Structural Health Monitoring Based On Wavelet Analysis

Damage detection is the precondition of structural health monitoring (SHM). For the purpose of structure health monitoring and diagnosis, techniques based on the wavelet transform and wavelet package analysis is studied for structure damage detection in this paper.The necessity and urgency of civil engineering SHM is discussed firstly. Secondly, the concept of SHM & damage detection, and the architecture of SHM system are introduced. Then, damage detection techniques and their development are reviewed. Moreover, the time-frequency properties of wavelet function and scaling function, the principle of multi-resolution analysis and orthogonality of wavelet transform are investigated. Wavelet transform makes analysis on both time domain and frequency domain at the same time by decomposing a signal into different frequency-band. It is showed by experiment: (1) orthogonal wavelet transform possesses a perfect filtering property. (2) Instantaneous abrupt change in wavelet coefficients can be used to detect the discontinuity of a signal. (3) Frequency-band energy distribution of wavelet package decomposition can indicate the energy variation of components in a signal. Wavelet package analysis can give us a finer analysis approach for signal processing and feature extraction.A structure damage detection approach is addressed by using wavelet analysis. Based on SHM benchmark of ASCE, response signals of the structure are processed by using orthogonal wavelet transform, it is demonstrated by researches: a spike in high-frequency detail components of wavelet decomposition can be used to detect damage and its occurrence moment. For the case of damages occurring serially, spikes in the details can be represented the sequence of these damages happened accurately. On the other hand, the damage region can be determined by the spatial distribution pattern of the observed spikes. Furthermore, the choice of wavelet basis function is very important for damage feature extraction. Damage feature extraction performances are different by applying Daubechies wavelets with different supported intervals. For Daubechies wavelet family, the bigger supported intervals a wavelet has, the better orthogonality the wavelet possesses, then damage feature extracted is more distinct.The structure damage detection approach, which based on the wavelet package frequency band energy decomposition, monitors a structure damaged or not by using the relative energy distribution on the different frequency-band. Taking the orthogonal wavelet as the basis function, acceleration vibration signal of the structure is decomposed, and the...