Experimental study on alarming of concrete micro-crack initiation based on wavelet packet analysis

Wavelet packet analysis and digital image correlation (DIC) have been applied extensively owing to their respective advantages. In this work, a novel approach is presented to realize micro-damage alarming and identification of concrete by the coupling of wavelet packet transform and DIC technology. DIC measurement system is utilized to measure the damage strain field of static three-point bending of concrete specimen. According to excellent characteristic of time-frequency localization of wavelet packet analysis, the strain nephograms are decomposed by wavelet packet transform. Through wavelet packet analysis, the eigenvectors of the component energy are constructed, based on which the alarming index of concrete micro-crack initiation is obtained. The experimental results show that our novel approach can effectively predict the micro-crack initiation and can automatically achieve alarming. Furthermore, the initiation position of micro-cracks and micro-damage degree can be accurately determined by damage strain field. It is beneficial to damage prediction and safety control of concrete structures.