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DEM modelling and quantitative validation of flow characteristics and blending of pellets in a planar siloKasina, Veera Pratap Reddy January 2016 (has links)
Blending processes in a silo minimise the fluctuations in the property of bulk solids with the blending performance being strongly influenced by the flow pattern and operating mode among other process parameters such as batch size and type of input fluctuations. An accurate prediction of flow characteristics such as flow channel boundary and velocity profiles is important for understanding and quantifying the blending performance, thereby increasing the scope for new design by minimising the number of expensive pilot scale experiments required. In this thesis, the Discrete Element Method (DEM) is deployed to predict and understand the flow characteristics and blending of cylindrical plastic pellets in a planar flat bottom silo and a multi-flow blender (a silo with an insert and a blending tube). The predictions are validated against high-resolution velocity measurements analysed using Particle Image Velocimetry (PIV) technique. A planar model silo was built to measure the flow of pellets using PIV technique. The existing GeoPIV Matlab module was customised to extract the velocity fields in the Eulerian frame of reference and its accuracy has been verified. The developed tool was then applied to quantitatively investigate the mechanism of evolution of flow in a flat bottom silo and the dependency of the state of developed flow on the depth of the planar silo. It was shown that the development of flow during discharge can be divided into two stages: a rapid upward propagation of plug flow followed by a widening of the flow channel with increasing shearing boundaries. The size of the flow channel was found to be increasing with the depth of the silo. For the 100 mm deep silo, the flow is three dimensional with significant retardation in velocity at the frontal walls, whilst a negligible retardation was found for the 20 and 40 mm deep model silos. The thickness and frontal wall friction in planar silos thus play an important role in the development of flow patterns in model silos. In this thesis, DEM model calibration relating the macro-scale bulk friction and micro- scale particle friction at different rolling friction values was developed from DEM simulations of Jenike direct shear box. During the direct shear simulation, a constant normal force was achieved with the use of a shear lid geometry made with glued spheres thereby eliminating the use of a traditional servo control function. The influence of particle rotations and rolling friction on the limiting bulk friction for different particle sliding friction coefficients was explored. The accuracy of the calibration data was assessed by simulating the flow in a flat bottom silo and comparing the model predictions of flow rate, velocity profiles and flow channel boundary with the experiments. A good quantitative agreement was found between the experiment and simulations. The DEM model predictions were also compared with the kinematic model. Following the validation of the model, it was shown that the frontal friction and rolling friction are the influential parameters in simulating the flow patterns such as semi-mass and internal flow. It was further shown that flow transits from semi-mass flow to internal flow with the increase of frontal wall friction. The drastic influence of frontal wall friction on stress, flow patterns and force chains were analysed highlighting its implications on interpretations in 2D test silos. Finally, the developed DEM and PIV tools are employed to investigate blending in a flat bottom and multi-flow blender silo for different flow patterns. The analysis showed that the blending is more effective with the internal flow when compared to semi-mass flow in a flat bottom silo, in both continuous and discontinuous modes for a variety of process conditions such as batch size, the number of recirculation and frequency of input fluctuations. An algorithm was developed to evaluate the blending performance from the spatially averaged Eulerian velocity fields. The flow in a relatively large-scale multi-flow blender comprising nearly 606,000 particles, thereby fully replicating the test silo, was simulated and the challenges in reproducing the test conditions of continuous and discontinuous modes of operation were discussed. The flow patterns and blending were first analysed from the experiments in different configurations of the insert. Using the same input parameters for the model, it was shown that the model predictions of the velocity profiles along the height of the silo are in good agreement with the experiments. Internal flow, mixed flow and mass flow were predicted for the diverging, straight and converging insert configurations respectively and the blending performance for each of these configurations suggests an optimal configuration of the blender thereby demonstrating the potential of PIV and DEM in design optimisation. The possibility of conducting the DEM simulations under increased gravity in order to reduce the computational time has also been explored.
