Adhesive curing effect of bonded piezoelectric transducer on electromechanical impedance-based concrete structural damage detection

Complete understanding of the adhesive curing effect of a bonded piezoelectric lead zirconate titanate (PZT) sensor on the electromechanical admittance (EMA, inverse of impedance) facilitates the accurate diagnosis of structural damages when employing the impedance technique for structural health monitoring. This article analytically and experimentally investigated the curing effect of adhesive layer on the EMA-based concrete structural damage detection. Curing effect was theoretically incorporated into shearing mechanism of adhesive layer to formulate a new one-dimensional PZT-structural impedance model. Analytical analysis of the curing effect on the EMA signature as well as the EMA-based damage diagnosis was calculably interpreted through the model. Proof-of-concept experiment was performed on testing a four-point bending reinforced concrete (RC) beam bonded with multiple PZT patches under adhesive curing. Experimental results demonstrated that singular shift in the EMA spectra under adhesive curing could be turned into three typical shifts when structural damage occurred, which cogently validated the analytical results. Quantifiable signal index further provided useful information for the identification of crack occurrence, progression, and reinforcement yielding of the RC beam. Results of this study potentially promoted the real-life engineering applications of impedance technique inclusive of deficient adhesive condition.