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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。
In this paper, we compare the gradation curve of the concrete with the three-dimensional Fuller gradation curve, and provide the basis for the numerical simulation of the mesostructure of the specimen in the stochastic aggregate model based on Wallavin’s formula. Based on this, the degeneration of elastic damage in each phase of the concrete is described by the double-break damage evolution model. The wet-screened concrete specimens, the uniaxial compressive strength test specimens and the full-grade concrete three-point Numerical simulation of meso - structure of beam bending. Through the uniaxial compression numerical experiment, the influence of different aggregate distribution, finite element unit size and specimen size on the ultimate load calculation results are discussed. The results show that: (1) the influence of different random aggregate distributions within the same level is within the statistical range of the experimental results; (2) In order to fully reflect the inhomogeneity of the meso-characteristics of concrete, the unit size should be less than the minimum aggregate size (3) The numerical simulation results of the wet sieve specimen and the full-scale specimen verified the size effect of the specimen. In the simulation calculation of full-grade concrete quarter bending test, the influence of interface unit and cured cement mortar substrate strength and damage parameters on the calculation results is discussed. Through the numerical simulation of meso-structure, the process of microcrack generation, propagation and destabilization at different loading stages and the change of its macro-stress-strain curve are visually displayed by the uniaxial compression test and the three-point beam bending test of concrete specimens . The numerical simulation results obtained based on the parameters of each phase of concrete given in the literature are consistent with the experimental statistics.