Abstract

The main purpose of this work is to develop a reliability analysis of concrete cover against the ingress of airborne chloride ions, and then to use it to determine the appropriate thicknesses of concrete cover or the water–cement or water–binder ratios of concrete (W/C or W/B) for meeting a reliability requirement. At first, for determining the corrosion occurrence time of reinforcing bars embedded in concrete, in addition to the one-dimensional diffusion model of chloride ions in concrete, a two-dimensional diffusion model for circular RC piers is developed. In order to be applicable in engineering practice, an amplification factor of chloride concentrations of the concrete surfaces is proposed to modify the one-dimensional diffusion model of chloride ions in concrete for considering the two-dimensional diffusion effect. In addition to Monte Carlo simulation (MCS), the first-order reliability method (FORM) and the moment method are used to calculate the reliability of concrete cover against the ingress of airborne chloride ions. Based on the comparison results of various reliability analysis methods, the third-moment reliability design procedure is selected to determine the appropriate thickness of concrete cover or, W/C or W/B of concrete for meeting a reliability requirement.

摘要

这项工作的主要目的是开发混凝土保护层抵抗空气中氯离子进入的可靠性分析，然后用它来确定混凝土保护层的适当厚度或混凝土的水灰比或水胶比（W /C 或 W/B) 以满足可靠性要求。首先，为确定混凝土中预埋钢筋的腐蚀发生时间，除建立了混凝土中氯离子的一维扩散模型外，还建立了圆形钢筋混凝土桥墩的二维扩散模型。为适用于工程实际，提出混凝土表面氯离子浓度放大系数，修正混凝土中氯离子一维扩散模型，考虑二维扩散效应。除了蒙特卡罗模拟 (MCS) 外，还使用一阶可靠性法 (FORM) 和矩法来计算混凝土保护层抵抗空气中氯离子侵入的可靠性。根据各种可靠度分析方法的比较结果，选择三阶矩可靠度设计程序来确定合适的混凝土保护层厚度或混凝土的W/C或W/B以满足可靠度要求。