Research On The Testing Of Grouting Defects In Prestressed Channels Based On Impact-Echo Method

The prestressed structure,especially the bonded post-tensioned prestressed structure,assists the rapid development of the bridge project.However,in the construction operation,the grouting due to mechanical,artificial and other factors is not compact and exists in large areas over the years due to grouting.The bridge accident caused by the loss of pre-stressed steel beam corrosion and pre-stress caused by the defect frequently occurs,which seriously affects the durability and safety performance of the bridge structure.Therefore,an urgent and important issue has been studied in the detection of grouting defects in post-tensioned prestressed pipelines.The shock echo method using low-frequency stress waves as the medium is currently considered to be the most promising method in this field.Current impact echoes The statutory testing pipeline grouting quality technology has matured.However,the precise positioning of defects and quantitative testing research are still lagging because of too many factors.This paper mainly focuses on the finite element of pipe grouting defects affecting several typical factors of precise positioning and quantitative testing.Simulation analysis and laboratory test study,and a preliminary discussion of the quantitative test defect size,related work:1.Review domestic and foreign literature,compare and analyze the advantages and disadvantages of various non-destructive testing techniques in the detection of grouting defects in pipelines,and focus on the research status of the grouting quality of impact echo testing pipelines at home and abroad,and demonstrate its feasibility.2.From the discussion of the stress wave theory,the basic theories of the shock echo method are introduced,and the method of detecting the grouting defect of the pipeline by the shock echo method is introduced.3.Integrate with the actual project,the typical factors affecting the precise positioning and quantitative detection of the pipeline material,defect size,defect-critical interface position,and prestressed steel strands.Arrange the corresponding engineering model,and use finite element soft ABAQUS to perform various tasks.Under the condition of impact echo response simulation calculation,the relevant conclusions are obtained through calculation and analysis as follows:(1)The pipeline material has a greater influence on the accuracy of the test results;(2)When the defect critical interface position is parallel to the test surface(web work In addition,the difficulty of the test increases;(3)Under certain conditions,the depth signal of the pre-stressed tendon can be tested,and its presence and location status have littleeffect on the defect test;(4)Less common steel reinforcement The interference of the test results on the depth of the defect is not significant;(5)The frequency(or wave velocity)calibration of the plate thickness must be considered in the actual test;(6)The initial quantitative determination is based on the frequency drift rate of the plate thickness and the depth frequency of the defect.The degree of defect is feasible.5,using pre-stressed concrete beam multi-function detector(SPC-MATS)to carry out experimental research on the test model produced under typical conditions,the experimental results and the finite element simulation results are in good agreement.6.Comprehensively summarize the relevant conclusions of the finite element simulation analysis and experimental research,provide some guidance for practical engineering testing,and provide relevant theoretical support for further research.