Research On Connection Technology Of Hollow Grouting Sleeve Steel Bar

In recent years,grouted sleeve connection technology,as one of the steel bar connection technologies of precast concrete structures have gradually become a new direction of research and development in the field of construction in China.However,the existing grouted sleeve products have some problems,such as high production requirements,high cost,not easy filling,difficulty of detecting the grouting quality and so on,this paper proposes a new type of opening sleeve,which can alleviate the above problems.The sleeve can be produced by ductile iron within only one working procedure.The fabrication is convenient and the cost is low.The structure of the opening is more conducive to filling grout and quality detection.Through theoretical analysis,experimental research and numerical simulation,this paper explores the influence of different size parameters on the performances of the new type of opening sleeve and the mechanical properties of the new opening sleeve structure.The main research contents and results are as follows:(1)Through the theoretical design of the opening sleeve structure,the finite element simulation and the unidirectional tension test,the influence of different parameters on splice performance was analyzed.It was found that the length distribution of the holes which is the short length near the ends of the sleeve and long length near the middle of the sleeve is more reasonable.In addition,the longer the sleeve length,the wider the ring rib width,the more holes in the longitudinal direction,the smaller the sleeve inner diameter,the better the performance of the grouted splice.It is concluded that the final sleeve structure which can connect 16 mm steel bars is 350 mm in length,31 mm in Inner diameter,4 holes in 1/2 sleeve length and 7 mm in ring rib width.(2)According to the final sleeve structure,3 grouted splice specimens were made and the unidirectional tensile test was carried out.The ultimate bearing capacity and deformation of the grouted splice specimens obtained from the tests meet the requirements of the code.The ring rib closest to the middle of the sleeve has the strongest restraint effect on grout and bars.The middle part of the sleeve has entered the yield stage,and the axial deformation is the largest,while the other parts of the sleeve are still in the elastic stage,and the axial deformation is small.high stress repeated tension-compression test and the large deformation repeated tension-compression test.(3)According to the final sleeve structure,6 grouted splice specimens were made and repeated tension-compression tests were carried out.The residual deformation of the 3specimens in high stress repeated tension-compression test is less than 0.3 mm,with an average of 0.24 mm.The residual deformation of the 3 specimens in large deformation repeated tension-compression test is less than 0.3 mm,with an average of 0.27 mm,and the residual deformation after the eighth cycle is less than 0.6 mm,with an average of0.52 mm,which all meet the requirements of the code.(4)The finite element model of the final opening sleeve grouted splice was established.The simulation results were basically consistent with the experimental results.The optimization of sleeve structure waas analyzed by finite element simulation.It is found that it is effective to add a ring rib in the middle of the sleeve to reduce the deformation in the middle of sleeve.