Damage Monitoring Using Piezoceramics For A Half Cross-section Column Of Concrete-filled Steel Tubulars

The concrete-filled steel tubulars(CFSTs) have been widely emplo yed in super high-rised building and lo ng-span bridges due to improved structural performance, high-speed construction and less materia l consumpt ion.The interface between the steel tubular and the confined concrete core can weaken the confinement and decrease the mechanical characterist ics including load-carrying capacit h and duct ilit y. So it's significant to detect and asess the bonding condit ion between steel tubular and core concrete. However, it's not suitable to detect the interface debonding defect with the convent ional non-destruct ion detecting method.In this art icle, a wave propagat ion measurement method is proposed based o n Piezoelectric ceramic materials for interfacial debonding o f a half cross-sect io n co lumn o f a CFST by excluding the the stress waves propagat ion along th e tubular, and this method is tested on a certain circular CFST. The major contents o f this stud y are as fo llow:Firstly, the fabricat ion o f the emplo yed embedded PZT-based funct ional element s(EPFEs) in detailand their stat ic and dynamic performances are studied and calibrated. Results show that the developed EPFEs has a good linear behavior wit h the input vo ltage level.Secondly, a half cross-sect ion co lumn of a concrete-filled steel tubular model with interface debonding defect is designed and fabricated in lab with PZT-based functional elements embedded acting as actuators and sensors. Measurements are made by EPFEs under sinuso idal and sweep sinu so idal excitat ion signals and the measurement single amplitude under sinusoidal signal and the wavelet packet energ y under sweep sinuso idal excitat ion anlysis are used to detect the interface debonding defect and corresponding damage indices are defined.Test results show that the proposed method and damage indices are effect ive to ident ify the debonding defect.Thirdly, the Frequency response funct ion(FRF) method based on wave propagat ing measurement is proposed using surface-mounted embedded PZT patches on the surface o f a steel tubular under impulse hammer excitation. By means o f analysing the frequency response function(FRF) indices at different frequency bands of the measurement o f each sensor,interface debonding defect at different locat ion o f the cross-sect ion co lumn of the concrete-filled steel tubulars is ident ified successfully.Finally, the extent o f art ificially mimicked and actual interface debonding defects of a certain circular CFST are monitored by the the wavelet packet anlysis and FRF on the wave propagat ion measurement. The result show that the feasibilit y and sensit ivit y of the method on the interface debonding defect o f CFST based on the piezo ceramic materials.