Research On Performance Monitoring And Defect Recognition Of PC Structure Sleeve Connector Based On Piezoelectric Ceramics

In recent years,prefabricated buildings have been vigorously promoted and applied as a construction industrialized production model strongly advocated by the country.Sleeve grouting connection,as the main connection method of reinforced steel bars in the precast concrete structures,is widely used in the assembly and connection of prefabricated components.The strength of grouting material and the fullness of grouting in the reinforced sleeve grouting connection are important factors affecting the quality of connection.However,due to factors such as on-site construction operation environment,grouting technology,construction organization and management level,and professional quality of construction personnel,quality defects such as less grouting material and strength of grouting material do not meet the specification requirements often appear inside the sleeve.The lack of grouting material strength and the existence of grouting quality defects will have a greater impact on the integrity and safety of the structure.But the concealment and invisibility of the reinforced sleeve grouting connection make it difficult to detect grouting material strength and grouting quality defects.Therefore,it is of great significance to study an economical and simple monitoring method of grouting material strength and grouting quality defects.Piezoelectric ceramic material is a new type of intelligent material used in the field of civil engineering structural health monitoring in recent decades.It has the advantages of low price,good reliability,high sensitivity,and dual effects of sensing and driving.It provides a new idea for the monitoring of grouting material strength and grouting quality defects of the sleeve grouting connection.In this paper,from the perspective of experiment,based on the principle of wave method,a method for monitoring the strength of grouting material and the quality defects of sleeve grouting using piezoelectric ceramics is proposed.The main work and research results are as follows:(1)A new generation PZT based function element is introduced detail.Related performance tests were performed on a structural health monitoring system composed of test components embedded with piezoelectric ceramic and related test equipments.The results show that the system has good linear performance,sensitivity,stability and frequency response characteristics.(2)In order to monitor the early strength development of sleeve grouting material in practical engineering,a method for monitoring the early strength of grouting material using PZT is proposed,and the early strength monitoring test research of grouting material is carried out.The test results show that the amplitude of the received signal of the sensor decays rapidly during the first 5 days of the age,while the grouting material strength increases rapidly.Then the change of the two gradually slows down and eventually stabilizes with age,which indicates that the changing trend of signal amplitude of PZT sensor can perfectly reflect the strength development trend of grouting material.The signal amplitude and grouting material intensity values are normalized and then data fitting analysis is performed.The optimal fitting relation between signal amplitude ratio and intensity ratio is obtained by comparing the goodness-of-fit parameters,which provides a reference for practical engineering applications.(3)A set of grouting sleeve models with different types of grouting quality defects were designed and fabricated,and the piezoelectric ceramic functional elements were used to identify grouting quality defects.Taking the two signal characteristic parameters of signal amplitude and energy value as the research object,two sleeve grouting quality defect identification indicators based on the amplitude of the sinusoidal signal and the energy value of the wavelet packet of the swept frequency signal are proposed.The results show that the defect identification indicators based on the amplitude of the sinusoidal signal and the energy value of the wavelet packet of the swept frequency signal can effectively identify the quality defects of the grouting.The discriminating results are in accordance with the quality defects of sleeve grouting simulated in advance,and the feasibility and effectiveness of using piezoelectric ceramics to identify quality defects of sleeve grouting are verified.(4)Using the piezoelectric ceramic-based grouting quality defect monitoring method proposed in this paper,a prefabricated shear wall connected with a grouting sleeve was used to monitor and evaluate the grouting quality,and through direct observation of the grouting quality inside the split sleeve to verify the monitoring and evaluation results.The results show that the results of grouting quality evaluation using defect identification indexes CV and ECV are consistent with the internal grouting quality of the sleeve after dissection,proving that the method for monitoring the quality defects of sleeve grouting using piezoelectric ceramics proposed in this paper is in the actual structure applicability.