【摘要】 本文将常用混凝土级配曲线与三维富勒级配曲线作了对比分析,从而为基于瓦拉文公式的随机骨料模型对试件内截面进行细观结构的数值模拟提供了依据。在此基础上,采用双折线损伤演化模型描述混凝土细观各相弹性损伤退化,利用有限元方法进行了混凝土湿筛试件、全级配试件单轴受压和全级配混凝土三分点梁弯拉细观结构数值模拟。通过单轴受压数值试验讨论了同一级配不同骨料分布、有限元单元尺寸及试件尺寸对极限荷载计算结果的影响。结果显示:(1)同级配不同随机骨料分布的影响在试验结果统计范围之内;(2)为了充分反映混凝土细观特性的非均性,单元尺寸应小于最小骨料粒径的三分之一;(3)湿筛试件与全级配试件数值模拟结果验证了试件的尺寸效应。在全级配混凝土三分点梁弯拉试验的模拟计算中,讨论了界面单元、固化水泥砂浆基底强度及损伤参数对计算结果的影响。通过细观结构数值模拟,直观显示了混凝土试件单轴受压和三分点梁抗弯曲试验在不同加载阶段微裂缝产生、扩展直至失稳的过程,及其宏观应力-应变曲线的变化情况。基于有关文献资料给定的混凝土各相参数得到的数值模拟结果与试验统计结果相符。更多还原

【Abstract】 The comparison of gradations of three commonly used concretes with the Fuller gradation reveals that they accord very well. It infers that the Walraven function can be used to generate the random aggregate model (RAM) by means of Monte-Carlo method. On this basis, concrete is taken as a type of three-phase composite material composed of mortar matrix, aggregates and bonds connecting the matrix and aggregates. Based on the RAM and bilinear damage model the nonlinear finite element is adopted to numerically simulate the propagation process of cracks and fracture configuration in wet-screened specimen and full grading specimen under axial compression and in the concrete trisection beams under bending load. It is found that: 1. the influence of different aggregate distributions with the same gradation on computation result is not significant; 2. the calculated ultimate load of the specimen is not effected by the element dimension which is smaller than one third of the smallest aggregate; 3. the macro-strength of concrete mainly depends on the strength and damage-evolving characteristics of the bonds connecting concrete mortar and aggregates. The computational results are in good agreement with the experimental data.更多还原