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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.
11

Design de uma peneira rotativa para colheitadeira de grãos

Hoher Junior, Alberto January 2011 (has links)
A ênfase deste trabalho está voltada ao desenvolvimento de um novo sistema de limpeza para a colheitadeira de grãos visando, principalmente, a utilização de uma nova geometria. O design de um sistema com peneiras rotativas vem de encontro a todos os sistemas conhecidos até o momento, este sistema visa eliminar sistemas eletrônicos cada vez mais complexos e caros. Uma descrição sobre os sistemas de colheita e máquinas agrícolas, principalmente colheitadeiras, é apresentada neste trabalho, já que a bibliografia sobre este assunto é bastante restrita. A utilização de métodos computacionais, voltados à análise de fluídos foi utilizada com o intuito de nortear o desenvolvimento de protótipos reais. O método computacional dos fluídos dinâmicos simula diversas hipóteses de maneira mais rápida e mais barata até que sejam alcançados resultados suficientemente bons que compensem a fabricação de um protótipo real. Com o protótipo real os resultados virtuais podem ser validados e comparados com outros sistemas. Os resultados obtidos foram bons, a peneira rotativa tem um ótimo desempenho em testes realizados no plano, com perdas inferiores comparativamente às peneiras planas. Nos testes realizados com inclinação o desempenho não foi bom, devido a alguns problemas no duto de ar. Com relação à qualidade dos grãos separados, não foram detectadas quaisquer avarias que pudessem ter sido resultadas da peneira. / The emphasis of this work is dedicated to the development of a new cleaning system for grain harvester aiming mainly to use a new geometry in this part of the machine. The design of a system with rotary sieves comes against all systems known at this time; this system seeks to eliminate electronic systems increasingly complex and expensive. A description of the harvesting systems and agricultural machinery, harvesters mainly, is been presented in this work, since the literature on this subject is very limited. The use of computational methods, focused on the analysis of fluid was used in order to guide the development of prototypes. The method of computational fluid dynamic simulates scenarios faster and cheaper to achieve results that are good enough to compensate the fabrication of a real prototype. With the real prototype, virtual results can be validated and compared with other systems. The results achieved were good. The rotary sieve cleaning system shows excellent performance when testing on level ground with lower losses than a flat sieve system. In tests on slopes, the performance was not as good due to some problems in the air duct. With regard to grain quality, no mechanical damage that could have been produced by the screens was detected in either test.
12

Design de uma peneira rotativa para colheitadeira de grãos

Hoher Junior, Alberto January 2011 (has links)
A ênfase deste trabalho está voltada ao desenvolvimento de um novo sistema de limpeza para a colheitadeira de grãos visando, principalmente, a utilização de uma nova geometria. O design de um sistema com peneiras rotativas vem de encontro a todos os sistemas conhecidos até o momento, este sistema visa eliminar sistemas eletrônicos cada vez mais complexos e caros. Uma descrição sobre os sistemas de colheita e máquinas agrícolas, principalmente colheitadeiras, é apresentada neste trabalho, já que a bibliografia sobre este assunto é bastante restrita. A utilização de métodos computacionais, voltados à análise de fluídos foi utilizada com o intuito de nortear o desenvolvimento de protótipos reais. O método computacional dos fluídos dinâmicos simula diversas hipóteses de maneira mais rápida e mais barata até que sejam alcançados resultados suficientemente bons que compensem a fabricação de um protótipo real. Com o protótipo real os resultados virtuais podem ser validados e comparados com outros sistemas. Os resultados obtidos foram bons, a peneira rotativa tem um ótimo desempenho em testes realizados no plano, com perdas inferiores comparativamente às peneiras planas. Nos testes realizados com inclinação o desempenho não foi bom, devido a alguns problemas no duto de ar. Com relação à qualidade dos grãos separados, não foram detectadas quaisquer avarias que pudessem ter sido resultadas da peneira. / The emphasis of this work is dedicated to the development of a new cleaning system for grain harvester aiming mainly to use a new geometry in this part of the machine. The design of a system with rotary sieves comes against all systems known at this time; this system seeks to eliminate electronic systems increasingly complex and expensive. A description of the harvesting systems and agricultural machinery, harvesters mainly, is been presented in this work, since the literature on this subject is very limited. The use of computational methods, focused on the analysis of fluid was used in order to guide the development of prototypes. The method of computational fluid dynamic simulates scenarios faster and cheaper to achieve results that are good enough to compensate the fabrication of a real prototype. With the real prototype, virtual results can be validated and compared with other systems. The results achieved were good. The rotary sieve cleaning system shows excellent performance when testing on level ground with lower losses than a flat sieve system. In tests on slopes, the performance was not as good due to some problems in the air duct. With regard to grain quality, no mechanical damage that could have been produced by the screens was detected in either test.
13

