PC桥梁氯离子侵蚀模型及试验研究

发布时间：2018-11-10 09:50

【摘要】：预应力桥梁因其可不带裂缝工作而被认为具有良好的耐久性,以前往往忽略了预应力桥梁的耐久性问题。然而事实上,预应力桥梁同样也会发生耐久性病害问题,预应力桥梁的特点决定了其失效破坏的突然性和破坏后果的更加严重性,因此研究预应力桥梁的耐久性问题具有重大的实际意义。氯离子侵蚀是导致混凝土结构产生耐久性病害的一大要素,本文主要从氯离子侵蚀入手研究预应力桥梁的耐久性问题。对预应力桥梁氯离子侵蚀模型的研究往往从荷载对混凝土渗透性能的影响着手,目前大多数学者都是根据试验结果得出定性判断或给出荷载对氯离子传输影响的经验公式,很少有学者从理论方面深入研究,解释荷载作用对混凝土微观结构的影响机理,进而建立荷载对氯离子传输的影响修正模型或修正系数。本文从荷载作用对混凝土孔隙结构的影响机理入手,分析了荷载作用对混凝土扩散性能的影响,建立了适用于预应力桥梁的氯离子侵蚀模型,并进行了持荷状态混凝土小梁的盐雾侵蚀试验,验证所建立模型的可靠性。本文主要研究的内容和结论有:(1)研究碳化作用对氯离子传输的影响机理,建立了碳化作用对氯离子扩散系数的修正模型;(2)荷载作用改变了混凝土孔隙结构特征是荷载改变混凝土渗透性的本质,孔隙结构特征的改变包括弹性变形和损伤两部分,基于此提出了考虑混凝土应变、损伤和孔隙率的氯离子扩散系数修正;(3)在现有的研究成果的基础上,结合荷载作用对氯离子扩散的影响机理,建立了预应力桥梁的氯离子侵蚀模型。(4)将荷载作用、碳化作用、氯离子扩散系数、水分扩散系数均与混凝土的孔隙率建立了关系,进而建立了它们之间的耦合关系;(5)进行持荷状态混凝土小梁的盐雾侵蚀试验,并采用有限元软件建立模型进行理论求解,经过对比可知试验结果和本文建立的预应力桥梁氯离子侵蚀模型有很好的相关性。
[Abstract]:Prestressed bridge is considered to have good durability because it can work without cracks. In the past, the durability of prestressed bridge is often neglected. However, in fact, the durability of prestressed bridges will also occur. The characteristics of prestressed bridges determine the sudden failure of the bridge and the more serious consequences of failure. Therefore, it is of great practical significance to study the durability of prestressed bridges. Chloride ion erosion is one of the main factors leading to the durability of concrete structures. This paper mainly studies the durability of prestressed bridges from chloride ion erosion. The study of chloride ion erosion model of prestressed bridge usually starts with the influence of load on the permeability of concrete. At present, most scholars get the empirical formula of the influence of load on chloride ion transmission based on the test results. Few scholars have studied deeply in theory to explain the mechanism of the influence of load on the microstructure of concrete and then to establish a modified model or correction coefficient of the effect of load on chloride ion transport. In this paper, the influence of load on concrete pore structure is analyzed, and the chloride erosion model suitable for prestressed bridge is established. The salt spray erosion test of the concrete trabeculae under load condition was carried out to verify the reliability of the established model. The main contents and conclusions of this paper are as follows: (1) the mechanism of carbonation on chloride ion transport is studied and a modified model of carbonation on chloride diffusion coefficient is established. (2) the change of pore structure is the essence of load changing the permeability of concrete. The change of pore structure includes elastic deformation and damage. Based on this, the strain of concrete is considered. Modification of chloride ion diffusion coefficient of damage and porosity; (3) on the basis of the existing research results and combined with the influence mechanism of load action on chloride ion diffusion, the chloride ion erosion model of prestressed bridge is established. (4) load action, carbonation effect, chloride ion diffusion coefficient, The water diffusivity is related to the porosity of concrete, and then the coupling relationship between them is established. (5) the salt fog erosion test of concrete trabeculae under loading condition was carried out, and the finite element software was used to establish the model for theoretical solution. By comparing the test results with the chloride erosion model of prestressed bridge, the results were well correlated.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U446

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