Study On Mechanical Properties Of Grouting Sleeve Under Reciprocating Load

In recent years,the prefabricated building has been developing more and more rapidly in our country,and various provinces and cities have pushed forward the reform of prefabricated building.This method of on-site prefabrication and assembly can save materials and shorten the construction period.In a document issued on February 21,2016,the CPC Central Committee and the State Council issued a number of opinions on further strengthening urban planning,construction and management,it was proposed to vigorously promote the prefabricated building and strive to take about 10 years,the prefabricated building accounted for 30 percent of new construction.The most important thing for the prefabricated building is to ensure the reliable connection of the tendons in the precast members,which is the key to ensuring the seismic performance of the structure.The steel bars between the precast members are connected through a grout sleeve,resulting in a joint with high ultimate bearing capacity.Because the development of the assembled structure in our country is relatively late,the research and development of the grouting sleeve is still at the initial stage,and the sleeve types in the domestic market are few and expensive,so in order to promote the application of the assembled structure,we urgently need to develop our own sleeve,affordable and reliable performance.This topic comes from the follow-up research on the key technology and design theory of the assembled monolithic concrete structure system of the National Natural Science Foundation of China(No.51278312),the group has tested and simulated the influence of several factors,such as the inner diameter of the sleeve,the distance between the ring ribs and the rib height,on the mechanical properties of the new-type grout sleeve,and determined a group of optimum combination values.On this basis,this paper further studies the mechanical behavior of the new type of reinforced sleeve grouting connections under reciprocating load.A total of 6 specimens were divided into group I and group J,each group of 3 specimens,group I for high stress repeated tension compression,group J for large deformation repeated tension compression.The main contents of the study are the failure mode of the specimen joint,the ultimate bearing capacity of the joint,the bond strength,the load-displacement curve and the Stress–strain curve of the reinforcing bar and sleeve.The experimental results show that:(1)there is only one failure mode in the test,that is,the pull-out failure of reinforcing bar,which is the ideal failure mode.(2)the strain of the anchorage section decreases from the end of the sleeve to the middle of the sleeve,and the strain on the surface of the sleeve decreases from the middle to the end of the sleeve.(3)the maximum stress of reinforcement in Anchorage section is at the end,and the maximum stress of sleeve is at the middle.(4)thebond between steel bar,sleeve and grout is good.The ultimate bearing capacity of the joint depends on the minimum values of bond bearing capacity between reinforcement and Grout,tensile bearing capacity of reinforcement and tensile bearing capacity of sleeve.In this paper,on the basis of the test and through the ABAQUS finite element software to do simulation analysis,according to the specific shape of the reinforced sleeve to establish the corresponding finite element model,the ultimate bearing capacity of the joint under repeated tension and compression with high stress and large deformation was analyzed.The load-displacement curve was compared and analyzed,this shows that the result of finite element simulation analysis is reasonable,and the finite element model can better represent the joint performance.