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Ministries and departments of transportation are working to undertake assessments of deteriorated metal culverts. To assist with these assessments by developing rational methods of classifying culverts, to select those requiring replacement or repair, the current thesis studied the effects of metal corrosion and backfill erosion on culvert stability. Finite element calculations were used to explain how stability is jeopardized by two forms of deterioration, both material failure (yield in the steel) and geometrical nonlinearity (bucking failure). The stability assessments are presented for structures designed using limit states design procedures in the Canadian Highway Bridge Design Code and the LRFD Bridge Design Code of the American Association of State Highway and Transportation Officials. It was found that yield in culverts in intact ground is proportional to plate thickness (thrust and moment are not affected). Buckling strength changes as corrosion occurs, but does not become critical in structures supported by good quality backfill (without erosion). Surprisingly, thrusts decrease when erosion develops adjacent to the culvert, and this implies that factor of safety against yield is increased. However, substantial decreases in buckling strength occur, and elastic instability can then become the critical performance limit after erosion. Three dimensional finite element analysis indicates that local buckling can develop before global buckling, for new structures featuring thin plates, or for thicker structures after corrosion. This form of elastic instability may not be safely estimated using current culvert buckling equations which consider global buckling. Local buckling results were not effectively estimated using the Bryn’s equation (the conventional method used for stiffened plate structures); therefore a preliminary design equation for assessment of local buckling is provided. After verifying the results obtained from this thesis with physical experiments, these findings can provide practitioners with useful evaluation tools for a quantitative assessment to the stability of buried culverts subjected to these two different kinds of deterioration (corrosion and erosion) in order to augment engineering experience or judgment, which is the primary tool currently being used. Moreover, the current study helps future experimental and numerical studies by investigating various significant deterioration scenarios, and the impacts of these scenarios. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2009-10-08 12:56:13.218

Members of the Sco protein family have been proposed to function in the assembly of cytochrome c oxidase in the respiratory chain of all aerobic life forms. The Sco protein in Bacillus subtilis, BsSco, is characterized for its folding/unfolding behavior in the presence or absence of Cu(II) in this study. The folding/unfolding of apo-BsSco is investigated by CD and fluorescence spectroscopies. BsSco follows an apparent two-state mechanism in both folding and unfolding processes. The two apo forms of BsSco, reduced and oxidized, exhibit similar equilibrium stabilities suggesting that the formation of an intramolecular disulfide in oxidized apo-BsSco does not add to BsSco’s overall stability. In contrast, Cu(II) binding to reduced apo-BsSco results in extreme stabilization and resistance to unfolding in urea. However, when Cu(II) is present with unfolded, reduced apo-BsSco, the protein is rapidly oxidized. Another widely used denaturant, GdnHCl, is able to unfold Cu(II)-BsSco by allowing the loss of Cu(II) from the metal/protein complex. When the presence of Cu(II)-BsSco complex and the protein’s folded state are monitored simultaneously, the unfolding of Cu(II)-bound BsSco occurs coincidently with Cu(II) dissociation. We suggest that the loss of Cu(II) binding and the loss of BsSco’s native conformation are coincident, which leads to the conclusion that Cu(II)-BsSco does not unfold until it forfeits Cu(II). The kinetics of folding/unfolding of reduced, oxidized and Cu(II) bound BsSco are explored by stopped-flow fluorescence spectroscopy. The rate constants at which the two apo forms of BsSco fold and unfold are measured and plotted versus denaturant concentration. Reduced and oxidized forms of apo-BsSco are similar in folding and unfolding kinetics. Cu(II)-involved refolding kinetics of BsSco show that Cu(II) is able to accelerate the rate of refolding. However, the involvement of Cu(II) in the refolding process results in two competing processes: oxidation and Cu(II) binding. Which process predominates depends on the refolding rate which further depends on the denaturant concentration. This study has provided direct evidence for metal-involved stabilization of BsSco which is beneficial to efficiently fulfill its copper trafficking duty in a cellular environment. / Thesis (Master, Biochemistry) -- Queen's University, 2010-12-17 17:24:09.598