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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.
71

Liggingsanalise van graansilo's met rekenaarkartografiese metodes

Erasmus, Pieter Francois 25 September 2014 (has links)
M.Phil. (Geography) / Please refer to full text to view abstract
72

Dejstva uskladištenog zrnastog materijala na armiranobetonske cilindrične ćelije silosa / Аctions of a stored granular material on reinforced concrete cylindrical silo cells

Tatomirović Milorad 28 April 2015 (has links)
<p>U radu se analiziraju analitički postupci za određivanje<br />opterećenja u silosima, prema teorijskim postupcima i<br />tehničkoj regulativi. Metoda integralnih relacija je<br />primenjena kod formiranja postupaka analize stanja napona u<br />silosima sa pravougaonim ćelijama i silosa sa kružnim<br />ćelijama. U analizama je uvedeno granično stanje ravnoteže i<br />asimptotsko stanje napona materijala u silosu. Na primerima<br />je dato upoređenje rezultata analize stanja napona u silosima,<br />kao i kod analize statičkih uticaja kod kružnih ćelija od<br />dejstva dodatnog lokalnog opterećenja i nesimetričnog<br />opterećenja pri pražnjenju sa velikim ekscentricitetom.</p> / <p>This paper analyzes the analytical procedures for the determination of<br />loads in silos, according to theoretical procedures and technical<br />regulations. The method of integral relations was applied for the<br />establishment of procedures for analyzing the stress state in silos with<br />rectangular cells and silos with circular cells. The analysis is<br />introduced limit state of equilibrium and asymptotic stress state of the<br />material in the silo. The examples given comparison of the results of<br />the analysis of stress state in silos, as well as in the analysis of static<br />forces of circular cells from the effects of patch load and discharge<br />loads for circular silos with large outlet eccentricities.</p>
73

Alternativas estruturais em paredes de concreto prémoldado de silos horizontais

Rasi, José Roberto 10 April 2014 (has links)
Made available in DSpace on 2016-06-02T20:09:21Z (GMT). No. of bitstreams: 1 6217.pdf: 9751021 bytes, checksum: f4e903592a5f282dc704b60ca3b66462 (MD5) Previous issue date: 2014-04-10 / This paper aims to present studies of various structural alternatives for precast concrete walls for horizontal silos considering the implementation of actions caused by the earth pressure of the stored products. The Horizontal pressure was determined by the GOMES (2000) model. Determining the displacements and the bending moment through the finite element method, manufacturing costs and presents the results of each panel type studied and compares the results obtained. Six types of panels with the same concrete volume: flat panel bi-supported, panel with exposed edges beans bi-supported, and panel TT bi-supported, flat panel bi-supported and supported by floor, panel with exposed edges beans bi-supported and supported by floor and panel TT bi-supported and supported by floor. These panels were considered initially as vertical slabs with horizontal load subjected to two conditions of support: simply supported on two pillars precast reinforced concrete and simply supported on two pillars precast reinforced concrete floor and the horizontal silo through embed hardware. The concrete columns and floors were admitted no displacement. The studies conducted in this work indicate that the panel bi-supported had the highest simply supported had the biggest displacement. The panel with exposed edges beans bi-supported and supported by floor was the alternative structure which had the lowest maximum displacement and the flat panel simply supported and supported by floor was the lower cost alternative manufacturing. The flat panel bi-supported presented excessive displacement in the higher loading. / Este trabalho tem como objetivo apresentar estudos de varias alternativas estruturais para paredes em painéis pré-moldados de concreto para silos horizontais, considerando a aplicação de ações causadas pelo empuxo dos produtos armazenados. As pressões horizontais causadas pelo empuxo dos produtos armazenados foram determinadas pelo método proposto por GOMES (2000). Determina os momentos fletores e os deslocamentos através do Método dos Elementos Finitos, os custos de fabricação e apresenta os resultados de cada tipo de painel estudado e compara os resultados obtidos. Foram estudados seis painéis pré-moldados com o mesmo volume de concreto: painel liso bi-apoiado, painel com vigas nas bordas bi-apoiado, painel TT bi-apoiado, painel liso bi-apoiado engastado no piso, painel com vigas nas bordas bi-apoiado e engastado no piso e painel TT bi-apoiado e engastado no piso. Estes painéis foram considerados inicialmente como lajes verticais com carregamento horizontal submetido a duas condições de apoios: simplesmente apoiado em dois pilares pré-moldados em concreto armado e simplesmente apoiados nos dois pilares pré-moldados em concreto armado e com restrição horizontal, através de ferragem de engaste junto ao piso. Os pilares de concreto armado e o piso foram admitidos como indeslocáveis. Os estudos realizados neste trabalho indicaram que o painel simplesmente apoiado apresentou o maior deslocamento de todos os painéis. O painel com vigas nas bordas apoiado nos pilares e engastado no piso foi a alternativa estrutural que teve o menor deslocamento máximo e o painel liso simplesmente apoiado e engastado no piso foi a alternativa de menor custo de fabricação. O painel liso bi-apoiado apresentou deslocamento excessivo na zona de maior carregamento.
74

