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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Innovative Systems for Arch Bridges using Ultra High-performance Fibre-reinforced Concrete

Salonga, Jason Angeles 22 February 2011 (has links)
In this thesis, new design concepts for arch bridges using ultra high-performance fibre-reinforced concrete are developed for spans of 50 to 400 m. These concepts are light-weight and efficient, and thus have the potential to significantly reduce the cost of construction. Lightness is achieved by the thinning of structural components and the efficient use of precompression in the arch, rather than by the decrease of bending stiffness. Using the advanced properties of the material, the design concepts were shown to reduce the consumption of concrete in arch bridges by more than 50% relative to arches built using conventional concrete technology. In addition to span length, other design parameters including span-to-rise ratio and deck-stiffening were considered, resulting in a total of seventy-two design concepts. Other important contributions made in this thesis include: (1) the development of a simple analytical model that describes the transition of shallow arches between pure arch behaviour and pure beam behaviour, (2) a comprehensive comparative study of 58 existing concrete arch bridges that characterizes the current state-of-the-art and serves as a valuable reference design tool, and (3) the development and experimental validation of general and simplified methods for calculating the capacity of slender ultra high-performance fibre-reinforced concrete members under compression and bending. The research presented in this thesis provides a means for designers to take full advantage of the high compressive and tensile strengths of the concrete and hence to exploit the economic potential offered by the material.
42

Performance of Steel Fibre Reinforced Concrete Columns under Shock Tube Induced Shock Wave Loading

Burrell, Russell P. 19 November 2012 (has links)
It is important to ensure that vulnerable structures (federal and provincial offices, military structures, embassies, etc) are blast resistant to safeguard life and critical infrastructure. In the wake of recent malicious attacks and accidental explosions, it is becoming increasingly important to ensure that columns in structures are properly detailed to provide the ductility and continuity necessary to prevent progressive collapse. Research has shown that steel fibre reinforced concrete (SFRC) can enhance many of the properties of concrete, including improved post-cracking tensile capacity, enhanced shear resistance, and increased ductility. The enhanced properties of SFRC make it an ideal candidate for use in the blast resistant design of structures. There is limited research on the behaviour of SFRC under high strain rates, including impact and blast loading, and some of this data is conflicting, with some researchers showing that the additional ductility normally evident in SFRC is absent or reduced at high strain loading. On the other hand, other data indicates that SFRC can improve toughness and energy-absorption capacity under extreme loading conditions. This thesis presents the results of experimental research involving tests of scaled reinforced concrete columns exposed to shock wave induced impulsive loads using the University of Ottawa Shock Tube. A total of 13 half-scale steel fibre reinforced concrete columns, 8 with normal strength steel fibre reinforced concrete (SFRC) and 5 with an ultra high performance fibre reinforced concrete (UHPFRC), were constructed and tested under simulated blast pressures. The columns were designed according to CSA A23.3 standards for both seismic and non-seismic regions, using various fibre amounts and types. Each column was exposed to similar shock wave loads in order to provide direct comparisons between seismic and non-seismically detailed columns, amount of steel fibres, type of steel fibres, and type of concrete. The dynamic response of the columns tested in the experimental program is predicted by generating dynamic load-deformation resistance functions for SFRC and UHPFRC columns and using single degree of freedom dynamic analysis software, RCBlast. The analytical results are compared to experimental data, and shown to accurately predict the maximum mid-span displacements of the fibre reinforced concrete columns under shock wave loading.
43

Polymer-Shell Bonded Phase for Improving Online LC-MS Analysis of Intact Proteins, mAbs, and ADCs

