基于可靠指标的混凝土箱梁桥氯离子扩散效应分析与寿命预测

为了准确模拟和分析氯离子在混凝土中扩散的随机效应,从概率论的角度出发,在Fick第二定律的基础上,建立了考虑氯离子随机扩散效应的元胞自动机模型。同时结合结构可靠度设计理论,基于结构可靠指标,提出了一种能够预测结构耐久性使用寿命的预测方法。以某单箱双室系杆拱桥为例,对氯离子的侵蚀过程进行了模拟,并对结构耐久性使用寿命进行了预测。研究结果表明:建立的氯离子随机扩散模型可以有效模拟氯离子在扩散过程中的随机性和不确定性,能够反映工程中氯离子的实际侵蚀过程;对具有复杂截面形式的混凝土箱梁而言,为了能够获得准确的计算结果,在进行氯离子扩散效应分析时应充分考虑截面的几何特征;预测结果表明,该结构服役45年左右时将达到结构耐久性极限设计状态。

Chloride Diffusion Effect Analysis and Life Prediction of Concrete Box Girder Bridge Based on Reliability Index

In order to accurately simulate and analyze the random effects of chloride ion diffusion in concrete.Based on the Fick's second law and probability theory,the cellular automata model that took into account the effect of random diffusion of chloride ions was established.Meanwhile,combined with structural reliability design theory and the structural reliability index,a prediction method that could predict the durability of the structural durability was proposed.Taking a single-bin dual-chamber tied arch bridge as an example,the erosion process of chloride ions was simulated and the durability of the structural life was predicted.The results show that the chloride ion stochastic diffusion model established can effectively simulate the randomness and uncertainty of the chloride ion diffusion process,and can reflect the actual erosion process of chloride ions in the project.For a concrete box girder with a complex cross-section.In order to obtain accurate calculation results,the geometrical characteristics of the cross-section should be fully considered in the analysis of chloride ion diffusion effects.The prediction results show that the structure will reach the structural durability limit design state when it is in service for 45 years.