低应变率下混凝土动态拉伸破坏尺寸效应细观模拟

在混凝土静态破坏尺寸效应方面已取得了较完善的成果，而在动态破坏尺寸效应方面，包括其产生机制及对应的尺寸效应律的研究则非常匮乏。为探讨动态荷载作用下混凝土尺寸效应行为，从细观角度出发，结合混凝土细观结构特征，考虑动态加载下细观组分应变率效应的影响，建立了混凝土破坏行为研究的细观力学分析模型与方法。以双边缺口混凝土试件为例，对其在低应变率（10-5 s-1~1 s-1）下混凝土动态拉伸破坏行为及尺寸效应进行细观数值模拟，并分析了应变率效应对动态破坏尺寸效应的影响。最后，结合应变率效应对强度及尺寸效应的影响规律—“强度增强效应”与“尺寸效应削弱效应”，在静态破坏尺寸效应律的基础上，建立了混凝土拉伸强度的“静动态统一”尺寸效应理论公式，并验证了理论公式的准确性和合理性。

MESO-SCALE SIMULATION OF SIZE EFFECT OF DYNAMIC TENSILE STRENGTH OF CONCRETE UNDER LOW STRAIN RATES

Great progresses have been made in static size effect of concretes,while few efforts have been conducted in dynamic size effect of concretes.Herein the study,in order to explore the size effect of concrete under dynamic loadings,considering concrete heterogeneities and the strain rate effect for the meso components,a meso-scale simulation method was built.Taking the double notched concrete specimens as examples,the dynamic tensile failure and the size effect of concrete under low strain rates from 10^-5 s^-1 to 1 s^-1 were investigated using the meso-scale simulation method.The effect of strain rate on the size effect in tensile strength of concrete was also analyzed.Finally,based on the influencing mechanism of strain rate effect on dynamic strength and size effect,i.e.the enhancement of strength and weakening of size effect,a“static-dynamic unified size effect law”for dynamic tensile strength of concrete was established.The proposed size effect law was also calibrated by meso-scale simulation results.