This project studied the effects of wind tunnel test loads applied to purlins in low rise steel buildings compared to those determined with currently recognized wind loading provisions. The National Institute of Standards and Technology (NIST) database of low-rise building wind tunnel test data, which was collected at the University of Western Ontario (UWO) boundary layer wind tunnel, was used to model a realistic wind load scenario. Pressure coefficient data recorded in the database was applied statically to individual purlins in a typical design for the size of buildings studied. These results were then compared to those obtained using the wind design provisions in ASCE 7-16 Chapter 30 for Components and Cladding. The primary data of interest was shear and moment values along the length of the purlins, which were modeled as continuous beams. Comparisons were made between the resultant shear and moment from both the wind tunnel load and ASCE 7-16 load values at 1-foot increments along the length of the purlin. The results showed that the overall peak values obtained from wind tunnel test loads were 3% to 49% higher than those calculated using ASCE 7-16 for purlins that were on the windward edge of the building. Purlins on the interior of the building varied in whether they exceeded the loads calculated with ASCE 7. Changing the height of the structure and the terrain roughness both increased the number of purlins that were lower than the values provided in ASCE 7-16 in the interior of the structure. / Master of Science / Purlins are roof members used in low rise steel buildings to transmit wind loads applied to the roof of the structure to the frame of the building. This project studied the effects of applying loads to purlins using methods specified by the code compared to those found in a wind tunnel, to look at the similarity of the values and model the actual behavior of the purlins more accurately. For this study, wind tunnel test data obtained from the National Institute of Standards and Technology (NIST) database was applied to the purlins and the shear and moment was calculated. These results were compared to the current code requirements provided in the American Society of Civil Engineers (ASCE) 7 document: Minimum Design Loads and Associated Criteria for Buildings and Other Structures. The results showed that the loads developed in the purlins subjected to wind tunnel test loadings were 3% to 49% higher on the edge of the building than those that had the ASCE 7 design loads applied. More accurately modeling the behavior of the purlins using wind tunnel test data and beam models showed that in locations where the purlins received the maximum wind force, the ASCE 7 requirements for components and cladding tended to be lower than the wind tunnel test data. However, in locations where the purlins were not experiencing the maximum wind force, the ASCE 7 requirements tended to overpredict the loads, based on the use of symmetric high wind areas to design for all wind angles.

Yes / The suspected scaphoid fracture remains a diagnostic conundrum with over-treatment a common risk-averse strategy. Cross-sectional imaging remains the gold standard with MRI recommended but CT used by some because of easier access or limited MRI availability. The aim of this feasibility study was to evaluate whether cone beam computed tomography (CBCT) could support early diagnosis, or exclusion, of scaphoid fractures. Patients with a suspected scaphoid were recruited fracture between March and July 2020. All underwent a 4-view X-ray. If this examination was normal, they were immediately referred for a CBCT scan of the wrist. Those with a normal scan were discharged to research follow-up at 2 and 6-weeks. 68 participants were recruited, 55 had a normal or equivocal X-ray and underwent CBCT. Nine additional radiocarpal fractures (16.2%) were demonstrated on CBCT, the remainder were discharged to research follow-up. Based on the 2-week and 6-week follow up three patients (4.4%) were referred for MRI to investigate persistent symptoms with no bony injuries identified. CBCT scans enabled a rapid pathway for the diagnosis or exclusion of scaphoid fractures, identifying other fractures and facilitating early treatment. The rapid pathway also enabled those with no bony injury to start rehabilitation, suggesting that patients can be safely discharged with safety-net advice following a CBCT scan.

This work included two separate studies; the common theme in each was the use of mode-I fracture testing to evaluate wood adhesion. In the first study, mode-I fracture testing was used to compare the thermal stability of polyurethane (PUR) and resorcinol-formaldehyde (RF) wood adhesives. Bonded specimens for both adhesives were subjected to prolonged thermal exposure, and fracture testing was subsequently conducted after re-equilibration to standard test conditions. It was found that both PUR and RF suffered a significant fracture energy loss after heat treatment, and that RF was more thermally stable than PUR, as expected. However, both adhesives suffered significant thermal degradation, and fracture testing did not distinguish the RF system as being clearly superior to PUR. Dynamic mechanical analysis (DMA) was also used to analyze and compare the thermal softening of PUR and RF in terms of the decline in storage modulus. DMA results indicated that PUR specimens suffered greater stiffness loss due to simple thermal softening. Because fracture testing indicated that both adhesives suffered significant degradation, the DMA results suggested that the generally superior fire resistance of RF adhesives is born from greater high temperature stiffness; whereas the more compliant PUR suffers greater immediate softening during thermal exposure. In other words, both systems suffer from thermal degradation, but the more highly cross-linked RF system suffers less thermal softening and therefore maintains a greater load carrying capacity during fire exposure. In the second study, mode-I fracture testing was used to test the effects of wood surface thermal deactivation (surface energy reduction) on the adhesion between southern pine wood (Pinus spp.) and polyethylene (PE). Pine specimens were progressively surface deactivated by 185°C heat treatments for periods of 5, 15, and 60 minutes. Control and deactivated pine laminae were subsequently hotpressed/bonded using PE film as the adhesive. Mode-I fracture testing was conducted under the assumption of linear elasticity, however load/displacement test curves suffered from a severe degree of nonlinearity believed to be caused by PE bridging behind the advancing crack tip. Instead of applying a nonlinear data analysis, a standard linear elastic analysis was conducted and deemed acceptable for comparative purposes within this study. Under dry conditions (unweathered specimens), 5 and 15 minute thermal treatments resulted in progressively worse adhesion (lower fracture energies) when compared to control surfaces; but the 60 minute heat treatment improved adhesion relative to 5 and 15 minute treatments, and showed a trend of improving adhesion as surface deactivation became more extreme. Simulated-weather resistance was also studied and it was determined that the highest degree of surface deactivation slightly improved weather durability in comparison to control surfaces. Overall, the findings here were similar to those in a previously published work- thermal deactivation of wood surfaces shows promise as a method to improve adhesion between wood and nonpolar polyolefins. / Master of Science

