Numerical modelling of braided fibres for reinforced concrete

Fire has been always a major concern for designers of steel and concrete structures. Designing fire-resistant structural elements is not an easy task due to several limitations such as the lack of fire-resistant construction materials. Concrete reinforcement cover and external insulation are the most commonly adopted systems to protect concrete and steel from overheating, while spalling of concrete is minimised by using HPFRC instead of standard concrete. Although these methodologies work very well for low rise concrete structures, this is not the case for high-rise and inaccessible buildings where fire loading is much longer. Fire can permanently damage structures that cost a lot of money. This is unsafe and can lead to loss of life. In this research, the author proposes a new type of main reinforcement for concrete structures which can provide better fire-resistance than steel or FRP re-bars. This consists of continuous braided fibre rope, generally made from fire-resistant materials such as carbon or glass fibre. These fibres have excellent tensile strengths, sometimes in excess of ten times greater than steel. In addition to fire-resistance, these ropes can produce lighter and corrosive resistant structures. Avoiding the use of expensive resin binders, fibres are easily bound together using braiding techniques, ensuring that tensile stress is evenly distributed throughout the reinforcement. In order to consider braided ropes as a form of reinforcement it is first necessary to establish the mechanical performance at room temperature and investigate the pull-out resistance for both unribbed and ribbed ropes. Ribbing of ropes was achieved by braiding the rope over a series of glass beads. Adhesion between the rope and concrete was drastically improved due to ribbing, and further improved by pre-stressing ropes and reducing the slacked fibres. Two types of material have been considered for the ropes: carbon and aramid. An implicit finite element approach is proposed to model braided fibres using Total Lagrangian formulation, based on the theory of small strains and large rotations. Modelling tows and strands as elastic transversely isotropic materials was a good assumption when stiff and brittle fibres such as carbon and glass fibres are considered. The rope-to-concrete and strand-to-strand bond interaction/adhesion was numerically simulated using newly proposed hierarchical higher order interface elements. Elastic and linear damage cohesive models were used effectively to simulate non-penetrative 'free' sliding interaction between strands, and the adhesion between ropes and concrete respectively. Numerical simulation showed similar de-bonding features when compared with experimental pull-out results of braided ribbed rope reinforced concrete.

Molecular and biological characterisation of orthobunyaviruses

Orthobunyaviruses are the largest genus within the Bunyaviridae family, with over 170 named viruses classified into 18 serogroups (Elliott and Blakqori, 2001; Plyusnin et al., 2012). Orthobunyaviruses are transmitted by arthropods and have a tripartite negative sense RNA genome, which encodes 4 structural proteins and 2 non-structural proteins. The non-structural protein NSs is the primary virulence factor of orthobunyaviruses and potent antagonist of the type I interferon (IFN) response. However, sequencing studies have identified pathogenic viruses that lack the NSs protein (Mohamed et al., 2009; Gauci et al., 2010). The work presented in this thesis describes the molecular and biological characterisation of divergent orthobunyaviruses. Data on plaque morphology, growth kinetics, protein profiles, sensitivity to IFN and activation of the type I IFN system are presented for viruses in the Anopheles A, Anopheles B, Capim, Gamboa, Guama, Minatitlan, Nyando, Tete and Turlock serogroups. These are complemented with complete genome sequencing and phylogenetic analysis. Low activation of IFN by Tete serogroup viruses, which naturally lack an NSs protein, was also further investigated by the development of a reverse genetics system for Batama virus (BMAV). Recombinant viruses with mutations in the virus nucleocapsid protein amino terminus showed higher activation of type I IFN in vitro and data suggests that low levels of IFN are due to lower activation rather than active antagonism. The anti-orthobunyavirus activity of IFN-stimulated genes IFI44, IFITMs and human and ovine BST2 were also studied, revealing that activity varies not only within the orthobunyavirus genus and virus serogroups but also within virus species. Furthermore, there was evidence of active antagonism of the type I IFN response and ISGs by non-NSs viruses. In summary, the results show that pathogenicity in man and antagonism of the type I IFN response in vitro cannot be predicted by the presence, or absence, of an NSs ORF. They also highlight problems in orthobunyavirus classification with discordance between classical antigen based data and phylogenetic analysis.

