Compression Fracture and Size Effect in High-Strength Concretes

高强混凝土的压缩断裂和尺寸效应

• 批准号: 9713944
• 负责人: Zdenek Bazant
• 金额: $ 25.01万
• 依托单位: Northwestern University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-10-01 至 2003-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9713944&HistoricalAwards=false
• 关键词: Compression; Fracture; Size; Effect; Strength

9713944 Bazant The fracture mechanics of concrete has progressed greatly, but only for tensile fracture, which is essentially a uniaxial phenomenon. The fracture mechanics of compression fracture, which is a triaxial phenomenon, is essentially unavailable. The present proposal, involving both theoretical and experimental studies, attempts to fill this gap. The theoretical program involves: (1) energy-based mathematical model for the propagation of a band of axial splitting crack (with internal buckling of microcracked material); (2) asymptotic analysis of size effect and shape effect, leading to simple `asymptotic-matching' formulas; (3) formulation of size-effect method for deternining compression fracture characteristics; (4) generalization of the existing microplane model for damage in compression, with consideration of the effect of time or loading rate; and (5) application to the analysis of explosive failure of high-strength concrete columns or walls subjected to fire. The experimental program, designed to verify and calibrate the theory, involves: (1) size-effect tests of double- cantilever fracture specimens with compression-tension loading; (2) size effect tests of compression fracture of cylindrical specimens with small or large notches; and (3) tests of the influence of rate or time. ***

9713944 Bazant混凝土的断裂力学已经有了很大的进展，但仅限于拉伸断裂，这本质上是一种单轴现象。 压缩断裂是一种三轴现象，其断裂力学基本上是不可用的。 本建议，涉及理论和实验研究，试图填补这一空白。 理论课程包括：（1）轴向劈裂裂纹带扩展的能量数学模型（2）尺寸效应和形状效应的渐近分析，导出了简单的“渐近匹配”公式，（3）确定压缩断裂特性的尺寸效应方法的公式，（4）确定了压缩断裂特性的尺寸效应方法。（4）推广了已有的压缩损伤微平面模型，考虑了时间或加载速率的影响，（5）应用于高强混凝土柱或墙在火灾下的爆炸破坏分析。 为验证和校正理论而设计的实验程序包括：（1）压-拉载荷下双悬臂断裂试样的尺寸效应试验;（2）小切口和大切口圆柱形试样压缩断裂的尺寸效应试验;（3）速率或时间影响试验。 ***