考虑材料组成特性的混凝土轴拉破坏过程细观数值模拟

MESO-STRUCTURAL ANALYSIS OF CONCRETE SPECIMENS UNDER UNIAXIAL TENSION BASED ON COMPOSITION CHARACTERISTICS

为反映骨料、砂浆及其之间的界面过渡区的组合特点和材料性能,基于材料细观非均匀性和有限元方法的混凝土破坏过程细观数值模拟需进行复杂、细致的网格剖分,导致了繁重的前处理工作和可观的计算量。该文对混凝土材料细观单元材质组成的单一化假定进行改进,将内嵌界面过渡区材料的规则化单元视为一种广义复合材料单元,建立了复合型界面损伤模型。采用等效方法确定单元的复合弹性关系,通过有限元法计算单元的局部应力;用细观层次上弹性力学性能的弱化描述单元组成材料的损伤,混凝土材料的破坏过程通过单元各组分的损伤模拟。应用该复合型界面损伤模型研究了混凝土试件的单轴拉伸破坏过程,细观数值模拟结果符合混凝土试件的宏观破坏特征,表明该模型可作为分析混凝土材料破坏过程的一种有效途径。

The behaviour of concrete can be simulated by the mesoscopic numerical model based on the finite element method and introducing the heterogeneity of materials. The relatively fine meshes of concrete would be practically impossible with the standard software, which are needed to reflect the geometry and properties of the aggregate, interracial transition zone and matrix at the meso-level. In this construction, a mixed interface damage constitutive model is applied to develop a meso-structural model for simulating the fracture behavior of the concrete specimen loaded in uniaxial tension in 2D. Using the material mechanics method, the influence of the interracial transition zone is smeared into a small region of the adjacent intact materials （aggregates and matrix）. The elastic constants in the region are defined in terms of the constitutive properties of both the intact materials and the interfacial transition zone as well as the geometry of the homogenized domain. An elastic finite element program is employed as the basic stress analysis tool while elastic purely brittle damage mechanics is used to describe the constitutive law of a meso-level element. The maximum tensile stress is utilized as a damage threshold for all elements, especially for each material of composite elements. The numerical results show a good qualitative agreement with the macro fracture mechanism of concrete from experiment observations and illustrate the capabilities of the model.