【作者】 李政；

【导师】 王元丰；

【作者基本信息】 北京交通大学 ， 结构工程， 2008， 硕士

【摘要】 徐变作为混凝土一种重要的长期性能,对混凝土结构特别是大型混凝土结构有重要的影响。国内外已有众多对徐变的研究。在混凝土徐变的研究中,混凝土所处的环境因素一直是国内外学者关注的焦点。环境因素中的环境湿度被普遍认为是影响混凝土徐变的重要因素。自然环境中干湿循环、混凝土水分散失以及地下结构中高湿环境均会对混凝土长期徐变产生重要影响。目前国内研究中,混凝土内部湿度传导理论相对不足;混凝土徐变计算模型对环境湿度因素考虑较少,相对不完善,与实际相差较大。因此,混凝土湿度徐变的研究有重要的理论价值及工程意义。基于以上的研究背景,本文依据混凝土湿度传导理论采用有限元方法模拟了混凝土处于不同外部湿度条件下其内部湿度场的分布,并且和已有的混凝土湿度传导经验公式作了对比。结果显示,采用有限元方法不仅可以计算环境恒定湿度条件及湿度变化条件下混凝土内部稳态湿度场和瞬态湿度场,计算模拟混凝土内部湿度场变化与实际吻合良好。根据混凝土内部湿度场的变化结合改进的微预应力固结理论,本文分析了湿度因素对混凝土徐变的影响,分析了恒定湿度条件下混凝土徐变规律以及湿度变化条件下混凝土徐变的规律。在现有分析结果的基础上和现有能考虑混凝土湿度徐变的模型作了对比。改进的微预应力固结理论能良好的反应混凝土在湿度作用下徐变的规律。而且有限元模拟湿度场与改进的微预应力固结理论相结合对于徐变因素考虑更加完整,计算更吻合工程实际。更多还原

【Abstract】 Creep as one of the most important long-term properties of concrete has important influences on concrete structures especially large-scale concrete structure. Within the researches of concrete creep, environmental factors have always been the concern of many scholars. It is generally accepted that environment humidity as one of the environmental affects concrete creep considerably. The environmental humidity cycling, drying and high level humidity on concrete structures have significant effects on concrete creep. In present domestic researches, studies on humidity diffusion within concrete are relative inadequate; and few models can take comprehensive consideration on humidity factors. So study on effect of environmental humidity is quite helpful to both on theoretical research and engineering practice.According to humidity diffusion theory of concrete, this paper studied the distribution of humidity field within concrete at both constant humidity condition and variable humidity condition using finite element method. The calculated results are compared with that using empirical method. It can be shown from the comparison that the finite element method it has satisfied accuracy on simulation of interior humidity field of concrete. Coupled with the changing of humidity field within concrete and improved microprestress solidification theory, creep of concrete at constant environment humidity and different humidity levels was studied. The results were compared with that calculated by B3 creep model. It can be concluded that the improved microprestress solidification theory can show the creep at different humidity condition well. Moreover, the coupling finite element method and the improved microprestress solidification theory can have a more comprehensive study on creep of concrete under environment humidity.更多还原