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Regional integration of financial services regulation and supervision in the Southern African Development CommunityChimbombi, Ame Rebecca January 2015 (has links)
Magister Legum - LLM / The purpose of this research is to examine the legal and institutional framework of financial services supervision and regulation in SADC. In doing so the study will probe the various models of financial services regulation with the purpose of discerning what each model sets out to do and how, in doing so, it effectively exercises its function. This study answers the question: Is there a model of financial services regulation and supervision that is legally sound and best embraces SADC’s circumstances? The legal soundness will be extracted by examining which model achieves the main objectives of independence and accountability to the greatest extent. The first objective of the study is to discuss the structure and operations of each of the identified primary models of financial services regulation with the aim of determining whether certain cardinal administrative law principles are upheld. Secondly, it then takes a practical look at how the primary models are applied and effectively work within some of the SADC Member States. Similarly, the study’s main focus will be to discern whether the financial services regulation models are ‘tangible’ when country dynamics are introduced. Thereafter, the study reconnoitres the possibility of SADC adopting a ‘harmonised’ financial services regulator and supervisor. It is worth noting that ideal as it may be; the author has no intention of prescribing one of the primary models but merely uses them as a springboard to ascertaining the viability of a single financial services regulator and supervisor in SADC. The objective is to assess how best SADC can deepen its integration levels in this area of concern. The ultimate result may very well be that such deeper relations are not feasible or that different components from the primary models be adopted to make SADC’s ‘unique’ model of financial services regulation and supervision.
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Análise estrutural das colunas de sustentação de um silo metálicoTriches, Fabio Junior January 2011 (has links)
Silos metálicos para armazenagem de diferentes tipos de produto são muito empregados no Brasil, isso faz com que compreender melhor o funcionamento deste tipo de sistemas estrutural possa levar a soluções mais inteligentes e econômicas. Com esse intuito no presente trabalho estudam-se as colunas de sustentação de um tipo de silo metálico para armazenagem de ração animal. Neste estudo as colunas foram analisadas seguindo as determinações da norma brasileira de dimensionamento de perfis conformados a frio e com modelos numéricos de diferentes níveis de complexidade. Primeiramente se estudou o perfil conformado a frio utilizado nas colunas dos silos através do método das faixas finitas e obtiveram-se as forças axiais de flambagem local e distorcional elástica. Estes valores foram utilizados no método da resistência direta para obtenção dos índices de esbeltez associados a estes modos de flambagem. Foram definidas as forças axiais de colapso, seguindo as metodologias da norma ABNT NBR 14762:2010 (método das larguras efetivas, seção efetiva e resistência direta) para diversos comprimentos do perfil. Foi desenvolvido um modelo numérico para cálculo via método dos elementos finitos, considerando não linearidades materiais e geométricas e imperfeições geométricas iniciais. Os resultados obtidos através deste modelo numérico foram comparados com os obtidos através da norma ABNT NBR 14762:2010. Após ajuste do modelo numérico se realizou um estudo paramétrico para conhecer a influência da rigidez de fixação, entre a coluna de sustentação e o corpo silo, na força de colapso do perfil. São aplicadas diversas condições de contorno com o objetivo de aproximar o modelo numérico das condições reais de fixação da coluna. Finalmente os resultados obtidos são utilizados para determinar a relação entre a força resistente do perfil e a força solicitante na coluna do silo segundo as condições usuais de segurança referentes aos estados-limites últimos determinados pela ABNT NBR 14762:2010. / Tubular steel silos for storage of different product types are widely used in Brazil. The knowledge of these structural systems can result to smarter and economic solutions. In this work is studied the structural columns of some bulk feed tanks with the national standard design code and numeric models with several complexity level. First were studied the cold-formed steel member used in the silo’s columns with the finite strip methods, and were obtained the elastic local/distorcional buckling axial forces. These values were used with the Direct Strength Method to find out slenderness ratios associated with these modes of buckling. The axial collapse forces were defined following the conception of standard ABNT NBR 14762:2010(using the methods of effective width, effective section and direct resistance) for several members’ lengths. A numeric model was development to calculate with finite elements method, considering materials and geometrics nonlinearities with initial geometric imperfections. The results obtained by this numeric model were compared with those obtained by the standard ABNT NBR 14762:2010. After the numeric model adjust, a parametric study was made to know the influences of the connection stiffness between the column and the silo’s cylindrical wall, in the member’s allowable axial strength. Several boundary conditions were applied with the main purpose to approximate the numeric model with the actual columns' end conditions. Finally the obtained results were used to determine the ration between the axial allowable strength and the required load on the silo’s columns by the usual safety conditions using the ultimate limit state determined by the ABNT NBR 14762:2010.
