考虑围压效应的混凝土统计损伤模型

Statistical Damage Model of Concrete Considering Confining Pressure Effect

为分析围压环境下混凝土宏观非线性本构行为和细观损伤机制,根据试验现象和统计损伤理论,本文建立了考虑围压效应的混凝土统计损伤本构模型.假设主压方向损伤由两侧向拉损伤控制,存在断裂和屈服两类细观损伤模式,通过假设两类损伤演化过程服从三角形概率分布引入材料细观非均质性,其分布形态可由4个特征参数表征.分析结果表明:等围压环境下围压的大小显著影响了混凝土细观损伤累积演化进程.随着围压的增大,两类细观损伤演化过程呈现出明显地规律性变化,可由模型中特征参数的演化规律表征;最终导致混凝土宏观非线性应力—应变行为呈现由"脆性"到"塑性"转变的特征.混凝土材料损伤演化过程不仅受其内部随机缺陷支配,同时受应力—应变状态影响;本模型为预测和分析围压环境下混凝土力学性能提供新的方法和工具.

On the basis of experimental phenomena and statistical damage theory and in consideration of the effect of confining pressure,a statistical damage constitutive model of concrete is presented to analyze the macroscopic nonlinear constitutive behavior of concrete and the microscopic damage mechanism under confining pressure.This model supposes that the damage in the main pressure direction is controlled by the lateral tensile damage,involving two meso-damage modes,namely,fracture and yield.The microscopic heterogeneity of the materials is considered,assuming that the evolution of the two meso-damage modes follow the triangular probability distribution with four characteristic parameters.Analysis results show that the value of confining pressure has a significant influence on the meso-damage evolution of concrete.The two types of meso-damage evolution show evident regular changes as the confining pressure increases.This result can be described by the evolution rules of the four characteristic parameters.Ultimately,changes at the mesoscopic level cause the macroscopic nonlinear stress-strain behavior of concrete to change from“brittleness”to“plasticity”.The damage evolution of concrete is not only dominated by its random defects in microstructure but also affected by the stress-strain state.The proposed model provides new methods and tools for predicting and analyzing the mechanical properties of concrete under confining pressure.