Modelling of failures in thin-walled metal silos under eccentric discharge

Sadowski, Adam Jan January 2010 (has links)
Eccentric discharge of granular solids is widely considered one of the most serious design conditions for thin-walled metal silos, and one which has been the cause of very many silo disasters in the past. Yet the reasons for these consequences have not been very well understood, given the serious difficulties inherent in measuring or modelling flow patterns of granular solids, wall pressures and the associated structural response. To this end, this thesis presents a programme of theoretical and computational analyses which investigate the effects of a very wide range of different discharge flow patterns from silos, including both concentric and eccentric flows. The critical effects of changes of flow channel geometry, silo aspect ratio, changes of plate thickness and geometric and material nonlinearity are explored in detail. The codified procedures and pressure distributions for concentric and eccentric discharge of the EN 1991-4 (2007) European Standard are analysed first on a number of example silos custom-designed according to EN 1993-1-6 (2007) and EN 1993-4-1 (2007), followed by the development and investigation of a more complete mixed flow pressure theory. The computational analyses presented in this thesis are thought to be the first of their kind.
75

Numerical investigation of granular flow and dynamic pressure in silos

Wang, Yin January 2012 (has links)
Although the flow of granular material in silos and the pressure acting on the silo walls have been studied for over a century, many challenges still remain in silo design. In particular, during the discharge process some dynamic phenomena in silos can often be observed to display large, self-induced and dynamic pulsations which may endanger the stability of the silo structure. The aim of this thesis is to study the flow and pressure in silos using numerical modelling and analytical methods, and to further understand the mechanical behaviour of granular material and mechanism of dynamic phenomena during silo discharge. The Finite Element (FE) method can be used to analyse the behaviour of the granular material in silos by considering the material as a continuum. In this thesis, FEM modelling of silo flow was developed using the Arbitrary Lagrangian-Eulerian (ALE) formulation in the Abaqus/Explicit program and the key parameters that affect the predictions of the flow and pressure during discharge were identified. Using the ALE technique, almost the entire silo discharge process can be simulated without mesh distortion problems. The mass flow rate and temporally averaged discharge pressure predicted by the FE model were first investigated in a conical hopper and were found to be in good agreement with those from the most commonly quoted theoretical solutions. The transient dynamic pressure fluctuations during incipient silo discharge were predicted and the causes for these dynamic events have been investigated which led to the conclusion that the stress wave propagation and the moving shear zone phenomena within the bulk solid were responsible for the dominant higher and lower frequencies effects respectively. A one-dimensional dynamic model of granular columns subject to Coulomb wall friction was developed to investigate the propagation of stress waves, focusing on the effect of geometry by examining converging and diverging tapered columns. The analytical solutions of this model are compared to the FE model based on the ALE formulation. This FE model was first validated using the known behaviour for cylindrical columns. In all cases, the stress impulse set off by incipient discharge at the silo outlet grew with the distance travelled up the column, however the rate was shown to depend on the halfangle of the taper. Over a range of small angles, the proposed analytical model was found to accurately predict this behaviour. After the successful application of the ALE technique for a conical hopper, the FE model was extended to simulate the granular flow in a flat-bottomed model silo. The FE predictions were compared with the silo pressure measurements in a model silo (Rotter et al, 2004). Pressure cells mounted along a vertical line on the silo walls were used to measure the pressure distribution in the silo tests using dry sand. The FE model was further extended to simulate the granular flow in a model silo consisting of a cylindrical section with a conical hopper. The prediction was compared with the experimental observations from a model silo (Munch-Andersen et al, 1992), together with the well-known theoretical solutions. Two numerical issues were addressed in some detail: one is the numerical treatment of the abrupt transition between the cylinder section and the conical hopper, the other is the interaction between the granular solid and the silo walls that was modelled using a dynamic friction model. In addition, the dynamic pressure events during discharge were examined and plausible explanations were given. Finally, this thesis deployed a non-coaxial elastoplastic constitutive model to explore the effect of non-coaxiality on silo phenomena. The non-coaxial FE modelling was performed on three problems: a simple shear test under various initial conditions, a steep hopper and a flat-bottomed silo. The results show that non-coaxiality did not influence the prediction of wall pressure during filling and storing, on the other hand, the discharge pressure was predicted to be larger when non-coaxiality is considered.
76

