2012 Theses Doctoral

Damage Detection and System Identification using a Wavelet Energy Based Approach

Joo, Duk Jin

Structural Health Monitoring (SHM) is central to the goal of maintaining civil engineering structures safely and efficiently, and thereby securing people's lives and property. Furthermore, it plays an essential role in infrastructure design at a fraction of the capital cost of construction. In this thesis, we seek to address two of the central concerns of the SHM: parametric system identification and damage detection. The first proposed method seeks to identify the physical parameters of an analytical model.

First, the connection coefficients for the scaling function were developed for deriving the responses of the velocity and displacement from the acceleration responses. Next, defining the dominant sets based on the relative energies of the Wavelet Components of the acceleration responses, the equations of motion of the system in the time domain were converted to a reduced representation of the equations of motion in terms of the DWT and of the DWPT. Finally, the least square error minimization was conducted over the dominant sets to estimate the best estimation of the physical parameters.

The second proposed method seeks to detect damage in a structure. Motivated by the fact that the Empirical Mode Decomposition is seen to have different features from the Discrete Wavelet Transform when one investigates nonstationary signals, we have combined the Empirical Mode Decomposition with the Discrete Wavelet Transform to enhance the performance of the proposed method for identifying damage in the structure.