Localization and Size Effect of Failure of Concrete Structures Subjected to Compression

当混凝土受压破坏时，破坏并非发生在整体上，而只集中在峰值后区域的部分混凝土上。通过压缩破坏的局部化，可以解释结构混凝土受压时尺寸效应的存在。为了定量地阐明局部化效应，本研究对混凝土进行了截面形状、高度比和截面宽度参数变化的单轴压缩试验。根据局部应变的测量结果，定量评价了局部能量吸收。通过该测量，明确了当高度与截面宽度之比增加到一定程度时，混凝土压缩破坏发生局部化。并且，发现局部化长度（破坏区域的长度）可以用与原截面具有相同横截面积的正方形的边长来计算。此外，还发现单位体积破坏区域的吸收能量（压缩断裂能）可以作为混凝土抗压强度的函数来评价。也就是说，压缩断裂能可以看作是材料的性能。将这些概念应用于钢筋混凝土深梁的剪压破坏，证实了局部化的概念可以应用于钢筋混凝土深梁。将压缩应力-应变关系根据单元长度进行修正，使能量吸收恒定，应用于后峰区钢筋混凝土深梁的分析。验证了深梁的荷载-变形特性和抗剪强度的尺寸效应是可以准确预测的。通过与实验结果的比较，验证了该方法的有效性。上述结果已在Journal of JSCE、Transactions of JCI以及FRAMCOS-4等国际会议上进行了总结和发表。少

When concrete is failed by compression, the failure does not happen throughout the whole body but it concentrates only in some portion of concrete in the post-peak region. By the localization of the failure in compression, the existence of the size effect in structural concrete subjected to compression can be explained.In this study, the uniaxial compression test of concrete in which the cross-sectional shape, the ratio of height and cross section width are parametrically changed has been carried out in order to quantitatively clarify the localization effect. Based on the measured results of local strain, the local energy absorption has been quantitatively evaluated. According to this measurement, it has been clarified that the localization happens for the compression failure of the concrete when the ratio of the height and the cross section width increases to some extent. And, it is found that the localization length (the length of the failure region) can be evaluated using the side l … More ength of the square having the same cross sectional area as the original cross section. In addition, it is found that the absorbed energy per unit volume of failure region (the compression fracture energy) can be evaluated as the function of the compressive strength of concrete. In other words, the compression fracture energy can be considered as the material property. These concepts have been applied to RC deep beams which fail in shear compression failure mode, and it has been confirmed that the concept of the localization can be applied for RC deep beams.The compressive stress-strain relationship which is modified according to the element length to make the energy absorption constant, has been applied for the analysis of RC deep beams in the post-peak region. Then, it has been confirmed that the load-deformation behavior and the size effect of shear strength of RC deep beams can be predicted accurately. The validity has also been confirmed by the comparison with the experimental result.The above results have been summarized and published in Journal of JSCE, Transactions of JCI and also international conference, such as FRAMCOS-4. Less