| The durability and sustainability of reinforced concrete structures have become a worldwide concern during the last several decades. The economic and environmental costs associated with structural replacements and repairs are enormous and, therefore, there is a definite need for more durable structures and efficient repair strategies.; Numerical simulation is a powerful tool that can be used, in conjunction with physical testing and structural monitoring, to study and predict structural concrete durability. In this dissertation, a lattice model is used to couple shrinkage due to moisture diffusion and cracking in cement-based materials. Both the moisture diffusion and elasticity problems are discretized using a Voronoi diagram on an irregular set of points. The Voronoi diagram provides scaling terms for the elemental diffusivity, stiffness and fracture relations, such that the model response to basic loadings is independent of mesh size and geometry.; Many forms of concrete deterioration are associated with the transport of moisture (and/or chemical agents) and crack formation. The accurate representation of these important aspects is therefore a basic requirement for simulating most forms of structural concrete deterioration. The mode I fracture model, developed in this dissertation, is verified through three-dimensional simulation of a three-point bend test of a notched concrete beam. The effects of moisture diffusion, elasticity, and fracture are combined in the simulation of shrinkage induced cracking of a structural concrete overlay system. The simulated crack formation and crack patterns agree with observations of restrained shrinkage cracking in natural and engineered systems. While the long term goal is the development of general and efficient simulation tools that account for the most relevant durability aspects, the primary scope of this dissertation is the development and verification of elasticity, fracture and moisture diffusion modeling for concrete materials using three-dimensional irregular lattice models. |
