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A fundamental task in structural stability analysis is to ensure the safety of structures throughout their operational life so as to prevent catastrophic consequences either at ambient or elevated temperatures. This thesis concerns the stability of unbraced steel frames due to abnormal loadings or fire loads, and develops practical methods to evaluate the stability capacity of unbraced steel frames at ambient temperature or in fire. The problem of determining the elastic buckling strengths of unbraced steel frames subjected to variable loadings can be expressed as an optimization problem with stability constraints based on the concept of storey-based buckling. The optimization problem can be solved by the linear programming method, which is considerably simpler and more suitable for engineering practice than the nonlinear programming method. However, it was found that the frame buckling strength obtained from the linear programming method based on Taylor series approximation on column stiffness may be overestimated in some cases. Thus, a secant approximation of the column stiffness was introduced, and a modified linear programming method based on the secant approximation was proposed. Numerical examples show that the linear programming method in light of the secant approximation can yield conservative results and maintain simplicity. In spite of the convenience of the modified linear programming method, numerical examples show that the linear programming method cannot accurately detect the maximum and minimum frame buckling strengths in some cases. Therefore, an alternative method to assess the lateral stiffness of an axially loaded column derived by using two cubic Hermite elements to signify the column is proposed. Unlike the column stiffness obtained from the Euler-Bernoulli beam theory containing transcendental functions, the stiffness in the proposed method includes only polynomials. Thus, the column stiffness within the proposed method enables the minimization and maximization problems to be solved by efficient gradient-based nonlinear programming algorithms, which overcome the inability of linear programming algorithm to detect the minimum frame buckling strength in some cases. The accuracy of the column stiffness associated with the proposed method was compared with that of the Euler-Bernoulli beam theory. Four unbraced steel frames were investigated to demonstrate the efficiency of the proposed method. It is known that the evaluation of the lateral stability of steel frames subjected to elevated temperatures is different from that at ambient temperature due to the degradation of material strength. Thus, the storey-based buckling method at ambient temperature was extended to evaluating the stability of unbraced steel frames subjected to elevated temperature. To simulate a steel column exposed to the elevated temperature, an analytical model was proposed to examine the effects of axial loading, elevated temperature, and thermal boundary restraints on the lateral stiffness of steel columns in unbraced frames. The procedure of evaluating the stability capacity of unbraced steel frames at elevated temperature was then concluded. Numerical examples are presented to demonstrate the evaluation procedure of the proposed method. The column model was then refined to evaluate the lateral stiffness of steel column subjected to non-uniform elevated temperature distributions along the longitudinal direction. The lateral stiffness equation of the column model was derived based on the Euler-Bernoulli beam theory. The procedure to evaluate the stability capacity of unbraced steel frames subjected to non-uniform elevated temperature distributions was then concluded. The numerical examples were investigated with the proposed method for non-uniform elevated temperature distributions. Finally, initial attempts were made to evaluate the stability of unbraced steel frames with fire-protected columns at different fire scenarios. A degradation factor charactering the variation of the Young's Modulus of steel at elevated temperature was introduced. The objective and constraint functions were constructed, and optimal tools were used to determine the buckling strength of an unbraced steel frame at different fire scenarios.

Polarized Raman spectroscopy has been used to measure the deuterium isotope effect, (delta)pK = pKD2O – pKH2O, for the second ionization constant of sulfuric acid in the temperature range of 25 °C to 200 °C at saturation pressure. Results for pK in light water agree with the literature within ± 0.034 pK units at alltemperatures under study, confirming the reliability of the method. The ionization constant of deuterated bisulfate, DSO4-, differs significantly from previous literature results at elevated temperatures. This results in an almost constant (delta)pK ≈ 0.425 ± 0.076 over the temperature range under study. Differences in (delta)pK values between the literature and current results can be attributed to the effect of dissolved silica from cell components. The new results are consistent with (delta)pK models that treat the temperature dependence of (delta)pK by considering differences in the zero-point energy of hydrogen bonds in the hydrated product and reactant species. The phosphate hydrolysis equilibrium was measured between the temperatures of 5 °C and 80 °C and the borate/boric acid equilibrium between the temperatures of 25 °C and 200 °C. The high alkalinity and temperatures experienced by these two systems had a significant impact on the glass dissolution and equilibrium. / Raman spectroscopy was used to measure the small differences in ionization constants for weak acids/bases as a function of temperature. / University of Guelph, Atomic Energy of Canada Limited (AECL), Bruce Power, University Network of Excellence in Nuclear Engineering (UNENE), National Sciences and Engineering Research Council of Canada (NSERC), Natural Resources Canada, Ontario Power Generation (OPG), Canada Foundation for Innovation

