Browsing by Author "Hamedzadeh, Amirhossein"
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- ItemOpen AccessDamage and Remodelling in Recruitment-Based Models for Biological Tissues(2018-06-18) Hamedzadeh, Amirhossein; Federico, Salvatore; Epstein, Marcelo D.; Di Martino, Elena S.; Wan, Richard; Steigmann, David J.This thesis focuses on the continuum mechanical modelling of soft biological tissues seen as composite material reinforced by collagen fibres. The fibres have a progressive recruitment mechanism, and the tissue can undergo damage or remodelling. The thesis consists of two major parts. In the first part of the thesis, the recruitment and damage of soft tissues are modelled by introducing a rigorous continuum treatment of the fibre seen as a bundle of fibrils. The fibrils have different initial undulation, and this is represented by the means of a recruitment probability distribution. By exploiting the recruitment distribution, we construct a recruitment and damage model, where the fibrils are progressively recruited and damaged. The model is implemented in a Finite Element package and, as an example, the damage of a human Achilles tendon is studied. The Finite Element model is capable of capturing the qualitative behaviour of the tendon under uniaxial tension. The second part of the thesis focusses on the remodelling of biological tissues in the framework of the theory of material uniformity. A constitutive evolution model is introduced, including fibre recruitment and reorientation, and subjected to the entropy inequality, which enforces the Second Principle of Thermodynamics. The model is applied to a numerical example describing a pressurised fibre-reinforced cylinder, roughly representing an artery, and is able to capture the major characteristics of remodelling in arteries, as reported in the literature. To summarise, this thesis provides a framework for modelling of the interaction of fibril recruitment and damage and of whole fibre recruitment and remodelling, and constitutes a promising starting point for a more general model capable of studying the interaction of damage, remodelling and healing.
- ItemOpen AccessOn The Shear Strength Of Partially Grouted Concrete Masonry(2013-09-06) Hamedzadeh, Amirhossein; Shrive, NigelMasonry shear walls are one of the most common structural elements in buildings. The in-plane shear capacity of load-bearing walls is of great importance in the seismic design of structures. This study focuses on the shear behaviour of wide-spaced reinforced partially grouted (WRPG) concrete masonry walls. Twenty one shear walls were constructed with reduced-scale concrete masonry units. The experimental program consisted of eight groups of tests, with two or three identical specimens in each group. The specimens were subjected to monotonic lateral load, under near pure-shear boundary conditions. The parameters of the study include methods of load application, boundary conditions, aspect ratio, initial axial stress and specimen size. The shear capacities of the walls were compared against the predicted shear from four empirical equations. The sensitivity of the initial stiffness and different methods for calculation of ductility are discussed in detail. Lastly, the idea of strut-and-tie modeling was investigated for WRPG walls.