Damage Monitoring Using Piezoceramics For Multi-cell Concrete-filled Steel Tubulars

Because of its excellent behavior, Concrete Filled Steel Tube (CFST) has beenextensively employed in skyscrapers and bridges increasingly, and the CFST isdeveloping into larger cross section members with multi-cell shapes. As the quality ofconcrete and the bonding of the interface greatly influence on the performance ofCFSTs, it’s significant to assess and monitor the CFSTs. However, it’s difficult todetect the damage and the conventional non-destruction detecting method is notsuitable, for the interfacial debonding of concrete core and steel tube is usuallyconcealed. In this paper, by fully developing the superiority of piezo ceramic (PZT)material, a detecting method is proposed based on the wave propagation for themulti-cell CFST interfacial debonding. And this method is tested on the full-sizemulti-cell CFST with two mimic damage types, which verifies the detecting efficiencyof this method for the two types. The specific study is listed as follow:First, the producing process of the embedded piezo intelligent block (EPIB) isintroduced in detail and then the static and dynamic performance of the piezoelectricactive health monitoring system is checked and the EPIBs are calibrated. The result isthat the static and dynamic performances of the system are both fine and thecalibrated EPIBs provide the test basis for the health monitoring study follow-up.Second, the damage in concrete core and the interface debonding of differentdamage degrees are both simulated in a full-size multi-cell CFST with a circular crosssection. The EPIBs and PZT patches bonded on the steel tube outside are used as theactuators and sensors. The wave propagation is analyzed under the two different typesof damages. Several parameters of the received data from the sensors are analyzedincluding amplitude in time domain, amplitude in frequency domain, wavelet packetenergy and its spectrum. And a few damage indices are defined based on theseparameters. The consequence shows that the damage on the path of wave propagationcauses the changes in the amplitude in time domain and frequency domain, thewavelet packed energy and its spectrum of the received signal, and damages withindifferent degrees are detected accurately. The experiment verifies the feasibility andefficiency of the method on the multi-cell CFST damage monitoring based on thepiezo ceramic.Third, the interfacial debonding beneath the horizontal diaphragm plate of the multi-cell CFST is monitored by the wave propagation analysis, based on the waveletpacket energy and its spectrum damage detection method. The results manifest thatthe interfacial debonding is detected efficiently and the wavelet packed energy isaffected by the PZT locations and wave propagating course, however, its spectrum isnot. This discovery provides the basis for decreasing the number of the PZT sensors,optimizing the sensor layout and reducing the post process of data.