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本文提供了用奇异性八结点四边形等参数单元算得的偏裂纹三点弯曲梁和四点弯曲梁的应力强度因子K_I和K_II.偏裂缝三点弯曲梁试件的跨度与高度之比分别为4、3和2.给出了计算偏裂纹三点弯曲梁的K_I和K_II的经验公式.用对称三点弯曲梁、偏裂纹三点弯曲梁和四点弯曲梁试件测定了混凝土的K_Ic、K_IIc和复合型(I、II型)裂纹的临界的K_I～K_II曲线.根据试验成果,建议了混凝土复合型(I、II型)裂纹断裂准则的经验公式和根据K_I/K_II值计算起裂角的经验公式.
In this paper, the stress intensity factors K_I and K_II of the three-point bending beam and the four-point bending beam are calculated using parametric elements such as the singular eight-node quadrilateral. The ratios of the span and height of the three-point bending beam specimen are: 4, 3, and 2. The empirical formulae for calculating the K_I and K_II of a three-point bending beam with partial cracks are given. The K_Ic of the concrete is measured using a symmetrical three-point bending beam, a three-point bending bending beam, and a four-point bending beam. Critical K_I~K_II curves for K_IIc and complex type (I, II) cracks. Based on the test results, empirical formulas for fracture criteria of concrete composite type (I, II) cracks and the calculation of the starting angle based on K_I/K_II values are proposed. The empirical formula.