Speech and narrative: characterisation techniques in the "Aeneid"

The thesis provides a comprehensive analysis of the characterisation of two of the major figures in the Aeneid, Aeneas and Turnus. Particular attention is paid to their direct speeches, all of which are examined and, where relevant, compared to Homeric models and parallels. To this purpose considerable use is made of the indices in Knauer's Die Aeneis und Homer. A more general comparison is made between the dramatic (direct speech) role of Aeneas and those of Homer's Achilles (Iliad) and Odysseus (Odyssey). An appraisal is made (from the viewpoint of depiction of character) of the relationship between the direct and indirect speeches in the Aeneid. Reasons are given to suggest that it is not mere chance, or for the sake of variety, that certain speeches of Aeneas and Turnus are expressed in oratio obliqua. In addition, the narrative portrayal of Aeneas and Turnus is considered in apposition to that of the speeches. A distinction is drawn between Vergil's direct method of characterisation (direct speeches) and his indirect methods (narrative/oratio obliqua). Inevitably, the analysis involves major consideration of the Roman values which pervade the work. All speeches, thoughts and actions of Aeneas and Turnus are assessed in terms of pietas, impietas, furor, virtus, ratio, clementia, humanitas (etc.). It is shown that individual concepts (such as pietas and impietas) are reflected in Vergil's direct and indirect methods of characterisation. The workings of fate and their relevance to the pietas concept are discussed throughout.

The structural and mechanical integrity of historic wood

Little is known about historic wood as it ages naturally. Instead, most studies focus on biological decay, as it is often assumed that wood remains otherwise stable with age. This PhD project was organised by Historic Scotland and the University of Glasgow to investigate the natural chemical and physical aging of wood. The natural aging of wood was a concern for Historic Scotland as traditional timber replacement is the standard form of repair used in wooden cultural heritage; replacing rotten timber with new timber of the same species. The project was set up to look at what differences could exist both chemically and physically between old and new wood, which could put unforeseen stress on the joint between them. Through Historic Scotland it was possible to work with genuine historic wood from two species, Oak and Scots pine, both from the 1500’s, rather than relying on artificial aging. Artificial aging of wood is still a debated topic, with consideration given to whether it is truly mimicking the aging process or just damaging the wood cells. The chemical stability of wood was investigated using Fourier-transform infrared (FTIR) microscopy, as well as wet chemistry methods including a test for soluble sugars from the possible breakdown of the wood polymers. The physical properties assessed included using a tensile testing machine to uncover possible differences in mechanical properties. An environmental chamber was used to test the reaction to moisture of wood of different ages, as moisture is the most damaging aspect of the environment to wooden cultural objects. The project uncovered several differences, both physical and chemical, between the modern and historic wood which could affect the success of traditional ‘like for like’ repairs. Both oak and pine lost acetyl groups, over historic time, from their hemicellulose polymers. This chemical reaction releases acetic acid, which had no effect on the historic oak but was associated with reduced stiffness in historic pine, probably due to degradation of the hemicellulose polymers by acid hydrolysis. The stiffness of historic oak and pine was also reduced by decay. Visible pest decay led to loss of wood density but there was evidence that fungal decay, extending beyond what was visible, degraded the S2 layer of the pine cell walls, reducing the stiffness of the wood by depleting the cellulose microfibrils most aligned with the grain. Fungal decay of polysaccharides in pine wood left behind sugars that attracted increased levels of moisture. The degradation of essential polymers in the wood structure due to age had different impacts on the two species of wood, and raised questions concerning both the mechanism of aging of wood and the ways in which traditional repairs are implemented, especially in Scots pine. These repairs need to be done with more care and precision, especially in choosing new timber to match the old. Within this project a quantitative method of measuring the microfibril angle (MFA) of wood using polarised Fourier transform infrared (FTIR) microscopy has been developed, allowing the MFA of both new and historic pine to be measured. This provides some of the information needed for a more specific match when selecting replacement timbers for historic buildings.