Application of PZT sensors for detection of damage severity and location in concrete

Piezoelectric ceramic lead zirconate titanate (PZT) based electromechanical impedance (EMI) technique has been applied for structural health monitoring (SHM) of various engineering systems. However, study on identification of damage severity and location is still in need. In the EMI method, the PZT electromechanical (EM) admittance is used as a damage indicator. Statistical techniques such as root mean square deviation (RMSD) have been employed to associate the damage level with the changes in the EM admittance signature. To achieve high sensitivity to damage, high frequency signatures (>200 kHz) have been used to monitor the region close to the PZT location. It has been reported that the use of RMSD as the damage indicator is difficult to specify the damage location and severity due to the inconsistency in the RMSD results. This paper proposes the use of large frequency (30-400 kHz) range and the RMSD values of sub-frequency intervals to eliminate the inconsistency in the results. An experiment is carried out on a real size concrete structure subjected to artificial damages. The PZT admittance signatures in a frequency range of 30 to 400 kHz for various structural damages have been recorded and the RMSD values of sub-frequency intervals of 10 kHz are calculated. Results show less inconsistency and uncertainties compared to the traditional method using limited high frequency range. It is observed that the damage close to the PZT changes the RMSD at high frequency range significantly; however the damage far away from the PZT changes the RMSD at low frequency range significantly.