This paper studies the method of determining the fracture parameters of pre-notched concrete beams with horizontal pre-set cracks and the influence of fracture intersection on fracture characteristics of concrete based on the three-point bending test. Pre-notched concrete beams with horizontal pre-set cracks were designed as 13 groups according to the different positions, lengths and widths of horizontal pre-set cracks. The fracture toughness was calculated on the basis of the cohesive force model of concrete, and the crack opening displacement obtained by using the digital image correlation technique. The study's results indicate that the distance between the pre-set crack and the notch tip as well as the pre-set crack length and width have various influences on the fracture propagation of edge mode I crack, the bearing capacity and unstable fracture toughness of concrete beams owing to varying degrees of loss of cohesion in the fracture process zone (FPZ). The study also finds that a large lack of cohesion in the FPZ indicates a high possibility of a reduction in the bearing capacity and unstable fracture toughness of concrete beams.

中文翻译：

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基于数字图像相关技术的裂缝对混凝土断裂参数的影响

本文基于三点弯曲试验研究了确定水平预置裂缝预制缺口混凝土梁断裂参数的方法及断裂交点对混凝土断裂特性的影响。根据水平预置裂缝的位置、长度和宽度的不同，将具有水平预置裂缝的预制缺口混凝土梁设计为13组。根据混凝土内聚力模型计算断裂韧度，利用数字图像相关技术获得裂缝张开位移。研究结果表明，预置裂纹与缺口尖端的距离以及预置裂纹的长度和宽度对边缘I型裂纹的断裂扩展有不同的影响，由于断裂过程区（FPZ）中不同程度的内聚力损失，混凝土梁的承载能力和不稳定的断裂韧性。研究还发现，FPZ 中大量缺乏内聚力表明混凝土梁的承载力和不稳定断裂韧性降低的可能性很高。