混凝土断裂过程区的虚拟裂纹粘聚力奇异性

混凝土断裂过程区视为具有粘聚阻力作用的虚拟裂纹，其非线性断裂和尺寸效应特性是与该虚拟裂纹粘聚力分布规律密切相关的。通过得到的粘聚应力分布函数解析结果，对该粘聚力分布特征的分析得知，在基于断裂过程区之外用线弹性场的力学模型上，该粘聚力随距离虚拟裂纹尖点的靠近，仍具有平方根奇异性。从而本文提出一个能够反映裂纹发展状态的粘聚应力奇异性强度参数，它是无粘聚力的线弹性裂纹应力强度因子和表征裂纹张开位移分布多项式参数的函数；因此，该参数可以作为混凝土非线性断裂的一个参量。文中就已有断裂试验测试结果进行了算例分析和相应的讨论。

Singularity of Crack Cohesive Stress Distribution Along the Fracture Process Zone of Concrete

As the Fracture Process Zone of concrete is considered as a virtual crack with cohesive force, the nonlinear fracture behavior of concrete and size effect are closely related with the cohesive stress distribution along FPZ. Based on the analysis result obtained recently by the authors, the character of cohesive stress distribution is analyzed in the present paper. There is a cohesive stress singularity at the fictitious crack tip. The index of cohesive stress singularity is square root, and it is a function of polynomial parameters expressing both the crack opening displacement and the stress intensity factor K of linear elastic body without cohesive force along the FPZ. So the singularity index may show the status of concrete fracture development, and is a material nonlinear fracture index. By the way, calculated results of the parameters of polynomial expressing COD distribution and cohesive stress singularity index are presented in the paper. And two approaches to determine polynomial parameters by the Least Square Method are introduced. Based on tested data for concrete fracture, some numerical examples and discussions are also given in the paper.