细观结构不均匀性对混凝土动弯拉强度的影响

Influence of meso-structure heterogeneity on dynamic bending strength of concrete

本文在随机骨料模型的基础上,提出了既能反映混凝土骨料分布随机性又能反映混凝土细观各相材料力学特性随机性的随机骨料随机参数模型。利用该模型并考虑材料的细观力学的应变率效应,对湿筛混凝土和全级配混凝土梁进行了三分点冲击弯拉断裂数值模拟,分析了混凝土材料参数的离散性、混凝土级配以及初始静预载水平对其动弯拉强度的影响。研究表明:(1)随混凝土材料的弹性模量和抗拉强度的离散性增大,静弯拉强度和动弯拉强度降低,但动弯拉强度增强系数得到提高;(2)一定条件下全级配的混凝土梁的动弯拉强度增强系数高于湿筛混凝土梁的动弯拉强度增强系数;(3)为了更准确地确定动弯拉强度增强系数,应该考虑混凝土级配和初始预静载水平所产生的应变率效应对其的影响。

Based on the random aggregate model a radom aggregated and random parametric model describing the random characteristics of meso-structure and mechanical properties of concrete material is proposed. The model is applied to numerically calculate the dynamic bending strength of concrete trisection beams subjected to impact load with the strain-rate effects of the meso-structure taken into account. The effects of concrete grading, divergence of elemental mechanical behaviors and static preload levels on dynamic bending strength are investigated. It is found that： 1. the static bending strength and dynamic bending strength decrease but the dynamic enhancement coefficients increase when the elastic modulus of concrete and the divergence of tensile strength increases;2, the enhancement coefficients of dynamic bending strength of full grading concrete beams are greater than those of wet-screened concrete,under the given condition;3, concrete grading and static preload effects should be considered in valuating the dynamic bending strength of concrete.