Oxide materials display a wide range of physical properties. Recently, doped complex oxides have drawn considerable attention for various applications including thermoelectrics. Doped complex oxide materials have high Seebeck coefficients (S) and electrical conductivities (o) comparable to other doped semiconductors but low thermoelectric figure of merit ZT values due to their poor thermal conductivities. For example, niobium doped strontium titanate (SrNbxTi_1-xO₃ or simply Nb:STO) has a power factor comparable to that of bismuth telluride. Semiconductor nanostructures have demonstrated a decrease in thermal conductivity (κ) resulting in an increase in the thermoelectric figure of merit (ZT). Nanostructures of doped oxides like niobium doped strontium titanate, may also lead to decreased κ and a corresponding increase in ZT. The major impediment to nanostructured oxide thermoelectric materials is the lack of suitable fabrication techniques for testing and eventual use. Electron Beam Lithography (EBL) was used to pattern poly-methyl-methacrylate (PMMA) resists on undoped single crystalline SrTiO₃ (STO) substrates which were then filled with Nb:STO using Pulsed Laser Deposition (PLD) at room temperature. This technique produced nanowires and nanodots with critical dimensions below 100 nm, and a yield of approximately 95%. In addition to scanning electron microscopy and atomic force microscopy morphological studies of the patterned oxide, thin film analogues were used to study composition, crystallinity and electrical conductivity of the material in response to a post deposition heat treatment. Since the thin films were grown under similar experimental parameters as the oxide nanostructres, the patterned oxides are believed to be stoichiometric and highly crystalline. The study found that using a combination of EBL and PLD, it is possible to produce highly crystalline, doped complex oxide nanostructures with excellent control over morphology. Furthermore, the technique is applicable to nearly all materials and provides the capability of patterning doped oxide materials without the requirement of etching or multiple lithography steps makes this approach especially interesting for future fundamental materials research and novel device fabrication. / Master of Science

Interactions of gas-phase molecules with surfaces are important in many ordinary events, such as ozone depletion, corrosion of metals, and heterogeneous catalysis. These processes are controlled by the bonding, diffusion, and reactivity of the impinging gas species. Our research employs molecular beam techniques and well-characterized surfaces to study these processes. The goal of this study is to better understand how the physical and chemical nature of the surface interface influences energy transfer dynamics in gas-surface collisions. An atomic beam is used to probe the energy transfer dynamics in collisions of Argon with model surfaces of functionalized self-assembled monolayers (SAMs) (1-dodecanethiol and 11-mercapto-1-undecanol) on gold. The beam is directed towards the surface at an incident angle of 30 degrees and the scattered Ar atoms are detected at the specular angle of 30 degrees. Time-of-flight scans measure the velocity distributions of atoms leaving the surface, which correlate with the energy transfer dynamics of the impinging gas atoms. Gas-surface energy transfer experiments are accomplished by directing an 80 kJ/mol Ar atomic beam at a clean Au(111) surface and surfaces composed of hydroxyl-terminated or methyl-terminated SAMs on Au(111). The fractional energy transferred to the bare gold surface is 69 %, while it is grater than 77 % for the monolayer-covered surfaces. The extent of thermalization on the surface during the collision is significantly greater for the methyl-terminated surface than for the hydroxyl-terminated surface. Since the two monolayers are similar in structure, packing density, and mass, the differences in scattering dynamics are likely due to a combination of factors that may include differences in the available energy modes between the two terminal groups and the hydrogen-bonding nature of the hydroxyl-terminated SAM. / Master of Science

Rigidizable/Inflatable space structures have been the focus of renewed interest in recent years due to efficient packaging for transport. In this work, we examine new mathematical systems used to model small-scale joint dynamics for inflatable space truss structures. We investigate the regularity and asymptotic behavior of systems resulting from various damping models, including Kelvin-Voigt, Boltzmann, and thermoelastic damping. Approximation schemes will also be introduced. Finally, we look at optimal control for the Kelvin-Voigt model using a linear feedback regulator. / Ph. D.

