混凝土细观扩展有限元法建模及宏观力学性能估算

Modeling of Concrete Based on XFEM and Estimation of Macroscopic Mechanical Properties

混凝土内部的界面过渡区是材料的薄弱环节,一定程度上控制着混凝土材料的宏观力学性能,在界面应力和界面相对位移的框架下描述界面过渡区的本构行为,首先在界面应力空间下构建一个能够综合反映界面过渡区纯拉、拉剪和压剪加载下的初始开裂滑移面,然后通过两个独立的断裂能释放率参数:I型断裂能释放率和渐进II型断裂能释放率,来控制开裂滑移面的后继软化过程,建立了界面过渡区的摩擦剪胀型本构模型.并把该本构模型嵌入到扩展有限元的模式下,建立了能够反映界面过渡区复杂力学行为的扩展有限元模型.将建立的扩展有限元模型应用到混凝土细观数值模拟中去,探究了界面过渡区的初始界面刚度、峰值强度和断裂能释放率对混凝土宏观力学性能的影响规律。

The interfacial transition zone in concrete is the weak link of the material,which restricts the macroscopic mechanical properties of concrete as a whole. Under the relationship framework between the interface stress and the interface relative displacement,the constitutive behavior of the ITZ is to be described. Firstly,in the interface stress space,we constructe an initial cracking surface of reflecting the initial failure status of the ITZ under the loading of pure tensile,tensile-shear and compression-shear. And through the two independent parameters,fracture energy release rates in corresponding of the type I and progressive type II,to control the subsequent softening process of the cracking surface,we establish a friction dilatancy constitutive model of the ITZ and embed it in the extended finite element model. Finally,the extended finite element model is applied to concrete the mesoscopic numerical simulation. The influences of the interface initial stiffness,tensile strength and fracture energy release rate of ITZ on the effective modulus of concrete are explored.