Study On Grouting Defect Detection For Grouted Splice Sleeve Connector Based On Stress Wave Measurement

At present,grouted splice sleeves(GSS)have been widely employed as major connectors for rebar in prefabricated concrete(PC)structures in China.The experience of engineering practice indicates that the grouting quality of GSS is greatly affected by the artificial factors such as the construction process and the technical level of the construction personnel,and the sense of responsibility,which is prone to grout defects.Moreover,the GSS connector is embedded in the interior of the PC member and grout defect is not visible,which poses a challenging problem to identify the grout defect.The quality of grouting construction is a key factor affecting performance of the structure.Once grouting is not full,the grout defect will affect the continuous force transmission of the main reinforced steel bars of the prefabricated building,and even have a negative impact on the integrity and safety of the structure.Therefore,it is of great significance to study the grout defect identification method of the GSS connector in prefabricated buildings.In this paper,a method based on piezoelectric intelligent material generating and measuring stress wave is proposed to detect grout defects of GSS connectors in prefabricated buildings.The main contents of this paper are as follows:1.Based on the analysis and summary of related studies on structural defect detection based on piezoelectric materials at home and abroad,a method for grout defects of GSS connectors based on piezoelectric intelligent material generating and measuring stress wave is proposed.Based on the analysis of its basic principles on the method of piezoelectric stress wave measurement,a grout defects detection system for GSS connectors is established,and the signal acquisition and analysis processing methods were introduced.2.In order to verify the feasibility of the proposed method,designed and produced double-ended grouting GSS connector and single-ended grouting GSS connector with different dimension defects in the laboratory,and carried out experimental verification study.A defect evaluation index was defined based on first wave amplitude of the received signal.The test results show that the proposed defect detection method can detect the grout defects artificially set in different specimens in advance,and the defined defect evaluation index can reflect the degree of defects well.The validity and feasibility of the proposed detection method proposed in this paper were verified by experiment.3.In order to further study the mechanism of the proposed method,based on the numerical simulation method to verify the feasibility of detecting the surface debonding defect of steel bars based on method of stress wave measurement,a three-dimensional electromechanical coupling model of GSS connectors with different defects was established.The finite element model performed multi-physics coupled finite element analysis on the stress wave field and the response output of the piezoelectric ceramic sensor of each test piece.The stress wave field analysis results show that the grout defect in the sleeve has a significant effect on the stress wave propagation process and the output of the piezoelectric ceramic sensor.The mechanism of the detection method proposed in this paper is clarified by numerical simulation.The law of defect evaluation index revealed by numerical simulation is consistent with the experimental research results.