混凝土拉压强度尺寸效应的细观非均质机理

Meso-heterogeneity mechanism of the concrete size effect of tension and compression strength

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.