混凝土梁四点弯曲试验的并发多尺度区域分解法模拟

Concurrent multi-scale domain decomposition method for four-point bending test of concrete beam

  • 摘要: 损伤在准脆性混凝土材料的非线性力学特性中占有重要地位。但有限单元法计算采用局部损伤模型时存在网格敏感性和零能耗问题。同时,传统单一网格有限元模型难以对构件的线弹性区域和非线性区域进行区别处理,无法将有限的计算资源集中在重点关注区域。通过局部子区域预设高精度有限元网格和引入尺度间线性多点约束法,实现并发多尺度方法和整体有限元撕裂对接法的结合,采用隐式梯度损伤模型描述混凝土材料的非线性本构关系,运用双重组装并行直接求解法进行模型的大型线性方程组求解,完成了混凝土损伤失效分析的并发多尺度区域分解模型构建。将该模型用于混凝土单边切口梁的四点弯曲试验模拟,并对可能损伤的纯弯拉区域分别采用了3种不同尺寸的有限元网格计算。算例分析表明,模型合理可靠且不具网格敏感性,能够重现混凝土的损伤失效全过程,可为混凝土构件开展损伤失效全过程分析提供多尺度数值模拟技术支持。

     

    Abstract: Damage plays an important role in nonlinear mechanical properties of quasi-brittle concrete materials. However, there are problems of grid sensitivity and zero energy consumption when local damage model is used in finite element method. At the same time, the traditional single mesh finite element model is difficult to treat the linear elastic region and nonlinear region of component in a different way, which can not focus the limited computation costs on the key areas. Through pre-setting high-precision finite element grids in local sub-domains and introducing inter-scale linear multi-point constraint methods, the concurrent multi-scale method and the total-finite element tearing and interconnecting method were combined. Meanwhile, the gradient-enhanced continuum damage model was applied to describe the nonlinear behavior of concrete. Furthermore, the dual assembly method was used to solve the large linear equations of the model. Then a concurrent multi-scale domain decomposition method was proposed for concrete failure analysis. The model was used to simulate the four-point bending test of a single notched concrete beam. Finite element meshes with three different precisions were generated for the pure bending regions where damage may emerge. The numerical results can reproduce the failure mode of concrete specimen, the model is reasonable and not mesh sensitive, which can provide a multi-scale numerical simulation technical support to explore the failure of concrete components with a clear damage pattern.

     

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