Réacteur-échangeur de type monolithe - stratégie de modélisation et description des phénomènes à l'échelle d'un canal catalytique unique / Reactor/heat exchanger of monolith type – modeling strategy and phenomena description at the catalytic channel scale

Durán Martínez, Freddy-Libardo 28 April 2017 (has links)
Les réacteurs structurés de type monolithe apparaissent comme une alternative intéressante aux réacteurs triphasiques conventionnels (à lit fixe ruisselant ou à suspension), car ils offrent dans leurs canaux millimétriques, dans une large gamme de débits, un écoulement bien défini, consistant en une succession de bulles et bouchons liquides (écoulement dit de Taylor). Celui-ci, proche de l'écoulement idéal " piston ", permet également une intensification du transfert gaz-liquide, notamment grâce à l'existence d'un film mince de liquide séparant les bulles de la paroi catalytique. Par ailleurs, les dernières technologies de fabrication additive offrent de nouvelles possibilités de réalisation de ce type de réacteur, sous la forme d'une structure métallique conductrice alternant canaux catalytiques et canaux dédiés au fluide caloporteur. Cette configuration efficace de réacteur-échangeur autorise à considérer le monolithe comme uniforme en température et à réduire sa modélisation à celle d'un canal unique isotherme. C'est la stratégie de modélisation adoptée dans ce travail de thèse, qui cherche à représenter chacun des phénomènes avec seulement le niveau de complexité nécessaire, en progressant de l'échelle locale à l'échelle du réacteur. L'outil choisi ici est le logiciel COMSOL Multiphysics pour sa capacité à traiter des problèmes multi-physiques et multi-échelles. Une approche classique pour les écoulements de Taylor est appliquée, construite autour d'une " cellule unitaire " qui se déplace à la vitesse diphasique le long du canal. Le champ hydrodynamique calculé sert alors de support au calcul du transfert de masse entre les phases. Le premier cas d'étude traité - transfert d'oxygène dans l'eau avec réaction de consommation de l'oxygène en paroi - sert à poser les bases du modèle, en examinant le bien-fondé de différentes hypothèses simplificatrices, concernant le nombre de phases modélisées, les conditions aux limites du domaine pour les équations résolues, ou encore la forme de bulle. Ce travail préliminaire a montré que la résolution de la phase liquide uniquement, autour d'une bulle de forme simplifiée, peut assurer une représentation satisfaisante des profils de vitesse dans les bouchons et dans le film de lubrification par rapport à des calculs diphasiques. Il a aussi permis d'évaluer de façon séparée les contributions au transfert gaz-liquide de chacune des zones d'interface (film, nez ou arrière de la bulle) et de quantifier l'influence sur l'efficacité du transfert de la fréquence de bullage, qui modifie à la fois l'aire interfaciale et l'intensité de recirculation dans les bouchons. La démarche est ensuite appliquée au cas de l'hydrogénation de l'alpha-pinène, et validée par une campagne d'essais réalisés pour un tube catalytique de 2 mm de diamètre et de 40 cm de longueur, fonctionnant sous 21 bar et entre 100°C et 160°C. Le modèle utilise pour la couche catalytique en paroi une loi cinétique intrinsèque, identifiée en réacteur autoclave agité (pour le même catalyseur de Pd/Al2O3, mais sous forme de poudre). Il suit par un calcul instationnaire la progression de la cellule unitaire jusqu'à la sortie du réacteur. Outre les effets des paramètres clés mis en évidence précédemment, ceux de la consommation de gaz le long du réacteur et des conditions " initiales " de saturation du liquide sont examinés. Le fonctionnement du monolithe peut être reproduit dans son intégralité à partir de ce modèle, par association de canaux recevant des débits individuels de gaz et de liquide représentatifs de la distribution des fluides observée expérimentalement, et en lui incorporant un module de mélange des fluides issus de chacun des canaux en sortie de réacteur. Ce modèle sert aussi