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Fracture Mechanics of High Strength Concrete and Size Effect

高强混凝土断裂力学与尺寸效应

基本信息

批准号：
04650510
负责人：
MIHASHI Hirozo
金额：
$ 1.54万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1993
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04650510/
关键词：
High Strength Concrete Fracture Mechanics of Concrete Size Effect Tension Softening Microstructure Brittleness Index Steel Fiber Reinforced Concrete 破壊力学破壊エネルギー

项目摘要

Crack resistance and size effect in high strength concrete were studied from the view point of fracture mechanics of concrete. The following results were obtained.1) Although fracture energy of concrete increases up to about 80MPa of the compressive strength, it turns to decrease beyound 100MPa of the compressive strength when RILEM standard notched beams of 100x100x8400 (mm) were used. On the other hand, wedge splitting compact tension specimens with a six times larger size give a higher values of the fracture energy than that of notched beams even for the very high strength concrete of about 100MPa.To investigate the mechanism to couse the difference, the changing rates of tangential stiffness load-CMOD curves were analyzed. It was shown that the fracture process zone in front of the crack tip was fully developed before the fracture in large specimens but not in smaller ones.2) While high strength concrete is realized by making the microstructure finer, it changes strongly the tension softening properties and especially increases the maximum cohesive stress. It was clarified that the maximum cohesive stress is empirically described as a function of the porosity.3) Brittle index defined with three parameters determined by standard tests, can well charcterize the crack resistance properties of concrete with various strength and sizes of specimens.4) Steel fiber reinforcement provides high strength concrete with higher crack resistance.

从混凝土断裂力学的角度研究了高强混凝土的抗裂性和尺寸效应。结果表明：（1）当采用RILEM标准切口梁（100 × 100 × 8400（mm））时，混凝土的断裂能在抗压强度80 MPa左右时有所增加，但在抗压强度100 MPa以上时，断裂能有所下降。而对于100 MPa左右的高强混凝土，6倍尺寸的劈裂紧凑拉伸试件的断裂能比缺口梁的断裂能高，通过分析切向刚度荷载-CMOD曲线的变化率，探讨了产生这种差异的机理。结果表明，大试件在断裂前，裂尖前的断裂过程区已充分发展，而小试件则未充分发展。2）细观结构细化实现高强混凝土的同时，也显著改变了混凝土的拉伸软化特性，特别是提高了混凝土的最大粘聚力。3）脆性指数由标准试验确定的3个参数定义，可以很好地表征不同强度和不同尺寸钢筋混凝土的抗裂性能; 4）钢纤维增强高强混凝土具有更高的抗裂性能。