摘要
准脆性混凝土自由裂缝前缘断裂过程区的发展与其非线性断裂特征及尺寸效应现象密切相关。它的物理力学行为的量化分析对理解混凝土断裂破坏机理和建立适用于混凝土结构裂缝稳定分析和安全评估断裂准则尤为重要,一直是混凝土断裂力学研究的核心问题。该文依据Hillerborg给出的断裂能定义,给出了计算单位长度断裂过程区发展能量耗散的通用表达式。以三点弯曲梁为例,采用非线性软化本构关系,进一步给出了计算此平均能量耗散的具体步骤及对应的公式。在根据实测的三点弯曲梁的断裂能回归拟合了特征裂缝张开位移w0后,计算了每个试件整个断裂全过程中不同荷载时刻断裂过程区耗能的平均值。结果表明:随着裂缝扩展,断裂过程区能量耗散的变化和试件尺寸无关,可描述断裂过程区混凝土材料的力学性能。
It is generally accepted that the development of fracture process zone （FPZ） in front of the stress-free crack in quasi-brittle materials like concrete is responsible for the non-linear fracture behavior of concrete and size effect phenomena. Therefore, since the beginning of concrete fracture mechanics, it has been believed that the quantitative analysis of both physical and mechanical behaviors of fracture process zone is of significant importance to better understand the potential fracture mechanisms in concrete fracture as well as to more accurately develop nonlinear fracture models for crack stability analysis and safety assessment in concrete. Considering this point, referring to the definition of fracture energy proposed by Hillerborg, a general equation for calculating average energy dissipation per unit length of FPZ propagation is presented in this paper. Taking three-point bending beam as an example, step-by-step procedures for computing this average energy dissipation are further given in details, in which Reinhardt＇s non-linear softening relationship is used. After obtaining the characteristic crack opening displacement wo by mathematic fitting according to nonlinear softening equation, in which fracture energy is approximately equal to the measured fracture energy of each specimen, during the entire fracture process the average value of energy dissipation in FPZ at any loading moment is calculated. The calculated results indicate that the change of energy dissipation in fracture process zone with crack propagation is independent of specimen size, and is a good description of mechanical behavior occurred in FPZ in concrete.
出处
《工程力学》
EI
CSCD
北大核心
2008年第7期18-23,共6页
Engineering Mechanics
基金
国家自然科学基金重点项目(50438010)
国家973项目(2002CB412709)
关键词
断裂过程区
平均能量耗散
三点弯曲梁
混凝土
断裂能
fracture process zone （FPZ）
average energy dissipation
three-point bending beam
concrete
fracture energy