The research projects presented in this thesis are mainly focused toward green chemistry and engineering: developing innovative strategies to minimize waste, improve process efficiency and reduce energy consumption. Specifically, the work was centered on the design and applications of green solvents and processes for the sustainable production of pharmaceuticals. The first project was focused on the use of CO₂ to enhance Suzuki coupling reactions of substrates containing unprotected primary amines. This work established that exceptionally challenging substrates like halogenated amino pyridines (i.e. 4-amino-2-bromopyridine and 4-amino-2-chloropyridine) are suitable substrates for Suzuki coupling reactions under standard conditions using CO₂ pressures, without the need for protection/deprotection steps which are traditionally considered to be necessary for these reactions to proceed cleanly. The second project explored the use of water at elevated temperatures (WET) for the sustainable and selective removal of protecting groups. The favorable changes that occur in the physiochemical properties (i.e. density, dielectric constant and ionization constant) of water at elevated temperatures and pressures make it an attractive solvent for the development of sustainable, environmentally green processes for the removal of protecting groups. The water-mediated selective removal of protecting groups such as N-Boc, N-Acetyl and O-Acetyl from a range of organic model compounds was successfully achieved by tuning the temperature (125 to 275°C) or properties of water. The third project investigated the use of Organic-Aqueous Tunable Solvents (OATS) for the rhodium catalyzed hydroformylation of p-methylstyrene. This enables the reactions to be carried out efficiently under homogeneous conditions, followed by a carbon dioxide (CO₂) induced heterogeneous separation. Modest pressures of CO₂ induced the aqueous-rich phase (containing the catalyst) to separate from the organic-rich phase (containing the reactant), thus enabled an easy separation and recycling of catalyst. The use of Al(OtBu)₃ as a potent catalyst toward continuous Meerwein-Ponndorf-Verley (MPV) reductions was established in the fourth project. The MPV reduction of model compounds like benzaldehyde and acetophenone to their corresponding alcohols was investigated in continuous mode as a function of temperature and catalyst loading. These results established a roadmap for the pharmaceutical industry to document the implementation of continuous flow processes in their manufacturing operations.

京都大学 / 新制・課程博士 / 博士(エネルギー科学) / 甲第24003号 / エネ博第439号 / 新制||エネ||83(附属図書館) / 京都大学大学院エネルギー科学研究科エネルギー基礎科学専攻 / (主査)教授 萩原 理加, 教授 佐川 尚, 教授 野平 俊之 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DFAM

abstract: Heating of asphalt during production and construction causes the volatilization and oxidation of binders used in mixes. Volatilization and oxidation causes degradation of asphalt pavements by increasing the stiffness of the binders, increasing susceptibility to cracking and negatively affecting the functional and structural performance of the pavements. Degradation of asphalt binders by volatilization and oxidation due to high production temperature occur during early stages of pavement life and are known as Short Term Aging (STA). Elevated temperatures and increased exposure time to elevated temperatures causes increased STA of asphalt. The objective of this research was to investigate how elevated mixing temperatures and exposure time to elevated temperatures affect aging and stiffening of binders, thus influencing properties of the asphalt mixtures. The study was conducted in two stages. The first stage evaluated STA effect of asphalt binders. It involved aging two Performance Graded (PG) virgin asphalt binders, PG 76-16 and PG 64-22 at two different temperatures and durations, then measuring their viscosities. The second stage involved evaluating the effects of elevated STA temperature and time on properties of the asphalt mixtures. It involved STA of asphalt mixtures produced in the laboratory with the PG 64-22 binder at mixing temperatures elevated 25OF above standard practice; STA times at 2 and 4 hours longer than standard practices, and then compacted in a gyratory compactor. Dynamic modulus (E*) and Indirect Tensile Strength (IDT) were measured for the aged mixtures for each temperature and duration to determine the effect of different aging times and temperatures on the stiffness and fatigue properties of the aged asphalt mixtures. The binder test results showed that in all cases, there was increased viscosity. The results showed the highest increase in viscosity resulted from increased aging time. The results also indicated that PG 64-22 was more susceptible to elevated STA temperature and extended time than the PG 76-16 binders. The asphalt mixture test results confirmed the expected outcome that increasing the STA and mixing temperature by 25oF alters the stiffness of mixtures. Significant change in the dynamic modulus mostly occurred at four hour increase in STA time regardless of temperature. / Dissertation/Thesis / M.S. Civil and Environmental Engineering 2013

