Experimental Research On New Grouting Sleeve Overlap-Joint Of Steel Bar

There are two main types of vertical steel bar connection methods for prefabricated shear wall structure systems: constrained grouting anchor lap connection and grouting sleeve connection.The two longitudinal bar connection methods have the disadvantages of long inserted steel bar,complicated sleeve style and high material requirements.In order to reduce the length of the connecting steel bar and improve the existing problems of the existing grouting sleeve connection,this paper combines the advantages of the grouting sleeve with good mechanical properties and strong restraining effects,and proposes a new grouting sleeve steel bar lap connection form based on the research of the research group.,And related research on joint connection performance and mechanism.The specific research contents are as follows:Through the comparison of grouting sleeve products at home and abroad,the advantages and disadvantages of the existing grouting sleeve products are summarized,and a new sleeve manufacturing method is proposed.The low-carbon steel pipe is processed into a threaded sleeve through a roller rolling process,and the spiral ribs on the inner wall of the sleeve and the spiral grooves on the outer wall are simultaneously formed by cold processing,and the processing technology is simple.The spiral ribs on the inner wall and the spiral grooves on the outer wall can greatly increase the mechanical bite force between the sleeve and the contact surface material.Summarizing the advantages of the grouting sleeve connection,combined with the research results of the research group's constrained lap connection,innovatively proposed a steel bar centering lap connection method,and continuously optimized the design according to the engineering practice,and proposed two other eccentric lap connections.The unidirectional tensile test was used to study the connection performance of the two new types of lap joints.It was found that when the lap length was 10 d,the strength and deformation of the new lap specimens met the specifications at the same time,which proved the feasibility of the new lap joint method.According to the test phenomena and results,combined with the theory of steel bar and concrete bonding and anchoring,the mechanical mechanism of the new connection joint is analyzed and the working mechanism of the connection joint is given.By comparing the restraining effect and strain of different test sleeves at home and abroad,it is found that the force of the lap joint sleeve is less than that of the butt joint.Comparing the two lap joints,it is found that the performance of the two is basically similar,but the eccentric lap joint deflects.The length of the lap determines the failure mode of the joint and is the most important factor affecting the bearing capacity of the joint.For the joints where the steel bar slips and pulls out of the grout,the factors affecting the bearing capacity of the joint include the strength of the grout and the inner diameter of the sleeve.The mechanical model of the new connection joint is given,and the calculation formula of the lap length of the connection joint is derived on the basis of the mechanical model of the spiral stirrup constrained slurry anchor,and the structural requirements related to the sleeve and the lap length are given.For the application of grouting sleeve connection technology is relatively complex,on-site operations are difficult,in order to ensure the quality of the new grouting sleeve,the accuracy of component production and installation,improve the efficiency of component manufacturing and installation,combined with the characteristics of the new grouting sleeve lap connection method and the preliminary research of the research group,The manufacturing process of the new sleeve and the manufacturing and installation method of the new connection prefabricated shear wall are proposed in detail.Aiming at the eccentric overlap of the grouting sleeve in the shear wall,the force deflection of the sleeve will cause the concrete wrapped in the sleeve to be damaged.It is proposed to use the centering lap connection,or to use the tie bars and stirrups through calculation and specification requirements.