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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.
1

Estudo do comportamento dinâmico de edifícios mistos (aço-concreto) submetidos à ação não determinística do vento. / Study of the dynamic behavior of steel-concrete buildings subjected to wind action non-deterministic.

Genival da Silva Filho 22 November 2012 (has links)
Fundação Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Considerando-se um cenário econômico bastante favorável em conjunto com avanços tecnológicos da ciência dos materiais e processos construtivos, nos últimos trinta anos, as cidades brasileiras têm apresentado um crescimento substancial, no que diz respeito à construção de edifícios residenciais e comerciais de múltiplos andares. Nos dias de hoje, estes edifícios apresentam níveis de esbeltez elevados e têm sido construídos com estruturas cada vez mais arrojadas englobando a experiência e o conhecimento dos engenheiros civis. Deste modo, o principal objetivo dos projetistas está associado à concepção de estruturas mais leves, nas quais o projeto estrutural requer um conhecimento teórico substancial, objetivando tornar compatíveis os requisitos arquitetônicos com as condições necessárias para a estabilidade. Assim sendo, o objetivo deste trabalho de pesquisa é o de investigar o comportamento estrutural estático e dinâmico de um edifício misto (aço-concreto) de 20 pavimentos quando submetido às ações dinâmicas do vento não determinísticas. Deste modo, no desenvolvimento do modelo computacional são empregadas técnicas usuais de discretização, via método dos elementos finitos, por meio do programa ANSYS. Para tal, o estudo apresenta os resultados de uma análise não linear geométrica para ações de serviço. A resposta dinâmica não determinística do modelo estrutural investigado, em termos dos valores máximos médios dos deslocamentos e das acelerações, foi obtida e comparada com os valores limites propostos por normas e recomendações de projeto. / Considering the favourable economic scenario and technological advances of material sciences and construction processes, in the last thirty years, the Brazilian cities have presented a substantial growth, with respect to construction of residential and commercial multi-storey buildings. Nowadays, these buildings present greater slenderness and have been constructed with more challenging structures that encompass the experience and knowledge of structural designers by using newly developed materials and technologies boosted by the ever-growing investigations on this field. As the structural designer main objective is related to produce increasingly lighter structures its conception requires a substantial amount of theoretical knowledge associated to structural design and construction processes, in order to make compatible the requirements of architecture with the necessary conditions for stability. This way, this research work aims to investigate the static and dynamic structural behaviour of a 20 story steel-concrete composite building, when submitted to the non-deterministic wind dynamic actions. The developed computational model adopted the usual mesh refinement techniques present in finite element method simulations implemented in the ANSYS program. The present study has considered the results of a geometric nonlinear analysis for serviceability limit states. The investigated structural model non-deterministic dynamic response, in terms of displacements and peak accelerations, was obtained and compared to the limiting values proposed by several authors and design standards.
2

Estudo do comportamento dinâmico de edifícios mistos (aço-concreto) submetidos à ação não determinística do vento. / Study of the dynamic behavior of steel-concrete buildings subjected to wind action non-deterministic.

