Evaluation of Fracture Properties of Various Concretes

各种混凝土断裂性能评价

• 批准号: 09650508
• 负责人: NIWA Junichiro
• 金额: $ 1.98万
• 依托单位: TOKYO INSTITUTE OF TECHNOLOGY (1998)Nagoya University (1997)
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1997
• 资助国家: 日本
• 起止时间: 1997 至 1998
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09650508/
• 关键词: High Strength Concrete; Self-Compacting Concrete; Fracture Mechanics; Fracture Energy; Tension Softening Curve; Fictitious Crack; J Integral; Size Effect; 仮想ひび割れ幅; High Strength Concrete; Self-Compacting Concrete; Fracture Mechanics; Fracture Energy; Tension Softening Curve; Fictitious Crack; J Integral; Size Effect; 仮想ひび割れ幅

As the first step of this research work, fracture properties of various concretes, such as high strength concrete, self-compacting high performance concrete, etc. have been evaluated based on the fracture mechanics of concrete. Self-compacting high performance concrete is a very promising new concrete because it does not need the compaction during casting. However, from the viewpoint of the fracture mechanics, it is found that it will provide less fracture energy compared with conventional concrete because the amount of coarse aggregates included in self-compacting high performance concrete is remarkably reduced to provide the sufficient flowability. On the other hand, the fracture energy of high strength concrete shows the same tendency as conventional concrete because the content of coarse aggregates in high strength concrete is not significantly different from conventional concrete.As the second step, the experimental method to determine the tension softening curve of concrete has been investigated extensively. The tension softening curve is one of the most important parameters for the fracture mechanics of concrete. In this research, the new method to determine the tension softening curve of concrete has been proposed. In this new method, the release of elastic strain energy is taken into account. Moreover, the extension of the fictitious crack can be evaluated accurately based on the measurement for longitudinal strain distribution. Although this new method is quite simple compared with inverse analysis, it can predict the tension softening curve of concrete with reasonable accuracy.Finally, the size effect of structural concrete using various concretes is numerically predicted based on the obtained fracture properties.

作为这项研究工作的第一步，已经根据混凝土的断裂力学评估了各种混凝土的骨折特性，例如高强度混凝土，自我压缩的高性能混凝土等。自我压缩的高性能混凝土是一种非常有前途的新混凝土，因为它在铸造过程中不需要压实。但是，从断裂力学的角度来看，发现与常规混凝土相比，它将提供较少的断裂能量，因为自我压缩高性能混凝土中包含的粗骨料量大大降低以提供足够的流动性。另一方面，高强度混凝土的断裂能显示出与常规混凝土相同的趋势，因为高强度混凝土中粗骨料的含量与常规混凝土没有显着差异。第二步，已经大量研究了混凝土的张力软化曲线的实验方法。张力软化曲线是混凝土断裂力学的最重要参数之一。在这项研究中，已经提出了确定混凝土张力软化曲线的新方法。在这种新方法中，考虑了弹性应变能的释放。此外，可以根据纵向应变分布的测量来准确评估虚拟裂纹的扩展。尽管与逆分析相比，这种新方法非常简单，但它可以以合理的精度预测混凝土的张力软化曲线。在本文中，基于获得的裂缝特性，在数值上预测了使用各种混凝土的结构混凝土的尺寸效应。