Numerical simulation data are used for the purpose of illustration. Two examples (i) a bi-linear structure with breakable springs causing stiffness degradation and (ii) a hysteretic system with continuous variation in stiffness with non-linearity involving displacement and velocity response are considered. Information regarding the stiffness degradation and temporal location of damage are successfully obtained from the wavelet coefficients of the response. The effect of system degradation is reflected in the time-frequency characteristics of the response and inferences on stiffness degradation can be obtained even without any apriori knowledge of the original structural system.