Experimental Study On Interface Debonding Of Steel Reinforced Concrete Columns Based On PZT

In recent years, a great number of super high-rise buildings with a design height about 600 meters have been under construction in China. Due to the excellent mechanical performance including high load-carrying capability, good ductility and energy assumption capability under strong dynamic excitations including earthquakes, the steel reinforced concrete(SRC) columns have been extensively adopted as vertical load-carrying structural components in super high-rise buildings. With the increase in the area of the cross section of SRC structures, vertical steel plates in two directions and the steel horizontal diaphragm usually form independent chambers in a single column, presenting a large-scale cross section and an irregular shape. The interface bonding condition between the concrete core and embedded steel plates remains significant concern because of the possible shrinkage of the mass concrete after curing, as well as the concrete defect under horizontal diaphragms.The monitoring and debonding defect detection for the interface between concrete core and steel plate is still a challenging task. It is hard for the traditional ultrasonic methods to detect the defect effectively due to the irregularity of the specimen and different materials of concrete and steel. Piezoelectric materials assimilate the functions of sensing and actuation, with quick response, high sensitivity, broadband frequency, good linear relationship and other superior characteristics, providing a new approach to detecting the interface defects of steel reinforced concrete composite structures. In this study, a piezoceramics zirconate titanate(PZT) based active interface debonding defect detection approach for multi-chamber irregular SRC columns is proposed and validated experimentally with an irregular scale multi-chamber SRC specimen with artificially mimicked interface debonding defects. Then the proposed approach is applied to a high-rise building under construction. The main contents are shown as follows:Firstly, the principle of the proposed approach for interface debonding detection by the use of the embedded piezoelectric actuator and sensor is introduced. The selection of actuation signals and the analysis methods are introduced.Secondly, a scale multi-chamber irregular SRC column specimen with artificially mimicked interface debonding defects is constructed, and experimental study on the interface debonding detection using embedded piezo-based functional elements(EPFEs) installed close to the steel plates and the PZT patches bonded on the surface of the steel plates as actuators and sensors respectively is carried out. Results show that the amplitude excited by sinusoidal signal and the wavelet packet energy under sweep sinusoidal signals of the measurement of the PZT sensors in the debonding region is obviously less than that in bonding region. The effectiveness of the proposed method for interface debonding defects detection was verified.Thirdly, based on the finding from the test on the scale multi-chamber irregular SRC column specimen, the proposed approach is applied to evaluate the condition of fill scale irregular SRC columns in a super high-rise building under construction. Results show that the results made at two different times agree well, which indicates no obvious interfacial debonding defects can be detected in the SRC columns.