Active Debonding Detection for Large Rectangular CFSTs Based on Wavelet Packet Energy Spectrum with Piezoceramics

Abstract

The debonding between the steel tube and the confined concrete core of concrete-filled steel tubes (CFSTs) can weaken the confinement effect of the steel tube on the concrete core and may induce a decrease in the load-carrying capacity and in the ductility. The debonding detection technique for CFSTs is still a challenging problem resulting from the inaccessibility and invisibility of the interface. In this paper, by embedding piezoelectric lead zirconate titanate (PZT) based functional smart aggregates (SAs) in concrete core as actuators and pasting PZT patches on the predetermined locations of the outer surfaces of the specimen as sensors, a novel active interface condition monitoring approach for rectangular CFST members is proposed and is experimentally validated with a scale rectangular CFST specimen with artificial debonding defects. Analysis of the wavelet packet energy spectrum (WPES) of the measurements of PZT patches is carried out, and a damage index, called the weighted variation of WPES (WVWPES) is defined to detect the artificial debonding regions. The results show that the proposed WVWPES index is sensitive to the debonding defect. Finally, the proposed approach is applied to evaluate the interface condition of a large rectangular CFST column of a super high-rise building.