| FRP bars have the advantages of light weight,high strength,non-magnetic,corrosion resistance,and good anti-fatigue properties.As a stress bar and structural bar,it has gradually been widely used in the field of engineering construction.Due to the constraints of production and transportation conditions,the length of FRP ribs before delivery is limited,but the FRP ribs required in actual projects are always long;therefore,the connection of FRP ribs has become an inevitable problem in engineering applications.Due to the limitation of the material properties of FRP bars,it is difficult to directly transplant the existing mature connection methods of steel bars,such as welding and mechanical connections;although banding and overlapping can be used,the specifications have a relatively limited scope of use.At present,domestic and foreign research on FRP rib connection methods,especially sleeve butt connection and product component research and development is still in its infancy.The FRP rib connection mechanism and evaluation method are not yet perfect;therefore,it is necessary to carry out research on its connection method.Based on this,this paper designs a sleeve for butt connection of FRP bars,and completes a series of analysis and research work in order to effectively solve the engineering problems of FRP bar connections.(1)Based on the characteristics of FRP tendons,combined with the principle of the connection of steel grouting sleeves,based on the principle of equal strength of FRP tendons and sleeves,this paper initially designed steel sleeves and fiber composite sleeves;14 sleeves were performed.Pull test of FRP bar specimen under restraint.The bonding performance of FRP bars in structural adhesives under the constraint of sleeves,the mechanism of force transmission,failure modes and their influencing factors were studied,and the bond-slip curve of the interface between FRP bars and structural adhesives was obtained.(2)Based on the theoretical analysis of the micro section of the FRP tendon force system under the sleeve restraint,the calculation expressions of the axial stress and the bond stress of the FRP tendon and the sleeve during the FRP tendon pull-out process are derived;The change law of stress is compared with the drawing test,and the results are in agreement.At the same time,the expression of the pull-out load when the colloid is cracked is derived;on this basis,the design of the FRP tendon sleeve glued butt joint and the calculation method of the basic anchor length are proposed.(3)Based on a series of test results and theoretical analysis,the sleeve's geometric size and structure have been continuously optimized,and a fiber composite sleeve for FRP rib butt connection has been designed and manufactured;FRP rib sleeve glued butt joint has been given.Test method for tensile properties.On this basis,the unidirectional tensile and repeated tensile and compression tests of 15 joint test pieces were completed,and the unidirectional tensile and repeated tensile and compression properties of the joints were obtained.The results show that the FRP sleeve designed in this paper can butt-join FRP bars,and the formed butt joint can make use of the strength of FRP bars.The proposed design method of FRP-bar sleeve connection can effectively solve the problem of FRP bar connection.Provide a new reference for future engineering applications. |
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