MESOSCOPIC STRUCTURAL ANALYSIS OF NONLINEAR MECHANICAL PROPERTIES OF CONCRETE

本研究通过以下数值分析和实验，建立了一种考虑细观结构影响的混凝土破坏时非线性力学行为的数值模拟方法。数值分析方法的发展：提出了用微观单元元模拟混凝土破坏行为的数值分析方法。微观单元单元由两个刚性块组成，在界面处由非线性弹簧在法向和切向连接。本方法既具有使用混凝土单元的组合单元法的优点，又具有单独单元法的优点。数值模拟结果表明，该方法可以有效地分析混凝土破坏时的非线性力学行为，包括应变软化。数值分析方法计算效率的研究：证实了将并行计算技术与区域分解方法相结合可以有效地减少计算时间。混凝土模型试件试验验证数值分析方法：通过钢瓶集料混凝土二维模型试件的单轴压缩试验，验证了数值分析方法的适用性。试验结果表明，骨料的形状、尺寸、配布、骨料与砂浆的粘结、砂浆的强度等因素对应力-应变关系和破坏模式的影响较为明显。将现有的数值分析方法应用于更大的问题，使其更具实用性，可视为本研究的延伸。

The following numerical analysis and experiment were conducted in this study to develop a numerical simulation method for the analysis of the nonlinear mechanical behavior of concrete at failure considering the effect of its mesoscopic structure.1. Development of numerical analysis method :A numerical analysis method using microscopic unit elements was developed to simulate the failure behavior of concrete. A microscopic unit element is composed of two rigid blocks connected by nonlinear springs in the normal and tangential directions at the interface. The present method has the advantages of both the method using composite elements called concrete element and the distinct element method. It was confirmed through numerical simulations that the present method is effective to analyze the nonlinear mechanical behavior of concrete at failure including the strain softening.2. Investigation of computational efficiency of numerical analysis method :It was confirmed that the use of the parallel computational technique with the domain decomposition method is effective to reduce the computation time.Experiment of model concrete specimen to examine the numerical analysis method :Uniaxial compression tests of two-dimensional model concrete specimens using steel cylinders for aggregates were conducted to examine the appropriateness of the present numerical method. The influence of the factors such as the shape, the size and the allocation of aggregate, the bond between aggregate and mortar, and the strength of mortar on the stress-strain relationship and the failure mode became clear from the test results.Applying the present numerical analysis method to larger problems and making it more practical may be considered as the extension of the present study.