适用于混凝土结构非线性分析的损伤本构模型研究

Study of damage constitutive model applied to simulate nonlinear behavior of concrete structures

基于不可逆热力学原理提出一种简单的混凝土类准脆性材料的损伤本构模型,具有参数相对少、公式表达简单、易于数值实现等特点。采用双标量损伤变量来描述混凝土的拉伸和压缩不等性、刚度及强度退化特性;通过分解自由能为体积和剪切两部分,在体积部分引入单边效应函数来考虑裂纹闭合效应;通过对损伤变量的黏性化处理以及附加弹性条件来考虑率相关性。给出混凝土试件在单轴拉伸和压缩、双轴加载、三轴压缩以及应变率影响的不同加载条件下的数值计算结果,与试验结果比较吻合。通过对缺口梁三点弯曲加载破坏过程和重力坝地震响应的数值模拟,验证损伤模型在大尺度混凝土结构的非线性分析方面,具有较好的收敛性和计算能力。

A simple damage constitutive model for concrete-like quasi-brittle materials within the framework of irreversible thermodynamics is developed. The model needs fewer parameters, is simpler in mathematical expression and more convenient for numerical calculation. Different responses under tensile and compressive loadings as well as degradation of stiffness and strength are considered by employing two scalar damage variables. In order to take the microcrack closure effect into consideration, the Helmholtz free energy is decomposed into hydrostatic and deviatoric components, and a unilateral effect function is introduced in the hydrostatic part. The rate effect is considered by introducing viscous regularizations into the damage variable and combined with an additional elastic condition. The cases of uniaxial tensile and compressive, biaxial and triaxial compressive loadings for a concrete specimen are studied. The results agree well with the experiment. The proposed model is employed in the analyses of a three-point bending beam and a gravity dam subjected to earthquake loading. Numerical results show that the proposed model has good convergence and high computation efficiency for the nonlinear analysis of large structures.