Performance Of Prestressing Anchor For CFRP And CFRP To Curved Surface Concrete Bonded Joints

Prestressed Concrete Cylinder Pipe(PCCP)has been widely used in long-distance water transfer engineering.However,prestressed steel wire wrapped around the outside of concrete is prone to hydrogen embrittlement and corrosion,which brings serious quality problems to the quality of PCCP,such as cracking and bursting.Carbon Fiber Reinforced Plastics(CFRP),on the other hand,possess excellent properties such as lightweight,high strength,and corrosion resistance.This article proposes the use of CFRP cloth instead of steel wires to design and produce prestressed CFRP concrete cylinder pipes.It is necessary to first solve the anchorage problem of CFRP on the pipe body and make the corresponding curved surface concrete specimen according to the outer diameter of PCCP and paste CFRP to carry out single shear test to explore its bonding performance with the curved surface concrete of the outer wall of steel cylinder concrete pipe,and carry out corresponding finite element analysis.The main research results are as follows:1.Design and production are carried out separately for fixed and tensioning end anchors.The fixed-end anchor adopts a clamped cylindrical shaft,CFRP is first wound on the shaft and then clamped between the plates.The tension anchor adopts a toothed plate anchor with an embedded strip,which is applied at the insertion part of the concrete core.The pull-out and prestress loss tests were carried out for the fixed end and the tension end anchorage.Taking the torque and the winding length in the anchorage as variables,the loading reaction frame was designed and manufactured for the test.On this basis,the prestress loss test was carried out on the anchorage of the system.The cylindrical shaft and embedded strip of the two anchorages have a significant effect on their performance,and the prestress loss rate is only5.84 % at higher stress level.2.The bond behavior between CFRP sheet and concrete with curved surface was tested,and the bond-slip constitutive model was given.The calculation formula of interfacial debonding bearing capacity between CFRP sheet and concrete with curved surface considering curvature was proposed.The test results show that when single-layer or doublelayer CFRP sheets are used,the curvature increases the debonding bearing capacity of the concrete interface on the curved surface.The maximum curvature of the single-layer bonded CFRP sheet to improve the interface performance is 1/800.When the double-layer bonded CFRP sheet,the bonding length is 160 mm and the specimen curvature is 1/800,the interface peeling bearing capacity is about 1.63 times that of the plane.3.The ABAQUS finite element software was used to simulate the bonding performance of CFRP sheet and curved surface concrete,and the influence of concrete strength and curvature was analyzed.The results show that when the concrete strength increases from C55 to C65,the interfacial debonding bearing capacity of the specimen with smaller curvature is almost unchanged.When the curvature of the specimen is 1/1800,the double-layer CFRP cloth makes the stress distribution of the bonding interface uniform,which significantly improves the interfacial debonding bearing capacity of the curved surface concrete.