de référence pour l'évaluation d'un outil de dimensionnement plus direct, basé sur une hydrodynamique simplifiée et des coefficients d'échange globaux évalués à partir de corrélations ou des simulations numériques dédiées. / Structured reactors of monolith type arise as an interesting alternative to conventional three-phase reactors (trickle-bed or slurry reactors), because they offer, in a wide range of flow rates, a welldefined flow structure in their millimetric channels, consisting of an intermittent series of gas bubbles and liquid slugs (i.e. Taylor flow). This flow regime, close to the ideal “plug flow” behavior, enables the improvement of gas-liquid mass transfer, thanks to the thin liquid film laying between the bubbles and the catalytic wall. Moreover, recent additive manufacturing technologies offer new possibilities for producing such a reactor, in the form of a metal heat-conducting block alternating catalytic channels and channels dedicated to the coolant. This efficient reactor/heat exchanger configuration allows the monolith to be considered as uniform in temperature and to reduce its modeling to that of a single isothermal channel. This is the modeling strategy adopted in this thesis, which aims to represent each phenomenon with the required level of complexity only, progressing from the bubble/slug scale to the reactor scale. COMSOL Multiphysics® software is selected as the numerical tool for its ability to handle multiphysics and multi-scale problems. The approach classically used for Taylor flows is applied, based upon a "unit cell" (gas bubble associated to a lubricating liquid film and two liquid half-slugs) that travels along the channel at the two-phase velocity. Solved hydrodynamics then serves as a basis for the calculation of gas-liquid mass transfer. The first study case - oxygen transfer into water with consumption at the channel wall – lays the foundations of the model, by examining the merits of various simplifying hypotheses concerning the number of phases to be considered (gas and liquid, or liquid only), the boundary conditions for the solved equations (periodicity, slip conditions at the gas-liquid interface), or the bubble shape (calculated or "simplified"). This preliminary work has shown that the simplest approach, which consists in solving the liquid phase only, as flowing around a bubble of simplified shape, can ensure a satisfactory representation of the velocity profiles in the liquid slugs and in the lubrication film, compared with two-phase flow (semi-analytical or CFD) calculations. This study also allows to evaluate separate contributions from different parts of the bubble surface (film, and front or back cap) to gas-liquid mass transfer, and to quantify the influence on transfer efficiency of bubble frequency, which affects both the interfacial area and the recirculation intensity in the slugs. The modelling approach is then applied to the hydrogenation of alpha-pinene and validated by an experimental tests carried out in a catalytic tube of 2 mm diameter and 40 cm length, operating at 20 bar and between 100°C and 160°C. The model uses an intrinsic kinetic law for the reaction occurring in the catalytic washcoat, identified in a stirred autoclave reactor (for the same Pd/Al2O3 catalyst, but in powdered form). Transient calculation follows the progression of the unit cell until the reactor exit. In addition to the effects of the key parameters previously identified, those of gas consumption along the reactor (hydrogen being here the limiting reactant) and "initial" saturation conditions of the liquid are examined. The behavior of the entire monolith can be mimicked from this model by combining, in a mixing module, the outflows of channels whose individual gas and liquid flow rates match a measured fluid distribution. This model also serves as a reference for evaluating a more direct reactor sizing tool, based on simplified hydrodynamics and overall exchange coefficients evaluated from correlations or dedicated numerical simulations.
14

