Research On The Finite Element Model Of Chloride Ions' Diffusion In The Concrete Structures

The diffusion of chloride ions in reinforced concrete seriously influence the durability of the structure,thus this problem has been widely concerned by researchers.We use the finite element method to study two-dimension chloride ions' diffusion.Firstly,consider the two-dimension finite element model with constant diffusion coefficient.However,in the real environment,the diffusion coefficient of chloride ions is not constant,the diffusion coefficient with time varying is considered.Secondly,the triangular subdivisions of the area are more flexible than the rectangular subdivisions,which are used when establishing the finite element models.Thirdly,based on the linear interpolating basis functions,the finite element models with constant diffusion coefficient and time-varying diffusion coefficient are established.Furthermore,the quadratic interpolating basis functions are used,which have higher accuracy.Fourthly,not only the ideal constant boundary conditions are considered,but also the linear boundary conditions and the periodic triangular boundary conditions are discussed,which are more accurate to reflect the practical cases.Finally,the convergence of the above models are proved,that is,the Crank-NicolsonGalerkin fully discrete model based on the finite element model method.It is shown that the converging speed of the quadratic interpolating basis function is faster than that of the linear interpolating basis function.In addition,a numerical method for calculating the physical parameters of bulk building materials is discussed,which can obtain the thermal conductivity and thermal diffusivity of the material.Considering the correction time is fixed and not fixed,the excessing temperature of the materials is obtained by Gauss-Newton method according to the experimental data,which is consistent with the actual results.