| The degradation of the bearing capacity of concrete flexural members caused by the corrosion of steel bars has always been the focus and difficulty of the durability research of concrete structures.The main path of chloride ion intrusion into concrete components is through the concrete protective layer covering the surface of the steel.In concrete components,the thickness of the protective layer of reinforced concrete slabs is usually thinner.If chloride ions exist in the service environment,its service life will be reduced.Therefore,the corrosion expansion and cracking mechanism of the protective layer of concrete slabs and the degradation of bonding performance can be studied for concrete.The durability design,reliability analysis and life evaluation of the board provide conditions,which are of great significance.Based on COMSOL and ABAQUS finite element software,this paper proposes a three-dimensional whole process of flexural failure of corroded reinforced concrete slabs.The main research contents are as follows:1.The theoretical model and numerical model of concrete damage under non-uniform corrosion of steel bars were established,and the middle and corner steel bars with different boundary conditions were taken into consideration.A three-dimensional model of cracking of corroded reinforced concrete specimens was established,and the expansion pressure of steel bars at different positions was discussed.The distribution,the cracking mode of concrete specimens,the critical corrosion rate of steel bars and the variation of the width of concrete surface cracks,as well as the influence of the ratio of the thickness of the protective layer and the diameter of the steel bars on the cracking of the protective layer.2.The finite element software ABAQUS is used to establish a cohesive element that can truly simulate the bond-slip layer between steel and concrete.Deduced the reinforced concrete bond-slip constitutive without stirrups that fits the actual working conditions of reinforced concrete slabs,and explored the cracking mode of reinforced concrete specimens,the slip distribution in the bonded section of the steel bar,the difference in crack width and bearing capacity The simulation results,theoretical results and the existing experimental conclusions in the literature are compared and verified.3.Through theoretical analysis of the mathematical model of concrete deterioration,the bond-slip model of reinforced concrete interface corrosion,and the calculation of the initial corrosion damage of the steel bar,the mathematical model of the residual bearing capacity of the reinforced concrete slab after corrosion is derived,and the use of the slab under different service life in the chloride salt working environment is obtained.Life prediction model.The main research conclusions are as follows: The corner steel bars of the specimen are more severely corroded by chloride ion than the middle steel bars,and they are more prone to rust expansion and cracking.The mathematical model of bond degradation of corroded steel bars without stirrups is derived through theoretical analysis,and it is found that the ratio of the thickness of the concrete cover layer to the diameter of the steel bar has a more obvious effect on the degradation of the bond strength,the expansion and width of the surface cracks of the specimen,and the greater the ratio Larger,the smaller the critical corrosion rate of concrete surface cracking.The study found that different longitudinal reinforcement methods have an impact on the durability of the board in a chloride salt environment.Under the same protective layer and corrosion period,the corrosion rate of the steel bar with a larger diameter is lower and the corrosion products produced are less.The radial expansion stress to the surrounding concrete is small,the critical corrosion rate of concrete cracking is low,and the number of cracks at the bottom of the slab under the same load is small,and the maximum crack width is small. |
