| From the points of the whole life-cycle costs, during operational phases the construction costs for maintaince due to the problems of the structural durability should not be underestimated. For marine concrete structures, the steel corrosion caused by chloride is the main cause of structural durability problems. Therefore, it is important to study the durability and performance degradation mechanism of the structure during its operational phase. By the National Natural Science Foundation of "The study of concrete Structure durability of whole life performance and design theory based on Steel Corrosion(51378241)" funded, from the component level the durability and performance degradation mechanism evolution of reinforced concrete structural members during each life-cycle stage of deterioration have been conducted research. The main work in this paper including:1、Study on the probabilistic model of corrosion caused by chlorine salt erosion. Based on the existing chloride ion diffusion theoretical model, considering the uncertain of environment, materials and other factors, the main impact of the model parameters are regarded as random variables. Conbined with function a probability model of initial corrosion are proposed. Based on Monte Carlo method, using Matlab software a sample simulation is conduct. The study found that the distribution of chloride concentration surrounding steel bars after a certain stage of chloride erosion amostly submit to lognormal distribution. Finally, we using the model predicts the rust occurrence probability of inforced concrete structure in Lianyungang Port. This probability model can be used as a non-destructive testing method to predict internal chloride ion concentration in concrete, as well as provides a probabilistic approach for assessing the occurrence of corrosion in concrete reinforcement member.2、Study on the mechanical properities of non-uniformity corroded steel bars in the cracked reinforced concrete structures under the chloride erosion. An experiment of chloride salt drying-wetting cycles was carried out for pre-cracked reinforced concrete specimens. The total duration of testing and natural corrosion is nearly 4 years. Based on The residual diameter measurement and tensile testing, the reinforcement corrosion morphology and mechanical property of corroded reinforcements have been studied and discussed. The study found that significant localized corrosion can be observed for reinforcement around cracked areas, while slight uniform corrosion occurs for reinforcement in sound concrete; The uniformity coefficient S is proposed to describe longitudinal non-uniformity characteristics of steel corrosion. When the maximum the loss rate of diameter ρmax less than 13%( the mass loss rate between 3% ~ 6%), S and ρmax showed a good linear relationship; In the comparative analysis of the existing corroded reinforcement mechanical degradation model, several mathematical models have been built to predict the degradation of mechanical properties of corroded bars with η less than 6%, which taking the influence of S into account; Compared with non-uniform corrosion and uniform corrosion steel constitutive relation curve, it is indicated that the main reason of the disappearance of reinforced yield platform is non-uniform corrosion. Finally, a probability analysis method of corroded reinforced bearing capacity and reliability is estabilished.3、Experimental study on flexural capacity of corroded reinforced concrete members under chloride erosion. An experiment of chloride salt drying-wetting cycles was carried out for 6 reinforced concrete structures with different protective layer thickness, concrete composition and crack widths, nearly 4 years. During the test of the state of the steel corrosion has been regular test. Finally, the bending capacity test of the beams is carried out. The results of group in ths paper and the test results of the group in 2012 under the same environmental erosion after about 2 years are compared. The results show that for uncracked members, the corrosion rate rebound slightly after experiencing a period of stable rust.While for the cracked members, corrosion rate keeps steady; Comared with the cracks development, the strain changes and failure mode of the two groups with different erosion cycles, it is indicated that vertical cracks caused by bending gradually reduced and the inclined cracks fade away. Less brittle tendons typical characteristics of the test beam members became clear over time by erosion. Finally, considering the impact of crack on the test results of component capacity degradation model, flexural capacity and reliability of concrete structures is evaluated using probabilistic methods. |
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