【作者】 赵翔宇；

【导师】 黄煜镔；

【作者基本信息】 重庆大学 ， 土木工程， 2011， 硕士

【摘要】 混凝土结构常因氯离子侵蚀引起钢筋锈蚀,进而使结构性能退化、承载能力降低、甚至破坏。为此,不得不花费大量的资金和自然资源进行维修甚至重建,对国家造成了巨大的经济损失和严重的社会影响。本文针对氯离子侵蚀下混凝土结构的耐久性问题,以混凝土中钢筋初始锈蚀耐久性寿命为主线,从混凝土中氯离子浓度分布预测的数值模拟方法、混凝土中氯离子浓度预测数值模型、混凝土结构耐久性寿命预测的概率方法三个方面进行了以下的研究工作:利用混凝土中非稳态热传导能量守恒微分方程与基于Fick定律的混凝土中氯离子非稳态扩散质量守恒微分方程的相似性,通过对方程中各参数的合理等效,提出了一种基于ANSYS软件热分析模块的预测混凝土中氯离子浓度二维分布的有限元数值模拟方法,并通过与解析解的对比验证了该方法的有效性。运用该方法研究了扩散系数、扩散时间、表面氯离子浓度、构件的截面尺寸、钢筋的存在、钢筋直径大小、钢筋间距大小对混凝土中氯离子二维扩散的影响规律。基于上述有限元数值模拟方法,通过引入各种参数修正氯离子扩散系数,建立了考虑多种因素影响下的氯离子在混凝土中扩散的数值模型,并对模型中各参数进行了详细的讨论,给出了各参数的取值规律。运用该数值模型对一工程实例进行了模拟,通过模拟值与试验值的对比,验证了模型的实用性。基于上述数值模型,以钢筋表面的氯离子浓度达到临界浓度作为耐久性寿命终结的标志,考虑到基准氯离子扩散系数、保护层厚度、表面氯离子浓度和临界氯离子浓度的随机性,基于ANSYS软件概率分析模块建立了基于可靠度的混凝土结构耐久性寿命期望值及耐久性失效概率计算的数值方法。运用该方法分析了各参数的统计特征对耐久性寿命的影响规律。更多还原

【Abstract】 Concrete structures often causes the corrosion of steel bar due to erosion of chloride ion, thus the structural behavior is degenerated and the carrying capacity is reduced and even the structure is destroyed. In this connection, it is a must to spend a lot of money and natural resources on maintenance and reconstruction. Thus huge economic loss and sever social influence are caused to the state. This paper performs the following research work with focus on the problem of durability of the concrete structures if eroded by chloride ion by taking the initial corrosion durability life of steel bars in concrete as the mainline from three perspectives of numerical simulation method for predicting chloride ion concentration distribution in concrete, numerical model of predicting chloride ion concentration in concrete as well as probabilistic method for predicting durability life of the concrete structure:By utilizing the similarity of differential equation for unsteady state heat conduction & energy conservation in concrete with differential equation for unsteady state diffusion & mass conservation of chloride ions in concrete based on Fick’s law and having rational equivalence of each parameter of the equations, propose a finite element numerical simulation method for predicting two-dimensional distribution of chloride ion in concrete based on the thermal analysis module in ANSYS and verify the effectiveness of this method through comparison to the analytic solutions. Study the influence law of diffusion coefficient, diffusion time, chloride ion concentration on the surface, sectional dimension of the constructional element, existence, diameter and space of steel bars on the two-dimensional diffusion of chloride ion in concrete.Revise diffusion coefficients of chloride ion by introducing various parameters based on the foregoing finite element numerical simulation method, establish the numerical module of chloride ion diffusion in concrete under the influence of many factors, discuss the parameters of the module in great detail and give law of taking value for each parameters. Simulate an engineering case by application of the numerical model and verify the practicability of the model through comparison of the simulation value to the experimental value.Based on the foregoing numerical model with the critical concentration that the chloride ion concentration on the surface of the steel bar as the symbol of the termination of durability life and in view the randomness of standard diffusion coefficient of chloride ion, thickness of the protective layer chloride ion concentration on the surface and the critical concentration of chloride ion, based on the PDS in ANSYS establish reliability-based numerical method for calculating the expected value of durability life of the concrete structure and failure probability of durability, then analyze the influence law of the statistical characteristic of each parameter on durability life by application of this method.更多还原