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Dimensionamento de silos metálicos para armazenagem de grãos / Design of steel silos for grain storageScalabrin, Luciano Argenta January 2008 (has links)
Neste trabalho, apresentam-se as formas mais comuns de acidentes em silos buscando explicar as causas que ocasionaram o colapso. Trata-se de analisar a teoria e as recomendações de duas das principais normas para a determinação das pressões devidas aos grãos armazenados no interior do silo. Desenvolvem-se planilhas de cálculo para auxiliar o dimensionamento de um silo. Busca-se maximizar a força de tração admissível para cada espessura de chapa lateral com o intuito de obter silos mais leves e conseqüentemente mais econômicos. Da mesma forma, uma planilha de cálculo é apresentada para maximizar a força de compressão para diferentes espessuras de montantes. Um configurador de silo é apresentado no decorrer do trabalho, tendo como dados de entrada o diâmetro e altura do silo e obtendo as diferentes espessuras de chapa laterais com relação à altura bem como os diferentes montantes. Apresentam-se formas de análise de silos, quando vazios, submetidos à carga de vento e a necessidade de colocação de anéis de reforço na circunferência e sua distribuição na altura. Trata-se de analisar o efeito de silos quando vazios pelo método dos elementos finitos, levando em consideração a rigidez da chapa lateral. / In this work, some accidents in silos are presented and the causes are discussed. The theory and the recommendations of two standards for determination of pressure due to grain stored inside the silo are presented. Sheets for silos design are developed. The goal is to maximize the tension force in the silos lateral sheet for each thickness, in order to improve economical benefits. Similarly, another sheet is developed with the goal to maximize the compression force in the stiffeners for different thicknesses. A design sheet for silos is presented in the course of the work; diameter and height of the silo are the input data and different thicknesses of lateral sheet and stiffeners are output data. Different approach for empty silos considering wind loads are presented and the use of wind-rings are verified. Empty silos are examined by the finite elements method considering lateral rigidity of the lateral sheet.
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Avaliação de silagens de espécies de potencial uso forrageiro no semiáridoSilva, Marcos Deames Araújo January 2012 (has links)
SILVA, Marcos Deames Araújo. Avaliação de silagens de espécies de potencial uso forrageiro no semiárido. 2012. 88 f. : Dissertação (mestrado) - Universidade Federal do Ceará, Centro de Ciências Agrárias, Departamento de Zootecnia, Fortaleza-CE, 2012 / Submitted by Nádja Goes (nmoraissoares@gmail.com) on 2016-08-05T12:50:59Z
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Previous issue date: 2012 / The objective of the study was to evaluate the nutritional quality of silage shrub-tree adapted to semi-arid northeastern Brazil, and includes some of the species studied as additives in elephant grass silage with function improve fermentation characteristics and chemical, qualitative characteristics of silages. The collection of forage and silage production were performed in the Forage Section of the Federal University of Ceara and the analysis bromatological performed in the Laboratory of Animal Nutrition of the Federal University of Ceara. The first experiment was to evaluate the chemical composition of the silages of forage legume adapted to arboreal-shrubby Caatinga. The experimental design was a completely randomized design with four replications and six treatments which consisted of the silages jurema preta, sabia, algaroba, jucá, leucaena and gliricidia. As experimental silos were used mini silos with dimensions of 0.10 m in diameter by 0.35 tall, with ensiled material density around 600 kg/m³ based on natural. For silages of leguminous shrub-tree period for opening the silage was 42 days after the making thereof, sufficient time for the anaerobic fermentation material. We analyzed chemical composition of silages of forage species to see which silages from legumes had good chemical, qualitative