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本文基于分形理论,以混凝土试件细观结构中的骨料面积-界面周长关系作为细观结构的表征指标,通过分形维方法将其量化,利用数值方法研究了混凝土试件的细观结构变化规律,分析了试件细观结构变化对其力学性能的影响,并在此基础上进一步探讨了细观结构变化对试件力学特性的影响机理。研究发现:(1)试件骨料投放率的变化对细观结构影响甚小,而试件尺寸的变化则对其影响较大;(2)试件尺寸变化对试件承载力学性能的影响更大,而骨料投放率变化对其影响则较小:骨料投放的增多对承载力的提升作用和对整体应力水平的降低作用在大尺寸试件中更为明显;(3)骨料投放率的增大能提升试件局部开裂应力,但会降低开裂应变,增大开裂脆性,试件破坏呈现出明显的局部特性。
Based on fractal theory, the relationship between aggregate area and interface perimeter in meso-structure of concrete specimen is taken as the characterization index of mesostructure. The fractal dimension method is used to quantify the mesostructure. The mesoscopic structure of concrete specimen is studied by numerical method The influence of the change of microstructure on the mechanical properties of the specimen was analyzed. Based on the analysis, the influence mechanism of the microstructure change on the mechanical properties of the specimen was further discussed. The results show that: (1) The change of aggregate loading rate has little effect on the microstructure, while the change of the specimen size has a great influence on it; (2) The influence of specimen size on the mechanical properties of the specimen But the change of aggregate placement rate had less influence on it: the increase of aggregate placement was more obvious in large-sized specimens for the enhancement of bearing capacity and the reduction of overall stress level; (3) The increase of the loading rate can improve the local cracking stress of the specimen, but it will reduce the cracking strain and increase the cracking brittleness, and the specimen destruction shows obvious local characteristics.