Sensitivity of embedded active PZT sensor for concrete structural impact damage detection

Lead zirconate titanate (PZT) actuator/sensor is generally surface-bonded to structure in the electromechanical impedance (EMI) technique for structural health monitoring. However, in consideration of fragility and fugitiveness of surface-bonded PZT patch, it may lose serviceability when external impact happens especially in real-life applications. This paper covered the sensitivity of a new kind of embedded active PZT sensor in structural impact damage detection through theoretical and experimental analysis. Firstly, a new embedded 2D electromechanical impedance model was formulated, in which the PZT patch can be protected from external impact or disturbance. The proposed model was verified by experimental result of testing a manufactured embedded PZT sensor. Then the embedded PZT sensors were qualitatively compared with surface-bonded ones in the experiment of detecting a concrete beam which was damaged by successively knocking off concrete covers. Finally, the effectiveness of embedded PZT sensor in quantification on structural damage was investigated by using slope-based root mean square deviation (RMSD) index. Moreover, a new baseline-changeable RMSD index was also proposed to evaluate the impact effect for the two types of PZT sensor. It was found that the embedded PZT sensor can effectively filter out the impact effect in structural damage indication and quantification, which benefits the accurate evaluation on structural damage.