Experimental And Numerical Study Of Flexural Behavior Of Reinforced Concrete Beams Strengthened With CFRP Considering Secondary Forces

According to the data,many buildings in China have entered the aging stage,and these buildings are in urgent need of reinforcement and repair.Carbon Fiber Reinforced Plastics(CFRP)has the advantages of light weight,high strength,convenient construction and good durability,which makes it widely used in concrete structure reinforcement engineering and improves the reinforcement performance of concrete structures.In the actual reinforcement project,the concrete structure has undergone a stress and reinforcement,so it is more practical to study the reinforced concrete reinforcement performance under the secondary force.Based on experimental research and numerical simulation,the bending performance of reinforced concrete beams strengthened with carbon fiber cloth under secondary stress is discussed in depth.The specific research contents and research results are as follows:(1)Theoretical study on CFRP reinforced concrete beams under secondary stress:The basic assumptions and analytical models are expounded.The failure mechanism and theoretical calculation values of CFRP reinforced concrete beams under secondary stress are analyzed.(2)Experimental study on CFRP reinforced concrete beams under secondary stress:Firstly,the concrete properties of concrete,steel bars and CFRP were tested to obtain the material properties of these materials.Secondly,considering the reinforcement ratio and the magnitude of one stress.In the change,three groups of 9 reinforced concrete beams were designed and fabricated.The ultimate bearing capacity and load-deflection curve of reinforced concrete beams under the secondary stress of 0.3P_u and 0.6P_u(P_u is the ultimate load of the beam)were studied by the bending test.5 steel strain,crack distribution and the influence of carbon fiber cloth strain.The test results show that when the reinforcement ratio is the same,the larger the proportion of pre-applied load,the smaller the ultimate bearing capacity of CFRP reinforced concrete beams is,and the smaller the maximum deflection variation of the beam and the crack spacing,and the smaller the beam spacing.The number of cracks increases.With the increase of initial load and reinforcement ratio,the ultimate bearing capacity of CFRP reinforced concrete beams decreases,while the ultimate tensile strain of carbon fiber cloth increases.(3)Numerical simulation of CFRP reinforced concrete beams under secondary stress:A three-dimensional finite element analysis model of CFRP reinforced concrete beams under unstressed reinforced concrete beams and secondary forces was established by ABAQUS and numerical analysis was carried out.The finite element analysis results are compared with the experimental results to verify the validity of the finite element analysis model.The research results prove that carbon fiber reinforced concrete beams can delay and inhibit the development of cracks.(4)Based on the research results of deflection of CFRP reinforced concrete beams under secondary stress,the influence of U-shaped anchor on the deflection of CFRP reinforced concrete beams is analyzed in depth.The statistical fitting of the anchoring measures of CFRP concrete beams is carried out to obtain CFRP.The correction formula for the stiffness of the reinforced concrete beam is 0.9.This value can optimize the structural design while ensuring structural safety,and can be used as a reference and reference for the actual reinforcement project.