Shear performance monitoring of GFRP reinforced concrete beams based on piezoelectric sensors

This study investigates the shear performance monitoring of concrete beams reinforced with Glass Fiber Reinforced Polymer (GFRP) bars using piezoelectric sensors. The research explores the effect of shear damage in the shear span region on the response signals of the concrete beams under loading. Piezoelectric ceramic sensors were attached as actuators and receivers to the concrete beams, and loads were applied until shear failure occurred. When cracks developed in the shear span, stress waves propagated through the material and interacted with the cracks, leading to reflection and refraction, which caused the attenuation of the wave energy. While piezoelectric sensing and wavelet-based analysis have been explored in RC structures, real-time quantitative monitoring of brittle shear failure in GFRP-reinforced beams remains largely under-investigated, especially in relation to crack localization and damage indexing. Time-domain signal amplitude and wavelet packet energy were analyzed under different damage states. Frequency-domain analysis confirmed that high-frequency components (40–80 kHz) in the healthy state and low-frequency components (10–30 kHz) in the damaged stage were most sensitive to shear crack propagation, validating the effectiveness of frequency-domain analysis in shear damage assessment. The Shear Damage Index (SDI), proposed in this study, decreased from 1.0 (undamaged state) to approximately 0.0 (severe damage) as the shear cracks propagated. Among the sensors, those located at the bottom of the beam exhibited the fastest signal degradation, allowing for the identification of crack height progression. Finite element simulations confirmed that increasing crack length and inclination enhanced stress wave attenuation, with their time-domain, frequency-domain, and energy attenuation trends consistent with experimental results—validating the theoretical model’s ability to replicate stress wave attenuation behavior under shear damage. These findings demonstrate that the proposed monitoring method enables real-time, quantitative evaluation of shear damage in GFRP-reinforced concrete beams, providing a practical and sensitive tool for structural health monitoring.