Tse-Hong Chen (7013258) 13 August 2019 (has links)
<p>LC-MS of protein drugs requires new ideas in bonded phase design rather than adapting bonded phases from the realm of small-molecule drugs. The polymer-shell bonded phase is designed to interact with larger molecules and to shield proteins from the silica substrate. The particles consist of a core of solid silica and a shell of dense polymer brush. The polymer layer is thick enough to protect the protein from interactions with silanols to reduce peak tailing. The polymer contains multiple functional groups that introduce more selectivity. This design gives unprecedented LC resolution and MS sensitivity. Our group has developed polymer shell bonded phases for hydrophobic interaction chromatography (HIC-MS) of antibody-drug conjugates (ADCs), hydrophilic interaction liquid chromatography (HILIC-MS) of glycoproteins, and reversed-phase liquid chromatography (RPLC-MS) of monoclonal antibodies. Since HIC is not in-line compatible with MS due to the high salt levels, it is laborious to identify the constituents of HIC peaks. An MS-compatible alternative to HIC is reported here: native reversed phase liquid chromatography (nRPLC). This employs a mobile phase 50 mM ammonium acetate for high sensitivity in MS, and elution with a gradient of water/isopropanol. The nRPLC-MS data show that all ADC species, ranging from drug-to-antibody ratios of 1 to 8, remained intact and native on the column. As we adapt this concept to intact proteins, we find that lysozyme and α-chymotrypsinogen A are both eluted in their native conformations. We also use the polymer-shell concept to resolve IgG1 free thiol variants by RPLC-MS with 0.5% formic acid. Since there are always other variants besides the intended ones, the need for high MS sensitivity is desired to distinguish subtle mass change between disulfide bond and free thiols. Overall, MS sensitivity increases 10X relative while all of the thiol variants are well resolved by the polymethylmethacrylate bonded phase.</p>
44

Evaluation of the Performance of Multi-Component Cementitious Composites: Multi-Scale Experimental Characterization and Numerical Simulation

January 2018 (has links)
abstract: Being a remarkably versatile and inexpensive building material, concrete has found tremendous use in development of modern infrastructure and is the most widely used material in the world. Extensive research in the field of concrete has led to the development of a wide array of concretes with applications ranging from building of skyscrapers to paving of highways. These varied applications require special cementitious composites which can satisfy the demand for enhanced functionalities such as high strength, high durability and improved thermal characteristics among others. The current study focuses on the fundamental understanding of such functional composites, from their microstructural design to macro-scale application. More specifically, this study investigates three different categories of functional cementitious composites. First, it discusses the differences between cementitious systems containing interground and blended limestone with and without alumina. The interground systems are found to outperform the blended systems due to differential grinding of limestone. A novel approach to deduce the particle size distribution of limestone and cement in the interground systems is proposed. Secondly, the study delves into the realm of ultra-high performance concrete, a novel material which possesses extremely high compressive-, tensile- and flexural-strength and service life as compared to regular concrete. The study presents a novel first principles-based paradigm to design economical ultra-high performance concretes using locally available materials. In the final part, the study addresses the thermal benefits of a novel type of concrete containing phase change materials. A software package was designed to perform numerical simulations to analyze temperature profiles and thermal stresses in concrete structures containing PCMs. The design of these materials is accompanied by material characterization of cementitious binders. This has been accomplished using techniques that involve measurement of heat evolution (isothermal calorimetry), determination and quantification of reaction products (thermo-gravimetric analysis, x-ray diffraction, micro-indentation, scanning electron microscopy, energy-dispersive x-ray spectroscopy) and evaluation of pore-size distribution (mercury intrusion porosimetry). In addition, macro-scale testing has been carried out to determine compression, flexure and durability response. Numerical simulations have been carried out to understand hydration of cementitious composites, determine optimum particle packing and determine the thermal performance of these composites. / Dissertation/Thesis / Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2018
45

Performance of Steel Fibre Reinforced Concrete Columns under Shock Tube Induced Shock Wave Loading