Genival da Silva Filho 22 November 2012 (has links)
Fundação Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Considerando-se um cenário econômico bastante favorável em conjunto com avanços tecnológicos da ciência dos materiais e processos construtivos, nos últimos trinta anos, as cidades brasileiras têm apresentado um crescimento substancial, no que diz respeito à construção de edifícios residenciais e comerciais de múltiplos andares. Nos dias de hoje, estes edifícios apresentam níveis de esbeltez elevados e têm sido construídos com estruturas cada vez mais arrojadas englobando a experiência e o conhecimento dos engenheiros civis. Deste modo, o principal objetivo dos projetistas está associado à concepção de estruturas mais leves, nas quais o projeto estrutural requer um conhecimento teórico substancial, objetivando tornar compatíveis os requisitos arquitetônicos com as condições necessárias para a estabilidade. Assim sendo, o objetivo deste trabalho de pesquisa é o de investigar o comportamento estrutural estático e dinâmico de um edifício misto (aço-concreto) de 20 pavimentos quando submetido às ações dinâmicas do vento não determinísticas. Deste modo, no desenvolvimento do modelo computacional são empregadas técnicas usuais de discretização, via método dos elementos finitos, por meio do programa ANSYS. Para tal, o estudo apresenta os resultados de uma análise não linear geométrica para ações de serviço. A resposta dinâmica não determinística do modelo estrutural investigado, em termos dos valores máximos médios dos deslocamentos e das acelerações, foi obtida e comparada com os valores limites propostos por normas e recomendações de projeto. / Considering the favourable economic scenario and technological advances of material sciences and construction processes, in the last thirty years, the Brazilian cities have presented a substantial growth, with respect to construction of residential and commercial multi-storey buildings. Nowadays, these buildings present greater slenderness and have been constructed with more challenging structures that encompass the experience and knowledge of structural designers by using newly developed materials and technologies boosted by the ever-growing investigations on this field. As the structural designer main objective is related to produce increasingly lighter structures its conception requires a substantial amount of theoretical knowledge associated to structural design and construction processes, in order to make compatible the requirements of architecture with the necessary conditions for stability. This way, this research work aims to investigate the static and dynamic structural behaviour of a 20 story steel-concrete composite building, when submitted to the non-deterministic wind dynamic actions. The developed computational model adopted the usual mesh refinement techniques present in finite element method simulations implemented in the ANSYS program. The present study has considered the results of a geometric nonlinear analysis for serviceability limit states. The investigated structural model non-deterministic dynamic response, in terms of displacements and peak accelerations, was obtained and compared to the limiting values proposed by several authors and design standards.
3

Viabilidade econômica de sistemas de produção de ciclo completo de bovinos de corte / Economic viability of production systems in full cycle of beef cattle

Ávila, Mozer Manetti de 11 February 2015 (has links)
Conselho Nacional de Desenvolvimento Científico e Tecnológico / Currently there is a constant pressure on producers of beef cattle, fruit of the need of the markets, which became increasingly stringent, remunerating better for animals better finished and in earlier ages. To this end, producers end up having to seek the viability of the system through different production alternatives. Therefore, are shown as alternatives productive cycles of one or two years, aiming at reduce the time of finishing of the males or reduction in the age of first pregnancy of the females through the intensification of the production. This study aimed to evaluate the economic viability of four distinct systems of full cycle in beef cattle. The experiment was conducted at Animal Science Department of the Federal University of Santa Maria, from March 2013 to July 2014. Were considered four productive systems: system one year with animals finished on pasture (1P), or finished in feedlot (1C), and systems two years with animals finished in pasture (2P) or finished in feedlot (2C). The zootechnical data were obtained via meta-analysis. The prices of costs and income were obtained from historical data practiced in state of Rio Grande do Sul. The deterministic economic analysis was performed via economic indicators. According to economic indicators, the only system that become feasible at the end of the planning horizon was the system in two years finished in pasture, where others did not report results as feasible investment project. The largest cost centers were depreciation, feeding supply and taxes. The economic indicators presented themselves as attractive alternatives for the measurement of the economic viability of investment projects in beef cattle at short and long term. / Atualmente ocorre uma constante pressão sobre os produtores de bovinos de corte, fruto da necessidade dos mercados que apresentam-se cada vez mais exigentes, remunerando melhor por animais com melhor acabamento e idade mais precoce. Para tanto, os produtores acabam tendo que buscar a viabilidade de seu sistema através de diferentes alternativas de produção. Sendo assim, apresentam-se como alternativas os sistemas produtivos de ciclos de um ou dois anos, que visam diminuir o tempo de terminação dos machos ou a diminuição na idade de entoure das fêmeas através da intensificação de produção. Este trabalho objetivou avaliar a viabilidade econômica de quatro sistemas distintos de ciclo completo de bovinos de corte. O experimento foi desenvolvido no Departamento de Zootecnia da Universidade Federal de Santa Maria, no período de março de 2013 a julho de 2014. Foram considerados quatro sistemas de produção: Sistema de um ano com animais terminados em pastagens (1P) ou terminados em confinamento (1C) e sistema dois anos com animais terminados em pastagens (2P) ou terminados em confinamento (2C). Os dados zootécnicos foram obtidos via metanálise. As cotações dos itens de custos e receitas foram obtidas de dados históricos praticados no estado do Rio Grande do Sul. A análise econômica determinística foi realizada via indicadores financeiros. Segundo os indicadores econômicos, o único sistema que apresentou-se viável ao final do horizonte de planejamento foi o sistema dois anos em pastagem, onde os demais apresentaram resultados não viáveis como projeto de investimento. Os maiores centros de custos foram com depreciação, alimentação e impostos. Os indicadores econômicos apresentaram-se como alternativas interessantes para a mensuração da viabilidade econômica dos projetos de investimento em bovinocultura de corte á curto e longo prazos.
4