characteristics and which had better potential for silage production. All silages, except the sabia, showed good chemical composition, especially with good crude protein and neutral detergent fiber digestibility and in vitro, demonstrating the potential for a good intake and utilization of roughage. The second experiment evaluated the inclusion of sabia and jurema preta in elephant grass silage. The experiment and analyzes the example of the first was held in the same locations. Treatments were the inclusion of 0, 10, 20 and 30% of jurema and/or sabia in elephant grass silages. In elephant grass silages with increasing levels of sabia and jurema preta, plus reviews of chemical-bromatological characteristics were calculated losses of silage fermentation (losses effluent gases and total losses). The elephant grass silages with inclusion levels of sabia and jurema preta reduced effluent losses influenced by levels of addition, but the elephant grass silage added with sabia increased by gaseous losses and total losses. Regarding the chemical-bromatological composition of silages with addition of legumes, improvements were observed in fermentation characteristics in terms of decreasing the losses effluents, besides improving its features chemical-bromatological character due to the inclusion of forage. / O objetivo do estudo foi avaliar a qualidade nutricional das silagens arbustivo-arbóreo adaptadas ao semiárido nordestino brasileiro, além de incluir algumas das espécies estudadas como aditivos na silagem de capim-elefante com função de melhorar as características fermentativas e as características químico-bromatológicas das silagens. A coleta das forrageiras e a confecção das silagens foram realizados no Setor de Forragicultura da Universidade Federa do Ceará (UFC) e as analises químico-bromatológica realizadas no Laboratório de Nutrição Animal da UFC. O primeiro experimento consistiu na avaliação da composição quimico-bromatológica das silagens de forrageiras leguminosas arbustivas-arbóreas adaptadas à Caatinga. O delineamento experimental utilizado foi o inteiramente casualisado com seis tratamentos e quatro repetições os quais consistiam nas silagens de Jurema Preta, Sabiá, Algaroba, Jucá, leucena e gliricidia. Como silos experimentais foram utilizados mini silos com dimensões de 0,10m de diâmetro por 0,35 de altura, com densidade do material ensilado em torno de 600 kg/m³ com base em matéria natural. Para silagens das espécies leguminosas arbustivas-arbóreas o período para abertura das silagens foi de 42 dias após a confecção das mesmas, tempo suficiente para fermentação anaeróbia do material. Foi analisada composição químico-bromatológica das silagens das espécies forrageiras para verificar quais silagens confeccionadas a partir de leguminosas possuíam boas características químico-bromatológicas e quais possuíam melhor potencial para produção de silagem. Todas as silagens, exceto a do Sabiá, apresentaram boa composição químico-bromatológica, especialmente com bons teores de proteína bruta e fibra em detergente neutro e digestibilidade in vitro, demonstrando potencial para um bom consumo e aproveitamento do volumoso. No segundo experimento foi avaliada a inclusão do Sabiá e Jurema Preta na silagem de capim elefante. O experimento e as análises a exemplo do primeiro foi realizada nos mesmos locais. Os tratamentos consistiram na inclusão de 0; 10; 20 e 30% da jurema e/ou Sabiá nas silagens de capim-elefante. Nas silagens de capim-elefante com níveis crescentes de inclusão do Sabiá e Jurema Preta, além das avaliações quimico-bromatológicas foram calculada perdas resultantes do processo de ensilagem (perdas por efluentes, gases e perdas totais). As silagens de capim elefante com níveis de inclusão do Sabiá e Jurema Preta reduziram as perdas de efluentes influenciados pelos níveis de adição, porém a silagem de capim elefante adicionada de Sabiá apresentou um aumento de perdas gasosas e perdas totais. Quanto à composição químico-bromatológica das silagens com adição das leguminosas, observaram-se melhorias nas características fermentativas com relação à diminuição das perdas por efluentes, além de melhorar suas características químico-bromatológica em função da inclusão das forrageiras.
