Numerical Simulation Study On Corrosion And Shear Capacity Of Studs Considering Chloride Diffusion In Concrete

Steel-concrete composite beams work by combining steel beams and concrete slabs through shear connectors,and have the advantages of both steel and concrete structures.For a combined structure in an ocean or harsh environment,the corrosion of chloride ions in the environment causes corrosion of the stud,resulting in a drop in the mechanical properties of the stud,which seriously affects the overall performance of the combined structure.Since it is difficult to monitor the corrosion of studs in composite structures in service,it is particularly important to accurately simulate the stud corrosion process caused by the diffusion of chloride ions in concrete.In this paper,the coupling analysis of chloride ion diffusion and stud corrosion in concrete is carried out to study the stud corrosion process and the degradation law of mechanical properties of composite structures during their service life.The main research contents of this article are as follows:(1)Establish a coupling analysis method for chloride ion diffusion and steel corrosion.Based on the Butler–Volmer equation and the electrochemical reaction of steel corrosion in concrete,iteratively calculates the iterative calculation of steel corrosion in concrete in a single time step,and implements long-term corrosion calculation through integration.A chloride ion diffusion module was introduced to take into account the desensitization of steel bars caused by the increase of chloride ion concentration in concrete,and a coupling calculation program for chloride ion diffusion and steel corrosion was established.An example of coupled analysis and calculation of reinforcement in the side and corner areas is given to verify the rationality of the calculation results of the program.(2)The long-term corrosion process of studs is calculated by the coupling of chloride ion diffusion and steel corrosion.There are two kinds of chloride ion exposed surfaces.When the top surface of the concrete slab is the exposed surface,the corrosion position gradually develops downward over time,the cross section of the stud remains round,and the form of corrosion in the length direction of the top rod is "two ends thick and thin.When the bottom surface of the concrete slab is the exposed surface,the location of corrosion gradually develops upwards with time.The cross section of the stud is close to an ellipse,and the form of corrosion in the length direction of the top rod is "the upper end is thicker and the lower end is thinner." The rule of bolt corrosion is as follows: the closer to the boundary concrete,the earlier the corrosion occurs,and the greater the depth of corrosion,the location of the corrosion is basically the same as the direction of chloride ion diffusion.(3)Since the irregular shape of the corroded studs is not convenient for finite element modeling and calculation,the shape of the corroded studs is simplified,and the mechanical properties of the studs under the two chloride ion exposed surfaces at different corrosion times are modeled and analyzed,respectively.The mechanical degradation curve of two kinds of studs with time.The conclusions are as follows: the ultimate shear bearing capacity of studs also gradually decreases with the increase of exposure time.The ultimate shear bearing capacity of two types of studs after 100 years of exposure has decreased to about half of the original.Under the same conditions,the studs with the bottom surface as the exposed surface The risk of reduced bearing capacity is greater.