Burrell, Russell P. 19 November 2012 (has links)
It is important to ensure that vulnerable structures (federal and provincial offices, military structures, embassies, etc) are blast resistant to safeguard life and critical infrastructure. In the wake of recent malicious attacks and accidental explosions, it is becoming increasingly important to ensure that columns in structures are properly detailed to provide the ductility and continuity necessary to prevent progressive collapse. Research has shown that steel fibre reinforced concrete (SFRC) can enhance many of the properties of concrete, including improved post-cracking tensile capacity, enhanced shear resistance, and increased ductility. The enhanced properties of SFRC make it an ideal candidate for use in the blast resistant design of structures. There is limited research on the behaviour of SFRC under high strain rates, including impact and blast loading, and some of this data is conflicting, with some researchers showing that the additional ductility normally evident in SFRC is absent or reduced at high strain loading. On the other hand, other data indicates that SFRC can improve toughness and energy-absorption capacity under extreme loading conditions. This thesis presents the results of experimental research involving tests of scaled reinforced concrete columns exposed to shock wave induced impulsive loads using the University of Ottawa Shock Tube. A total of 13 half-scale steel fibre reinforced concrete columns, 8 with normal strength steel fibre reinforced concrete (SFRC) and 5 with an ultra high performance fibre reinforced concrete (UHPFRC), were constructed and tested under simulated blast pressures. The columns were designed according to CSA A23.3 standards for both seismic and non-seismic regions, using various fibre amounts and types. Each column was exposed to similar shock wave loads in order to provide direct comparisons between seismic and non-seismically detailed columns, amount of steel fibres, type of steel fibres, and type of concrete. The dynamic response of the columns tested in the experimental program is predicted by generating dynamic load-deformation resistance functions for SFRC and UHPFRC columns and using single degree of freedom dynamic analysis software, RCBlast. The analytical results are compared to experimental data, and shown to accurately predict the maximum mid-span displacements of the fibre reinforced concrete columns under shock wave loading.
46

Load-carrying and energy-dissipation capacities of ultra-high-performance concrete under dynamic loading

Buck, Jonathan J. 06 April 2012 (has links)
The load-carrying and energy-dissipation capacities of ultra-high-performance concrete (UHPC) under dynamic loading are evaluated in relation to microstructure composition at strain rates on the order of 10⁵ s⁻¹ and pressures of up to 10 GPa. Analysis focuses on deformation and failure mechanisms at the mesostructural level. A cohesive finite element framework that allows explicit account of constituent phases, interfaces, and fracture is used. The model resolves essential deformation and failure mechanisms in addition to providing a phenomenological account of the effects of the phase transformation. Four modes of energy dissipation are tracked, including pressure-sensitive inelastic deformation, damage through the development of distributed cracks, interfacial friction, and energy released through phase transformation of the quartz silica constituent. Simulations are carried out over a range of volume fractions of constituent phases to quantify trends that can be used to design materials for more damage-resistant structures. Calculations show that the volume fractions of the constituents have more influence on the energy-dissipation capacity than on the load-carrying capacity, that inelastic deformation is the source of over 70% of the energy dissipation, and that the presence of porosity changes the role of fibers in the dissipation process. The results also show that the phase transformation has a significant effect on the load-carrying and energy-dissipation capacities of UHPC for the conditions studied. Although transformation accounts for less than 2% of the total energy dissipation, the phase transformation leads to a twofold increase in the crack density and yields nearly an 18% increase to the overall energy dissipation. Microstructure-behavior relations are established to facilitate materials design and tailoring for target-specific applications.
47

Versuchstechnische Ermittlung und mathematische Beschreibung der mehraxialen Festigkeit von ultra-hochfestem Beton (UHPC) - Zweiaxiale Druckfestigkeit; Im Rahmen des Schwerpunktprogramms 1182 Nachhaltiges Bauen mit Ultra-Hochfestem Beton (UHPC) / Experimental Investigation and Mathematical Analysis of Multiaxial Strength of Ultra High Performance Concrete (UHPC) - Biaxial Compressive Strength

