含V型切口混凝土梁Ⅰ、Ⅱ复合型断裂特性研究

Study on Fracture Characteristics of V-notched Concrete Beams

通过采用三点弯曲加载,结合电阻应变片法以及数字图像相关法,研究初始缝高比、偏心距以及切口角度对V型切口混凝土梁荷载值和断裂过程区的影响,最后运用有限断裂力学进行理论分析,并与平均应力准则做比较。试验结果说明,起裂荷载和破坏荷载的变化随着缝高比的增大而减小,不同范围内的切口角度对起裂荷载和破坏荷载的影响也有差别,起裂荷载和破坏荷载随着加载偏心距增加而增大起裂时刻和最大荷载时刻的断裂过程区等于裂缝长度,而失稳时断裂过程区远远小于裂缝长度,断裂过程区以切口角度120°为界,具有不同的变化趋势;平均应力准则下的裂缝扩展长度随着切口角度的增加整体呈现下降趋势,无论是临界破坏荷载还是裂缝扩展角度,有限断裂力学准则的理论预测值较平均应力准则更为接近试验结果。

Using three-point bending loading and combining with resistance strain gauge method and digital image correlation method,the effects of initial seam height ratio,eccentricity and notch angle on the load value and fracture process area of V-notched concrete beam are studied. Finally,finite frac-ture mechanics is applied to conduct theoretical analysis. The result is compared with the average stress criterion. The test results show that the variation of the cracking load and the failure load de-crease with the increase of the joint height ratio. The notch angles in different ranges have different im-pact on the cracking load and the breaking load. The cracking load and the breaking load increase with the eccentricity. The fracture process zone corresponding to the time of crack initiation and the maxi-mum load is equal to the length of the fracture. But the fracture process zone at failure is much smaller than the fracture length. Fracture process zone has a different change rule when the notch angle reach-es 120°. The crack propagation length under the average stress criterion decreases with the increase of the notch angle. The theoretical prediction value of the finite fracture mechanics criterion is closer to the experimental results than the average stress criterion regardless of the critical failure load or the crack propagation angle.