Research On Mechanical Properties Of 600MPa Grade Steel Bar Sleeve Grouting Connection

At present,the connection modes of longitudinal reinforcement in prefabricated concrete structure mainly include sleeve grouting connection and slurry anchor lap joint.Among them,the sleeve grouting connection has good force transmission form,less restrictions on the diameter of reinforcement and the height of building,and has a wider range of application.In the face of the new requirements of the state and people on the seismic grade and green safety of buildings,more and more high-strength steel bars such as 600 MPa are put into use in high-rise concrete buildings.In response to the requirements of the "14th five year plan",this paper uses 600 MPa Steel Bar with diameter of 22 mm,GDPS sleeve and high-strength cement-based grouting material to make steel sleeve grouting joint.Through uniaxial tensile test and ABAQUS numerical simulation,the main research contents and results are as follows:(1)A total of 12 groups of specimens were designed,two in each group,a total of 24 specimens.The results of uniaxial tensile test show that there are four failure modes: the upper reinforcement pulling out,the upper reinforcement breaking,the lower reinforcement pulling out and the lower reinforcement breaking.Before the load reaches the yield strength,the load displacement curves of all specimens increase linearly.(2)By drawing the curves of ultimate bearing capacity and residual deformation of specimens under different parameters,the influence of reinforcement anchorage length,grouting material strength and sleeve rib number on the mechanical properties of joints is obtained: after the reinforcement anchorage length reaches 7 days,increasing the reinforcement anchorage length or sleeve ring rib number has little effect on the ultimate bearing capacity of joints;the bearing capacity of specimens increases with the increase of grouting material strength The residual deformation decreases with the increase of temperature.(3)By analyzing the load-strain curve of the sleeve surface,the axial strain and circumferential strain of the sleeve surface are obtained: the axial strain and circumferential strain of the middle part of the sleeve are the largest,and the absolute value of the circumferential strain is less than the axial strain at the same position of the sleeve;the axial strain of the smooth part of the sleeve is tensile strain,and the axial strain of the deformed part is compressive strain;the circumferential strain of the sleeve is compressive strain,and the larger the axial strain is The strain near the middle of the sleeve is larger.(4)Considering the interaction between reinforcement and grouting material,grouting material and sleeve,ABAQUS finite element software is used to establish the numerical model of the test component,and on this basis,the component parameters are modified to obtain the mechanical properties of the reinforced sleeve grouting connection component under more variables.Through the displacement time curve of the output node,the relative slip between the reinforcement and the grouting material,the grouting material and the sleeve is obtained;the strain distribution law of the sleeve and the influence law of different parameters on the components are verified,and finally it is concluded that for the 600 MPa grade reinforcement with nominal diameter of 22 mm,the sleeve can choose the steel pipe with outer diameter of57 mm and wall thickness of 5 mm.If four ring ribs are set on each side of the sleeve,the anchorage length of the reinforcement needs to reach 9d;if five ring ribs are set on each side,the anchorage length of the reinforcement can reach 8d,because after the anchorage length of the reinforcement reaches 8d,the influence of the increase of the number of ring ribs on the bearing capacity and deformation of the joint decreases.