A damage localization approach for concrete structure using discrete wavelet transform of electromechanical admittance of bonded PZT transducers

Accurate damage localization in concrete structures or components holds the key to characterizing the defects for structural damage identification and health monitoring. Traditional electromechanical impedance/admittance (EMI/EMA) technique employing the raw data or statistic indicators is difficult to evaluate the specific loci of damages due to its intrinsic localized sensing essence. To this end, this paper proposed an accurate damage localization approach using derived indicators of frequency-domain EMA signatures by discrete wavelet transform (DWT) and Gamma distribution probability-weighted imaging algorithm. In the approach, the EMA signatures of distributed piezoelectric ceramic lead zirconate titanate (PZT) transducers were first collected at pristine and post-damaged states, and the signatures were decomposed using DWT technique to derive damage indicators including the wavelet energy, the mean, the variance and the entropy. Regression models accounting for these indicators were established to predict damage distance, and Gamma distribution of the predicted and actual damage distances was introduced to visualize damage location. Rigorous proof-of-concept experiment was performed on characterization of artificial cracks as well as load-induced crack damages in a reinforced concrete (RC) slab through using surface-bonded PZT sensor array. Experimental results demonstrated that the proposed approach could achieve precise localization of concrete cracks with error as small as 0 mm, and that using the wavelet mean and energy presented the highest accuracies for localizing artificial and load-induced cracks, both better than that using traditional root mean square deviation (RMSD) and correlation coefficient (CC) indexes. Promising results in this study potentially provided a way of the decomposed EMA signatures for characterization of concrete structural damages.