The objective of this research work was to develop a design tool to analyze and design undamped beam and rotor systems in two dimensions. Systems modeled in two dimensions, such as beams with different moments of inertia, could produce varying responses in the each direction of motion. A coupling between the vertical and horizontal motions also exists in rotor systems mounted of fluid film bearings. The computer program called 2DBEAM has been developed to model and provide analyses of such systems in two dimensions. The tool has been based on an existing design package, BEAM9, which in its present state provides the response of beams and rotors in one plane of motion. The 2DBEAM program has the capability of performing the static response, free vibration, forced dynamic response, and frequency response analyses of a system. The Transfer Matrix Method has been used in the development of the software and an explanation of the method is included in this thesis. Mathematical problems and solutions encountered while developing 2DBEAM are also documented in this study. The code has been tested against analytical and published solutions for the types of analysis mentioned above and on coupled and uncoupled system models. / Master of Science

This work describes the development of an improved mode I fracture testing procedure for adhesively-bonded wood, and demonstrates the sensitivity of this approach. The two significant improvements were: 1) the use of the flat double cantilever beam (DCB) geometry, which has been uncommon for wood and 2) the application of an established and powerful data analysis using a corrected compliance method from beam theory. Three studies were conducted using various wood adhesives and DCB specimens were fabricated from yellowpoplar (Liriodendron tulipifera) sapwood. The sensitivity of this methodology showed significant differences in fracture performance as the degree of cure increased for a phenol formaldehyde adhesive, and yielded maximum strain energy release rate (SERR) values of 370 - 560 J/m2. A second study showed performance differences between two polymeric diphenylmethane diisocyanate (pMDI) adhesives and one polyurethane adhesive. Typical maximum SERR values were 160 and 130 J/m2 for the pMDI adhesives and 160 J/m2 for the polyurethane adhesive. A third study investigated the effect of loading rates on a cross-linked polyvinyl acetate adhesive and maximum SERR values of 370 - 560 J/m2 were achieved. Adhesive penetration and cure were determined by image analysis with fluorescence microscopy, and by micro-dielectric analysis, respectively. Since the geometry of the fracture procedure dictates the absence of wood failure, the resulting fractured surfaces were readily analyzable. The surface analysis techniques of laser ionization mass analysis, solid-state nuclear magnetic resonance and field emission scanning electron microscopy were used to investigate the locus of failure for the smooth fractured surfaces. / Master of Science

Crash tests of strong-post w-beam guardrail have focused entirely on the performance of new guardrail. The risk posed by minor damage modes, e.g. small deflections and missing posts, has never been evaluated. Using finite element models validated by real world crash tests, this study assessed the safety risk of crashes into guardrail with minor damage. The minor damage modes under consideration for this study were rail and post deflection, missing posts, rail flattening, and post/rail separation. Each of these damage modes was evaluated according to the testing protocols laid out in National Cooperative Highway Research Program (NCHRP) Report 350, test level 3. A number of minor damage modes were found to pose significant risks to vehicle occupants and should be repaired as soon as possible. In order of priority of repair, these modes are missing posts, rail and post deflection over 6â , and rail flattening over 50%. Damage modes of less concern were rail and post deflections less than 6â , rail only deflection up to 6â , flattening less than 50%, and separation of the posts from rails. These recommendations were on the conservative side because preventing occupant injury was the highest priority of guardrail performance. Guardrails with rail and post deflection posed a risk of vehicle vaulting due to lowered rail height and failure of the posts to separate from the rails. This risk would be even greater for guardrails embedded in soft soils, which allow for greater deflection. Guardrails with missing posts frequently resulted in snagging of the vehicle tire on the downstream posts, as well as large increases in the tension carried by the rails during impact. Flattened rails posed a risk of vehicle rollover as they provided a ramp-like surface which caused the side of the vehicle to move upward, greatly increasing the change of override. Flattening also occurs frequently with other damage modes. Pre-existing separation of posts from the rails was found to have very little effect on the crash outcome. Separation of the posts from the rails was desirable as it prevented failure modes that were observed for the rail and post deflection simulations while maintaining the post contributions to lateral strength of the guardrail. / Master of Science

The purpose of this research is to analyze the statics and dynamics of steel smoke stacks subject to excitation by aerodynamic forces. The wind loads experienced by smoke stacks arise from various phenomenon, the most prominent of which are static drag load, vortex shedding, and atmospheric turbulence. The nature of these loading sources around a cylinder are studied in detail. Both static and dynamic loads are capable of producing large tip deflections, and are of the most prominent design criteria for stack designers. A computer program, STACK1, has been created by modifying an existing analysis code, BEAM8, to be used specifically for stack analysis. This analysis code utilizes the transfer matrix method to perform detailed bending and vibration analyses. This new software has been developed to check stack designs for compliance with appropriate steel stack standards, and provide the designer with information regarding the static and dynamic response of the structure. A detailed analysis is performed to demonstrate the validity of approximating a tapered Timoshenko beam with a series of continuous, constant cross-section beams. / Master of Science