Curbach, Manfred, Speck, Kerstin 18 September 2007 (has links) (PDF)
Der vorliegende Bericht beschreibt das Verhalten von ultrahochfestem Beton unter zweiaxialer Druckbeanspruchung. Bisher wurden ein Feinkornbeton und zwei Grobkornbetone mit unterschiedlichen Faserzusätzen untersucht. Die Zylinderdruckfestigkeiten nach 28 Tagen betragen rund 150, 160 und 170 N/mm². Besonders bei dem Feinkornbeton wurde eine überwiegend horizontale Ausrichtung der Stahlfasern festgestellt, die zu einer Anisotropie im Materialverhalten führte. Zusammenfassend muss festgestellt werden, dass die zweiaxiale Druckfestigkeit von UHPC nur geringfügig größer ist als die einaxiale. Für die Mischungen mit 2,5 Vol.-% Fasergehalt übersteigt die Festigkeit bei einem Spannungsverhältnis von Spannung 1 zu Spannung 2 gleich Eins die einaxiale Festigkeit um 7 bzw. 10 %. Bei dem Beton mit 0,9 Vol.-% Fasergehalt lag diese zweiaxiale Festigkeit sogar geringfügig unter der einaxialen. Bei der Bemessung von UHPC dürfen somit die vom Normalbeton bekannten Festigkeitssteigerungen unter mehraxialer Druckbelastung, wie sie z.B. bei reinen Druckknoten von Stabwerkmodellen angesetzt werden, nicht verwendet werden! Für die Beschreibung der Bruchkurve kann nach jetzigem Erkenntnisstand das Bruchkriterium nach OTTOSEN als eine gute Näherung empfohlen werden. Die Versuche haben gezeigt, dass sich UHPC in vielen, zum Teil sicherheitsrelevanten Bereichen anders verhält als Normalbeton. Für eine umfassende Beschreibung des Tragverhaltens sind weitere Versuche unter dreiaxiale Druckbelastung und kombinierter Druck-Zug-Belastung notwendig.
48

Innovative Systems for Arch Bridges using Ultra High-performance Fibre-reinforced Concrete

Salonga, Jason Angeles 22 February 2011 (has links)
In this thesis, new design concepts for arch bridges using ultra high-performance fibre-reinforced concrete are developed for spans of 50 to 400 m. These concepts are light-weight and efficient, and thus have the potential to significantly reduce the cost of construction. Lightness is achieved by the thinning of structural components and the efficient use of precompression in the arch, rather than by the decrease of bending stiffness. Using the advanced properties of the material, the design concepts were shown to reduce the consumption of concrete in arch bridges by more than 50% relative to arches built using conventional concrete technology. In addition to span length, other design parameters including span-to-rise ratio and deck-stiffening were considered, resulting in a total of seventy-two design concepts. Other important contributions made in this thesis include: (1) the development of a simple analytical model that describes the transition of shallow arches between pure arch behaviour and pure beam behaviour, (2) a comprehensive comparative study of 58 existing concrete arch bridges that characterizes the current state-of-the-art and serves as a valuable reference design tool, and (3) the development and experimental validation of general and simplified methods for calculating the capacity of slender ultra high-performance fibre-reinforced concrete members under compression and bending. The research presented in this thesis provides a means for designers to take full advantage of the high compressive and tensile strengths of the concrete and hence to exploit the economic potential offered by the material.
49

Avaliação da estabilidade de extratos hidroalcoólicos de Mikania laevigata e Mikania glomerata por cromatografia líquida de ultra eficiência acoplada a espectrometria de massas / Evaluation of the stability of hidroalcoholic extracts of Mikania laevigata and Mikania glomerata by Ultra-high performance liquid chromatography-mass spectrometry

