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Application of Stochastic Geometry for Evaluating Damage Level due to Cracking in Concrete Structures

随机几何在评估混凝土结构裂缝损伤水平中的应用

基本信息

批准号：
13650613
负责人：
MIHASHI Hirozo
金额：
$ 2.75万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13650613/
关键词：
Concrete Crack Damage level Fractal analysis Microscope observation Multifractal

项目摘要

While geometrical randomness of cracks in concrete structures on micro, meso and macro levels were taken into consideration, methodologies for evaluating the damage level developed and fundamental studies to apply these methodologies for existing damaged concrete structures were carried out. Obtained results are summarized as follows:1) As a fundamental study to link crack information and damage level of concrete structures, microcracks on the surface of concrete cylinders were observed by means of microscope. Then relationships between the crack information and the stiffness reduction, and/or the velocity of ultrasonic wave were studied experimentally.2) Microcracks in concrete specimens damaged by freezing and thawing action or cyclic loading were statistically analyzed. Since the microcracks due to freeze and thawing action were so thin and densely distributed that ordinary counting methods don't work sufficiently, a new method was developed on the basis of a stochastic geometry concept. These microcracks due to freezing and thawing actions were remarkably accumulated in an early stage of the cycles and then gradually increased.3) Strain-rate calculated by the differential of the stress-strain curve showed a possibility to be treated as an index to quantify the damage level.4) Fractal analyses were carried out to analyze crack patterns observed in existing structures so as the fractal dimension to be a meso level parameter. Damage levels of existing concrete structures were qualitatively evaluated from the typical crack patterns.5) Multifractarity was examined in cracks on concrete walls. Macroscopic changing patterns of the fractality in each sub-area were also investigated by analyzing the subdivided concrete walls.

在考虑混凝土结构裂缝在微观、细观和宏观层面上的几何随机性的同时，开发了用于评估损伤水平的方法，并进行了将这些方法应用于现有损伤混凝土结构的基础研究。1）作为混凝土结构裂缝信息与损伤程度联系的基础性研究，利用显微镜观察了混凝土圆柱体表面的微裂缝。通过试验研究了混凝土微裂缝信息与刚度折减、超声波传播速度之间的关系。2）对冻融作用和循环荷载作用下混凝土试件的微裂缝进行了统计分析。由于冻融作用产生的微裂纹细而密集，普通的计数方法不能充分工作，一个新的方法的基础上发展的随机几何的概念。这些微裂纹由于冻融作用，在循环的早期阶段显着积累，然后逐渐增加。3）通过应力-应变曲线的微分计算的应变率显示了可能被视为一个指标，以量化的损伤水平。4）进行分形分析，以分析在现有结构中观察到的裂纹图案，使分形维数是一个细观层次的参数。从典型裂缝形态中定性地评估了在役混凝土结构的损伤程度。5）研究了混凝土墙体裂缝的多重分形特征。通过对混凝土墙体的分块分析，研究了各分区分形度的宏观变化规律。