Research On Flexural Behavior Of RC Beams Strengthened With CFRP Plates Held By End Locked U-straps

The flexural reinforcement of reinforced concrete beams with carbon fiber reinforced polymer(CFRP)plate can effectively improve the bearing capacity of specimens,the simplest way is external bonding method.However,the pure paste CFRP plate is prone to premature brittle debonding failure,which is not conducive to the safe service of the structure and the full play of the material properties.Therefore,a U-strap with self-locking anchor plate at the end is proposed to strengthen the anchoring of CFRP plate to prevent interface stripping damage.Four point bending tests of five reinforced concrete beams are designed,numerical simulation was carried out on the reinforced beams,and the characteristic loads were calculated and analyzed,and the following conclusions were obtained:(1)The mechanical properties of beams reinforced with pure paste CFRP plates and reinforced with end locked U-shaped fiber belt are compared,including failure modes,ultimate bearing capacity and deformation of specimens.The experimental results show that anchoring CFRP plate with end locked U-straps can effectively delay the stripping of CFRP plate,significantly improve the ultimate load of specimens,improve the ductility of failure and improve the utilization rate of materials,which proves the effectiveness of the anchorage mode of end locked U-straps.(2)The influence of wide and thin sheet and narrow and thick sheet on the reinforcement effect was studied under the same reinforcement amount.The results show that the thinner CFRP plate is beneficial to delayed stripping,and the bearing capacity and ductility of the reinforced beam are improved.The initial peeling load and ultimate load of the severely damaged beam reinforced by end locked U-straps are both higher than those of the undamaged beam reinforced by pure adhesive.(3)ABAQUS is used to establish the nonlinear finite element model,and the comparison of the ultimate load,deflection and strain of mid-span CFRP plate showed that the simulation results were in good agreement with the test results.(4)The characteristic loads of the reinforced beam are calculated and compared with the experimental values.The calculated values of cracking load,yield load and initial peeling load are in good agreement with the experimental values,which verifies the applicability of the formula.