The research on headed stud connections described in this thesis forms a part of a larger program with the objective of predicting the behaviour of precast concrete panel buildings under earthquake loads. The first objective of this research is to produce experimentally a concrete failure of the connection and to compare the actual failure load to the one predicted by the PCI design handbook. The tests show that the PCI shear-tension interaction equation for single headed studs can be used for the prediction of a concrete failure for a connection of the type tested. This method yields conservative results if a special equilibrium model for the determination of the stud tension force is used, and the bearing capacity of the structural steel angle on the concrete is neglected. The second objective of this research is to determine the bearing capacity of a reversed angle connection. Experiments show that this bearing capacity is equivalent to a force resulting from a stress equal to the concrete strength uniformly distributed over the concrete area enclosed by the structural steel angle 2" x2". Furthermore, the location of this force can be assumed in the center of gravity of the structural steel angle shape, regardless of whether or not there is an endplate present. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

The Utah Department of Transportation (UDOT) is interested in the application of rehabilitation techniques to strengthen their AASTHO prestressed bridge girders for shear. Utah's bridges are exposed to deterioration from rain, snow, and the introduction of salt for ice removable. This requires innovative rehabilitation techniques to address the deteriorations of their highway bridges, especially the ends of bridge girders where water and salt are more common due to construction joints. Carbon Fiber Reinforced Polymers (CFRP) are becoming more prevalent as a tool in highway bridge rehabilitation. This research investigates the application of various CFRP systems that can be used as shear reinforcement for prestressed concrete girders. The experimental program involved full-scale destructive testing of six 40-year-old, AASHTO prestressed I-girders that were salvaged from the 45th South/I-215 bridge in Salt Lake City, Utah. The testing involved retrofitting five of the girders with various configurations of CFRP fabric. Based on the initial tests, the most effective configuration was then applied to another set of I-shaped concrete girders for verifications. After the experimental testing, two analytical models developed for predicting the additional shear contribution of the CFRP reinforcement were compared with the measured results from the experimental program. After testing and comparisons, a CFRP reinforcement configuration and theoretical model was selected as a reliable and effective method for application of external shear reinforcement of AASHTO prestressed I-shaped girders.

This research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, in partial fulfilment of the requirements for the degree of Master of Science in Dentistry. School of Oral Health Science, Faculty of Health Sciences, University of the Witwatersrand, South Africa Johannesburg, 2017 / Purpose: Resin restorative materials have improved over the years. A major obstacle to the acquisition of acceptable bond strength of bonding agents is the presence of contaminated dentine cavity preparations. The purpose of this study was to investigate the effects of oral contaminants such as blood, saliva and a disinfectant contamination on the shear bond strength of a nanocomposite on a self-etching adhesive system. Materials and Methods: Thirty-six caries free premolar teeth were extracted and placed in a disinfectant solution containing 0.5 % Chloramine T solution, and then randomly distributed into four groups. Each tooth was then placed into a stainless steel ring supported by clear self-curing acrylic. They were thereafter immersed into a saline solution of 37 ̊C - 37.5 ̊C in an incubator for 24 hours. The enamel surfaces of the premolars were then ground with a Pro-trim 1725 Hertz grinder using 600 grit silicon carbide fine grinding paper to expose the dentine surface of each tooth. The sample was then re-immersed in the saline solution and incubated at 37°C - 37.5°C. The teeth were then arranged into the four groups: Group 1 (control group); Group 2 (human blood contamination at 5 seconds); Group 3 (human saliva contamination at 5 seconds) and Group 4 (chlorine dioxide contamination at 5 seconds). A self-etching adhesive bonding system (Scotchbond universal™) and Filtek supreme XTE composite was applied to the exposed dentine surface. Samples were randomised and then sheared using an Instron testing machine to determine their bond strengths. The fractured components of each sample were measured, compared and further examined under a stereo microscope to determine the modes of failure. The data were analysed using a one-way analysis of variance (ANOVA) and the level of significance was set at a p-value of less than 0.05. Results: A significant difference was found in the shear bond strength between the control (group 1) and the blood contaminated group (group 2) (p-value of 0.00064). The chlorine dioxide group (group 4) that had no effect on shear bond strength to dentine (p-value of 0.55). Adhesive failures (between bonding agent and dentine) were predominant in group 2 and to a lesser extent in group 3. Most group 4 samples had cohesive fractures (within the dentine). Conclusion: The bond strength to dentine using a self-etching adhesive was reduced when contaminated with blood. Group 2 samples (blood) caused significantly greater bonding failure as compared to all the other groups. Chlorine dioxide solution is a powerful disinfectant and does not affect the bonding to dentine. The null hypothesis statement, which stated that there was no difference in the shear strength between any of the conditions, was thus rejected. Further studies on the application of chlorine dioxide as a disinfectant on cavity preparations need to be considered given the surprising positive results of chlorine dioxide group. / MT2018

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<p> Since Newton's definition of viscosity does not lead to a useful description of non-Newtonian flow, two other model liquids, the Maxwell liquid and the Prandtl-Eyring liquid are discussed. Equations describing the flow behaviour of these liquids in narrow capillaries are derived and discussed. </p> <p> A thorough analysis is given of corrections that are, or may be, necessary in capillary viscometry, and the influence of non-Newtonian flow on these corrections is discusses, both for cylindrical and spherical bulbs. </p> <p> The significance of measurements of non-Newtonian flow in dilute solutions of macromolecules is discussed in terms of recent theories. It is shown that a capillary viscometer has inherent limitations for such measurements, but that a properly designed capillary viscometer can give precise and reliable data at shear rates down to 50 sec^-1, provided that the system is not too shear-dependent. </p> <p> A new variable shear capillary viscometer-- a modification of the Ubbelohde suspended level viscometer-- is describes. It was designed to be rugged, convenient and precise, to eliminate or minimize the kinetic energy correction and surface tenison effects, and to permit dilution of a solution while in the instrument. Three different viscometers of this type have been constructed, calibrated and tested, and proved sound in design and convenient in use. </p> <p> The usefulness of the viscometers has been demonstrated in three diverse investigations: (i) the shear dependence in aqueous solutions of a high molecular weight dextran, (ii) the temperature dependence of the zero-shear intrinsic viscosity in a good solvent of a very high molecular weight fraction of polystrene, (iii) the shear dependence of the interaction coefficient k' in the systems polystyrene-toluene and poly(n-octyl-methacrylate). </p> / Thesis / Master of Science (MSc)