Design de uma peneira rotativa para colheitadeira de grãos

Hoher Junior, Alberto January 2011 (has links)
A ênfase deste trabalho está voltada ao desenvolvimento de um novo sistema de limpeza para a colheitadeira de grãos visando, principalmente, a utilização de uma nova geometria. O design de um sistema com peneiras rotativas vem de encontro a todos os sistemas conhecidos até o momento, este sistema visa eliminar sistemas eletrônicos cada vez mais complexos e caros. Uma descrição sobre os sistemas de colheita e máquinas agrícolas, principalmente colheitadeiras, é apresentada neste trabalho, já que a bibliografia sobre este assunto é bastante restrita. A utilização de métodos computacionais, voltados à análise de fluídos foi utilizada com o intuito de nortear o desenvolvimento de protótipos reais. O método computacional dos fluídos dinâmicos simula diversas hipóteses de maneira mais rápida e mais barata até que sejam alcançados resultados suficientemente bons que compensem a fabricação de um protótipo real. Com o protótipo real os resultados virtuais podem ser validados e comparados com outros sistemas. Os resultados obtidos foram bons, a peneira rotativa tem um ótimo desempenho em testes realizados no plano, com perdas inferiores comparativamente às peneiras planas. Nos testes realizados com inclinação o desempenho não foi bom, devido a alguns problemas no duto de ar. Com relação à qualidade dos grãos separados, não foram detectadas quaisquer avarias que pudessem ter sido resultadas da peneira. / The emphasis of this work is dedicated to the development of a new cleaning system for grain harvester aiming mainly to use a new geometry in this part of the machine. The design of a system with rotary sieves comes against all systems known at this time; this system seeks to eliminate electronic systems increasingly complex and expensive. A description of the harvesting systems and agricultural machinery, harvesters mainly, is been presented in this work, since the literature on this subject is very limited. The use of computational methods, focused on the analysis of fluid was used in order to guide the development of prototypes. The method of computational fluid dynamic simulates scenarios faster and cheaper to achieve results that are good enough to compensate the fabrication of a real prototype. With the real prototype, virtual results can be validated and compared with other systems. The results achieved were good. The rotary sieve cleaning system shows excellent performance when testing on level ground with lower losses than a flat sieve system. In tests on slopes, the performance was not as good due to some problems in the air duct. With regard to grain quality, no mechanical damage that could have been produced by the screens was detected in either test.
15

Modélisation et identification de lois rhéologiques de polymères chargés. Application au procédé de moulage par injection de poudres de superalliages. / Modelling and identification of rheological laws adapted for loaded polymers. Applications for the process of superalloy powder injection moulding

Claudel, Dimitri 04 February 2016 (has links)
Le sujet de thèse de doctorat s’inscrit dans le cadre d’un projet de recherche collaboratif entre l’Institut FEMTO-ST et le groupe SAFRAN/SNECMA. Une partie des travaux de cette thèse concerne les caractérisations thermo-physiques de polymères chargés pour différentes nuances et granulométries de poudres de superalliage destinés à être mis en forme par le procédé de Moulage par Injection de Poudre. Pour ces travaux de thèse de doctorat, trois nuances de polymères chargés composé de poudres de superalliages ont été investiguées. Deux nuances sont composées de poudres utilisées par Snecma en réparation (René 80®/Amdry D15® et RBD61) et un autre est composée de poudre d’Inconel 718. Différentes caractérisations ont été réalisées et ont permis d’optimiser le développement de mélanges chargés conduisant à l’élaboration de matériaux homogènes et injectables tout en possédant des taux de charge en poudres les plus élevés possible.Les résultats de ces travaux sont ensuite utilisés afin d’identifier différents termes présents dans les modèles analytiques de rhéologie usuels. Le développement de modèles de rhéologies spécifiques a été réalisé en incorporant aux lois rhéologiques usuelles différents termes dépendant de la surface spécifique, de la viscosité des liants employés au sein de la formulation. Le développement de ces modèles de viscosité de plus en plus complets permet d’améliorer les lois de comportements et de mieux décrire le comportement rhéologique de polymères chargés. Enfin, une simulation de l’étape de moulage par injection d’un composant aéronautique a été réalisée à l’aide du logiciel Moldflow© pour la nuance de René 80®/Amdry D15®. / The works presented in this paper were realized in collaboration between the mechanical department of FEMTO-ST Institute and the company SAFRAN/SNECMA. A part of the works of this thesis focused the thermo-physical characterizations of loaded polymers that is mixtures based of thermoplastic binders and metallic powders suitable be shaped by powder injection molding process.For this work, three different loaded mixtures composed of superalloy powder were investigated.Two were supplied by SAFRAN/SNECMA used to repair (Rene80®/AmdryD15® and RBD61) and another is composed of Inconel 718 powder. Characterizations were to carry out to optimize the development of loaded polymers and to obtain homogenous materials with high solid fraction. Then, the data were used to identified parameters of usual rheological laws. The development of specific rheological models were realized by including different parameters related to the specific surface area, binder viscosities used in the formulation. The development of these models increasingly exhaustive allows the improvement of behavior laws and to better describe the rheological behavior of superalloy-loaded polymers. Finally, a simulation of the injection molding stage of a aeronautical component was realized in the Moldflow© software for the Rene80®/AmdryD15® loaded polymer.
16

