混凝土箱梁的碳化性能研究

发布时间：2018-05-21 05:47

本文选题：混凝土 + 箱梁　；参考：《兰州交通大学》2017年硕士论文

【摘要】：混凝土耐久性问题,因为与混凝土结构的长期使用和安全有着密切关系而越来越受到各界关注。碳化又是影响混凝土耐久性很重要的一个方面,最显著的影响是改变了混凝土内部的酸碱性,引发钢筋锈蚀、膨胀,严重的还会导致混凝土保护层开裂甚至剥落,给结构物的使用和安全带来重大隐患。(1)对碳化机理进行了阐述,推导扩散控制方程,并对比了有限元软件中热传导问题与碳化问题的相似性。现有的相关研究都是采取一定方法,对碳化过程进行了简化和近似,得到各种理论模型。也有很多研究是针对影响碳化的各种因素,研究其影响程度,特别是利用计算机技术研究碳化问题时,直接将多种影响因素耦合成一个主要系数,这种方法更为直观,也有显著的效果和成果。本文基于现有的这些混凝土碳化模型和相关研究结论,从混凝土碳化问题相关的各种理论出发,着重考虑了混凝土箱梁在构造特别是力学方面的特性进行综合分析。(2)对混凝土箱梁模型进行快速碳化试验,探究箱梁的特殊构造对碳化产生的影响。借助有限元软件,编写APDL程序,对该箱梁模型进行数值模拟。同时,结合碳化试验与数值模拟的结果,对数值模型进行校准,同时也验证了利用这种方式研究混凝土碳化问题是可靠、有效的。统计结果表明,受二维碳化作用的外角部区域混凝土的碳化深度最大,是非角部混凝土的1.56倍,约为内角部混凝土的2倍。翼缘端头区域的碳化,在早期时为简单的一维碳化作用,随着反应进行到后期,由于顶板上下边缘的碳化深度的增加达到混凝土内部,该处碳化反应也明显加快。(3)对处于自然环境的混凝土箱梁,在应力条件下的碳化性能进行了数值分析。自然环境中由于CO2浓度很低,混凝土碳化反应需要很长的时间,对于需要在相对较短时间内得出研究结论而指导实际的这个前提而言,长期暴露试验就有了很大的局限性,因此用数值分析的方法研究碳化问题的优势显而易见。通过分析,得到箱梁截面上碳化深度的分布规律,并对达到混凝土箱梁保护层厚度所需的时间进行了预测。结果表明,应力状态下与非应力状态下的混凝土箱梁,受二维碳化作用的外角部是受碳化影响最大的区域,该处碳化反应速率高于其他部位。
[Abstract]:The durability of concrete has attracted more and more attention because of its close relationship with the long-term use and safety of concrete structures. Carbonation is also an important aspect that affects the durability of concrete. The most significant effect is to change the acidity and alkalinity of concrete, causing corrosion and expansion of steel bars, and even cracking and even spalling of concrete cover. The carbonation mechanism is expounded, the diffusion control equation is derived, and the similarity between heat conduction problem and carbonation problem in finite element software is compared. The existing research methods have been used to simplify and approximate the carbonization process, and various theoretical models have been obtained. There are also many studies aimed at the factors that affect carbonization, and the degree of their influence, especially when using computer technology to study the carbonization problem, and directly coupling a variety of factors into a major coefficient, this method is more intuitive. Also has the remarkable effect and the result. Based on the existing concrete carbonation models and related research conclusions, this paper starts from various theories related to concrete carbonation. This paper focuses on the comprehensive analysis of concrete box girder structure, especially the mechanical properties of concrete box girder, and makes a rapid carbonation test on concrete box girder model, and probes into the influence of the special structure of concrete box girder on carbonization. With the help of finite element software and APDL program, the box girder model is simulated numerically. At the same time, combined with the results of carbonization test and numerical simulation, the numerical model is calibrated, and it is proved that it is reliable and effective to study the carbonation problem of concrete in this way. The results show that the carbonation depth of the concrete in the outer corner is the largest, 1.56 times that of the non-angle concrete, and about 2 times that of the inner corner concrete. The carbonation of the flange end region is a simple one-dimensional carbonation in the early stage. As the reaction progresses to the late stage, the carbonation depth of the upper and lower edges of the roof reaches to the concrete interior. The carbonation behavior of concrete box girder in natural environment is analyzed numerically under stress conditions. Because of the low concentration of CO2 in the natural environment, the carbonation reaction of concrete takes a long time. For the premise that we need to draw the research conclusion in a relatively short time and guide the practice, the long-term exposure test has great limitations. Therefore, the advantages of numerical analysis in carbonation are obvious. The distribution law of carbonization depth on the section of box girder is obtained, and the time required to reach the thickness of the protective layer of concrete box girder is predicted. The results show that the external corner of the concrete box girder under the stress state and the non-stress state is the area most affected by the carbonization, and the carbonation reaction rate is higher than that in the other parts.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U445.57

【参考文献】