This thesis presents the results of a research programme to investigate the behaviour and robustness of reinforced concrete (RC) frames in fire. The research was carried out through numerical simulations using the commercial finite element analysis package TNO DIANA. The main focus of the project is the large deflection behaviour of restrained reinforced concrete beams, in particular the development of catenary action, because this behaviour is the most important factor that influences the frame response under accidental loading. This research includes four main parts as follows: (1) validation of the simulation model; (2) behaviour of axially and rotationally restrained RC beams at elevated temperatures; (3) derivation of an analytical method to estimate the key quantities of restrained RC beam behaviour at elevated temperatures; (4) response and robustness of RC frame structures with different extents of damage at elevated temperatures. The analytical method has been developed to estimate the following three quantities: when the axial compression force in the restrained beam reaches the maximum; when the RC beams reach bending limits (axial force = 0) and when the beams finally fail. To estimate the time to failure, which is initiated by the fracture of reinforcement steel at the catenary action stage, a regression equation is proposed to calculate the maximum deflections of RC beams, based on an analysis of the reinforcement steel strain distributions at failure for a large number of parametric study results. A comparison between the analytical and simulation results indicates that the analytical method gives reasonably good approximations to the numerical simulation results. Based on the frame simulation results, it has been found that if a member is completely removed from the structure, the structure is unlikely to be able to develop an alternative load carrying mechanism to ensure robustness of the structure. This problem is particularly severe when a corner column is removed. However, it is possible for frames with partially damaged columns to achieve the required robustness in fire, provided the columns still have sufficient resistance to allow the beams to develop some catenary action. This may be possible if the columns are designed as simply supported columns, but have some reserves of strength in the frame due to continuity. Merely increasing the reinforcement steel area or ductility (which is difficult to do) would not be sufficient. However, increasing the cover thickness of the reinforcement steel to slow down the temperature increase is necessary.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21066号 / 工博第4430号 / 新制||工||1688(附属図書館) / 京都大学大学院工学研究科建築学専攻 / (主査)教授 西山 峰広, 教授 原田 和典, 教授 河野 広隆 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Composite materials are under consideration for the replacement of steel helical tendons in unbonded flexible pipes utilized by the offshore oil industry. Higher strength to weight ratios and increased corrosion resistance are the primary advantages of a composite material for this application. The current study focuses on the life prediction of a PPS/AS-4 carbon fiber composite proposed for the above employment. In order to accomplish this task, the properties of the material were experimentally characterized at varying temperatures, aging times and loadings. An analytic technique was developed to predict tensile rupture behavior from bend-compression rupture data. In comparison to tensile rupture tests, bend-compression rupture data collection are uncomplicated and efficient; thus, this technique effectively simplifies and accelerates the material characterization process. The service life model for the flexible pipe composite armor was constructed with MRLife, a well established performance simulation code for material systems developed by the Materials Response Group at Virginia Tech. In order to validate MRLife for the current material, experimental data are compared to life prediction results produced by the code. MRLife was then applied to predict the life of the flexible pipe composite armor in an ocean environment. This analysis takes into account the flexible pipe structure and the environmental and mechanical loading history of an ocean service location. Several parameter studies of a flexible pipe in a hypothetical environment were conducted. These analyses highlight certain loadings and conditions which are particularly detrimental to the life of the material. / Master of Science

[pt] O concreto é conhecido por ter um bom desempenho quando exposto a altas temperaturas pelo fato de apresentar baixa condutividade térmica, ser incombustível e não exalar gases tóxicos. Entretanto, devido à sua composição heterogênea, o concreto sofre alterações físicas, químicas e mecânicas que podem comprometer sua integridade estrutural. Em estruturas de concreto armado, deve-se ter atenção especial aos pilares, cuja capacidade portante é reduzida significativamente em altas temperaturas e seu colapso, de natureza brusca, pode resultar na instabilidade global da estrutura. As reduções nas propriedades mecânicas dos materiais aliadas a lascamentos, fissuras e deformações excessivas podem comprometer seu desempenho, tornando-se necessária a verificação da segurança em situações de incêndio. Com o objetivo de analisar a resistência residual de colunas de concreto armado submetidas a altas temperaturas, foram realizados ensaios de compressão em corpos-de-prova cilíndricos de concreto simples de 5x10 cm submetidos a diferentes temperaturas (200, 400, 600, 800 e 1000 graus Celsius) e de concreto armado de 15x30 cm com diferentes configurações de estribos e submetidos a distintos tempos de exposição (30, 60, 90 e 120 minutos). Em ambos os ensaios, os corpos-de-prova foram resfriados em temperatura ambiente. Os resultados do programa experimental comprovam a perda de resistência à compressão e seus valores foram comparados a modelos numéricos e ao Método da Isoterma de 500 graus Celsius constante na ABNT NBR 15200 de 2004 e no EUROCODE 2. / [en] Concrete is well-known for exhibiting good performance when exposed to elevated temperatures because its low thermal conductivity coefficient, noncombustible properties and reduced emission of toxic gases. However, due to its heterogeneous composition, concrete undergoes physical, chemical and mechanical alterations that can compromise its structural integrity. In reinforced concrete structures, special attention should be paid to the columns, in bearing capacity is reduced significantly at elevated temperatures and their collapse, naturally brittle, may result in overall instability of structure. Reductions in the mechanical properties of the steel and concrete combined with spalling, cracking and excessive deformation compromise its performance, making it necessary to verify the safety in fire situations. In order to analyze the residual strength of reinforced concrete columns submitted to elevated temperatures, compression tests were carried out on plain concrete cylindrical specimens of 5x10 cm exposed to different temperatures (200, 400, 600, 800 and 1000 degrees Celsius) and on reinforced concrete of 15x30 cm considering different stirrups configuration and exposure times (30, 60, 90 and 120 minutes). In both tests, the specimens were cooled to room temperature. The results of the experimental program demonstrate the loss of compression strength and their values were compared to those obtained numerical models and to the Isotherm Method of 500 degrees Celsius, recommended in ABNT NBR 15200 of 2004 and in EUROCODE 2.