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配筋率对混凝土I-II复合型断裂过程声发射特征的影响
巩妮娜,胡少伟,范向前,蔡小宁
1.江苏海洋大学;2.南京水利科学研究院
摘要:
为了探讨配筋率对混凝土I-II复合型断裂过程及声发射特征的影响,本文通过4组直偏裂缝钢筋混凝土三点弯曲梁进行I-II复合型断裂试验,同时采集加载全过程的声发射信号,分析了不同配筋率下混凝土I-II复合型断裂特征,加载过程的振铃计数、累计计数、峰频特性等变化规律。研究结果表明:随着配筋率的增加,失稳荷载近似线性增加,配筋率的不同能够改变混凝土I-II复合型断裂模式;裂缝稳定扩展过程中振铃计数出现若干个峰值,累计计数的突变可以表征I-II复合型断裂临界状态,且三个参数间具有较强的相关性;声发射峰频点均呈现分频段集中的现象,从85%荷载水平开始,140~155kHz的频段占比减小,同时30~45kHz频段占比增加,临近失稳临界状态时峰频分布趋于分散。
关键词:  配筋率  混凝土:I-II复合型断裂,声发射参量
DOI:
分类号:
基金项目:国家自然科学基金(51739008,51679150,51508220,51878315);国家重大科研仪器研制项目(51527811);江苏省产学研合作项目(BY2019145);住建部科技项目(2019-K-053);江苏省高校自然科学研究项目(19KJB570003);
Effect of reinforcement ratio on acoustic emission characteristics during I-II mixed-mode fracture process of concrete
Gong Nina1, Hu Shaowei2, Fan Xiangqian2, Cai Xiaoning3
1.Jiangsu Ocean University;2.Nanjing Hydraulic Research Institute;3.Jiangsu Ocean University
Abstract:
In order to study the effect of reinforcement ratio on fracture property and acoustic emission characteristics of I-II mixed-mode fracture in concrete, four groups of three-point bending beams with straight offset notches in reinforced concrete were carried out for I-II mixed-mode fracture experiments, and acoustic emission signals of the whole process of loading were collected. The fracture characteristic and the rules of ringing count, cumulative count and peak frequency during loading process were analyzed. The results showed that with the increase of reinforcement ratio, the unstable load increased approximately linearly, and the different ratio of reinforcement can change I-II mixed-mode fracture mode of concrete. There were several peaks in the ringing count during the stable fracture propagation. The abrupt change of the cumulative count could represent the critical state of I-II mixed-mode fracture, and the three parameters had strong correlation. The peak frequency points of acoustic emission concentrated in different frequency bands. Starting from the 85% load level, the proportion of frequency band in 140~155kHz decreased, while proportion of frequency band in 30~45kHz increased. When specimens approached the unstable critical state, the peak frequency distribution tended to disperse.
Key words:  reinforcement ratio  concrete  I-II mixed mode fracture  acoustic emission(AE) parameters
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