Study On Constitutive Relation Model Of Carbon Fiber Mesh Confined Concrete Under Uniaxial Compression

Fiber reinforced composites(FRP)have the advantages of lightweight,high-strength,and corrosion resistance.A lot of studies show that FRP confined concrete columns can improve the mechanical properties of concrete columns,and can be used in the reinforcement and repair of existing buildings.At present,there are many kinds of FRP materials,such as carbon fiber mesh(CFRP mesh),FRP cloth and so on.Because of its unique shape and characteristics,carbon fiber cloth grid has a unique advantage in the reinforcement and reconstruction of existing buildings.At present,there is little research on the relationship between the main structure of cfrp-confined concrete,and other models are not applicable to the relationship between the main structure.In this paper,through experimental analysis,theoretical derivation,and numerical simulation,the mechanical properties,restraint mechanism,and internal structural relationship model of CFRP confined concrete were studied,the main studies and conclusions are as follows:(1)The uniaxial compression tests of concrete columns confined by CFRP gratings are carried out.In order to record the damage patterns and characteristics of concrete columns confined by CFRP grids under axial compression,the effects of the number of CFRP grid layers and the number of CFRP grid bars on the peak load-carrying capacity,peak displacement and ductility coefficient of CFRP grid-confined concrete are studied.The experimental results show that the bearing capacity and ductility of CFRP confined concrete columns are improved to a certain extent compared to non confined concrete columns,the stress-strain curve shows a softening section after the peak of stress.(2)The main structural relationship model of concrete confined by carbon fiber mesh under uniaxial compression is established.Based on the analysis of the constraint mechanism and loading process of cfrp-confined concrete columns,the loading process of cfrp-confined concrete columns was divided into three stages.On the basis of the existing Stress–strain curve calculation model,the loading process of cfrp-confined concrete columns was divided into three stages,by introducing the effective restraint zone and effective lateral restraint coefficient,the structural relationship model of concrete confined by CFRP grid under uniaxial compression was established.Finally,the stress strain curve is compared with the experimental results,and the results agree well,verifying the effectiveness of the intrinsic structural model.(3)Numerical simulation of concrete confined by CFRP grids under uniaxial loading.Using Abaqus software,a finite element model of CFRP mesh constrained concrete under uniaxial compression was established for numerical simulation analysis.The results of numerical simulation,experiment,and theoretical calculation agree well with the stress-strain curves,indicating that the finite element model established in this paper is reasonable.(4)Analysis of mechanical properties of CFRP mesh constrained concrete.A finite element model was established to investigate the effects of concrete strength grade and CFRP mesh size on the mechanical properties of CFRP confined concrete columns.The results show that the plastic deformation resistance of concrete decreases as the strength grade of concrete increases,and the confinement effect of CFRP on core concrete is poor,the size of carbon fiber grid also affects the restraint effect of carbon fiber grid,and the larger the size of carbon fiber grid,the worse the restraint effect.