Experimental Study On The Anchorage Length Of A New-type Grouted Pipe Splice Under Incremental Tensile Load

Compared with the traditional cast-in-situ concrete structure,prefabricated concrete structure has the advantages of high quality,high efficiency,energy saving and environmental protection.Itis an important direction for the development of building structure.it is conducive topromote the development of China’s buildingindustrialization and residential industrialization.In the precast concrete structure,bar connection between precast units is the key to ensure good integrity.Reinforcing bars between precast units were connected by grouting sleeve,and the formation of joint has the advantages of high ultimate bearing capacity,deformation performance.This type of reinforcing connection technology has been widely applied in precast concrete structure.With the funds support of National Natural Science Foundation of China(Grant No.51278312),this paper introduced and summariedthe grouted sleeve in the market at present,a new kind of reinforced grouted sleeve-welding shaping sleeve is proposed.Compared with the ductile iron sleeve and and the sleeve with cutting process,this kind of sleeve has the advantages of simple machining operation,low cost and stable connection performance.It is of great significance and value for the popularization of the precast concrete structure in our country.In this experiment,three groups of specimens(a total of 6)were made by the three kinds of sleeves,and allthe specimens were tested under incremental tensileload and structural performance of the sleeve was studied.The main research contents include the failure mode of the joints,ultimate bearing capacity,load-displacementcurves and strain distribution of barsin anchor length,strain distribution of the sleeve.Research shows that:(1)Two faiure modes including bond slip failure and bar fracture failureoccurred in the experiment.As for the specimensmade by the same type of steel sleeve,with the increase of the length of anchor bar,the failure mode of joint is changing from bond slip failure to bar fracture failure.(2)As forreinforced bar withthe diameter of 25mm,bar gauge of HRB400,to ensure that the joint with enough bearing capacity,it is more reasonable that the type of A,B,C required anchorage length respectively by 6d,7d,8d(d is bar diameter).(3)The bonding property between the grouting material and the sleeve is very good,and the phenomenon that the grouting material pulles out from the sleeve doesn’t happen.It is shown that the design for the number and the spacing of ribs issuccessful.(4)The tests shows that the strain of steel bar has a decreasing trend from the end part of the sleeve to the middle of the sleeve and the strain of the bar is basically axisymmetric.The strain of sleeve have a increasing trend from the end of the sleeve to the middle of the sleeve and the strain of the sleeve isbasically axisymmetric.The grout-filled pipe splice was alsostudied by finite element numerical software.According to the actual structure of grouting sleeve for rebar’s splicing,the numerical model of grouting sleeve for rebar’s splicing at static response along the axial direction was established.The result of finite element analysis tallies with the experimental result well.Result shows that:(1)The load-displacement curve calculated by finite element simulation wasin accordance with the test value,so the the finite element model is correct.(2)Obtained from finite element analysis,Mises stress distribution of joints,steel bar and sleeve is consistent with the experimental results,and the yieldconditionof the new sleeve is also in accordance with the experimental results.