Reaearch On Prediction For Durable Life Of Concrete Structures Under The Coupling Action Of Load And Chlorine Erosion

As the main structure forms nowadays, reinforced concrete structure has beenwidely used in harbor and marine engineering. With the growing of using time, alarge amount of reinforced concrete structures face durability damage under chlorinesalt erosion. As a result, service life prediction for reinforced concrete structuresunder chlorine salt erosion is a crucial problem to solve for durability and designevaluation. Besides, in actual engineering, most reinforced concrete structures underload work with crack, and the crack intensifies durability problems. Hereby,according to the most obvious problem of reinforced concrete structure under chlorinesalt erosion among durability problems, the paper builds prediction model for durablelife of reinforced concrete structures under the coupling action of constant load andchlorine salt erosion.First, the paper introduces traditional chloride’s diffusion model in concrete, andsummarizes influencing factors and statistical characteristics of the parameters. On thebasis of this, analysis of the statistical characteristics of initial corrosion time ofreinforcing bar is done with sampling simulation method, and it is found that theyfollow lognormal distribution. The paper finds that surface chloride concentration,critical chloride concentration and cover thickness have significant effect on initialcorrosion time by analyzing sensitivity of the parameters which influence initialcorrosion time.Second, the load and crack width model and the crack width and chlorine salterosion model are built. The models consider the impact of single maximum crackwidth on chlorine diffusion coefficient, the reducing of chlorine diffusion coefficientwith time and the growth of crack width with time. The paper builds2-D chlorinediffusion models with finite differential equations.Third, calculation of an actual project is done with the model of coupling actionof load and chlorine salt erosion. According to the results, chloride ion defuses fasteraround crack and it is better approximated as one-dimensional diffusion far to thecrack. The characteristic, that chloride diffusion coefficient reduces with time, hassignificant impact on diffusion of chloride ion. As is shown in the analysis results ofsensitivity, in order to increase service life, we should think first about the reductionof concrete W/C, and improving concrete cover thickness next. Finally, the paper simulates the change of failure probability with time by usingprobabilistic method——Monte Carlo sampling method. The results show that thecover thickness has great effect on the failure probability of concrete members.Besides, the paper makes comparison of the results of probabilistic method and that ofdeterministic method, and it is found that the latter results are greater that the formerones. So the results of probabilistic method are more conservative.The paper is based on traditional diffusion equation, and builds prediction modelfor durable life of reinforced concrete structures under the coupling action of load andchlorine salt erosion, the results of which can provide theoretical basis for durabilitydesign of concrete structures in marine environment.