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DevOps-Kultur : En explorativ fallstudie på Arbetsförmedlingens IT-avdelningHolm, Adam, Virtanen, Johan January 2018 (has links)
Information Technology has taken a larger focus in today’s society and become a more centralized part of IT-organizations and other businesses. The traditional management models for manufacturing and production has become harder to apply in the software lifecycle. This is since the software no longer is produced and launched with no follow-up. Today’s IT- organization needs to continuously handle, operate and maintain their software. In recent years a new philosophy has emerged within the IT community, DevOps. DevOps aims to erase the silos built-in to the business to become a more efficient and optimized organization regarding their software delivery. This exploratory case study has been conducted at the Swedish Governmental Employment Services IT-department. It aims to expand the existing knowledge base regarding DevOps and the aspects of the organizational culture the philosophy claims. This study aims to investigate how organizations work while trying to introduce a DevOps culture. The potential difficulties an organization could face in relation the organizational culture described for DevOps, seen as a management model, will also be a focus of this study. In-depth interviews and observations have been conducted with the employees at the named IT-department in order to analyze and create an overview of the current culture in the department. The study has shown new angles regarding financial and resource management, dependencies between teams and the importance of an existing leadership. New perspectives have also been provided towards organizational change. Key Words: DevOps, Organizational Culture, Organizational Change, Leadership, Dependencies, IT-organizations, Communication, Information, Team, Silos, Self-Leadership
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Diagnóstico informatizado de eficiência energética: uma proposta às agroindústriasAbrão Neto, Félix [UNESP] 17 December 2004 (has links) (PDF)
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abraoneto_f_dr_botfca.pdf: 1704052 bytes, checksum: c40f5cee0dd90d9b6eb056101fb47328 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Universidade Estadual Paulista (UNESP) / A conservação de energia elétrica na agroindústria necessita de uma melhor avaliação, considerando suas características e os tipos de atividades desenvolvidas, visto que, outros segmentos industriais, já estão há algum tempo se preocupando, instalando controladores de demanda, motores de alto rendimento, banco de capacitores automatizados e quando necessário redimensionando os motores elétricos. Tendo em vista o aprimoramento e a necessidade de se dispor de uma ferramenta computacional que agilizasse a realização de diagnóstico energético nas instalações. Este trabalho tem como objetivo desenvolver um software para avaliar o consumo de energia de uma agroindústria, observando o custo da eficiência energética em cada etapa, fazendo de maneira prática e de fácil aplicação para o usuário. Foi testado em uma empresa de secagem e armazenamento de cereais, denominada Produsoja Cereais Ltda, situada no município de São Gabriel do Oeste - MS. Foram obtidos em relatório de memória de massa fornecido pela concessionária de energia os dados de consumo no horário de ponta, consumo horário fora de ponta, demanda em horário de ponta, demanda em horário fora de ponta. Os dados de tensão, 2 corrente, demanda, e fator de potência, através de medições locais com auxílio de um analisador portátil de energia. Estes dados serviram para alimentar o software, com a finalidade de se analisar a eficiência energética da agroindústria. Com a aplicação do software pode-se determinar o índice total de energia consumida para o processamento completo de um produto ou serviço, sendo um dos parâmetros de maior importância em estudo que desenvolve o uso racional e a conservação de energia,... / Electric energy conservation in industry requires a better evaluation due to its features and the kind of activities developed, considering that other industry segments have being conserned with the instalation of demand control, engines of high performance, authomatized capacitor data bases and when necessary, correction the dimention of eletric engines. Having in mind the iprovement and necessity of computer tool which could speed the accomplishment of energy diagnoses in installations. This study aims at developing a software to evaluate the energy consuption in the agroindustry, observing the energy efficiency costs in each phase, in a practical way and of easy aplicability to the user. It was tested in a drier and storage cereal company named Produsoja Cereais Ltda, located in São Gabriel city- MS. In mass memory reports provided by the energy concessionaire were obtained consume data in the tip schedule, consume in the out of pick, demands in and out the pick schedule, and the tension data, corrent, demand and powerfactor, were obtainde trhough local measurements with help of energy portable analyser. These data were used to feed the software aiming at analysing the energy efficiency in the agroindustry. With the applicability of the software, it was verified which is the best fee option based on the criteria of the fee structure in practice; proposing the adequacy of motor force based on the index of energy loading in order to verify highly dimentioned engines, the use of frequency invertors, the use of fix and authomatic databases capacitors according to the criterium of operation, tension level analysis provided by transformer and energy concessionaires and the use of engines of high perfomance proper to the charge and schedule situation of meaningful operation.
