Study On Ultrasonic Detection Of Grouting Defect In Grouted Splice Sleeve Connector Based On Wavelet Packet Energy

Grouted splice sleeve(GSS)connector is widely used in reinforced precast concrete members.When the construction is improper,grouting defect appears easily.The defect will affect the effective connection between the members and the mechanical properties of the whole structure,leading to major safety risks.There are some shortcomings,like low precision and limited adaptability,existing in current method such as impact echo method and ground penetrating radar method.By comparison,ultrasonic detecting method has the advantages of strong penetration,rich information and good adaptability.Thus,it is more suitable for this detection.In order to detect the grouting defects effectively,a new detecting method is proposed,which combines the ultrasonic detecting method and the wavelet packet analysis algorithm.The effectiveness of the method and its main influencing factors are simulated and studied.And this paper has carried out the following research work.The ultrasonic detecting method of grouting defect in GSS connector based on wavelet packet energy is proposed.By analyzing the types and the forming reasons of grouting defect in GSS connector,three typical grouting defects are determined: top defect,middle defect and eccentric defect of connecting rebar.And then,the time-frequency characteristic analysis of ultrasonic wave propagation under the influence of random distribution of aggregates is carried out.It is clear that the amplitude of detecting signal in time domain or frequency domain is very different between different concrete.The influence of grouting defects on ultrasonic signal energy is analyzed,and the ultrasonic detecting method of grouting defect in GSS connector based on wavelet packet energy is proposed.The specific implementation method and grouting defect index(DI)are also given.The effectiveness and influencing factors of ultrasonic detecting method of grouting defects are analyzed.Based on the concrete meso-models,the effect of random distribution of aggregates on the energy of ultrasonic detecting signal at different frequencies is analyzed,and the validity of 50 kHz ultrasonic excitation signal is determined.And then,the influence of different defect sizes on the variation law of DI are studied.It is found that the DI increases with the increase of defect size.Furthermore,the influence of sleeve size and sleeve wall thickness on grouting defect detection is analyzed.It is found that with the increase of sleeve size,the DI decreases under the same defect size,and the DI increases with the increase of sleeve wall thickness and the same defect size.The ultrasonic detecting test of grouting defect in GSS connector is carried out.By preseting 5 kinds of grouting defect size,the ultrasonic testing effect of different defect size is explored,and the influence of different splice sleeve arrangements and different splice sleeve sizes on ultrasonic testing method is explored by setting 3 kindsof specimen of concrete menbers with GSS connector.The indentification baseline of grouting defects of specimens is given by analyzing the test result.The result shows that DI is less sensitive to small size grouting defects,but this method can effectively identify the larger size grouting defects in the specimens.