考虑非均质特征界面的混凝土材料破坏机理精细化分析及应用

Many studies found a significant effect of micro-structure properties on the macroscopic mechanical behavior of concrete. A refinement analysis model is proposed to establish a quantitative relations between heterogeneous meso-structural properties of concrete and its localized damage mechanism. Synthetically combining of theoretical analysis, experimental study and numerical simulation will be tackled to develop the proposed model. A heterogeneous composite model of concrete will be constructed. Generalized eigenvalue algorithm will be utilized to establish a more accurate geometric model of course aggregates satisfying real constrains of volumetric ratios and grading ratios, where mechanical properties of interfacial transfer zones around course aggregates are heterogeneous and their thicknesses are various with aggregates dimensional size. Displacement type of damage evaluation equations will be developed to reduce mesh sensitivity in numerical procedures. By Interface Program, the developed damage evaluation equations will be combined with multi-scale meshing method, and an integration model of concrete will be developed encompassing functions of preprocessing and computing. With the developed integration modeling technology, we will establish a geometrical and physical model closer to the real state of the concrete material. A rigid loading system will be exploited to study the dynamic failure procession of concrete with controlling displacement increment. Using grey-scale correlation analysis, a theory of image processing will be established to detect the crack tip and to measure the whole paths of dynamic cracks. With comparison of measured information by the dynamic crack test system and computed results, the developed integration model will be verified and validated. With the modified integrating concrete material model, we will quantitatively analyze the affections of interfacial transfer zone, mechanical properties of cementations, and geometric distribution of coarse aggregates on concrete apparent strengthen. Furthermore, coupling effects of these factors on concrete apparent strengthen will be analyzed. Failure modes of concrete under typical meso-structural characteristics will be simulated, and a statistics failure model of concrete will be constructed with probability theory. A more scientific model for evaluating security of concrete structures could be obtained.

研究发现微细观结构显著影响混凝土宏观力学行为。针对细观非均质结构特征与混凝土失效破坏行为间的关系，以建立混凝土精细化分析模型为目标，系统开展理论分析、实验研究和数值模拟。从混凝土非均质复合模型的生成出发，采用广义特征值算法，求解包含非均质、变厚度界面过渡区的粗骨料随机分布问题，构建满足体积分数和级配要求的混凝土几何模型。引入位移模式的损伤本构表征方法，探讨不依赖于网格尺寸的混凝土损伤全过程分析方法，综合运用多尺度网格技术，编制接口程序，发展几何建模和力学分析一体化的求解技术，建立更接近真实状态的混凝土材料计算模型。研制刚度可控加载系统，结合图像采集及灰度相关性分析系统，实现细观裂纹的动态观测，进而验证和修正一体化分析模型。依据一体化模型，分析界面过渡区、基质以及骨料等单一和多重物理力学因素与混凝土宏观强度间的定量关系，构建混凝土失效破坏的概率统计模型，为科学评估混凝土结构的安全性提供基础。

本项目针对细观非均质结构特征与混凝土失效破坏行为间的关系，以混凝土精细化分析模型为目标，系统开展了理论分析、实验研究和数值模拟技术的研究工作。.建立了混凝土非均质特征界面多边形骨料细观模型，发展了面向多边形骨料的自适应网格生成技术，引入位移模式的损伤本构表征方法，探讨了不依赖于网格尺寸的混凝土损伤全过程分析方法。综合运用多尺度网格技术，编制接口程序，发展了几何建模和力学分析一体化的求解技术，建立了更接近真实状态的混凝土材料计算分析模型。.项目组研制了刚度可控加载系统，结合图像采集及灰度相关性分析系统，实现了细观裂纹的动态观测，进而验证和修正一体化分析模型。.开展了界面过渡区及混凝土细观结构影响下混凝土材料力学行为及损伤破坏机理的研究，分别研究和建立了混凝土细观疲劳分析模型、考虑内部材料界面影响的混凝土本构模型、混凝土细观损伤动力分析等模型。发展了混凝土材料细观疲劳损伤分析技术，开发了细观、宏观模型转换的损伤跨尺度演化分析方法，最后完成了考虑界面过渡区细观结构及其力学性质梯度特征的混凝土多相细观模型的构建。并以此模型开展了混凝土材料多相复合材料模型的多尺度建模及模型修正技术，发展了面向混凝土材料微细观破坏过程模拟的Lattice模型修正技术，分析了全耦合与部分耦合迭代算法对于计算精度和效率的影响。项目的研究成果为科学评估混凝土结构的安全性提供了坚实的基础。