Irregular lattice simulation of cement composite materials and structures

The response of cement-based materials to various types of severe loading is often governed by complicated fracture processes and toughening mechanisms. As a compliment to experimental testing, a 3D numerical model is developed to study the fracture properties of cement composites at different length scales, specifically at the meso and macroscale. The model is based on an irregular lattice representation of the material continuum.; The material domain is discretized as a Voronoi tessellation of an irregular set of points. Nodal connectivity of the lattice is defined by the dual Delaunay tessellation. An efficient grid search algorithm based on domain partitioning has been developed to generate the point set at O( n) complexity.; At the macroscale, the cement composite (such as ordinary concrete) is treated as a homogeneous material. Curvilinear reinforcement can be introduced into the material irrespective of the domain discretization. The bond shear stress-slip response of the reinforcement is based on mechanics of reinforcement-matrix interface. At the mesoscale, the composite has three distinct phases consisting of a matrix media, spherical inclusions, and the matrix-inclusion interface. Spherical aggregates are individually discretized within the domain with control over the thickness of the matrix-inclusion interface. A macroscopic fracture model, which lumps all the fracture mechanisms into a prescribed softening relation, was implemented to relate cohesive stress to crack opening displacement. This modeling of fracture is energy conserving and objective with respect to both loading and mesh orientation. More brittle fracture laws are used when the material is modeled at the mesoscale. Verifications of the accuracy and applicability of this lattice model are obtained through analyses of deflection of prestressed concrete beams, fiber restraints on drying shrinkage of overlay systems, and fracture of notched beams.