配筋率对混凝土Ⅰ-Ⅱ复合型断裂过程声发射特征的影响

Effect of reinforcement ratio on acoustic emission characteristics duringⅠ-Ⅱmixed-mode fracture process of concrete

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,通过4组直偏裂缝钢筋混凝土三点弯曲梁开展Ⅰ-Ⅱ复合型断裂试验及声发射信号采集,并分析试验结果。结果表明:随着配筋率的增加,失稳荷载近似线性增加,配筋率影响混凝土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3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,140~155 kHz的频段占比减小,30~45 kHz频段占比增加,临近失稳临界状态时峰频分布趋于分散。

In order to study the effect of reinforcement ratio on fracture property and acoustic emission characteristics ofⅠ-Ⅱmixed-mode fracture in concrete,four groups of three-point bending beams with a straight offset notch in reinforced concrete were used forⅠ-Ⅱmixed-mode fracture experiments and collection of acoustic emission signals.The test results were analyzed.The results show that with the increase of reinforcement ratio,the unstable load increases approximately linearly,and reinforcement ratio can influenceⅠ-Ⅱmixed-mode fracture mode of concrete.There were several peaks in the ringing counts during the stable fracture propagation.The abrupt change of the cumulative counts could represent the critical states ofⅠ-Ⅱmixed-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 140~155 kHz decreased,while proportion of frequency band in 30~45 kHz increased.When specimens approached the unstable critical state,the peak frequency distribution tended to disperse.