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Development of Techniques Searching Damaged Locations and Evaluating their Damage Levels in Concrete Structures Through AE Wave Monitoring

通过声发射波监测寻找混凝土结构损坏位置并评估其损坏程度的技术开发

基本信息

批准号：
59850076
负责人：
SATAKE Masao
金额：
$ 4.86万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Developmental Scientific Research
财政年份：
1984
资助国家：
日本
起止时间：
1984 至 1985
项目状态：
已结题

项目摘要

Various researches were carried out in order to search damaged locations and to evaluate their damage levels through the AE wave monitoring and the main results were explained belows.(1) The Kaiser effect in the uniaxial compression tests of concrete specimens, the splitting tests of them, the same tests for the cores cut out of concrete and reinforced concrete beams and the bending tests of reinforced concrete beams were examined. Except the uniaxial compression and splitting tests for the cores, the maximum past loads in the specimens and beams were evaluated with sufficient accuracy for engineering. In addition, it was clarified that in the uniaxial compression tests of cubic concrete specimens and the splitting tests of cylindrical ones, the Kaiser effect in different loading directions was independent one another and this effect was remarkably affected by the method keeping concrete specimens.(2) Through researches to evaluate the damage levels in concrete from the information of AE waves, it was shown that the change of AE energy distribution with increasing load was closely related to the microfracture mechanisms and AE activity factors, which were defined by the logarithm of AE energy per unit inelastic lateral strain, had close relation to the strength of concrete specimens and the past damage in them. Further, the relation between lateral strain and AE cumulative event count and the evaluation of AE sources from frequency spectra were researched.(3) In order to search damaged locations in concrete, the monitoring system for three dimensional AE source location, which was equiped with the softwares trasmitting AE waves from six transient memory units to a fixed disk unit and determing arrival times of AE waves automatically, was developed. By use of this system, the three dimensional AE source location was carried out in concrete specimens and AE sources in the region surrounded by six transducers were located within error of distance 1 cm.

为了通过声发射波监测来寻找损伤位置并评估其损伤程度，主要研究结果如下：(1)检验了混凝土试件单轴压缩试验、混凝土试件劈裂试验、混凝土和钢筋混凝土梁切出核心的相同试验以及钢筋混凝土梁弯曲试验中的凯撒效应。除了岩芯的单轴压缩和劈裂试验外，还以足够的工程精度评估了样本和梁中的最大过去载荷。此外，还明确了在立方体混凝土试件的单轴压缩试验和圆柱体混凝土试件的劈裂试验中，不同荷载方向上的凯撒效应是相互独立的，而这种效应受混凝土试件的保存方式的影响显着。(2)通过声发射波信息评价混凝土损伤程度的研究，结果表明，随着荷载的增加，声发射能量分布的变化为与微断裂机制密切相关的声发射活动因子由每单位非弹性横向应变的声发射能量的对数定义，与混凝土试件的强度及其过去的损伤密切相关。进一步研究了横向应变与声发射累积事件数之间的关系以及频谱评价声发射源。(3)为了搜索混凝土中的损伤位置,开发了三维声发射源位置监测系统,该系统配备了将声发射波从六个瞬态存储单元传输到固定磁盘单元并自动确定声发射波到达时间的软件。利用该系统对混凝土试件进行三维声发射源定位，将6个换能器包围区域内的声发射源定位在距离误差1cm以内。