Determination of the working stage of beam-to-column connections using longitudinal guided wave

Monitoring the working stages of beam-column connections is an important part of the earthquake-resilient structure. Guided waves have broad application prospects as a monitoring method. Despite the emergence of new guided wave monitoring methods, wave propagation in beam-column connections still needs detailed understanding. Especially, the dispersion and attenuation problems encountered when guided waves assess beam-column connections. Hence, based on the time-reversal theory, this paper developed a novel guided wave strategy that understands the working stages of precast joints by monitoring the energy-consuming bolt (EB). The fundamentals of time-reversal in EB structures were first investigated. The time reversibility of EBs with different elongations was studied, and the sensitivity of the reconstructed signal to damage was then verified. Compared to the conventional index, the indexes proposed based on the time-reversal operator have a higher sensitivity to damage, because the time-reversal method can overcome the difficulty of extracting the index caused by the guided wave. Finally, cyclic loading and guided wave monitoring tests were performed on four full-scale beam-column connections. Four groups of experimental results show that the time-reversal signal can reflect the stage of whole structures and then accurately guide the post-earthquake repair plan for precast structures.