Research On The Flexural Behavior Of RC Beams Strengthened By CFRP Under Quadratic Loading

Recently, a new composite material named Carbon Fiber Reinforced Plastic (CFRP) is becoming increasingly popular as a kind of reinforcement material. It is widely used in the field of reinforcement region of concrete structures because it has many advantages such as high tensile strength, high modulus of elasticity, lightweight, corrosion resistance and good workability.In the theoretical analysis,the flexural behavior of reinforced concrete(RC) beams reinforced by CFRP under quadratic loading are studied in this paper. According to analysis,the calculation expression of normal section bearing capacity of CFRP is set up, and it is put forward that strength reduction factorψshould be multiplied in the calculation of normal section bearing capacity of CFRP.In the numerical analysis, twenty simply supported beam specimens with the dimensions of 150mm×300mm×2000mm are investigated. Among them, there are two non-strengthened control beams and six RC beams reinforced with CFRP directly and twelve secondary-loading RC beams reinforced with CFRP. Concrete strength grade is C30,the main parameters is initial load,reinforcement ratio, CFRP layers and pasting length. The simulation analysis indicates that the normal section flexural bearing capacity and stiffness of beams are significantly increased after strengthened. CFRP sheet layers have effect on strengthening effect of beams, flexural bearing capacity of beams increase with the increase of CFRP sheet layers. However,the increase extent of them is not linear. Pasting length of CFRP is the longer, flexural bearing capacity increases the larger, but increase extent of the length has a reasonable scope. Analysis results show that when pasting length is the length of pure bending section plus twice the beam's height, the strength effect is more obvious.Finally, based on theoretical analysis, numerical simulation and test verification, the strength reduction factor and the calculation expression of normal section bearing capacity of CFRP are given.