Experimental Study And Equivalent Stress-strain Relationship Model Of Half-grouted Sleeve Connection Of Reinforcement

Prefabricated buildings are assembled on site with factory-prefabricated components,which are strongly supported by China's policies due to their advantages of energy conservation and environmental protection.Grouted sleeve splice is the most common and mature joint connection in prefabricated buildings.For grouted sleeve over the years many of the study,achievement is mainly focused in: the development of new grouted sleeve,the bond strength calculation of grouted sleeve,the study of finite model of grouted sleeve.There are few researches on the deformation capacity of the grouted sleeve,which focus on the microscopic analysis of the contact surface between the grouted sleeve wall and the grouting material,and between the grouting material and the reinforcement."Technical specification for grout sleeve splicing of rebars"(hereinafter referred to as the " code ")for grouted sleeve only have 8 times the diameter of the embedment length of rebar and bearing capacity requirements,therefore,this paper applies more widely in the engineering of half grouted sleeve splice as object,proposed an equivalent stress-strain model which can be used in component analysis of prefabricated building.The model mainly considers the influence of the change of rebar diameter and embedment length in grouted length.In this paper,taking rebar diameter of half-grouted sleeve splice and the embedment length of the rebar in the grouted length as variables,66 half-grouted sleeve splice members with three connecting diameters of 14 mm,18mm and 22 mm as well as eight to four times rebar's embedment lengths and two loading systems of monotone and repeated loading are designed to research their performance,aims to explore the influence of embedment length on the performance of half grouted sleeve splice and propose the stress-strain relationship of the half-grouted sleeve which is convenient to be used in engineering.Now the main work results are summarized as follows:(1)Half grouted sleeve's test curve is similar to rebar,divided into elastic,yield,Strengthening,necking four stages,when the embedment length is obey to not less than 8 times the diameter of rebar in the " code " : the failure form of half grouted sleeve with diameter of 14 mm is that the grouting material is pulled out,the failure form of half grouted sleeve with diameter of 18 mm is that the rebar's fracture,and the failure form of half grouted sleeve with diameter of 22 mm is that rebar's fracture and the grouting material is pulled out.When the embedment length of half grouted sleeve with a diameter of 18 mm steel bar is reduced from 8 to 6 times rebar diameters,the bearing capacity decreases slightly,and the failure mode is that rebar's fracture.(2)When the embedment decreases from 8 times the diameter of the rebar,the binding capacity of the half grouted sleeve for the grouting material decreases,the slip between the sleeve and the grouting material increases,and the slip between the grouting material and the rebar decreases relatively.Under the same load level,the slip between the reinforcement and the grouting material decreases gradually;under the same load level,when the embedment length decreases,the calculated length of the average bonding stress decreases and the average bonding stress increases.(3)The equivalent stress-strain model is proposed for half grouted sleeve splice,skeleton curves for the double broken line,the parameters include: half grouted sleeve equivalent elastic modulus,yield strain and loading and unloading rigidity of the half grouted sleeve under repeated loading.Model parameters are determined by the ratio of the inner diameter of the half grouted sleeve to the diameter of the rebar,the elastic modulus and the yield strain of the rebar.