1,720,956 research outputs found
Estudo de lajes lisas de concreto com visão integrada de flexão e punção
Get PDFTese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Civil, Florianópolis, 2016.Muitas vezes, a verificação da punção é feita sem uma análise adequada do modelo usado para a verificação da flexão da laje. Uma vez que a normalização usa esforços normais e momentos fletores que atuam no pilar, e esses esforços são decorrentes da análise estrutural, uma visão integrada é essencial para a verificação da punção. O objetivo deste trabalho é estudar, com um enfoque voltado para projeto, os esforços e as tensões solicitantes em lajes lisas de concreto armado, obtidos por diferentes métodos de análise e modelagens de pilar, analisando suas variabilidades e efeitos na verificação da punção. São revistos os métodos de análise de lajes lisas mais difundidos, incluindo diferentes métodos dos pórticos equivalentes. Para os métodos numéricos, são exploradas diversas maneiras de modelar o pilar para solucionar o problema da singularidade que ocorre ao representar o pilar como apoio pontual diretamente na laje. É apresentada uma revisão de pesquisas que tratam da punção, de modo a explicitar o alheamento destas em relação à visão integrada de flexão e punção. A análise dos resultados é dividida em duas abordagens: a primeira estuda a variabilidade dos resultados dos modelos de flexão que são aplicados na verificação da punção pela NBR 6118/14; a segunda estuda as tensões de cisalhamento no perímetro crítico c' da norma brasileira, obtidas de modelos numéricos. Na primeira abordagem, as variabilidades das forças de reação do pilar resultaram pequenas, independente do modelo de análise, enquanto que os momentos desbalanceados apresentaram coeficientes de variação muito elevados. Nas análises pela segunda abordagem, as tensões de cisalhamento no perímetro de controle c' do modelo numérico se mostraram bastante sensíveis à modelagem do pilar e ao refinamento da malha. As variabilidades dos esforços e das tensões no perímetro c' foram adaptadas na forma de variáveis aleatórias de incerteza de modelo, que foram usadas em estudos simplificados de confiabilidade.Abstract : Punching shear design is often made without a proper analysis of the model used for the slab bending design. Since codes use normal forces and tranferred bending moments to the column, and these forces are obtained from a structural analysis, an integrated approach is essential for checking the punching shear. The objective of this thesis is to study, with a focused approach to design, the forces and stresses in reinforced concrete flat slabs, obtained by different analysis methods and models, analyzing their variability effects on the punching shear verification. The most widespread flat slab analysis methods are visited, including different equivalent frame methods. For the numerical methods, various ways to model the column to solve the problem of the singularity that occurs when representing the column supported directly on the slab are explored. A review on the punching shear is presented, in order to explain the alienation of those in relation to the integrated view of bending and punching. The analysis is divided into two approaches: the first one studies the variability of the results of bending models that are applied to the punching shear check by the NBR 6118/14; the second approach studies the shear stresses in the critical perimeter c' of the Brazilian code, obtained from numerical models. In the first approach, the variability of the reaction forces are minor, regardless the analysis model, while the unbalanced moments presented very high coefficients of variation. In the second approach, shear stresses on the perimeter control c' of the numerical model proved to be quite sensitive to the column modeling and of the mesh size. Variabilities of forces and stresses on the perimeter c' were adapted in the form of model uncertainty, which were used in simplified reliability studies
Análise comparativa de normas para a punção em lajes de concreto armado
Get PDFDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Civil, Florianópolis, 2010Os sistemas estruturais usados em pavimentos de concreto armado, em que as lajes se apóiam diretamente sobre os pilares, sem o uso de vigas, têm, entre suas características, a existência de tensões concentradas elevadas nas ligações laje-pilar, tensões estas que podem até levar à ruína. A esse efeito dá-se o nome de punção. Como a ruptura das ligações por punção é do tipo frágil, sem aviso, é extremamente importante que seja feita a verificação da resistência da ligação. As crescentes inovações técnicas e a análise dos critérios normativos propostos pelo ACI 318/08, BS 8110/97, NBR 6118/03 e EUROCODE 2/04 para o dimensionamento ao esforço de punção em lajes lisas de concreto armado são as diretrizes da elaboração do presente estudo. Dentro deste cenário, o objetivo desta dissertação é avaliar a acessibilidade, aplicabilidade, limitações e economia destes critérios por meio da comparação de resultados obtidos na análise de pilares internos em três configurações diferentes de lajes, variando suas espessuras. Foram analisados os seguintes parâmetros: a) para laje sem armadura de punção, compararam-se as relações entre tensões resistentes e solicitantes; as máximas reações que podem ser aplicadas à laje; a proporcionalidade do efeito dos momentos em relação a uma carga simétrica; excentricidades médias em relação às reações máximas suportadas pela Norma Britânica e um coeficiente estipulado para simular o efeito dos momentos fletores supondo-se uma carga de reação simétrica. B) para lajes com armadura de punção, compararam-se as relações entre tensões resistentes e solicitantes e o consumo de armadura de punção necessária segundo as recomendações de cada norma.The structural systems in reinforced concrete, where the slab is directly supported by the columns, without the use of beams, has, among its aspects, the existence of great tensions distributed in small areas, which can lead the structure to collapse. This effect is called punching shear. As the punching shear collapse occurs without warning, it is of extreme importance that the slab-column resistance verification is made. The increasing technical innovations and analysis of normative criteria proposed by ACI 318/08, BS 8110/97, NBR 6118/03 and EUROCODE 2 / 04 for punching analysis in flat slabs of reinforced concrete are the guidelines of this study. In this scenario, the main objective of this work is to evaluate these punching shear design procedures in terms of accessibility, applicability, limitations and economy, comparing the results obtained on analysis of a internal column in three different slabs configurations, varying their thicknesses. The following parameters had been analyzed and compared, as the recommendations of each code: a) for slabs without links, the relation between the resisted and applied tension, the maximum actions that can be applied, the representativeness of the unbalanced moment to the load reaction, and a increase coefficient to consider the effects of unbalanced moments; b) for slabs with links, the relation between resisted and applied tension and the armor consumption necessary to resist the loads for each case had been compared, according the recommendations of each code
Atividades desenvolvidas na Semana Nacional de Ciência e Tecnologia de 2017: Exposições e Oficinas relacionadas à área de Estruturas dos cursos de Edificações e Engenharia Civil
Get PDFA Semana Nacional de Ciência e Tecnologia do ano de 2017 foi um grande momento de apresentar a comunidade interna e externa ao IFSC todo o potencial na área de estruturas trabalhado nos cursos técnico e de graduação do DACC.Com o objetivo de aproximar o público dessa área que tantas vezes a repele, foram criados espaços para manipulação de game estrutural, manuseio de simuladores de estabilidade dos elementos estruturais e concurso para identificar a ponte de palitos mais resistente.DOI: http://dx.doi.org/10.35700/ca.2018.ano5n9.p59-63.245
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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