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混凝土材料宏观力学行为的非线性及尺寸效应根源于其内部组成的非均质性。考虑材料细观结构非均质性的影响,建立由骨料颗粒、砂浆基质和界面过渡区组成的混凝土细观尺度力学模型。对尺寸为150 mm、250 mm、350 mm和450 mm的混凝土立方体模型劈裂抗拉破坏行为进行细观数值模拟,探讨骨料粒径(最大粒径分别为:10 mm、20 mm、30 mm和40 mm)的影响机制,并与试验结果进行对比分析。结果表明:1)混凝土材料的劈裂抗拉强度随着骨料粒径增大而略微降低,最大骨料粒径达到30 mm左右时,强度降低趋势变缓;2)四种骨料粒径下混凝土立方体劈裂抗拉强度均存在尺寸效应现象,相比于大骨料试件,小骨料试件的破坏更具脆性,因而其尺寸效应更显著;3)混凝土劈裂抗拉强度尺寸效应行为与Ba?ant和Weibull提出的尺寸效应理论相吻合。
The nonlinear and dimensional effects of macroscopic mechanical behavior of concrete are due to the heterogeneity of its internal composition. Considering the influence of the mesostructure heterogeneity, a mechanical model of concrete with mesoscopic scale composed of aggregate particles, mortar matrix and interfacial transition zone was established. The numerical simulation of splitting tensile failure behavior of concrete cubical model with dimensions of 150 mm, 250 mm, 350 mm and 450 mm was carried out. The effects of aggregate size (maximum particle size: 10 mm, 20 mm, 30 mm And 40 mm), and compared with the test results. The results show that: 1) the splitting tensile strength of concrete decreases slightly with the increasing of the aggregate size, and the decreasing trend of strength decreases when the maximum aggregate size reaches 30 mm; 2) The cubic concrete cubical splitting tensile strength has the size effect phenomenon. Compared with the large aggregate specimen, the fracture of the small aggregate specimen is more brittle, so the dimensional effect is more remarkable. 3) The splitting tensile strength of the concrete The effect behavior is consistent with the size effect theory proposed by Ba? Ant and Weibull.