钢筋锈蚀率概率分布的动态演进模拟

为获得钢筋混凝土（RC）材料性能在氯离子侵蚀作用下的衰退规律,研究了RC构件中钢筋锈蚀率（SCR）的概率密度函数(PDF)随时间演进的过程.引入路径概率模型（PPM）分析了给定服役时间下SCR的PDF,把钢筋锈蚀过程按照初锈阶段和锈蚀扩展阶段划分为一系列路径,计算每一条路径下SCR的无条件概率分布,并用概率求和方法获得所有路径下SCR的无条件概率分布,在PPM的基础上,考虑不同的服役时间,用Monte Carlo方法模拟SCR的PDF动态演进过程;结合具体算例进行了模拟分析,给出了SCR的PDF随服役时间的演进结果;分析了上述模拟过程的有效性和参数敏感性.结果表明,PPM可以较为准确地估计出SCR的概率分布参数,SCR的概率分布的分布参数、分布形式随服役时间不同而变化,因此,在设计中,预先给定一种SCR概率分布的形式可能导致显著的偏差.

Dynamic simulation method for probability evolution of reinforcement steel corrosion

The probability density function(PDF) of steel corrosion ratio(SCR) evolving with service time(ST) was simulated to study the performance degradation of chloride-ingress RC member.A path probability method(PPM) was suggested to analyze the PDF of SCR under given ST.In PPM,the whole corrosion process of the given ST is divided into a series of paths constructed by corrosion initiation phase and corrosion expansion phase,the probability of which can be described by the probability of corrosion initiation and the conditional probability of SCR,in condition that the corrosion initiation has happened,respectively.The unconditional SCR's PDF of given ST can be achieved by summing unconditional PDF of all paths after the unconditional PDF of each path is evaluated by Bayesian formula.Based on PPM,the dynamic evolution of SCR's unconditional PDF with increasing series of STs was simulated through Monte Carlo simulation technique.A practical engineering RC member was analyzed to illustrate the evolution results.The validity of the simulation method and the sensitivity of input parameters were studied.The results showed that the distribution parameters of SCR can be effectively evaluated by PPM,and that both the probability distribution types and the distribution parameters change with ST.So that it could induce bias in design if only one probability distribution type is used.