Microanalysis Of Steel Fiber Corrosion Failure Of Steel Fiber Reinforced Concrete Based On Cohesive Force Model

With the rapid development of economy and science and technology,ordinary concrete has been unable to meet the needs of today’s building development.Adding appropriate amount of steel fiber into concrete can effectively increase ductility and ultimate bearing capacity of members,so steel fiber concrete is widely used in tunnel,bridge deck pavement,pavement structure and other projects.But in recent years,the corrosion of steel fiber has become more and more obvious,which seriously affects the safety and service life of the structure.The mechanical properties of corroded steel fiber reinforced concrete after research focuses on the test,the numerical simulation study of steel fiber corrosion problem is less,so this study based on the related experimental research,the micromechanical finite element numerical simulation method,the simulation analysis of rusting of the macro mechanical properties of steel fiber reinforced concrete members,after damage failure process and damage failure mechanism.The main contents of this paper are as follows:(1)Two forms of steel fiber corrosion are studied in this paper: uniform corrosion and local corrosion.The calculation of steel fiber corrosion layer thickness refers to the empirical formula proposed by the existing research,and is verified with the test results.The elastic modulus of the corrosion layer and the bond strength between the corrosion layer and mortar after corrosion of steel fiber are determined.(2)The random aggregate model was established,and the monte Carlo method and Valavin formula were used to transform the THREE-DIMENSIONAL model into a two-dimensional model.In combination with the mixture design adopted in the experimental study,a two-dimensional microscopic finite element analysis model of steel fiber corroded concrete member was established.(3)the micromechanical finite element method(fem)is adopted to corrosion of steel fiber concrete in the macro elastic modulus and poisson’s ratio and so on macroscopic mechanical properties of the accurate prediction,and with the relevant test,this paper compares and analyzes steel fiber corrosion rate are 3.418% and 4.963%respectively,this paper,the finite element simulation results with the test result error is6.1%,4.1%,based on the micromechanical finite element method is feasible and provides reliable alternative to reduce the testing work.(4)To study the damage and failure process of steel fiber reinforced concrete(SFRC)members after steel fiber corrosion under uniaxial tension,compression and three-point bending and other working conditions,as well as the law of crack generation and propagation,and its influence on the overall macro performance.In order to establish accurate and reliable finite element calculation models,cohesive force units were embedded in the mortar and the interfaces between mortar and aggregate,mortar and steel fiber corrosion layer,and steel fiber corrosion layer.(5)based on the numerical simulation of steel fiber corroded concrete members under uniaxial compression,stretching and three point bending test,the following main conclusions: uniaxial tensile,compression,the cohesive force of unit was opened,the first destructive for mortar and rust layer interface,interface and the internal cracks,cement mortar after the final formation of cracks.For the three-point bending simulation,the crack gradually starts from the crack in the lower part of the beam because of the maximum stress.they make tiny cracks,which then move upwards until they break through.Considering the influence of the three factors on the fracture development path,the reduction of elastic modulus and bond strength will change the fracture development path,the number of cracks will increase,and the ultimate load and ductility will also decrease.