Melo, Lucilia Vilela de, 1984- 08 February 2013 (has links)
Orientador: Alexandra Christine Helena Frankland Sawaya / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-23T15:24:02Z (GMT). No. of bitstreams: 1 Melo_LuciliaVilelade_M.pdf: 3774406 bytes, checksum: 3c653ac94937b307fae09a72aa334f79 (MD5) Previous issue date: 2013 / Resumo: No Brasil, as espécies Mikania glomerata e Mikania laevigata, conhecidas popularmente como guaco, são muito utilizadas na forma de xarope devido ao seu efeito broncodilatador. A comercialização de medicamentos fitoterápicos no Brasil é regida por diversas legislações que primam pela qualidade destes, porém a qualidade da matéria-prima pode interferir de forma fundamental na segurança e eficácia do medicamento. Diante disso, este trabalho realizou um estudo de estabilidade do extrato hidroalcoólico das espécies citadas, conforme preconiza o "Guia para a realização de estudos de estabilidade de medicamentos" publicado pela ANVISA na RE 01, de 29 de julho de 2005. Folhas das duas espécies de Mikania foram secas em estufa a 40 °C e em liofilizador, foram preparados extratos hidroalcoólicos por maceração, que foram submetidos a estudo de estabilidade acelerado por 6 meses, e estudo de estabilidade de longa duração por 12 meses. As amostras ficaram armazenadas em diferentes temperaturas (22°C, 30°C e 40°C), com e sem incidência de luz, e a cada 3 meses foram analisadas por UHPLC-MS, para acompanhar seu perfil químico, quantificar a cumarina e ácido clorogênico. Em todas as condições do estudo, observou-se uma redução do teor do marcador químico desta espécie, a cumarina, maior que 5 %, sendo assim, não é possível atribuir o prazo de validade de 2 anos para extratos hidroalcoólicos desta espécie / Abstract: In Brazil, the species Mikania glomerata and Mikania laevigata, known popularly as guaco, are widely used in syrup form due to its bronchodilator effect. The marketing of herbal medicines in Brazil is governed by various laws that guarantee the quality of these, but the quality of the raw material can interfere, fundamental safety and efficacy. Therefore, a stability study of the hydro alcoholic extract of the species mentioned was conducted as recommended by the "Guidelines for conducting stability studies of drugs" published by ANVISA in RE 01 of July 29, 2005. Leaves of both species of Mikania were dried in an oven at 40 ° C and by freeze drying, hydro alcoholic extracts prepared by maceration, which underwent accelerated stability study of 6 months, and long term stability study for 12 months. Samples were stored in different temperatures (22 ° C, 30 ° C and 40 ° C) with and without incident light, and every 3 months were analyzed by UHPLC-MS to monitor their chemical profile, quantifying coumarin and chlorogenic acid. At all conditions of the study, we observed a reduction of the content of the chemical marker of this species, coumarin, greater than 5%, so a shelf life of 2 years cannot be assigned to the hydro alcoholic extracts of these species / Mestrado / Fármacos, Medicamentos e Insumos para Saúde / Mestra em Biociências e Tecnologia de Produtos Bioativos
50

Influence du revêtement sur le comportement en fatigue des dalles orthotropes : étude d'une solution en BFUP / Influence of topping layer on fatigue behaviour of orthotropic steel bridge deck : study of an UHPFRC solution

