Modelling warp and dimensional stability in softwood

Seasoned softwood board exposed to in-service moisture variations is subject to dimensional changes and distortions. In-service dimensional instability of a board is a critical issue since it causes serious problems in buildings and other engineering structures. This thesis presents research involving the development of numerical models to describe the in-service changes in dimension, at a board scale, for small variations in the moisture content. The models used input data defining the properties of the microstructural components that make up the cellular structure of the wood resulting in the cells having heterogeneous anisotropic properties. The application of full cyclic constraint to the boundaries of the elements that made up the representative volume element was investigated and used to determine the equivalent homogenised properties. A cellular model was developed to describe the behaviour of the wood as a function of density, microfibril angle, spiral grain angle and moisture content. The resultant finite element board models used a database generated from the cellular model to describe the dimensional changes associated with small in-service changes in moisture content. In conjunction with the development of this model the candidate carried out an experimental programme using a specific supplied pinus radiata log. The determination of the cellular shrinkage/swelling coefficients, using an experimental technique developed for this research, verified the accuracy of the homogenization method and its subsequent application to the cellular model. The results from the sawn boards were compared with the results from the finite element board models

Characterisation of the shear stud-concrete connection using finite element analysis

The degradation of the connection between shear studs and concrete is a complicated phenomenon that depends on many factors, including; interfacial properties, concrete crushing and steel yielding. The purpose of this paper is to outline the scope and methodology of the research project being undertaken to characterise the shear stud-concrete interface of a composite beam using finite element analysis. A mesoscopic model will be created for a section of the interface. With the use of a multi-scale approach, the mesoscopic model will be incorporated into a global model. The influence of steel roughness and mechanical properties will be included. Concrete is to be modelled as heterogeneous, comprising discrete regions of aggregate, cement matrix, and an interfacial transition zone (ITZ). The effect of the ITZ will be taken into account using a zero thickness cohesive element. Experimental testing using a push-up rig is to be conducted to verify the numerical models. The ultimate aim is to develop a simplified representation of the shear stud-concrete interface that can be used in a large scale finite element model of a composite member to correctly capture the behaviour of the shear stud-concrete interface in the elastic and inelastic state

Interfacial fracture of polymer foam-metal composites at micro-scale using finite element analysis

Foam-metal composites are being increasingly used in a variety of applications. One important aspect in the structural integrity of foam-metal interface is the ability to resist failure around the interface whilst ensuring required load bearing capacity. This study investigated the mechanical and failure behaviour at the interface region at micro scale. The foam-metal composite consisted of polyurethane foam directly adhered to a galvanised steel face sheet. Optical, scanning electron and atomic force microscopy were used to examine the interface geometry and to obtain a realistic surface profile for use in a finite element (FE) model. Finite element analysis (FEA) was used to study the effects of different interfacial roughness profiles on mechanical interlocking and modes of failure, which are directly related to interfacial strength. A set of finite element models of idealised surface pairs of different geometries and dimensions were developed based on the microscopic observations at the foam-metal interface. The finite element modelling results show that the micro- scale roughness profile at the foam-metal interface causes mechanical interlocking and affects the stress field at the scale of the interface surface roughness, which consequently governs the specific failure mode and the relative proportion of the cohesive to adhesive failure in the interface region for a given foam-metal interface. It was found that the aspect ratio (relative width and height) and width ratio (relative spacing) of roughness elements have a significant effect on the stresses and deformations produced at the interface and consequently control the modes (cohesive or adhesive) of failure

The Epidemiology of Invasive Haemophilus influenzae Non-Serotype B Disease in Ontario, Canada from 2004 to 2013.

Since the widespread use of Haemophilus influenzae (Hi) type b (Hib) vaccines among children aged <5 years, an increase in invasive non-Hib disease incidence has been reported internationally. We sought to describe the epidemiology of invasive non-Hib disease in Ontario, Canada (population ~13.5 million).Confirmed invasive non-Hib cases (non-typeable [NTHi] and serotypes a, c, d, e, and f) were obtained from the provincial laboratory data system from 2004-2013. Data were deterministically linked to the provincial reportable disease system to provide further case information. Antibiotic resistance data were analysed separately from 2010-2014. Descriptive analyses included incidence rates, age group, serotype, site of specimen collection and resistance patterns; ethnicity data were not available. Temporal trends were evaluated by Poisson regression and p-values <0.05 were considered significant.A total of 1307 cases of invasive non-Hib disease were included, increasing from 0.67 cases to 1.60 cases /100,000 from 2004 to 2013. Significant increases in the incidence of NTHi (0.50 to 1.28 cases/100 000 population), Hia (0.02 to 0.08 cases/100, 000) and Hif (0.13 to 0.18 cases/100, 000 population) were seen. Among persons aged 40-64 years, 3 Hi strains significantly increased over time; NTHi (0.22 to 0.99 cases/100, 000), Hia (0.00 to 0.06 cases/100, 000) and Hif (0.05 to 0.21 cases/100, 000). Among persons aged 65-84 years, there was a significant increase of NTHi (1.62 to 3.14 cases/100, 000) and Hia (0.00 to 0.34 cases/100, 000). Among persons aged 85+ years, only NTHi significantly increased from 4.89 to 10.28 cases/100, 000). Antimicrobial resistance (AMR) to ampicillin and clarithromycin was seen in greater than 25% of isolates but AMR did not increase over the duration of this study.The incidence of invasive non-Hib disease has increased over time; NTHi, Hif and Hia are emerging pathogens, and should be monitored

Incidence rate of invasive non-type b Hi by serotype and age group in Ontario, 2004–2013 (n = 1,290).

<p>Incidence rate of invasive non-type b Hi by serotype and age group in Ontario, 2004–2013 (n = 1,290).</p

Incidence rate of invasive non-type b Hi by serotype in Ontario, 2004–2013 (n = 1,307).

<p>Incidence rate of invasive non-type b Hi by serotype in Ontario, 2004–2013 (n = 1,307).</p

Antimicrobial resistance of invasive non Hib strains isolated in Ontario, 2010–2014 (n = 664).

<p>*indicates resistance breakpoints have not been established</p><p>#indicates both resistance and intermediate category. Non-susceptible and intermediate (= NS)</p><p>Antimicrobial resistance of invasive non Hib strains isolated in Ontario, 2010–2014 (n = 664).</p