Cracking Monitoring of RC Joints under Cyclic Loadings Based on Wavelet Packet Analysis on Embedded PZT Measurements

The integrity of beam-column joints plays key roles in the earthquake resistant design of reinforced concrete (RC) frame structures. In post seismic behavior evaluation, it is still a challenging task to efficiently monitor the crack initiation and development of RC joints due to inaccessibility. In this study, an active cracking damage initiation and propagation monitoring approach for RC joints using embedded piezoelectric lead zirconate titanate (PZT) based functional elements as both actuators and sensors is proposed. Laboratory test on an exterior beam-column joint specimen subjected to incremental cyclic loadings is performed and the corresponding responses of different sensors are recorded when a certain designated embedded PZT actuator was excited with sweep sinusoidal signals. A health indicator based on the wavelet packet energy (WPE) of embedded PZT sensor measurements was defined to monitor initiation and propagation of cracks in different parts of the RC joint under various loading levels. The monitoring results agree well with the actual crack initiation and propagation pattern observed and the proposed approach by the use of embedded PZT based functional elements can be implemented in practice for the monitoring of RC joints in frame building structures under earthquake loadings.