Analytical impedance model for piezoelectric‐based smart Strand and its feasibility for prestress force prediction

The concept of the piezoelectric‐based smart strand has been recently developed for low‐cost prestress force monitoring of post‐tensioned structures. However, the previous study uses the single‐degree‐of‐freedom system that is inadequate to describe multiple resonances in a realistic electromechanical impedance (EMI) signature. Furthermore, the EMI‐based prestress force prediction has mostly relied on statistical regression models that are difficult to apply to existing prestressed structures, where the collection of EMI data in failure cases is almost impossible. In this study, we newly propose a high‐fidelity analytical EMI model for the smart strand technique and develop a simple model‐update‐based method for prestress force prediction. The experimental result shows that the proposed analytical model is capable to generate the realistic EMI response of multiple modes at a similar frequency band with identical patterns. Also, the prestress force in the smart strand can be reliably predicted by minimizing the gap between the analytical EMI response and the experimental data through a genetic algorithm‐based model‐updating process.