Study On Mechanical Properties Of Steel Sleeve Grouting Joints

Prefabricated buildings are buildings built with prefabricated parts and components assembled on the site.The development of prefabricated buildings is a major change in construction modes,which is conducive to promoting the development of new urbanization and building industrialization.It has the advantages of reducing construction pollution,improving production efficiency,saving resources and it is also the inevitable direction of the development of construction industry in China.The reinforced sleeve grouting connector is the main connection part of the prefabricated vertical structure,which is of great significance to the stability and integrity of the whole prefabricated building structure.In order to further understand the reliability of reinforced sleeve grouting connector in prefabricated building structures,based on uniaxial tensile test and high-stress repeated tensile-compression test in this paper,the stress characteristics of different reinforced sleeve grouting connectors in different length of anchoring bars are comparatively analyzed,and analysis of the reinforced sleeve grouting connector within the grouting material and anchor steel,grouting material and the inner surface of the sleeve between the constraints,bonding,anchoring and other mechanisms.This paper mainly adopts the methods of experimental research and theoretical analysis to further explore the stress performance of steel sleeve grouted joints.The main work has been done as follows:1.The development history,engineering application and research status of the reinforced sleeve grouting connectors of important vertical connection components in prefabricated buildings are summarized.2.The mechanical properties of 9 different types of 27 reinforced sleeve grouting connectors under uniaxial tensile test load are studied.Reinforced sleeve grouted joints exhibit two failure modes in the results of uniaxial tensile tests,one is tensile failure of connecting steel bar and the other is bond-slip failure of anchoring steel bar.The load-displacement curves corresponding to the tensile failure of connecting steel bars are basically the same as the change trend of of single steel bar,but the load-displacement curve of the specimen corresponding to the slip failure is obviously different,and and it shows a certain ductility at the destructive stage.3.In the uniaxial tensile test,the failure results of connecting steel bar breakage occurred in steel bar anchorage joints with anchorage lengths of 8.0d and7.0d,respectively.And They all meet the relevant provisions for the strength and deformation of Grade I connection joints in the "Technical Specification for Reinforcing Steel Mechanic Connections"(JGJ 107-2010).That is,the standard values of tensile strength of joints of reinforced sleeve grouting connectors are greater than 1.10 times of the standard values of the tensile strength of steel bars,the residual deformation is less than0.10 mm,while the reinforced steel sleeve grouted joints with anchorage length of 6.0d are the bond-slip damages of the anchoring steel bars inside the sleeve,and do not meet the reinforcement resistance standard value of the connection joints of steel sleeve grouted joints that is greater than 1.10 times.4.The mechanical properties of 9 different types of 27 reinforced sleeve grouting connectors under repeated high tensile stress tests are studied.The results of uniaxial tensile test showed that the steel sleeve grouted joints exhibited two failure modes,namely the breakage of the connecting steel bar and the bond-slip damage of the anchoring steel bars inside the sleeve.The tensile failure of the connecting steel bars occurs in the reinforced sleeve grouting connectors with the reinforcement anchoring lengths of 8.0d and 7.0d,respectively.And They all meet the relevant provisions for the strength and deformation of Grade I connection joints in the "Technical Specification for Reinforcing Steel Mechanic Connections"(JGJ 107-2010).That is,the standard value of the tensile strength of the connection joints of the tubular grouted joints is greater than 1.10 times of the standard value of the tensile strength of steel bars and the residual deformation is between 0.15 and0.25 mm.5.Using the principle of elasticity mechanics to simplify the analysis of the steel sleeve grouted joints,it is found that the restraint stress between grouting material and anchorage steel bar is smaller than that between grouting material and inner surface of sleeve,which leads to bond slip failure of inner anchorage steel bar in sleeve usually occurs between anchorage steel bar and grouting material,while the bond slip failure occurs in anchorage steel bar,and the stress redistribution occurs in the internal restraint of the joints.The critical value of the minimum anchorage length of the anchor bar is deduced to be 6.5d using the theoretical formula,which is consistent with the conclusion in the experiment.6.Comprehensively summarize the research content and achievements,and make a preliminary analysis of future research directions.