This paper presented an experimental study on piezoelectric impedance based cubic and axial compressive strength gain
monitoring in concrete during curing process. The piezoceramic (PZT) patch was attached on the concrete specimen to
collect the monitoring signal. The electro-mechanical impedance (EMI) spectra of surface bonded PZT patch were
collected using an impedance analyzer by sweeping the frequency. A regression analysis is conducted to establish the
empirical relationship between the relative strength gain of concrete and the monitored relative resonant frequency
change of the EMI spectra. The established empirical formula is used for concrete strength monitoring via EMI spectra.
The results tell that the EMI technique is a practical and reliable nondestructive test method for concrete strength gain
monitoring.
This paper presents a numerical simulation study on electromechanical impedance technique for structural damage
identification. The basic principle of impedance based damage detection is structural impedance will vary with the
occurrence and development of structural damage, which can be measured from electromechanical admittance curves
acquired from PZT patches. Therefore, structure damage can be identified from the electromechanical admittance
measurements. In this study, a model based method that can identify both location and severity of structural damage
through the minimization of the deviations between structural impedance curves and numerically computed response is
developed. The numerical model is set up using the spectral element method, which is promised to be of high numerical
efficiency and computational accuracy in the high frequency range. An optimization procedure is then formulated to
estimate the property change of structural elements from the electric admittance measurement of PZT patches. A case
study on a pin-pin bar is conducted to investigate the feasibility of the proposed method. The results show that the
presented method can accurately identify bar damage location and severity even when the measurements are polluted by
5% noise.
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