Study On The Flexural Behavior Of Prefabricated Beams Connected By RPC

The development of prefabricated concrete structure is one of the important ways to realize the construction industrialization and promote the supply side structural reform of the construction industry.At present,the development of prefabricated buildings in China is still relatively slow,which is due to many reasons,such as immature assembly technology,high cost and insufficient market acceptance,but the main technical bottleneck restricting its development is the connection problem of prefabricated joints.Reactive powder concrete(RPC)is a new type of cement-based composite material with ultra-high strength,toughness and durability.RPC connected prefabricated beam is an assembled beam structure formed by applying reactive powder concrete with excellent mechanical properties and durability to the joint pouring materials,and connecting the prefabricated beam with the prefabricated beam through certain structural measures.The research on the fabricated beam is the important foundation for the application of this joint in beam to column joints,column to column joints,wall to wall joints and other fabricated joints.In addition,the shear resistance of the joint surface is the key to determining the bonding performance of the RPC post-cast joint of the assembled beam.At present,domestic and foreign research on the shearing problem of the joint surface of prefabricated members mainly focuses on the roughness of the joint surface,the number and size of keyways,the diameter,depth,and quantity of buried steel bars.However,there are few studies on the shape of the joint surface that is easy to manufacture and has a significant effect on the bonding performance of the post-cast joints.Therefore,the shape of the joint surface is used as the main parameter to investigate the shear and bending performance of the joint surface of the prefabricated beams connected by RPC.After the research,the main research contents and conclusions are as follows(1)By changing the shape of the joint surface,five types of "Z" type shear specimens were designed,mainly discussing the joint surface of the post-cast RPC and precast ordinary concrete members in the key groove flat interface,single oblique boundary surface,and double oblique boundary surface treatment methods shear resistance.The development patterns of failure modes,shear bearing capacity,load-displacement curve and strain of different types of joint surfaces are analyzed.The test results show that the shape of the joint has a great influence on the shear performance.The shear capacity of the single bevel joint is 26% higher than that of the keyway joint,and the double bevel joint is not fully developed because of the insufficient concrete strength.The embedded reinforcement can improve the ductility when the interface is damaged.In order to play the role of shear reinforcement,the reinforcement with a diameter of no less than 6mm should be selected and sufficient embedded depth and thickness of concrete cover should be ensured.(2)In this paper,seven RPC connected prefabricated beams and one ordinary concrete cast-in-situ comparative beam with different joint treatment are tested for flexural performance.The load deflection curve,strain,crack distribution and failure mode,as well as bearing capacity and deformation performance are mainly analyzed.The test results show that the load deflection curve of each test beam has three distinct stages,and the assembled beams with different joint surfaces have sufficient ultimate bearing capacity to ensure,but the crack development and failure patterns are quite different.The cracks on the keyway interface are developing rapidly,and the crack control ability of the single bevel and double bevel is better than the keyway interface.With comprehensive ultimate bearing capacity,deformation performance and failure form,it is recommended to use the 45° double bevel edge and 45° single bevel edge joint surface assembled beam.