论文标题
蠕变对腐蚀引起的破裂的影响
Effect of Creep on Corrosion-Induced Cracking
论文作者
论文摘要
对于腐蚀引起的钢筋混凝土的裂纹,天然发生的腐蚀速率如此之低,以至于在钢筋表面附近,锈蚀通常会在数十年中积累,然后在周围混凝土中产生了足够的压力,以引起混凝土盖上的裂纹。为了加快该过程,已经开发出具有印象深刻的电流的腐蚀测试,其中控制腐蚀速率是如此之高,以至于混凝土盖的破裂发生在几天之内。将这些加速测试的结果推断到天然发生的腐蚀的结果需要了解混凝土对腐蚀引起的开裂过程的长期蠕变变形的影响。在文献中的数学模型中,蠕变变形通常被加速而忽略,但以有效模量的形式考虑了自然腐蚀速率。在这里,提出了三种增加复杂性的数值模型,目的是研究蠕变对腐蚀引起的破裂的影响。最简单的方法是基于无裂缝的轴对称厚壁圆柱体,并结合了由锈蚀积累引起的径向压力的塑性极限。具有中间复杂性的模型包括一个厚壁的圆柱模型,分为内部破裂和外部无裂缝层。最全面的模型由三维晶格方法离散的厚壁圆柱体组成。通过Bažant和同事开发的B3模型,在所有三种方法中都预测了基本蠕变。使用FIB模型代码表达式对混凝土强度的时间依赖性进行建模。结果表明,对于综合晶格模型,蠕变对临界腐蚀渗透的影响有限,这表明临界腐蚀渗透对腐蚀速率的依赖性必须具有其他来源。
For corrosion-induced cracking in reinforced concrete, naturally occurring corrosion rates are so low that rust accumulates often over tens of years near the surface of the reinforcement bars before sufficient pressure in the surrounding concrete is generated to induce cracking in the concrete cover. To speed up the process, corrosion tests with impressed currents have been developed in which the corrosion rate is controlled to be so high that cracking of the concrete cover occurs within a few days. Extrapolating the results of these accelerated tests to those of naturally occurring corrosion requires an understanding of the influence of long-term creep deformations of concrete on the corrosion-induced cracking process. In mathematical models in the literature, creep deformations are often ignored for accelerated but considered for natural corrosion rates in the form of an effective modulus. Here, three numerical models of increasing complexity are proposed with the aim to investigate the effect of creep on corrosion-induced cracking. The simplest approach is based on an uncracked axis-symmetric thick-walled cylinder combined with a plastic limit on the radial pressure-induced by the accumulation of rust. The model with intermediate complexity comprises a thick-walled cylinder model divided into an inner cracked and an outer uncracked layer. The most comprehensive model consists of a thick-walled cylinder discretised by a three-dimensional lattice approach. Basic creep is predicted in all three approaches by means of the B3 model developed by Bažant and co-workers. Time dependence of strength of concrete is modelled using fib Model Code expressions. It is shown that for the comprehensive lattice model, creep has limited influence on critical corrosion penetration, which indicates that the dependence of the critical corrosion penetration on corrosion rate must have other sources.