Vady a vlastnosti masivních odlitků / Defects and properties of heavy castings

Sobotka, Petr January 2012 (has links)
A diploma thesis was objected to a figure analyzing and a figure interpretation of ingot processing. The described figures were obtained from samples which were taking from feeder-heads of ingot of lower ram, produced in Vitkovice Machinery Group. The thesis was focused on ingot solidification and segregation processes which were associated with this procedure. The figures obtained from numeric simulation of ingot solidification in defined places were analyzed using statistic method – linear regression, as well as linear regression was used for evaluation of explored samples, their chemical compositions and mechanical properties. In conclusion all acquired results were summarized.
17

Análise da base de pilares pré-moldados na ligação com cálice de fundação / Analysis of the precast concrete column base in the connection socket

Ebeling, Eimair Bottega 22 May 2006 (has links)
O trabalho apresenta a análise do comportamento da base de pilares de concreto pré-moldado na ligação com cálice de fundação, dando-se continuidade a estudos anteriores sobre este tipo de ligação. A pesquisa visa preencher a falta de informações sobre o comportamento da base de pilares na região de embutimento, já que praticamente não existem recomendações sobre o assunto. É realizada uma investigação experimental, com a construção de dois modelos, em que os cálices de fundação foram aproveitados de pesquisas anteriores. Os modelos possuem interface de contato lisa, com comprimento de embutimento diferente e foram submetidos a força normal com grande excentricidade. São apresentadas simulações numéricas pelo Método dos Elementos Finitos, com a consideração das não linearidades físicas, geométricas e de contato. É feita uma análise comparativa entre os modelos físicos e numéricos, sendo observados os deslocamentos, deformações na armadura longitudinal e transversal, fissuração e fluxo de tensões. Os resultados apresentados mostram que a ruína dos modelos ocorreu pela plastificação da armadura longitudinal tracionada, localizada fora da região de embutimento e que a armadura transversal foi pouco solicitada. São feitas recomendações sobre a ancoragem da armadura longitudinal e ao final do trabalho é sugerido um modelo de bielas e tirantes que represente o comportamento da base de pilares na região de embutimento / The study presents the analysis of precast concrete column base in the connection socket. This research follows previous studies on this connection type. The research aim to fill out the lack of information about column base in the embedded length, because almost do not exist recommendations about this subject. An experimental investigation was developed with the construction of two models, which connection sockets were reused from previous researches. The models have smooth contact interface with different embedded lengths and the axial load with great eccentricity was applied in the models. Numeric simulations are presented by using the Finite Element Method adopting non-linear physical, geometric, and contact. A comparative analysis was done between the tests and numeric models that were observed the displacements, longitudinal and transversal reinforcement strain, cracking, and stress flow. The results show that the ruin of the models occurred for large strain in longitudinal tensioned reinforcement located out of embedded length. The transversal reinforcement presents little strain. Recommendations are made for anchorage of longitudinal reinforcement and at the end of the research an analytical model for column base behavior is suggested for connecting foundation by socket
18

Influence de la stœchiométrie sur les propriétés physiques du multiferroïque BiFeO3 / Stoichiometry influence on physical properties of multiferroic BiFeO3

