基于线法的U形切口混凝土梁断裂参数研究

混凝土的断裂韧度是重要的材料参数，本文利用含U形切口的三点弯曲梁试验结合临界距离线法来获得混凝土的断裂韧度．理论推导了含断裂韧度与不同根部半径的断裂失效方程，采用有限元法计算了切口应力集中系数．根据断裂失效方程和试验中的材料几何参数，利用最小二乘法拟合计算得到混凝土材料的断裂韧度和抗拉强度．对小切口半径情形，采用双K断裂准则分析计算了混凝土起裂韧度和失稳断裂韧度，分析结果表明：临界距离线法得到的材料断裂韧度与双K断裂准则中的失稳断裂韧度吻合，同时获得相应临界距离值．

Investigation on Fracture Parameters of U-Notched Concrete Beams Based on Line Method

The fracture toughness for concrete is an essential material parameter. It is obtained by using the three-point bending U-notched beam combined with the critical distance line method in this paper. The fracture failure equation containing fracture toughness and different root radius is theoretically derived, and the notch stress concentration factors is calculated using finite element method. According to the fracture failure equation and the material geometric parameters, the fracture toughness and tensile strength are obtained through the least squares fitting method. For the small notch radius, the concrete initial fracture toughness and the unstable fracture toughness are calculated by the double-K fracture criterion. The analysis results show that the fracture toughness of the material obtained by the critical distance line method is consistent with the unstable fracture toughness calculated by double-K fracture criterion. Meanwhile, the corresponding critical distance can be obtained.