Detection Of Grout Fulfillment In Pre-stressed Tendon Duct And Interfacial Debonding Detection Of FRP Tendon And Concrete Based On Piezoelectric Ceramic Transducers

With the rapid development of the society,all kinds of large-scale complex engineering structures are constantly emerging in recent years,and structural health monitoring technology in civil engineering has gained extensive concerns from the academic.Piezoceramic materials,as one of the smart materials,has been used to develop transducers in structure health monitoring field,since the properties of sensing and actuating ability,low cost,fast response,low power,wide frequency range and cuttability.Taking advantages of piezoceramic materials,this dissertation proposed a new method based on piezoceramic and smart aggregate for structural health monitoring.The wave-based and electro-mechanical impedance(EMI)method are applied to monitor the grouting quality using piezoceramic transducers,and wave-based active sensing approach was proposed for monitoring the interfacial damage between FRP tendon and concrete,which have been proved an effective method for the detection of compactness and interfacial damage.The specific study is listed as follow:First,aimed at the lack of grouting in the ducts,a PZT EMI method was presented to detect the compactness of ducts.Four different grouting situations were simulated to investigated the grouting quality.By analying the change rule of the electric admittance,some general trend can be concluded for each of the piezoceramic transducers.The trend shows that the peak values of electric admittance curves shifted to the right with the increasing of the grouting level,and the peak values increase gradually.And the damage index proposed in this reasearch has relationship with the grouting quality of the ducts.This experiment validate that the PZT impedance method is feasible to monitor and identify the compactness of ducts.Second,a wave-based active sensing approach is proposed for the ducts compactness detection of concrete specimen.One smart aggregate was bonded with tendons to generate stress waves in vertical direction.Two PZT sensors bonded on top and one on bottom of the duct were utilized to detect the wave response.During the test,the grouting quality can effectively evaluated by analyzing the differences between received signal in different grouting events.Experimental results showed that the amplitudes of the signal demonstrates adecreasing trend with the increasing of defect in the ducts,and the damage index based on wavelet packet energy shows the same trend.The proposed method has potentials to be utilized to monitor the grouting quality of the ducts.Third,an wave-based active sensing approach is developed to monitor the development of bond-slip damage between FRP tendon and concrete.A pullout test was conducted on the FRP-concrete specimen to simulate the different degrees of interfacial debonding damage.The received singnal energy attenuations due to bond slip were clearly observed by the SA sensor signal in time domain.Furthermore,a damage index based on wavelet packet energy analysis is developed to evaluate the bond condition between FRP and concrete.The proposed method developed in this paper has potentials to be utilized to detect the the interfacial debonding condition of the FRP-concrete composite structures.