混凝土单轴动态拉伸强度随机性的统计特性分析

Statistical investigationon the randomness of uniaxial dynamic tensile strengths of concrete

混凝土拉伸破坏行为是混凝土试件及结构力学行为的重要组成部分,其与加载速率密切关联。针对混凝土材料静、动态拉伸强度的随机性和离散性,探讨了骨料分布形式的影响规律。从细观角度出发,假定混凝土是由骨料颗粒、砂浆基质及界面过渡区组成的三相复合材料,考虑各相材料动态加载下力学特性的应变率效应,建立了混凝土动态力学行为研究的细观尺度力学模型与方法。以双边缺口混凝土试件为例,对5组不同应变率下64个具有不同骨料分布形式的混凝土试件的单轴动态拉伸力学行为进行了数值试验。基于概率统计分析理论,对不同应变率下混凝土动态抗拉强度的离散性进行了统计分析,包括均值、方差及分布形式等概率统计特性。研究表明:混凝土动态抗拉强度服从双参数Weibull分布;随着应变率的增大,混凝土抗拉强度离散性逐渐减小。

Tensile failure behavior of concrete dominates the behavior of concrete specimens and structural elements. It is strongly affected by loading rate. To study the discreteness and randomness of concrete static / dynamic tensile strength,the influence of aggregate spatial distribution pattern was discussed. Taking account of the strain rate effect of meso-scale components under dynamic loading,a meso-scale mechanical model and method were established,in which the concrete was assumed to be composed of aggregate particles,mortar matrix,and the interfacial transition zones between the former two phases. Furthermore,the uniaxial dynamic tensile mechanical behavior of 64 sets of concrete with different aggregate distribution patterns was studied numerically,and the discreteness of concrete strength was analyzed statistically. The results indicate that： 1 the tensile strengths of concrete with different aggregate distribution obey the Weibull distribution; 2 with the increase of strain rate,the discreteness of the concrete tensile strength decrease gradually.