Diseño y comparación técnico-económica de silos de almacenamientos de ceniza y escoria, en hormigón armado y acero estructural, para centrales termoeléctricas de 300MW en Chile

Sepúlveda Solís, Néstor Samuel January 2015 (has links)
Ingeniero Civil / El problema a abordar en el presente trabajo de título es la elección del material de construcción óptimo para silos de almacenamiento de escoria y ceniza volante, para una central termoeléctrica de 350MW en Chile, considerando ambiente costero en la zona norte del país. Esto debido a que en la actualidad se utiliza acero estructural como práctica habitual en la construcción de estas estructuras y equipos, con montos importantes de inversión en suministro, construcción-montaje y mantención. El presente estudio considera realizar una evaluación comparativa de alternativas de suministro y construcción de estas estructuras en hormigón armado y acero estructural. Para esto, se presentan los diseños estructurales de estos silos con estos dos materiales, con un total de 4 silos diseñados con las capacidades necesarias para una Central PC (combustible pulverizado) de 350MW neto. El cálculo contempla estados de carga habituales en estas estructuras, como son peso propio, viento, temperatura, operación (material almacenado) y sismo, definidos por los criterios de diseño y la normativa chilena vigente. Esta memoria entrega una comparación de costos de suministro y construcción, mantención, plazos y aspectos técnicos respecto a suministro local o importado de la ingeniería y construcción. Además, se realiza un análisis de sensibilidad de los costos de construcción con respecto a los precios unitarios principales de los materiales seleccionados, para finalmente elaborar una matriz comparativa de resultados. En los 4 silos de almacenamiento estudiados, la solución con estructura de hormigón armado resultó ser el material seleccionado, debido a menores costos de inversión. Del estudio comparativo de estructura de acero versus hormigón armado, para el caso de menor precio de acero y mayor precio de hormigón armado, resultó un ahorro en los costos de inversión de un 19%. Considerando precios promedio de los materiales, esta diferencia aumenta en un 46%, y alcanza un 58% al revertir el primer escenario de precios unitarios.
77

Silos metálicos

Leite, Luís Miguel de Oliveira January 2008 (has links)
Tese de mestrado integrado. Engenharia Civil (especialização em Estruturas). Faculdade de Engenharia. Universidade do Porto. 2008
78

Through Emmaus eyes art, liturgy, and monastic ideology at Santo Domingo de Silos /

Blaettler, James Raymond, January 1989 (has links)
Thesis (Ph. D.)--University of Chicago, Dept. of Art, June 1989. / Includes bibliographical references.
79

Comparación técnico económica de los encofrados deslizantes vs. encofrados trepantes: caso específico de dos silos concéntricos

Masías Lagos, Dwight Antonio, Solano Guisbert, Juan Carlos 2013 March 1919 (has links)
Tesis
80

