CRACK PREDICTION OF HIGH DURABLE CONCRETE STRUCTURES BASED ON FRACTURE MECHANICS

研究了声发射技术在断裂力学中的应用，并配备了相应的实验装置。通过对素体混凝土和纤维增强混凝土断裂力学参数的试验研究，阐明了在分析混凝土裂纹扩展过程中应考虑纤维增强混凝土断裂力学参数的尺寸效应。定量声发射波形分析被发展为SiGMA程序，并应用于板样单轴压缩试验。结果证实了SiGMA程序在识别裂纹位置、裂纹类型和裂纹方向方面的有效性。应用边界元法（BEM）分析了混凝土裂缝在任意方向上的扩展。该分析方法非常有效，实验中得到的裂纹轨迹很容易通过边界元分析预测出来。为了确认由SiGMA程序确定的裂纹运动学，开发了后置分析。从断裂力学的角度研究了碳纤维和钢纤维混凝土等高耐久性混凝土的裂缝成核问题。通过缩小模型的研究，验证了边界元法预测裂纹的能力。

An application of acoustic emission (AE) techniques to fracture mechanics is investigated and experimental devices for the research purpose are equipped. Fracture mechanics (FM) parameters are studied in experiments of plain and fiber-reinforced concrete, and it is clarified that the size effect of FM parameters should be taken into account for the analysis of crack propagation in concrete. Quantitative AE waveform analysis is developed as SiGMA procedure and is applied to uniaxial compression tests of plate specimens. Results confirm the usefulness of the SiGMA procedure to identify crack locations, crack types, and crack orientations. The boundary element method (BEM) is applied to analyze crack propagation in concrete in arbitrary directions. The analytical procedure is so effective that crack traces obtained in experiments are readily predicted by the BEM analysis.In order to confirm crack kinematics determined by the SiGMA procedure, a post-analysis is developed. Crack nucleation in high durable concrete such as carbon-fiber and steel-fiber reinforced concrete is studied on the basis of fracture mechanics. The ability of the crack prediction by BEM is confirmed in the scaled-down model study.