基于细观离散元的混凝土端部效应分析

End effect of concrete by meso-scale discrete element modeling

为了研究端部效应对不同形状的混凝土试件强度的影响,采用三维颗粒离散元程序(PFC3d)对混凝土标准立方体与标准圆柱体试件在不同端部摩擦条件下的单轴压缩试验进行数值仿真.在细观层次假定混凝土材料力学性质符合Weibull概率统计分布来考虑混凝土材料的非均质特性,根据材料宏观力学参数反演计算出模型细观力学参数,进行数值仿真计算.模拟结果表明,端部摩擦对不同形状的混凝土试件的抗压强度、变形特征及破坏模式有较大影响;试件的形状效应随着加载板与试件间摩擦系数的增加而增强;当不采用减摩措施(f=0.6)时,测得两种试件强度的折算系数为0.795.仿真结果与规范的规定相符,证明了本文方法的可行性和有效性.

To investigate the influence of end friction on compressive strength with different specimen shapes, we present a three-dimensional particle element approach for concrete, a series of numerical uniaxial compressive tests for standard cube specimen and standard cylinder specimen are conducted. The material properties are assumed to conform to the Weibull distribution law in consideration of its heterogeneity, and a method of parameter inversion calculation is used to get the mesoscopic mechanics parameters based on the material mechanics parameters. The results show that the end friction influences the peak strength, deformation character and failure mode of different geometries of concrete specimen. Shape effect increases as the friction coefficient between the platens of the testing machine and the concrete specimen increases ; and the conversion ratio between cylinder and cube strength approaches 0. 795 without any friction-reducing measure （f = 0.6）. The simulation results accord well with the codes, which shows the feasibility and effectiveness of the method.