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该文设计了3种低强度混凝土三点弯曲切口梁,测试研究其双K断裂参数。试验中采用标距为5 mm和10 mm的应变片以半桥连接方式测量预制裂缝的起裂荷载,比较其工作性,发现应变片测量起裂荷载具有强度敏感性,短标距应变片更适宜测量本试验用低强度混凝土的裂缝起裂。试验中另沿韧带方向布置4组半桥应变片,根据各测点处拉应变回缩时的荷载与裂缝口张开位移,计算裂缝发展至测点高度时刻的等效裂缝长度,并与此时的实际缝长比较,结果表明双K断裂模型在预测裂缝长度方面具有较好的适用性。
In this paper, three kinds of low-strength concrete three-point curved notched beams are designed and tested for their double-K fracture parameters. In the experiment, the strain gauge with gauge length of 5 mm and 10 mm was used to measure the initiation and cracking load of prefabricated cracks by half-bridge connection. Compared with its workability, it was found that the strain gauge measured the initiation and loading load with intensity sensitivity and the short gauge strain gauge It is suitable to measure the crack initiation of low strength concrete in this experiment. In the experiment, four groups of half-bridge strain gauges were also arranged along the ligament direction. According to the load at the retraction point and the open displacement of the fracture opening at each measuring point, the equivalent fracture length at the time when the fracture developed to the measuring point height was calculated. The results show that the dual K fracture model has better applicability in predicting fracture length.