Piezoelectric Transducer-Based Damage Monitoring for Reinforced Concrete Beams at Lap Splices of Steel Reinforcement

This study proposes a novel method for damage assessment in reinforced concrete beams using bonded piezoelectric transducers (PZTs). By analyzing the transmission and reception of high-frequency waves through PZT pairs attached near lap splices in tensile reinforcement, a wavelet packet-based damage index (DI E ) was developed. Four reinforced concrete beams with varying lap splice lengths were subjected to cyclic loading, and the electrical signals from PZT sensors were analyzed. A significant reduction in signal amplitude (33–56%) was observed in lapped splices compared to continuous bars, indicating the discontinuities in the splice regions. The proposed DI E showed strong sensitivity in detecting internal damage before surface cracks became visible. In beams with insufficient lap splice lengths, the DI E values reached above 98% of the maximum damage threshold when 57% and 53% of breaking load were reached, confirming its high sensitivity to brittle splitting behavior. In contrast, beams with sufficient lap lengths showed a gradual increase in DI E values, reaching final damage levels of over 98% when 83% and 78% of the breaking load were attained, respectively, corresponding to ductile flexural failure.