Design And Study On Connection Properties Of A New Type Of Grouting Sleeve Based On High-performance Grouting Material

The prefabricated building is characterized by energy saving,environmental protection and fast construction.It is an important way to realize construction industrialization and residential industrialization.It has been included in the strategic development plan of construction industry and has become a nationally enforced construction method.The reliable connection of forced steel bars of prefabricated members is the key to ensure the safety performance of the prefabricated buildings.The grout sleeve splicing of rebar is consist of grouting material and grouting sleeve.The performance of grout sleeve splice is affected by the performance of grouting material and grouting sleeve and their cooperative work.At present,the research on grout sleeve splice is relatively insufficient in China.The study of high early strength performance is lack relatively,the existing grouting sleeve has fewer kinds and higher price,and the research on cooperative working performance of grouting material and grouting sleeve is insufficient.This has become one of the important factors restricting the promotion and application of the fabricated concrete structure in China.Based on the National Key Research and Development Plan of the 13 th Five-Year Plan(2016YFC0700904),high early strength and high performance grouting material was developed from component design and performance requirements,and a new grouting sleeve was designed.On this basis,the mechanical properties and application technology of reinforced sleeve grouting connection were studied systematically,which provides theoretical support and technical guidance for the promotion and application of sleeve grouting connection.The main research work and main innovations achievements are as follows:(1)Based on the experimental design and analysis of response surface methodology,the evolution rule of early strength of grouting materials was explored.The calculation models of early mechanical properties of different cementitious materials were established,and the design and optimization method of cementitious components of early strength grouting materials was put forward.The mechanism of early strength grouting materials was revealed based on the composite principle of material components and the analysis of functional components.Evolution mechanism of high fluidization and micro-expansibility of grouting material was proposed.Design and preparation methods of early strength high performance grouting material were put forward.High performance grouting material with 3-day compressive strength of 86.2 MPa(28-day design strength)and 28-day compressive strength of 110.8 MPa(130% of standard design value)was prepared.(2)The grouting sleeve with independent intellectual property rights was designed(GSWT grout Sleeve with Thread and Wedge),which is made of ordinary seamless steel tube by cold processing.The influence of the inner cavity structure,sleeve size,anchorage length and reinforcement size of grouting sleeve on the anchorage performance of reinforcement is studied by unidirectional tension and repeated tension-compression test system.The optimum sleeve parameters were studied,such as the height of thread teeth(1.5mm),inclination angle of wedge(14.5 degree s).The performance of grouting sleeve with reinforcing bar anchorage length achieved 6 times the diameter meet the requirements of joint performance standards.Based on the finite element simulation analysis,the stress model of GSWT grouting sleeve has been established,the working mechanism of GSWT grouting sleeve has been revealed,and the design method of new grouting sleeve has been discussed.(3)Based on the new grouting sleeve and high performance grouting material,the interfacial bond test method was used to study the cooperative working performance of sleeve grouting material and sleeve for the first time.The influence mechanism of mechanical strength and expansibility of grouting material on the anchorage performance of sleeve was revealed.A numerical model between bond strength and compressive strength of grouting material was established.Performance requirements of grouting material for reinforcing bar connection of length of 4-9 times diameter anchorage of bar was proposed.(4)The influence of construction defects such as eccentricity of bars and insufficient grouting on sleeve anchorage performance is systematically studied.The damage rules of anchorage performance: grouting insufficiency > eccentricity of bars,internal defects > end defects,horizontal defects > vertical defects et al are revealed.The control requirements of defect rate for different types of defects are put forward,which provides theoretical basis for sleeve grouting connection construction and acceptance.The simulation of building fire environment reveals the degradation rules of grouting connection performance of reinforced sleeve at different temperatures(200 ℃-800 ℃)and different thickness of protective layer(15mm-30mm).The mechanism of high temperature damage was revealed from the microscopic point of view of materials.The numerical model of grouting material strength and temperature response was established.And the fire resistance limit of grouting connection of reinforced sleeve(600℃)was put forward,which provides theoretical support for fire safety evaluation of assembled buildings.On the basis of summarizing the work of this paper,the research prospect of this topic is put forward.