Gomes, Fernanda 09 November 2012 (has links)
Les tabliers métalliques à dalle orthotrope sont sensibles au phénomène de fatigue produit par les charges des poids lourds du trafic. Ce comportement n'est pas précisément prédit avec les méthodes de l'Eurocode 3, compte tenu de la complexité des effets locaux et de la connaissance insuffisante du rôle mécanique du revêtement (diffusion des charges et participation à la flexion locale). De plus l'augmentation du trafic des camions et éventuellement celle des charges admissibles par essieu en Europe tend à rendre ce problème bien plus critique. Le renforcement de ces tabliers est donc souhaitable de façon à prolonger la durée de vie des ponts existants, et aussi augmenter la durabilité des nouveaux ponts. Le béton fibré à ultra hautes performances (BFUP) a été envisagé comme nouvelle solution de revêtement, étant donné ses propriétés mécaniques, ses possibilités de mise en œuvre et sa durabilité. L'objectif de cette thèse, réalisée dans le cadre du projet ANR Orthoplus, est de quantifier expérimentalement l'apport des revêtements couramment utilisés dans les structures à dalle orthotrope et de valider la solution innovante en BFUP. Des essais statiques et dynamiques sur corps d'épreuve à grande échelle (2,40x4,00) m2 ont été réalisés sur la plate-forme d'essai des structures de l'IFSTTAR. Quatre corps d'épreuve ont été testés : tôle de platelage de 14 mm non revêtue et revêtue de 80 mm de béton bitumineux, tôle de 10 mm revêtue de 35 mm de BFUP et tôle de 12 mm revêtue de 35 mm de BFUP. L'influence des différents types de chargement positionnés au centre des corps d'épreuve a été analysée : plaques métalliques type Eurocode 1 et vraies roues de camion. L'étude a porté sur le détail de fatigue: liaison auget-tôle de platelage entre pièces de pont. La contrainte géométrique de fatigue (extrapolation au point chaud) a été évaluée expérimentalement en utilisant deux schémas d'extrapolation linéaire des déformations à proximité du cordon de soudure du détail étudié, le schéma du rapport CECA et celui proposé par l'Institut International de Soudure, à partir des mesures réalisées au-dessous de la tôle de platelage (σT) et sur l'âme de l'auget (σA).La cohérence entre estimation quasi-statique des déformations et comportement sous cycles de fatigue a été vérifiée, ainsi que la rigidification importante apportée par le BFUP, bien que ce dernier ne participe pas avec une connexion totale. Les résultats expérimentaux ont été confrontés à des modèles de différents niveaux de complexité qu'il reste nécessaire de calibrer empiriquement pour prévoir les contraintes géométriques. A partir des contraintes de fatigue obtenues expérimentalement, nous avons calculé la durée de vie des dalles orthotropes testés à l'aide de la règle du cumul linéaire de l'endommagement. Enfin nous avons mené une étude par analyse de cycle de vie d'un pont à dalle orthotrope pour vérifier la pertinence environnementale des différentes solutions de revêtement. Les nombreuses données expérimentales acquises dans ce travail sont de nature à permettre une amélioration significative du dimensionnement rationnel des tabliers à dalle orthotrope et de leur revêtement pour une meilleure prise en compte de leur gestion durable / Orthotropic steel bridge decks are sensitive to fatigue damage induced by live heavy traffic loads. This behaviour is not precisely predicted by Eurocode 3, because of the complexity of local effects. The pavement overlay is not taken into account for calculating the fatigue resistance because of the lack of knowledge concerning its mechanical behaviour (loads diffusion and participation in the local deflection) and the behaviour of the composite structure. Moreover, the increase in heavy traffic and potential regulations evolution in Europe – towards an increase of acceptable loads of truck axles - tend to render the orthotropic decks fatigue behaviour an even more critical issue. The reinforcement of these steel decks is therefore crucial to extend the service life of existing bridges, and also increase the durability of new bridges. Ultra-high performance fibre-reinforced concrete (UHPFRC) has been chosen as a possible alternative topping layer considering its remarkable durability, flowability and mechanical properties. The purpose of this thesis, carried out within the framework of a joint R&D project called Orthoplus, is to quantify experimentally the mechanical contribution of topping layers currently used in orthotropic steel bridge decks and validate an alternative concept using UHPFRC coating. Static and dynamic tests of large scale panels (2,40x4,00) m2 were carried out at the IFSTTAR Structures Laboratory. Four prototypes have been tested: a 14 mm thick deck plate without surfacing, the same deck plate associated with 80 mm of bituminous concrete surfacing, a 10 mm thick deck plate topped with 35 mm of UHPFRC and a panel with the same UHPFRC topping layer and a 12 mm thick deck plate. The influence of different centered load types and configurations has been analyzed: rectangular steel plates according to Eurocode 1 and real truck wheels. The experimental programme has been focused on the rib-to-deck welded joints at mid-span between two transverse crossbeams. The fatigue geometrical stresses in the deck and the trough, respectively denoted as σD and σT, have been derived from two linear extrapolations of measured strains next to the toe of the welded joint: the extrapolation schemes from the ECSC report and from the IIW document. Consistency between quasi static strains and deflections estimate and behaviour under fatigue cycles has been verified, as well as the significant additional stiffness provided by the UHPFRC overlay, although its contribution does not correspond to a perfectly connected composite section. The experimental results have been compared to simple and more complex models which still need empirical calibration for predicting the geometrical stresses. Using the experimentally obtained fatigue geometrical stresses the service life of the tested prototypes were calculated using Miner's rule. Finally a life cycle assessment study of an orthotropic steel bridge deck was carried out to verify the environmental relevance of the alternative topping layer solutions. The numerous experimental data obtained from this work shall make it possible to significantly improve the rational design method of orthotropic slabs and their associated deck overlay, in view of a better accounting of their long term and sustainable structural management

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