时变扩散系数对混凝土结构服役寿命的影响

基于氯离子二维扩散模型考虑混凝土氯离子扩散衰减系数及其随机性,计算了氯盐侵蚀下混凝土结构的可靠度及服役寿命。为克服传统可靠度敏感系数的缺陷,分析氯离子扩散衰减系数及其随机性对混凝土结构耐久性的影响,根据全微分公式导出了可靠度对随机变量均值和变异性的无量纲敏感系数。计算结果表明,忽略氯离子扩散系数时变性会导致显著地低估结构服役寿命,而不考虑衰减系数的随机性又会明显地高估结构耐久性能。敏感性分析结果表明,混凝土氯离子扩散衰减系数与混凝土保护层厚度对氯盐侵蚀下混凝土结构耐久性的影响占主导地位,并随着服役时间的增加,衰减系数的影响会超过混凝土保护层厚度。

Reliability of Concrete Structures Considering the Time-varying Diffusion Coefficient

Based on the two-dimensional diffusion model of chloride ions, the chloride diffusion coefficient and the randomness of the chloride ion were taken into account. The reliability and service life of the concrete structure under chloride salt erosion were calculated. In order to overcome the shortcomings of the traditional reliability sensitivity coefficient and analyze the influence of the chloride ion diffusion attenuation coefficient and its randomness on the durability of the concrete structure, the dimensionless sensitivity coefficients of the reliability to the mean value and variability of random variables were derived based on the full derivative formula. The calculation results show that ignoring the time-dependent degeneration of the chloride ion diffusion coefficient leads to a significant underestimation of the service life of the structure, without considering that the randomness of the age factor will significantly overestimate the structural durability. The sensitivity analysis results show that the chloride ion diffusion age factor of the concrete and the thickness of the concrete cover play a dominant role in the durability of the concrete structure under the chloride salt erosion. With the increase of service time, the influence of the age factor will exceed the thickness of the concrete cover.