Elementos pre-moldados para silos quadrados de concreto armado

Silva, Eduardo Teixeira da 27 April 1998 (has links)
Orientador: Wesley Jorge Freire / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agrícola / Made available in DSpace on 2018-07-23T20:22:55Z (GMT). No. of bitstreams: 1 Silva_EduardoTeixeirada_D.pdf: 6045404 bytes, checksum: 4d838f655d9b73e6858857fc3f9a3862 (MD5) Previous issue date: 1998 / Resumo: Este trabalho foi desenvolvido com o objetivo de fornecer subsídios técnicos para projetos de silos multicelulares em concreto armado, pré-moldados, com forma quadrada, com capacidade de 60t ou 1St de milho por célula, mais especificamente para atender a pequenos e médios produtores, como também contribuir para o desenvolvimento da futura norma brasileira para silos. Devido à complexidade de um projeto completo de silos multicelulares, este estudo limitou-se ao comportamento dos elementos que formam o corpo do silo. Apresenta-se uma breve revisão sobre a situação da cultura do milho, relatando se sua produção, consumo por atividade e estimativa de suprimento, e também sobre a infra-estrutura de armazenamento, analisando-se a capacidade estática armazenadora e sua distribuição pelo território nacional. As propriedades físicas do milho, utilizadas em projetos de fluxo e pressão em silos, foram determinadas em equipamento recomendado por normas internacionais para este fim, conhecido como Jenike Shear Cell. Apresentam-se recomendações técnicas e práticas para projetos e construção de silos de concreto armado, dimensionamento, dimensões mínimas recomendadas, info mações a serem fornecidas ao projetista e ao usuário. Foram feitas análises teóricas e experimentais em dois modelos de elementos a fim de avaliar o compo_amento estrutural dos elementos isolados e encaixados, em escala natural, que formam as paredes de silos quadrados, modulares. Com base nas análises experimentais realizadas, conclui-se que o modelo utilizado com encaixe entre dois elementos (tipo macho-fêmea) comportou-se de maneira positiva, conferindo maior rigidez à região entre elementos. As tensões calculadas pelo método simplificado RA VENET (1992) e pela teoria de vigas bi-articuladas subestimam as tensões experimentais para os elementos de 1,5 e 2.0m de vão onde observou-se o aparecimento de fissuras no elemento. As tensões medidas em dois elementos encaixados, tanto para o elemento de 1,5m como para o de 2,Om de vão, apresentam comportamento similar entre os pontos de medições durante a fase de carregamento do elemento. Com base nas análises teóricas e experimentais conclui-se que os deslocamentos medidos apresentam comportamento similar aos deslocamentos calculados pela flecha máxima e flecha no meio do vão; para o caso do elemento de 1,5m e também para o elemento de 2,Om de vão os deslocamentos calculados foram superiores aos deslocamentos medidos / Abstract: This research work was developed to provide technical information for designing multicells reinforced concrete preformed silos, in square shape and 15 tons to 60 tons com capacity per cell, aiming small and medium agricultural producers and for the development of a brasilian standard for silo lately. Due to the complexity of a complet design of a multicell silo, this study was interestood in the behavior of the elements that compose the silo.A brief revision of com cultures situation is presented, relating, its production, consume per activity, supplying prediction, and the storage structure, evaluating its static storage capacity and the national distribution. The com physical properties applyed in flow and stress in silos designs were determined by the Jenike shear cell, equipment recomended by the intenational standard. Theoretical and experimental analysis were conducted by applying two models to evaluate the structural behavior of a real scale separeted element and coupled element which form the square wall of the modular silo. From the experimental analysis it was conc1uded that the two coupled elements models presented a satisfactory behavior where the most tough place was located on the link spot. _The stress values obtained from the RA VENET' s method (1992) and from the bi-articulable beam theory were lower than the values experimentally obtained for a 1.5 m shaft and for a 2.0 m shaft for which some fissures appeared on the elemento The values of stress measured in two coupled elements either for the 1.5 m or the 2.0 m shaft, presented similar behavior during the loading processo Based on the theorical and experimental analysis it was observed that the measured displacement exhibited similar behavior to the calculated displacement by applying the maximum inflection method and half shaft inflection method, however, for both, the 1.5 m and 2.0 m shaft the displacement values calculated were greater than the measured values / Doutorado / Doutor em Engenharia Agrícola

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