Interface Debonding Detection For Steel Reinforced Concrete Column With PZT Impedance

In recent years, numbers of high rise buildings with a design height about 600 meters are under construction in China. Due to the excellent mechanical performance including high load-carrying capability, good ductility and energy consumption capability under strong dynamic excitations including earthquakes, complex steel reinforced concrete (SRC) columns have been extensively adopted as vertical load-carrying structural components in super high-rise buildings.Vertical steel plates in two directions and the steel horizontal diaphragm usually form independent chambers in SRC structures. The interface bonding condition between the concrete core and embedded steel plates remain significant concern because of the possible shrinkage of the mass concrete after curing and the concrete defect under horizontal diaphragms. The interfacial performance monitoring and debonding defect detection is still a challenging task because traditional ultrasonic methods do not work.In this study, a Piezoelectric ceramic patch (PZT) based debonding defect detection approach for interface between embedded steel plates and concrete core of multi-chamber SRC columns is proposed with the electro-mechanical impedance (EMI) measurement of both PZT patches surface bonded on steel plate and embedded piezo-based functional elements (EPFEs). By taking the root mean square deviation (RMSD) of the measured EMI as a damage index, results show that the defined damage index is sensitive to the embedded interface debonding defects. The proposed approach is capable of detecting the interface debonding defects and provides a useful way for the interface debonding defect detection of large-scale multi-chamber SRC columns.The main contents are as follows:Firstly, the development and application of EMI based approach were introduced. The material properties of piezoelectric ceramic and structural health monitoring based on PZT are introduced briefly. The basic principle of the EMI method for interface debonding detection and the EMI test system was described in detail.Secondly, an experimental study on the interface debonding detection on scale multi-chamber SRC column specimen with mimicked interface debonding defects was carried outby the used of EPFEs and PZT patches. Results show that the defined damage index is sensitive to the embedded interface debonding defects.Finally, the interface condition monitoring for large-section irregular SRC columna of a high-rise building were carried out by measuring the EMI from both EPFEs and PZT patches. By comparing the measurements from both the EPFEs and PZT patches, it can be found that the measurement from either EPFEs or PZT patches meet well with each other. No obvious interfacial bonding condition observed in the monitored SRC column.