Research On Inspection Method Of Sleeve Grouting Connection Based On CT Technology

In recent years,with the rapid development of national economy and technology,the process of housing industrialization in China has accelerated,and higher requirements for building assembly rate have been put forward.With the characteristics of high construction quality,fast construction speed,saving resources and protecting the environment,the prefabricated construction has gradually become a structural form which the state and local governments are popularizing vigorously,and has become a hot research project in the field of construction engineering.The connection technology of steel sleeve grouting is mainly used in prefabricated construction in beams,columns and shear walls with steel,which is responsible for the quality of the prefabricated construction connection and the overall safety performance of the structure,is one of the key technologies of connecting prefabricated structural components,is also the main problem to be solved in the process of use and popularization of prefabricated buildings.At present,the majority of experts and scholars have focused on the bearing capacity and failure mode of reinforced sleeve grouting connections caused by the material and shape of the sleeve and the type of reinforcement.However,there are few studies on the internal defects of sleeve,mainly due to the lack of effective detection of location,size and distribution of specimen defects.The four kinds of sleeve grouting connection specimens including steel bar deviation and grouting material mixed with foam particle impurity are produced.Industrial CT,ultrasonic detector and profile cutting machine were used to conduct defect detection tests.The size,area and volume of the defect are calculated by CT software.The density of the material inside the specimen is analyzed by the gray value of the slice.According to the axial perspective and the CT three-dimensional image of the specimen,the distribution of the steel bar and the distribution of the defect are studied.In addition,the test data of ultrasonic detection and cutting test are also carried out,and the results and characteristics of the three detection methods are discussed.It is proved that the application of industrial CT to the defect detection of the reinforced sleeve grouting connector in the prefabricated construction is effective.The main conclusions of the study are as follows:(1)Industrial CT can quantitatively detect the size,area and volume of defects,determine the density of internal materials,and accurately determine the deviation of steel bars.The location of specimens,grouting holes and defects can be clearly observed by 3D reconstruction of CT software.Defects are mainly distributed in the groove on the inner wall of the sleeve,mainly located on one side of the grouting hole,showing holes or voids.(2)The ultrasonic can detect the defects qualitatively,and the accuracy is low.At the same time,it is necessary to compare the reference data of the standard test parts to analyze the influence of the defects on the density and strength of the specimen,easily leak out the defects,and can not detect the deviation of the steel bar.(3)Cutting inspection can directly see the shape and location distribution of the defects on the cutting surface,and the results are basically the same as those of CT.However,because of the limited cutting surface,the three-dimensional distribution of internal defects can not be determined.Moreover,when cutting the specimen,the saw blade will destroy the shape of the defect,making some defects difficult to detect after cutting.(4)The testing quality of industrial CT is higher than that of ultrasonic testing and cutting.For the sleeve grouting connection connecting the key nodes in the assembly building,it is suggested that the CT test is recommended after the maintenance of the same construction technology and material preparation on the site.