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Dimensionamento de silos metálicos para armazenagem de grãos / Design of steel silos for grain storageScalabrin, Luciano Argenta January 2008 (has links)
Neste trabalho, apresentam-se as formas mais comuns de acidentes em silos buscando explicar as causas que ocasionaram o colapso. Trata-se de analisar a teoria e as recomendações de duas das principais normas para a determinação das pressões devidas aos grãos armazenados no interior do silo. Desenvolvem-se planilhas de cálculo para auxiliar o dimensionamento de um silo. Busca-se maximizar a força de tração admissível para cada espessura de chapa lateral com o intuito de obter silos mais leves e conseqüentemente mais econômicos. Da mesma forma, uma planilha de cálculo é apresentada para maximizar a força de compressão para diferentes espessuras de montantes. Um configurador de silo é apresentado no decorrer do trabalho, tendo como dados de entrada o diâmetro e altura do silo e obtendo as diferentes espessuras de chapa laterais com relação à altura bem como os diferentes montantes. Apresentam-se formas de análise de silos, quando vazios, submetidos à carga de vento e a necessidade de colocação de anéis de reforço na circunferência e sua distribuição na altura. Trata-se de analisar o efeito de silos quando vazios pelo método dos elementos finitos, levando em consideração a rigidez da chapa lateral. / In this work, some accidents in silos are presented and the causes are discussed. The theory and the recommendations of two standards for determination of pressure due to grain stored inside the silo are presented. Sheets for silos design are developed. The goal is to maximize the tension force in the silos lateral sheet for each thickness, in order to improve economical benefits. Similarly, another sheet is developed with the goal to maximize the compression force in the stiffeners for different thicknesses. A design sheet for silos is presented in the course of the work; diameter and height of the silo are the input data and different thicknesses of lateral sheet and stiffeners are output data. Different approach for empty silos considering wind loads are presented and the use of wind-rings are verified. Empty silos are examined by the finite elements method considering lateral rigidity of the lateral sheet.
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Análise estrutural das colunas de sustentação de um silo metálicoTriches, Fabio Junior January 2011 (has links)
Silos metálicos para armazenagem de diferentes tipos de produto são muito empregados no Brasil, isso faz com que compreender melhor o funcionamento deste tipo de sistemas estrutural possa levar a soluções mais inteligentes e econômicas. Com esse intuito no presente trabalho estudam-se as colunas de sustentação de um tipo de silo metálico para armazenagem de ração animal. Neste estudo as colunas foram analisadas seguindo as determinações da norma brasileira de dimensionamento de perfis conformados a frio e com modelos numéricos de diferentes níveis de complexidade. Primeiramente se estudou o perfil conformado a frio utilizado nas colunas dos silos através do método das faixas finitas e obtiveram-se as forças axiais de flambagem local e distorcional elástica. Estes valores foram utilizados no método da resistência direta para obtenção dos índices de esbeltez associados a estes modos de flambagem. Foram definidas as forças axiais de colapso, seguindo as metodologias da norma ABNT NBR 14762:2010 (método das larguras efetivas, seção efetiva e resistência direta) para diversos comprimentos do perfil. Foi desenvolvido um modelo numérico para cálculo via método dos elementos finitos, considerando não linearidades materiais e geométricas e imperfeições geométricas iniciais. Os resultados obtidos através deste modelo numérico foram comparados com os obtidos através da norma ABNT NBR 14762:2010. Após ajuste do modelo numérico se realizou um estudo paramétrico para conhecer a influência da rigidez de fixação, entre a coluna de sustentação e o corpo silo, na força de colapso do perfil. São aplicadas diversas condições de contorno com o objetivo de aproximar o modelo numérico das condições reais de fixação da coluna. Finalmente os resultados obtidos são utilizados para determinar a relação entre a força resistente do perfil e a força solicitante na coluna do silo segundo as condições usuais de segurança referentes aos estados-limites últimos determinados pela ABNT NBR 14762:2010. / Tubular steel silos for storage of different product types are widely used in Brazil. The knowledge of these structural systems can result to smarter and economic solutions. In this work is studied the structural columns of some bulk feed tanks with the national standard design code and numeric models with several complexity level. First were studied the cold-formed steel member used in the silo’s columns with the finite strip methods, and were obtained the elastic local/distorcional buckling axial forces. These values were used with the Direct Strength Method to find out slenderness ratios associated with these modes of buckling. The axial collapse forces were defined following the conception of standard ABNT NBR 14762:2010(using the methods of effective width, effective section and direct resistance) for several members’ lengths. A numeric model was development to calculate with finite elements method, considering materials and geometrics nonlinearities with initial geometric imperfections. The results obtained by this numeric model were compared with those obtained by the standard ABNT NBR 14762:2010. After the numeric model adjust, a parametric study was made to know the influences of the connection stiffness between the column and the silo’s cylindrical wall, in the member’s allowable axial strength. Several boundary conditions were applied with the main purpose to approximate the numeric model with the actual columns' end conditions. Finally the obtained results were used to determine the ration between the axial allowable strength and the required load on the silo’s columns by the usual safety conditions using the ultimate limit state determined by the ABNT NBR 14762:2010.
