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Structural Damage Identification Using Wavelet Packet Analysis

Damage detection, which plays an important role in structural health monitoring, has been studied for many years. Fiber optical sensors, especially fiber Bragg grating sensors, are currently used for the health monitoring of various structures. However, fiber optical sensors are fragile and expensive, and offer only local measurements. Thus, their applications have been limited. On the other hand, piezoelectric-based approaches have provided an innovative approach for the structural health monitoring of civil structures with the advantages of structural simplicity, low cost, quick response and high reliability.

In this study, a smart aggregate-based active sensing system will be developed for the health monitoring of structures. The piezoelectric transducer in one smart aggregate is used as an actuator to send excitation waves. Other piezoelectric transducers are used as sensors. The crack or damage inside the structure acts as a stress relief in the wave propagation path. If a crack exists, the amplitude of the wave and the transmission energy will decrease. The drop value of the transmission energy can be correlated with the degree of the damage inside.

Wavelet analysis is a mathematical tool that provides a new feature extraction method for the study of structural damage identification. A wavelet is a waveform of effectively limited duration that has an average value of zero. In wavelet analysis, a signal is split into an approximation (low frequency information) and a detail (high frequency information). The approximation is then split into a second level approximation and detail, and the process is repeated.
In wavelet packet analysis, the details as well as the approximations can be split. The advantage of wavelet packet analysis is that it enables the inspection of relatively narrow frequency bands over a relatively short time window.

Students: Ms. Erica L. Wilkins & Ms. Brandi Dennis
Department of Technology
Jackson State University.