Finite Element Numerical Study On Durability Of Concrete Structure

Concrete has the extremely widespread application whether in the house and bridge or in the tunnel and city airport and so on,and it is an important structural materials.Its study about durability and service life has become the vital technology problems of academia at home and abroad.A large number of engineering practice shows that one of the main factors that reduce the durability of reinforced concrete structures is reinforcement corrosion.Under the chloride ion corrosion environment,chloride ions into the concrete causes rusting of the reinforced concrete,after steel corrosion causes the cracking of concrete cover,resulting in performance degradation of reinforced concrete structures.Therefore,studying the effect of chloride ion of reinforced concrete structure durability has significant academic value and practical significance.This paper presents cellular automata(CA for short)model to simulate the mechanism of chloride diffusion in concrete and the initial corrosion time of steel-bar,and beam element fiber model is adopted for corrosion damage of reinforced concrete structure performance were studied.The research content is as follows:Firstly,according to the principle of cellular automata,choose one and two dimentional Von Neumann cellular neighbor was simulated.Based on this idea,deduce perfectly the chloride ion diffusion equation,namely the Fick's second law(FSL),prove the correctness of the model of cellular automata in theory.In order to further verify the feasibility and effectiveness of cellular automata model,the model simulated values and the measured values of chloride ions concentration in concrete under deicing salt,salt lake or ocean chloride ion environment were compared,the results found that the CA simulation value was consistent with the measured value,the validation results obtained are satisfactory.Secondly,using the theory of cellular automata to establish the CA model of chloride ion diffusion within reinforced concrete,the model considering the time effect,water cement ratio and temperature.Based on the established CA model,by writing Matlab program to analyze one and two dimentional chloride ion diffusion behavior about the reinforced concrete plate,the square and circular reinforced concrete column,and predict the reinforced initial corrosion time.By the results compared with the existing analytical solution and numerical solution,further verify the validity of the model and the validity,and it has higher precision compared with other numerical methods.Thirdly,multi-factors coupling chloride ion diffusion model in concrete are established on the basis of the principle of cellular automata,this model considers the impacts of the water cement ratio,temperature,relative humidity,time effect,chloride ion binding ability and structure of micro defects and so on.Comparing multi-factors coupling CA simulationvalue with the measured values of the long exposure to chlorine ion corrosion environment,the comparison show that,the more considering influence factors,the higher the degree of match about the CA simulation value and the measured value.In addition,further discusses predicting the initial corrosion time of steel-bar under the influence of different factors.Forthly,The beam element and inner element fiber model is adopted to analyze the performance of reinforced concrete structures after corrosion damage.First of all,comparing the structure internal force of the uncorrosion damage reinforced concrete beam about rectangle and T section with the calculating results of theoretical method,and it verified the correctness of the beam element and inner element fiber model.Then,introducing concrete damage factor and reinforcing bar damage factor that change over time to modify the section stiffness matrix,the thought is used to analyze the structure performance of T section reinforced concrete continuous beam in the corrosion environment,the study found that the bending moment of joints decreases with the continuation of time,the mid-span moment increases with the increase of time.Finally,comparing the structure internal force with the structural resistance after corrosion damage,to accomplish the life evaluation of reinforced concrete structure.