混凝土细观力学仿真分析的块体元-有限元耦合方法

A coupled method of block element and finite element for concrete mesomechanical simulation analysis

假定混凝土是由砂浆和骨料组成的两相非均质材料,采用块体单元法模拟骨料,有限单元法模拟砂浆,基于虚功原理,建立了混凝土细观力学仿真分析的块体元-有限元耦合方法.假定混凝土骨料为刚体,砂浆为理想弹塑性材料,采用FORTRAN语言,编制了块体元-有限元耦合分析程序.运用该耦合分析程序,对耦合面刚度敏感性进行分析,得到了合适的耦合面刚度取值量级,在此基础上,采用Drucker-Prager准则,仅考虑砂浆单元的屈服,分别研究了二维和三维混凝土试件在荷载作用下的屈服、破坏过程,计算结果符合一般规律,验证了所提方法的有效性和正确性.块体元-有限元耦合分析方法兼具块体元法和有限元法的优点,前处理简单,单元数目少,计算量小,并且充分考虑了砂浆和骨料的材料力学特性差异,可以进行含有多面体骨料的三维混凝土模型的数值模拟,较精确方便地计算混凝土在荷载作用下的应力、应变,模拟混凝土的屈服、破坏过程.

Assuming that concrete is a two phase non-homogeneous material and it is comprised of mortar and aggregates, using block element to simulate aggregate and finite element to simulate mortar and based on the virtual work principle, a coupled method of block element and finite element is established. Assum- ing that the aggregate is rigid and mortar is ideal elastoplastic material, using Fortran language, the pro- gram for analysis of the coupling of block element and finite element is made. Using the program, the sen- sitivity of the stiffness of coupled surface is analyzed; and the suitable value of stiffness is obtained. On this basis, using Drucker-Prager criterion, the process of yielding and damage of the 2D and 3D concrete specimens under loading is researched respectively. The results of calculation accord with the general law, so as to prove the efficiency and accuracy of this coupled method. This method has advantages of both block element method and finite element method. Its processing is much simpler. The number of elements and the workload of calculation is also smaller. And it takes fully into account of the difference of mechani- cal properties of aggregate and mortar. So using this method, numerical simulation of 3D concrete model containing polyhedral aggregates can be done. The stress and strain can be calculated more precisely and easily. And the process of yielding and damage can be simulated.