Jarrier, Romain 06 February 2012 (has links)
Le matériau BiFeO3 (BFO) est le sujet de très nombreuses études fondamentales dans le domaine des matériaux multiferroïques. Cet intérêt est du au fait que cet oxyde présente deux ordres à longue distance à la température ambiante : ferroélectricité et antiferromagnétisme de type G (ce dernier est aussi non colinéaire avec la présence de faible ferromagnétisme ainsi qu’une modulation de spin de type cycloïdale possédant une longueur d’onde de 620 angstrœm). Il est alors possible d’étudier les comportements de couplage entre les propriétés électrique et magnétique. Ce travail concerne principalement la synthèse, les structures haute température, et les propriétés physiques (électronique et magnétique principalement) du matériau BiFeO3 ayant subi des recuits de différentes pressions partielles d’oxygène. La première étape de ce travail concerne l’étude de la synthèse afin de déterminer le protocole optimal de réalisation des céramiques. Les recuits sous atmosphère ont eu pour but de modifier la stœchiométrie en oxygène du matériau, afin d’affecter ses propriétés physiques. Des modifications de faible amplitude de certaines propriétés ont été détectées, mais à l’inverse, la température de Néel et la température de Curie ne sont pas affectées.Concernant la nature des structures haute température, les phases beta et gamma, sujettes à de nombreuses controverses dans la littérature, ont été étudiées par diffraction des rayons X et analyse DSC sur BFO pur ou avec excès de bismuth. Cet excès a permis de stabiliser la phase gamma entre 940 et 950°C, en évitant sa décomposition. Pour compléter ce travail sur BFO en phase pure, nous avons dopé des céramiques avec 10 % de Zr4+ pour étudier le comportement structurale à haute température, ainsi que les propriétés magnétiques et électriques de cette nouvelle composition. Enfin, des simulations numériques sur le composé stœchiométrique, lacunaire en bismuth ou en oxygène ont été réalisées pour comprendre les évolutions structurale, électronique et magnétique du matériau suite aux recuits. La dernière partie est une étude sur le comportement basse température de BFO pur sous différentes formes : nanotubes, céramiques et monocristaux. Nous avons analysé le comportement électrique (impédance, pyroélectricité, RPE et électrostriction), magnétique (aimantation en fonction de la température et du champ magnétique) et structurale (rayon X en thêta-2thêta et rasant, DSC, microRaman et résonance d’ultrasons). Suite à ces études, trois températures sont observées comme présentant un comportement particulier : 140 et 200 K, qui semblent liées par de nombreuses techniques d’analyses et ressortent comme étant une transition à la surface de BFO, mais aussi 180 K où nous avons un écart à la linéarité de la dilatation thermique et un effet d’électrostriction. / BiFeO3 material is the subject of number fundamental studies in multiferroic materials. This interest is mainly cause by the existence of two long range order at room temperature : ferroelectricity and G type antiferromagnetism (this one is also no collinear with the presence of a weak ferromagnetism, and a cycloidal spin modulation with a wave length of 620 angstrom). So, it is possible to study coupling behaviour between electrical and magnetic properties.This work is mainly about the synthesis, high temperature structures, and physical properties (principally electronic and magnetic one) in BFO material after sintering it under different oxygen partial pressure. The first step of this work is about the synthesis study in order to optimize the protocol of ceramic formation. The sintering under atmosphere are done in order to change the oxygen stoichiometry of BFO, we expected to affect this physical properties. We saw some weak modifications of few properties, but Néel and Curie temperature are not altered.Concerning the nature of BFO high temperature structure, beta and gamma phase, which are subject of number controversies in literature, were studied with X-rays and DSC analysis, in pure or in bismuth excess phase. This excess leads to stabilize the gamma phase between 940 and 950°C, and avoid decomposition. To complete this work on pure phase BFO, we doped ceramic with 10 % of Zr4+ in order to study the high temperature structural behaviour, electrical and magnetic properties of this new composition. At last, numerical simulation on the stoichiometric, bismuth or oxygen lacunar system are done to understand structural, electrical and magnetic evolution after the sintering.The last part is a study on behaviour of pure phase BFO at low temperature with different form : nanotube, ceramic and single crystal. We analysed electrical (impedance, pyroelectricity, EPR and electrostriction), magnetic (magnetization function of temperature and magnetic field) and structural comportment (X-rays in theta-2theta and grazing incidence, DSC, microRaman and ultrasonic resonance). It reveals that tree temperature show a specific behaviour : 140 and 200 K, which are link by several analysis technical and seems to be a surface transition (skin effect) in BFO, but also 180 K where we found a non constant evolution in the thermal dilatation, and an electrostriction effect.
19

Análise da base de pilares pré-moldados na ligação com cálice de fundação / Analysis of the precast concrete column base in the connection socket

