Sleeve Connection Reinforcement Technology With No Ribs Reserved For The Conversion Layer Of The Prefabricated Concrete Structure

Prefabricated concrete structures are mainly load-bearing components of prefabricated concrete components,which are connected by inserting steel bars into the metal sleeves embedded in the prefabricated concrete components and pouring grouting materials.Therefore,the connection nodes are the weak link in the theory of prefabricated concrete structures.However,there is currently a situation where the joint bars are not reserved locally or even throughout the transfer layer,which seriously affects the safety of the structure.Therefore,it is urgent to carry out repair and reinforcement.This project proposes a reinforcement and renovation plan that retains the grouting sleeve as a force transmission component based on engineering practice.The concrete around the grouting sleeve,the floor slab below the grouting sleeve,and some areas of the cast-in-place shear wall are chiseled out.Then,one end of the two connecting steel bars is fixed with the outer walls on both sides of the sleeve through single lap welding,and the other end is extended into the floor slab and the lower cast-in-place shear wall.Finally,the structural reinforcement grouting material is filled in the chiseling area.The main work completed and achievements achieved in the thesis include:(1)Study the weldability of grouting sleeve and steel bar.For grouting sleeve and steel bar welding of different materials,through manual arc welding and the selection of suitable welding rods,4 groups of 12 specimens were designed and produced,and combined with the "Rebar Welding and Acceptance Specification" JGJ/T 27-2014,12 specimens were subjected to unidirectional tensile tests.The results show that the weldability between the ductile iron grout sleeve and the HRB400 steel bar is poor,and the specimens are damaged at the weld or the welding heat affected zone.Q345 grout sleeve,No.45 steel grouting sleeve and HRB400 steel bar have good weldability,its tensile strength is greater than the standard value of steel bar tensile strength,and the specimens are all damaged by the steel bar base metal.(2)Study the mechanical properties of sleeve grouting connection for high welding temperature.Design and produce 2 groups of grouting and then welding specimens,2groups of welding and then grouting specimens,a total of 4 groups of 12 specimens and one-way tensile test.The results show that the high welding temperature has no obvious effect on the mechanical properties of the sleeve grouting connection.(3)Conduct experimental research on the welded connection between the grouting sleeve and the steel reinforcement.Two steel bars were welded on both sides of the grouting sleeve and grouting material was wrapped around the weld seam.Taking into account the influence of grouting material strength,relative protective layer thickness,and single side welding length on the connection performance,26 sets of 78 specimens were designed and manufactured.Through unidirectional tensile tests,the results show that the critical condition combination for the failure of the weld seam at the connection between the grouting sleeve and the steel bar is when the single side welding length of the grouting sleeve and the steel bar is 4d,the relative protective layer thickness is 2d,and the strength of the grouting material is C60.To ensure the quality of reinforcement in the later stage,the single side welding length should be 5d,the relative protective layer thickness should be 3d,and the strength of the grouting material should be C60.(4)Conduct experimental research on the bonding and anchoring performance of double anchor steel bars and grouting materials.Considering the effects of relative anchoring length,relative protective layer thickness,and grouting material strength on its anchoring performance,15 sets of 45 specimens were designed and manufactured and subjected to uniaxial tensile tests.The results indicate that when the relative anchoring length between the double anchor steel bar and the grouting material is 12 days,the relative protective layer thickness is 4 days,and the grouting material strength is C60,it is the critical condition combination for the specimen to undergo splitting failure.To ensure the quality of later reinforcement,the relative anchoring length should be 14 d,the strength of the grouting material should be C60,and the relative protective layer thickness should be 4d.And based on the experimental data,the calculation formula for the bonding and anchoring bearing capacity of the double anchor steel bar and grouting material was obtained.The theoretical data is in good agreement with the experimental data,which can be used as a reference for practical engineering.