http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Nonlocal Approach to Study Quasi Brittle Fracture with Graph Based Finite Element Analysis
Concrete is the most widely used quasi-brittle material in building and infrastructure constructions. Such structures can be exposed to various types of load conditions. Some of these can potentially result in the catastrophic fracture of such structures. Hence, it is imperative to study and understand the damage behavior of quasi-brittle materials in order to design the most optimal concrete-material composition and structure to prevent total failure of the structure. Various numerical models have been developed over the years to describe the characteristics of damage behavior in quasi-brittle materials. However, the following limitations exist with proposed models: (a) in extended finite element method (XFEM), a special finite element is required rather than using existing conventional finite elements; (b) in peridynamics, a substantial reformulation of the conventional balance laws introduces additional complexity; and (c) in phase field model, a crack closure behavior is described with a complex energy decomposition. In this thesis, a multiple cracking model is developed to overcome the the limitations of these existing models, where the model is formulated using the thermodynamically-consistent two- and three-dimensional Graph-based Finite-Element Analysis (GraFEA) framework. The key features of the model are as follows: (a) there is no need to reformulate the fundamental balance laws,(a) a discrete number of microcrack planes are introduced at each material point to describe a probabilistic description of damage evolution, (c) a purely kinematic approach to representing crack opening and closing is introduced, and (d) conventional elements typically found in the libraries of existing finite-element codes can be used to mesh the structures. The developed theoretical and computational approach has been used to simulate concrete fracture under quasi-static and low-speed impact conditions. Also, a fracture length scale controlled gypsum-based composite material is fabricated to study the fracture behavior under impact loading conditions. The obtained experimental data are used in the validation of the three-dimensional non-local GraFEA simulation. The crack patterns and load-time curves from the simulation are matched well with the experimental data. The electronic version of this dissertation is accessible from https://hdl.handle.net/1969.1/198704
Doctor of Philosophy Texas A&M University 2022 https://hdl.handle.net/1969.1/198704