混凝土给定超低温作用区间冻融性能试验研究
发布时间：2018-12-10 12:34
【摘要】：混凝土作为液化天然气领域极为重要的储罐结构受力材料,其受力与变形特性对此类工程的安全至关重要。实际工程中的混凝土罐壁可能暴露在超低温下,因此,20世纪70年代起,国内外学者开始研究混凝土超低温下受力性能变化。同时由于储罐储量变化、内外冷热交换,以及检修需求和闲置期的存在,储罐混凝土不可避免地遭受超低温与常温以及不同超低温间的冻融作用。已有研究涉及混凝土超低温冻融方面的极少,大多基于自然环境下的冻融作用进行研究。针对目前混凝土超低温冻融性能研究的缺乏,本超低温课题组开始对混凝土超低温冻融性能进行系列试验研究,本文所探讨的内容是其中的一部分。主要内容为对试件泡水、烘干等处理后进行10℃至-190℃区间的反复冻融试验,考察的影响因素主要包括含水率、冻融次数,以及回温速率等。试验还包含了对混凝土冻融后受力性能、变形性能的探讨,如受压强度、弹性模量、应力应变曲线等,并考察了目前研究缺乏的超低温作用导致的膨胀变形,通过试验获取混凝土超低温膨胀的全过程。上述试验及其结果分析表明,含水率对混凝土超低温冻融后的性能具有显著的影响,尤其是其受压强度与弹性模量,并据此回归得到其拟合公式;而冻融次数虽伴随着混凝土细观结构的损伤累积,但却并未总引起混凝土受力性能的衰退,尤其是其超低温下受压强度,常出现反向变化现象;回温速率影响较含水率、冻融次数要小,其主要通过混凝土冻融过程中温度分布均匀程度的差异影响其性能,并对混凝土内孔隙水的迁移产生一定影响;超低温作用导致的温度变形受各种因素影响、较为离散,其试验结果波动较大,相比之下冻融次数的影响更显著。随冻融次数增加,温度变形值渐趋于一致。本文还采用有限元方法,通过引入生死单元技术对混凝土超低温冻融的细观结构变化进行了模拟分析。通过适当的简化与假设反映了混凝土冻融过程中孔隙周围的损伤累积,并验证了其宏观性能的退化。本文的试验结果为混凝土超低温冻融性能的深入研究提供了数据支持,并在一定程度上弥补了相关研究领域的不足,给出的结论可为解决工程应用与设计中的一些基本问题提供了依据。
[Abstract]:Concrete is an important material for storage tank structure in the field of liquefied natural gas (LNG), and its mechanical and deformation characteristics are very important to the safety of this kind of engineering. Concrete tank walls in practical engineering may be exposed to ultra-low temperature. Therefore, since 1970s, scholars at home and abroad have begun to study the mechanical properties of concrete under ultra-low temperature. At the same time, the storage tank concrete is inevitably subjected to the freezing and thawing of ultra-low temperature, normal temperature and different ultra-low temperature because of the storage tank reserve change, the internal and external heat exchange, the maintenance demand and the idle period. There are few researches on freezing and thawing of concrete, most of them are based on freeze-thaw in natural environment. In view of the lack of research on the ultra-low temperature freeze-thaw performance of concrete at present, the research group of ultra-low temperature began to carry out a series of experimental studies on the performance of ultra-low temperature freezing and thawing of concrete, among which the content discussed in this paper is a part of it. The main contents are the repeated freezing and thawing test between 10 鈩，
本文编号：2370576
[Abstract]:Concrete is an important material for storage tank structure in the field of liquefied natural gas (LNG), and its mechanical and deformation characteristics are very important to the safety of this kind of engineering. Concrete tank walls in practical engineering may be exposed to ultra-low temperature. Therefore, since 1970s, scholars at home and abroad have begun to study the mechanical properties of concrete under ultra-low temperature. At the same time, the storage tank concrete is inevitably subjected to the freezing and thawing of ultra-low temperature, normal temperature and different ultra-low temperature because of the storage tank reserve change, the internal and external heat exchange, the maintenance demand and the idle period. There are few researches on freezing and thawing of concrete, most of them are based on freeze-thaw in natural environment. In view of the lack of research on the ultra-low temperature freeze-thaw performance of concrete at present, the research group of ultra-low temperature began to carry out a series of experimental studies on the performance of ultra-low temperature freezing and thawing of concrete, among which the content discussed in this paper is a part of it. The main contents are the repeated freezing and thawing test between 10 鈩，
本文编号：2370576
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