混凝土结构损伤过程区几何特性数值研究

NUMERICAL INVESTIGATION ON SIZE OF DAMAGE PROCESS ZONE OF CONCRETE STRUCTURES

梯度依赖损伤模型是研究具有局部化行为特性的混凝土结构时常用的模型。按照"能量耗散非局部化"的原理,梯度依赖损伤模型的特征长度应该是损伤演化相互影响物质点间的最大距离。对混凝土构件的塑性损伤演化行为进行了数值模拟研究,主要目的是获得典型混凝土构件损伤局部化带的几何分布特性,包括损伤过程区的长度参数大小及变化规律。采用的模型为四点剪切混凝土梁,使用ABAQUS/EXPLICIT作为数值工具,得到的主要结果有:(1)对于给定的宽高分别为0.15和0.40m的双边缺口梁,完整损伤区的长度为0.0421～0.0612m。损伤区长度在损伤演化过程中变化的原因是损伤区的应变状态发生了变化,由初始的剪应变为主的变形形式逐渐变为后期的拉伸应变为主的变形形式。(2)在加载后期会有次级损伤过程区出现,完整的次级损伤过程区的初始长度为0.0367m。(3)对于给定的宽高分别为0.10和0.44m的单边缺口梁,在损伤演化扩展过程中一个完整损伤区的长度为0.0473m。上述结果可供梯度依赖损伤模型为特征长度取值时参考。

Gradient-dependent damage model is widely used in the simulation of mechanical behaviours of concrete structures,which have localization phenomena. With the principle of nonlocal energy dissipation,the characteristic length of a gradient-dependent damage model should be the distance of two material points whose damage evolution processes can affect each other. Numerical simulations were performed on the evolution of damage process zone of concrete structures,and the size and evolution of damage process zone were studied. The adopted geometrical model is four-point-shearing beam,and ABAQUS/EXPLICIT software are taken as the numerical tools. The main results include:(1) The length of a complete damage process zone is between 0.042 1 and 0.061 2 m for the given double-notched beam,which is 0.15 m in width and 0.40 m in length. Variation of size of damage process zone is caused by variation of strain states,which are shearing dominated at beginning of deformation and tension dominated at the end of deformation. (2) Secondary damage process zone appeared at the end of deformation,and its size is about 0.036 7 m for the given structure. (3) For the single-notched beam with four-point shearing loads,which is 0.10 m in width and 0.44 m in length,the size of damage process zone is 0.047 3 m during deformation process. These results can be referred as the value of the characteristic length of a gradient-dependent damage model.