Nondestructive Testing Technology Of Rebar Sleeve Grouting Connection And Its Finite Element Simulation

In response to the national requirements and calls for green,circular and low-carbon development,prefabricated buildings have ushered in a new stage of development.The connection method between prefabricated building components is the focus of current design and construction,of which the rebar sleeve grouting connection is one of the most widely used connection methods.Rebar sleeve grouting connection is a hidden project,there are many problems such as high technical requirements,difficult grouting and complex construction technology,so the accuracy and coverage of the quality inspection of the connection node and the qualitative and quantitative analysis of defects have always been engineering problems.After unremitting exploration and efforts from all walks of life,the method of quality inspection of grouting connection of steel sleeve has been improved.According to the degree of damage to the connecting specimen,it can be divided into damage method,micro-loss method and non-destructive testing method.Obviously,in the actual engineering testing,the damage method and the micro-loss method have a certain degree of damage to the specimen,which will more or less affect the continued use of the specimen,so the non-destructive testing method is the most ideal detection method in the quality testing method of steel sleeve grouting connection.At present,the non-destructive testing methods available include embedded element method,X-ray method,mechanical wave method and circuit method.In this paper,aiming at the two non-destructive testing technologies of rebar sleeve grouting connection,the propagation law of ultrasonic method and impact echo method in concrete and the quality detection of specimens of different types and sizes of defects are explored through defect detection test and finite element simulation analysis.The specific work and research results are as follows:(1)When detecting sleeve grouting defect specimens by ultrasonic method,the method of finding defects by sound velocity and waveform is more intuitive,and the sound time value and amplitude value have certain reliability for the judgment of defects;It is difficult to distinguish defects of 10%of the sleeve volume with 50kHz ultrasound,and the identifiable limit defect size is related to the ultrasonic frequency.(2)The impact echo method detects grouting sleeve defect specimens,as long as the test is carried out in accordance with reasonable and standardized testing methods,the impact of staff differences on the test results can be ignored;Waveforms and spectrograms provide a visual representation of defects and locations inside the sleeve grout.(3)ABAQUS numerical simulation can effectively display the waveform propagation law and the location and situation of defects,and the simulation results are highly consistent with the experimental results,which proves the feasibility of numerical simulation.By introducing a mathematical model,the distance of ultrasonic diffraction propagation is calculated,which proves that the wave propagates radially in the sleeve with dense grouting,and diffraction occurs in the place of grouting defects;By intercepting the propagation image analysis of the wave at different time points,it can be intuitively observed that diffraction occurs in the place where the grouting is not dense,which further proves that the wave diffracts at the location of the grouting defect.