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Análise estrutural das colunas de sustentação de um silo metálicoTriches, Fabio Junior January 2011 (has links)
Silos metálicos para armazenagem de diferentes tipos de produto são muito empregados no Brasil, isso faz com que compreender melhor o funcionamento deste tipo de sistemas estrutural possa levar a soluções mais inteligentes e econômicas. Com esse intuito no presente trabalho estudam-se as colunas de sustentação de um tipo de silo metálico para armazenagem de ração animal. Neste estudo as colunas foram analisadas seguindo as determinações da norma brasileira de dimensionamento de perfis conformados a frio e com modelos numéricos de diferentes níveis de complexidade. Primeiramente se estudou o perfil conformado a frio utilizado nas colunas dos silos através do método das faixas finitas e obtiveram-se as forças axiais de flambagem local e distorcional elástica. Estes valores foram utilizados no método da resistência direta para obtenção dos índices de esbeltez associados a estes modos de flambagem. Foram definidas as forças axiais de colapso, seguindo as metodologias da norma ABNT NBR 14762:2010 (método das larguras efetivas, seção efetiva e resistência direta) para diversos comprimentos do perfil. Foi desenvolvido um modelo numérico para cálculo via método dos elementos finitos, considerando não linearidades materiais e geométricas e imperfeições geométricas iniciais. Os resultados obtidos através deste modelo numérico foram comparados com os obtidos através da norma ABNT NBR 14762:2010. Após ajuste do modelo numérico se realizou um estudo paramétrico para conhecer a influência da rigidez de fixação, entre a coluna de sustentação e o corpo silo, na força de colapso do perfil. São aplicadas diversas condições de contorno com o objetivo de aproximar o modelo numérico das condições reais de fixação da coluna. Finalmente os resultados obtidos são utilizados para determinar a relação entre a força resistente do perfil e a força solicitante na coluna do silo segundo as condições usuais de segurança referentes aos estados-limites últimos determinados pela ABNT NBR 14762:2010. / Tubular steel silos for storage of different product types are widely used in Brazil. The knowledge of these structural systems can result to smarter and economic solutions. In this work is studied the structural columns of some bulk feed tanks with the national standard design code and numeric models with several complexity level. First were studied the cold-formed steel member used in the silo’s columns with the finite strip methods, and were obtained the elastic local/distorcional buckling axial forces. These values were used with the Direct Strength Method to find out slenderness ratios associated with these modes of buckling. The axial collapse forces were defined following the conception of standard ABNT NBR 14762:2010(using the methods of effective width, effective section and direct resistance) for several members’ lengths. A numeric model was development to calculate with finite elements method, considering materials and geometrics nonlinearities with initial geometric imperfections. The results obtained by this numeric model were compared with those obtained by the standard ABNT NBR 14762:2010. After the numeric model adjust, a parametric study was made to know the influences of the connection stiffness between the column and the silo’s cylindrical wall, in the member’s allowable axial strength. Several boundary conditions were applied with the main purpose to approximate the numeric model with the actual columns' end conditions. Finally the obtained results were used to determine the ration between the axial allowable strength and the required load on the silo’s columns by the usual safety conditions using the ultimate limit state determined by the ABNT NBR 14762:2010.
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