Piezo-impedance based fatigue damage monitoring of restrengthened concrete frames

The present study proposes a novel application of wavelet transform energy of piezo-impedance signatures in monitoring the premature fatigue damage of restrengthened reinforced concrete (RC) frames. The steel plates on one column of the damaged RC frame and carbon fibre reinforced polymer (CFRP) wrap on the other are utilized as the local strengthening elements. The lead zirconate titanate (PZT) patches bonded externally to the retrofitted elements were used to acquire the global and local vibration response of the test frame under high-cycle and low-strain fatigue loading environment. The electro-mechanical impedance (EMI) technique combined with discrete wavelet transform (DWT) is employed on frequency domain PZT-admittance signatures to identify, localize, and quantify the severity of premature fatigue damages. The EMI-identified structural damping and DWT energy based damage dependent models shows extraordinary ability in estimating residual fatigue life of the structure. The results of combined local and global dynamics technique indicate the higher performance of the PZT-identified equivalent stiffness parameters (ESP) in detecting and quantifying plate debonding failures. Further, for the first time, the miniature AD5933 chipset displays a higher correlation of ESP in estimating premature fatigue damages, ultimately proving its efficacy for using it as a low-cost impedance-based health monitoring solution for retrofitted RC structures.