Multi-scale Analysis Of Corrosion Behavior Of Steel Bar In Reinforced Concrete Under Coupled Interaction Between Environment Factors And Loading

The main reason for the failure of concrete durability is the corrosion of steel bar,the volume expansion of corrosion products,Extruded surrounding concrete,Lead to tensile crack of concrete protective layer.Once the protective layer cracking,the harmful medium in the environment is penetrated into the surface of the steel bar directly by the rust expansion crack,rebar corrosion speed will be increased,Serious threat to the structure of the use of safety.Therefore,it is very important to study the crack of reinforced protective layer caused by steel corrosion,which is of great significance to the safety assessment and life prediction of concrete structure.It is well known that the concrete is a multiphase composite materials with multiple scale characteristics,and in practical engineering,most of the components are loaded,based on this.In this paper,the experimental research and numerical simulation method is adopted,A preliminary exploration and Research on the cracking of concrete protection layer under the coupling action of the continuous bending load and chloride corrosion environment is carried out from the multiple scales.The main research contents and conclusions are as follows:(1)Self designed continuous load loading device,using “electro osmosis-constant current-dry cycle ”accelerated corrosion method,Accelerated corrosion test of reinforced concrete specimens under different bending loads,analyzed the effect of bending load on the corrosion of specimens in chloride environment from several scales.Test shows:(a)coupling between bending load and chloride environment will accelerate the corrosion of steel bars in the beam,Influence fracture distribution;(b)coupling between bending load and chloride environment will cause the bearing capacity of the beam reduced,stiffness is increased,and the change is more obvious with the increase of the bending load.(2)Preliminary research on Corrosion of reinforcing steel bar in micro scale,The molecular dynamics simulation method is introduced to study the durability of reinforced concrete.The effects of the coupling action of tensile loading and chloride ions on the damage of the passive film on the surface of the steel bar and the oxidation degree of the steel were studied by using the ReaxFF simulation of the reaction force field.Molecular dynamics simulation results show that: the coupling of chloride ion andtensile loading accelerates the structural damage of the passive film on the steel surface,the degree of oxidation of reinforced iron matrix.(3)Code for the preparation of concrete random aggregate model based on Monte Carlo method in MATLAB software,combining finite element software to establish the meso scale model of concrete.Through the two dimensional reinforced concrete meso model,Numerical analysis of the process of concrete cracking caused by corrosion of reinforcing steel bar.The corrosion rate of steel bar in concrete surface is obtained by numerical simulation,and found that the interface between aggregate and mortar is the weakest part of the concrete,easy to produce internal damage.(4)Based on meso scale numerical model of concrete,the equivalent elastic modulus of concrete is obtained by using the theory of uniformity,and the model is brought into the macroscopic numerical model of reinforced concrete.simulating the method of non uniform corrosion of steel bar is simulated by using the linear temperature expansion of steel bar.numerical analysis of the influence law of coupling between bending load and expansion force of beams.The numerical results are in agreement with the experimental results,the coupling of bending load and corrosion expansion force will increase the surface stress of the specimen,make the surface of concrete easy to crack,the accuracy of the numerical model is proved.