Evaluation of structurally controlled rockfall hazard for underground excavations in seismically active areas of the Kiirunavaara mine

Fuentes Espinoza, Manuel Alberto January 2023 (has links)
Sublevel caving operations at great depths are subjected both to large stress concentrations that are redistributed as the mining front progresses and to mining-induced seismicity. This is the case for Kiirunavaara mine, Sweden’s largest underground mine. Since the mine was declared seismically active in 2007 / 2008, large rockfalls controlled by structures have happened in many parts of the mine, despite the use of rock support systems designed for bearing dynamic loads. A novel layout for sublevel caving operations, internally named “fork layout” is being tested at a satellite mine. This layout was conceived to place the ore-parallel longitudinal footwall drifts further away from the contact between the orebody and footwall drifts. That way, the differential stresses that generate stress-related damages are expected to be reduced. However, the effect of implementing the fork layout on the hazard potential for structurally controlled rockfalls has not been studied in detail yet. Large rockfalls that occurred in different parts of the mine were analysed with respect to their structures, location of the damage event and type of excavation. The majority of these occurred at footwall drift intersections. Information from damage mapping and seismic events that triggered these rockfalls was used to generate a conceptual model that illustrates the relative spatial relation between the seismic source and damage location. In addition, the seismic source parameters of the events that triggered these rockfalls were processed using scaling laws to obtain ground motion parameters such as peak particle velocity and acceleration at the damage site. The effect of implementing the fork layout on rockfall hazard was tested in the intersections between footwall drifts and crosscuts (FD-CC), and intersections between access and footwall drifts (AD-FD) in two production blocks, using the traditional layout for sublevel caving mining as a point of comparison. Two different fork layouts were tested, FD-CC at 80° (or AD-FD at 100°) and FD-CC at 70° (or AD-FD at 110°). Structural data available from face mapping and oriented core logging was used to define predominant joint sets at the investigated blocks. Using the structural input, wedge volumes at the intersections were modelled deterministically and probabilistically in Unwedge. The variations in wedge volumes formed at the intersections between layouts were used as a proxy for rockfall potential, meaning that if a layout reduced the wedge size, the smaller the rockfall hazard if triggered by a seismic event, and vice versa. It was concluded that most rockfalls at the FD-CC intersections are controlled by structures from three major joint sets. It was observed that rockfalls at FD-CC intersections occurred more often at certain footwall drift orientations. Many seismic events that triggered these rockfalls are located close to the ore passes and generated ground accelerations between 0.5 to 10 times the gravity acceleration. Implementing fork layouts with FD-CC at 80° intersection angle generates larger wedges than the traditional layout and thus, scenarios with a higher rockfall hazard. On the other hand, using fork layouts with FD-CC at 70° intersection angle reduces wedge size at the southern FD-CC intersections; hence, the rockfall hazard is reduced in these intersections. In the northern FD-CC intersections, the wedge volumes are increased and thus, a higher rockfall potential is generated in these intersections. AD-FD at 110° intersection angle generates also a smaller rockfall hazard than the traditional layout in both production blocks.

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