Eimair Bottega Ebeling 22 May 2006 (has links)
O trabalho apresenta a análise do comportamento da base de pilares de concreto pré-moldado na ligação com cálice de fundação, dando-se continuidade a estudos anteriores sobre este tipo de ligação. A pesquisa visa preencher a falta de informações sobre o comportamento da base de pilares na região de embutimento, já que praticamente não existem recomendações sobre o assunto. É realizada uma investigação experimental, com a construção de dois modelos, em que os cálices de fundação foram aproveitados de pesquisas anteriores. Os modelos possuem interface de contato lisa, com comprimento de embutimento diferente e foram submetidos a força normal com grande excentricidade. São apresentadas simulações numéricas pelo Método dos Elementos Finitos, com a consideração das não linearidades físicas, geométricas e de contato. É feita uma análise comparativa entre os modelos físicos e numéricos, sendo observados os deslocamentos, deformações na armadura longitudinal e transversal, fissuração e fluxo de tensões. Os resultados apresentados mostram que a ruína dos modelos ocorreu pela plastificação da armadura longitudinal tracionada, localizada fora da região de embutimento e que a armadura transversal foi pouco solicitada. São feitas recomendações sobre a ancoragem da armadura longitudinal e ao final do trabalho é sugerido um modelo de bielas e tirantes que represente o comportamento da base de pilares na região de embutimento / The study presents the analysis of precast concrete column base in the connection socket. This research follows previous studies on this connection type. The research aim to fill out the lack of information about column base in the embedded length, because almost do not exist recommendations about this subject. An experimental investigation was developed with the construction of two models, which connection sockets were reused from previous researches. The models have smooth contact interface with different embedded lengths and the axial load with great eccentricity was applied in the models. Numeric simulations are presented by using the Finite Element Method adopting non-linear physical, geometric, and contact. A comparative analysis was done between the tests and numeric models that were observed the displacements, longitudinal and transversal reinforcement strain, cracking, and stress flow. The results show that the ruin of the models occurred for large strain in longitudinal tensioned reinforcement located out of embedded length. The transversal reinforcement presents little strain. Recommendations are made for anchorage of longitudinal reinforcement and at the end of the research an analytical model for column base behavior is suggested for connecting foundation by socket
20

Dynamique morphosédimentaire de la baie d’Agadir : approche multi-méthodes et préconisations pour une gestion intégrée de la zone côtière / Sediment morpho dynamics of the bay of Agadir : multi-method approach and recommendations for an integrated management of the coastal zone

Aouiche, Ismail 20 May 2016 (has links)
Les systèmes côtiers, où le transport sédimentaire est perturbé par les aménagements côtiers sur la côte et l’avant côte, fournissent généralement d'excellents exemples permettant de mettre en lumière ces liens. Cela est faisable lorsque l’ensemble des données bathymétriques d’avant-côte, qui ne sont pas toujours disponibles, sont recueillies au fil du temps. La baie et la ville d'Agadir forment ensemble un des pôles de développement économique le plus important de la côte atlantique du Maroc. En utilisant une approche méthodologique basée sur la modélisation de la houle et des courants, le différentiel de levées topo-bathymétriques, la détermination de l’évolution du trait de côte et le suivi topographique de la zone intertidale, nous mettons en évidence les liens étroits entre les variations des petits fonds et la ligne du trait de côte. Ces liens impliquent à la fois les voies de transport cross-shore et longshore, les variations du budget sédimentaire et la détermination de cellules sédimentaires. Nous avons également suivi l’évolution morphologique de la zone intertidale de la baie en réponse à huit tempêtes qui ont lieu entre Janvier 2014 et Mars 2014. Les résultats obtenus par les simulations numériques montrent que les deux premières tempêtes sont responsables des changements morphologiques majeurs au niveau de la zone intertidale. / Coastal systems where sediment transport is perturbed by engineering interventions on the shoreline and shoreface commonly provide fine examples liable to throw light on these links. This is especially so where shoreface bathymetric datasets, which are generally lacking, are collected over time, enabling more or less fine resolution of the meso-scale coastal sediment budget. Agadir Bay and the city of Agadir together form one of the two most important economic development poles on the Atlantic coast of Morocco. Using a combined methodological approach based on wave–current modelling, bathymetric chart-differencing, determination of shoreline fluctuations, and beach topographic surveying, we highlight the close links between variations in the bed of the inner shoreface and the bay shoreline involving both cross-shore and longshore sand transport pathways, sediment budget variations and new sediment cell patterns. This work discusses also the morphological changes and evolution of Agadir Bay beach (Morocco) in response to eight storms between January 2014 and March 2014. A comparison is carried out of the evolution and variability of the beach in a sector of the bay protected by the commercial harbour of Agadir relative to a sector down drift of the harbour that is more exposed to waves, and changes affecting the beach following these storms are examined. Wave influence is evaluated using numerical simulations. The results show that despite being of relatively low intensity, the two first storm events, and especially storm 1, are responsible for major beach morphological changes.

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