عنوان مقاله [English]
Concrete is perhaps the most available manufactured material. The low cost, wide availability, ease of use and high durability of concrete has led to its continually increasing usage. It can be a hastily prepared, low-grade mixture for simple applications, or can be a firmly controlled, engineering material for high-performance structures. Complex physical and chemical interactions exist in cement, which plays a main role in the properties of concrete. This complicated structure leads to a complexity in fracture processes. Considering this reason, most mechanical properties of concrete and studies on its behavior are based on experimental results. Since experiments require time and money, providing mathematical models to simulate the behavior of concrete is necessary.
In general, modeling fracture and damage within concrete, and other quasi-brittle materials, has been classified as either continuum or discrete approaches. Continuum models provide an average description of material
behavior for a representative volume element. Because the width of the fracture process zone (FPZ) in concrete can be sizeable (roughly several times the maximum aggregate size), simulation of concrete fracture at meso-scale, with continuum approaches, is not suitable. Use of discrete micromechanical models is motivated by the need for fundamental knowledge, to improve material behavior. If the material structure (e.g at micro/meso scale of observation) is explicitly represented, the models provide a direct way for studying crack patterns; mechanisms of softening in post-peak branches and size effect/scaling phenomena.
In this paper, two-dimensional geometrical models for concrete are generated, taking the random distribution of aggregates at mesoscale into consideration. The generation procedure is based upon the Voronoi diagram method. The aggregate particles are constructed by several polygons and then placed into the concrete model, in such a way that there is no intersection between them. In this method, simulation of the fracture of aggregate in high strength concrete is feasible. The generated model can be used for modeling concrete
with the discrete method. Finally, the model analyzed using the discrete element method.