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为了在细观层次上研究混凝土梁的损伤断裂机理,将混凝土视为由骨料、水泥砂浆和界面组成的三相复合材料。基于三维随机骨料随机力学参数模型,建立了2个混凝土梁湿筛试件的数值模型;模型MX1模拟骨料的随机分布,模型MX2在MX1的基础上模拟混凝土各相材料参数的随机性,通过这2个模型的抗弯数值试验,展现了混凝土梁损伤断裂和裂缝萌生与扩展的渐进过程。结果表明:数值试验得到的混凝土梁弯拉强度与真实试验测得的弯拉强度较为接近;由于骨料分布的随机性,混凝土裂纹起裂和扩展表现出显著的不规则性和不连续性;受材料参数随机分布的影响,模型MX2较MX1承载力略有降低,变形稍有增加。
In order to study the damage and fracture mechanism of concrete beam in the meso-level, the concrete is regarded as the three-phase composite material composed of aggregate, cement mortar and interface. Based on the stochastic mechanical parameters model of three-dimensional random aggregate, two numerical models of wet-sieved concrete specimens were established. The model MX1 was used to simulate the random distribution of aggregates. The model MX2 simulated the randomness of material parameters of each phase of concrete based on MX1. Through the bending numerical tests of the two models, the progressive process of damage and crack initiation and propagation of concrete beams is demonstrated. The results show that the flexural strength of concrete beams obtained by numerical experiments is close to the flexural strength measured by real tests. Due to the randomness of aggregate distribution, the crack initiation and propagation of concrete show obvious irregularities and discontinuities. Affected by the random distribution of material parameters, the bearing capacity of MX2 is slightly lower than that of MX1, and the deformation is slightly increased.