中文摘要：

从非线性断裂力学模型的角度,开展准脆性材料（混凝土）裂纹过程区的有效模拟,是当前的研究热点之一.扩展比例边界有限元法（X-SBFEM）兼有扩展有限元法（XFEM）和比例边界有限元法（SBFEM）两种方法的优势,利用SBFEM求解裂尖段应力奇异性问题,利用XFEM模拟非裂尖段位移场不连续.为在X-SBFEM中增加非线性断裂模型,提出采用sideface力的形式,基于黏聚力模型,通过线性叠加迭代法来模拟准脆性材料（混凝土）裂纹过程区.最后,以数值算例——单边缺口的三点弯曲梁和四点剪切梁——模拟裂纹过程区能量耗散影响,验证了所提方法的精度与应用效果.

英文摘要：

The effective simulation of the fracture process zone （FPZ） of quasi - brittle material （concrete） by using nonlinear fracture mechanics model is one of the hot spots in the current research. Extended scaled boundary finite element method （X-SBFEM） has advantages of both extended finite element method （XFEM） and scaled boundary finite element method （SBFEM ）, making full use of XFEM to describe discontinuous displacement field in non-crack-tip area and SBFEM to precisely solve stress singular problems in the crack-tip area. For the application of nonlinear fracture models in X-SBFEM,based on the model of the cohesive traction,the FPZ of the quasi-brittle material （concrete） is simulated using the iterative method of linear superposition by the form of side-face traction. Finally,numerical examples of the three-point single notched bending beam and the four-point single notched shear beam are used to simulate the energy dissipation effect in the FPZ , which verify theaccuracy and application effect of the proposed method.