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End friction effects on concrete dynamic strength using meso-scale models based on XCT images

DOI：

 作者 单位 E-mail 黎超 浙江大学 changyonglc@163.com 杨贞军 浙江大学 zhjyang@zju.edu 黄宇劼 浙江省建筑设计研究院

本文基于微观X射线计算断层扫描(XCT)图像，采用像素替换为单元的方法建立真实普通强度混凝土试件的细观有限元模型。该模型包含骨料、砂浆、界面过渡区和孔洞，并采用ABAQUS中的混凝土损伤塑性本构模型(CDP)来模拟各相材料。本文对20个基于XCT图像的细观模型进行了中低应变率(10-5~2s-1)冲击作用下的端部摩擦效应的蒙特卡洛模拟；并对模拟结果进行统计分析和曲线拟合，获得了动态抗压强度和端摩擦系数及应变率之间的定量关系式，以及无摩擦时抗压强度提高因子(CDIF)与应变率之间的关系式。结果表明：端摩擦能够提高混凝土的抗压强度，但当摩擦系数达到0.3后其影响不再明显；CDIF与应变率的对数( )成二次抛物线关系；所拟合的关系式和实验结果吻合良好。

Based on micro X-ray computed tomography (XCT) images from in-situ tests, this paper replaces image pixels with finite elements to build two-dimensional meso-scale models of real concrete specimens. The concrete damaged plasticity (CDP) model in ABAQUS is used to simulate constitutive phases: aggregates, mortars, interfacial transition zones (ITZ) and pores. The end friction effect under low to medium strain rates (10-5~2s-1) is studied, and Monte Carlo simulations are conducted for 20 XCT image-based models. Through statistical analyses and curve fitting of the simulation results, a quantitative relation between the dynamic compressive strength and the end friction coefficient and strain rate is obtained. The results show that the end friction can increase the dynamic strength, but the effect becomes insignificant when the friction coefficient reaches 0.3. The fitted curve between CDIF and the logarithm of strain rate ( ) without end friction is quadratic parabolic and is in good agreement with the experimental results.
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