为了从材料细观非均质角度揭示混凝土强度尺寸效应机理，建立了混凝土细观单元等效非均质力学模型，开展了立方体抗拉、抗压强度尺寸效应细观数值模拟研究。研究结果表明：混凝土强度尺寸效应根源于材料细观非均质性，随着模型尺寸的增加，混凝土材料细观单元弹性模量变异系数增大，材料细观非均质性增强，大尺寸模型内部存在更多的低强度单元或缺陷，导致混凝土立方体抗拉、抗压强度降低，极限应变减小，脆性增大；混凝土损伤破坏由少量集中区域，发散扩展形成多条非贯通的裂纹带；数值模拟结果与尺寸效应实验数据相吻合。

In order to reveal the size effect meso-heterogeneity mechanism of concrete strength, the meso-element equivalent heterogeneity model was established. Tension and compression tests were simulated for different size meso-heterogeneity models. The results showed that the size effect of concrete is rooted in the meso-heterogeneity mechanism of materials. With the increase of model size, the variation coefficient of meso-element elastic modulus increases and meso-heterogeneity of concrete heightened. Also, more low-strength units or defects were discovered in the large-size model. As a result, the tension and compression strength of concrete and the ultimate strain decreased and the brittleness of concrete strengthened. Concrete damage region extended from the concentrated area to multiple non-penetrating crack zones.

国家自然科学基金(51408127)；中国地震局教师科研基金(20120104)