Debonding detection for rectangular CFST using surface wave measurement: Test and multi-physical fields numerical simulation

The interfacial debonding detection approach for concrete-filled steel tubular (CFST) members using surface-mounted piezoelectric-lead-zirconate-titanate (PZT) actuators and sensors is experimentally and numerically investigated. In this study, an interfacial debonding detection approach using surface wave measurement with PZT patches is propoed firstly and experimental investigation on the feasibility of the proposed approach with two CFST specimens with different levels of interface debonding defects is carried out. For comparison, a PZT sensor is also embedded in concrete core to measure the stress wave traveling from the surface-mounted PZT actuator. Experiment results indicate that the voltage amplitude of the embedded PZT sensor representing the wave propagation from the steel plate into the concrete core decreases due to the existence of interfacial debonding defect, but the output signal of the surface-mounted PZT sensor increases accordingly when interface debonding occurs. Moreover, the increment of surface-mounted PZT sensor measurement is related to the dimension of the interface debonding defects. The experimental finding implies that the interface debonding is detectable using surface wave measurement. In order to investigate the mechanism of the proposed approach, numerical study on the wave propagation process in CFSTs is further discussed by using three-dimensional (3D) solid element models and two-dimensional (2D) plane strain models, respectively. Finally, in order to consider the effect of nonhomogeneous meso-scale structure of concrete on the wave propagation, a random aggregate method (RAM) is employed to model the concrete core and multi-physical fields coupling numerical analysis on stress wave propagation of the CFST member with different interface debonding defects is performed. The numerical findings meet well with the experimental observations and the results indicate that the interface debonding of CFST can be detected efficiently using surface wave measurement.