Flexrual Behavior Of FRP-ECC Hybrid Strengthened Corroded Reinforced Concrete Beam

Due to its light weight,high strength,corrosion resistance,and good working performance,FRP reinforced technology has been gradually recognized and applied to reinforced concrete structure.At present,the externally bonded of FRP reinforcement is the most commonly used in reinforced technique.In the technique,the appearance of the bending-shearing cracks can lead to stress concentration of interface,thus causing the central debonding of FRP.Premature debonding reduces the utilization of FRP,at the same time reduces safety performance of the structure.In order to delay FRP debonding,the researchers proposed many methods,such as concrete surface treatment,near-surface mounting,mechanical anchoring,fiber anchor anchoring,hybrid bonding,etc.This paper proposes a new way of FRP-ECC hybrid reinforcement:use the ECC layer to replace the concrete layer in reinforced concrete beam lateral tensile,employing the ECC layer's good crack control ability to restrain the development of cracks in the upper concrete layer and ECC layer,like forming a crack resistance layer,thereby effectively delay the debonding of FRP,and even make the tension fracture of FRP,thus to give full play to the performance of FRP materials,structural bearing capacity increases significantly.Based on the above ideas,the flexural behavior of FRP-ECC hybrid strengthened corroded reinforced concrete beams are studied and analyzed theoretically,and the bearing capacity model of FRP-ECC hybrid strengthened reinforced concrete beam and ECC strengthened reinforced concrete beam are presented in this paper.The main contents include:?1?ECC is prepared and ECC's basic mechanical properties are determined:the compressive property of the cube,the flexural property of the prism and the tensile property of the dogs's specimen.At present,ultimate tensile strain of most ECC is less than 6%.However,this paper employs HPMC to increase the viscosity of slurry,in order to promote the uniform dispersion of fibers,consequently the ultimate strain of ECC can reach 7.3%.?2?Flexural behavior of FRP-ECC hybrid strengthened reinforced concrete beam without corroded steel carried out successful.By changing the parameters of the ECC's thickness to research the change of FRP-ECC hybrid strengthened beam under different ECC's thickness,and determine an optimal ECC's thickness,but also the flexural properties of FRP-ECC hybrid strengthened beams and separate EBR beams are compared and analyzed.The experimental results show that:the introduction of the ECC layer successfully changed the failure mode of the FRP,which takes place debonded failure no longer but tensile failure,and the ECC layer is just covered in the longitudinal bar with good performance.FRP-ECC hybrid strengthened beam's bearing capacity,the material utilization rate of FRP,energy consumption and ductility compared with only EBR beam have been significantly improved.?3?Flexural behavior of FRP-ECC hybrid strengthened corroded reinforced concrete beam carried out successful too.The effects of ECC reinforcement and FRP-ECC reinforcement are studied by changing the corrosion rate of reinforcement.Among them,the thickness of ECC layer is set to just cover the longitudinal bar.The experimental results show that:Compared with FRP-ECC hybrid strengthened reinforced concrete beam without corroded steel,the FRP-ECC hybrid strengthened corroded reinforced concrete beam has no essential difference,the introduction of ECC layer also caused FRP to break.Finally,by comparing the two reinforcement methods,it is more suitable to adopt FRP-ECC hybrid reinforcement when the corrosion rate of reinforcement is too high.?4?Based on the bearing capacity calculation of flexural members of reinforced concrete beams,the bearing capacity model of FRP-ECC hybrid strengthened reinforced concrete beam and ECC strengthened reinforced concrete beam are presented in this paper.It is proposed that the actual FRP's rupture strain should be calculated by 0.85?_{f u}(?_fu is the FRP's rupture strain obtained by flat coupon test)in FRP-ECC hybrid strengthened beam.