• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 50
  • 43
  • 10
  • 10
  • 9
  • 4
  • 2
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 155
  • 28
  • 19
  • 17
  • 17
  • 15
  • 15
  • 12
  • 12
  • 12
  • 11
  • 10
  • 9
  • 9
  • 9
  • 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

Performance of Deep Geothermal Energy Systems

Manikonda, Nikhil 29 August 2012 (has links)
Geothermal energy is an important source of clean and renewable energy. This project deals with the study of deep geothermal power plants for the generation of electricity. The design involves the extraction of heat from the Earth and its conversion into electricity. This is performed by allowing fluid deep into the Earth where it gets heated due to the surrounding rock. The fluid gets vaporized and returns to the surface in a heat pipe. Finally, the energy of the fluid is converted into electricity using turbine or organic rankine cycle (ORC). The main feature of the system is the employment of side channels to increase the amount of thermal energy extracted. A finite difference computer model is developed to solve the heat transport equation. The numerical model was employed to evaluate the performance of the design. The major goal was to optimize the output power as a function of parameters such as thermal diffusivity of the rock, depth of the main well, number and length of lateral channels. The sustainable lifetime of the system for a target output power of 2 MW has been calculated for deep geothermal systems with drilling depths of 8000 and 10000 meters, and a financial analysis has been performed to evaluate the economic feasibility of the system for a practical range of geothermal parameters. Results show promising an outlook for deep geothermal systems for practical applications.
72

Pitch direction perception and auditory global local processing in autism and typical development

Germain, Esther 08 1900 (has links)
Les personnes ayant un trouble du spectre autistique (TSA) présentent souvent une perception auditive atypique. Plusieurs études ont déjà mis en évidence une capacité hors norme, par exemple lorsqu’il s’agissait de discrimination élémentaire de stimuli auditifs (bas niveau) mais aussi à discerner la structure locale dans une tâche mélodique de niveau plus complexe (haut-niveau). Tout de même il n’est pas encore clarifié de quelle manière les niveaux hauts et bas de la perception auditive seraient liés, aussi bien en TSA qu’en développement typique (DT), ni si ce lien change avec l’âge et avec la rapidité de la présentation du stimulus. Dans l’étude présente 17 enfants avec TSA et 19 enfants DT appariés selon leur âge réel ont été testés avec une tâche auditive à bas-niveau et une tâche auditive mélodique à haut-niveau. Les deux groupes ont montré une performance similaire sur les deux tâches auditives. La performance sur la tâche à bas-niveau prédit par ailleurs fortement la performance sur la tâche à haut-niveau, et cet effet est plus prononcé dans le groupe TSA. Il n’y a pas eu d’effet principal d’âge sur la performance sur les deux tâches indépendantes, ni sur la relation entre la performance sur les deux tâches. Après avoir pris en compte la performance sur la tâche à bas-niveau, on distingue cependant un effet d’âge plus marqué dans le groupe DT que dans le groupe TSA concernant la tâche à haut-niveau. Finalement la rapidité de la présentation n’a pas d’effet sur la relation entre les performances sur les deux tâches dans les deux groupes. Ces résultats fournissent une meilleure compréhension de la façon dont les différents niveaux de la perception auditive sont associés chez les enfants DT comme chez les enfants affectés d’un TSA. Ils nous permettent par ailleurs de mieux appréhender les différences individuelles en perception auditive et d’affiner les phénotypes des TSA. / Individuals with Autism Spectrum Disorders (ASD) often present atypical auditory perception. Previous work has reported both enhanced low-level pitch discrimination and superior abilities to detect local pitch structure on high-level melodic tasks in ASD. However, it is unclear how low and high levels of auditory perception are related in ASD or typical development (TD), or how this relationship might change with development and rate of stimulus presentation. To these aims, in the present study, children with ASD and TD children matched in age were tested on a low-level pitch direction (PD) task and a high-level melodic task. Groups performed similarly on both pitch tasks. Moreover, lowlevel pitch direction ability predicted performance in high-level global-local (GL) pitch perception, but this relationship was stronger in ASD. Age did not affect the relationship between low-level and high-level pitch performance in either ASD or TD. However, there was a more positive effect of age on GL task performance in TD than ASD after accounting for the effect of low-level PD performance. Finally, there was no effect of stimulus rate upon the relationship between low-level and high-level pitch performance in either group. The present findings provide a better understanding of how perception is associated across levels in ASD versus TD. This work is key to better understanding individual differences in auditory perception and to refine ASD phenotypes.
73

Auditory pitch perception in autism spectrum disorder is associated with superior non-verbal abilities

Chowdhury, Rakhee 08 1900 (has links)
Le Trouble du Spectre Autistique (TSA) est souvent caractérisé par un profil auditif atypique et des atteintes au niveau du langage. Des études antérieures examinant la perception auditive simple et complexe dans les TSA et le développement typique présentent des conclusions mitigées quant à la nature des profils auditifs des deux groupes. De plus, des données contradictoires ont été rapportées en termes d’aptitudes cognitives chez les personnes atteintes de TSA. En conséquence, la relation qui existe entre la perception auditive et les habiletés verbales et non-verbales chez les TSA demeure mal comprise. En conséquence, cette étude cherche à mieux comprendre la relation entre le traitement du son et les aptitudes cognitives, en visant de comparer des enfants atteints de TSA à des enfants au développement typique. Dans la présente étude, les participants ont effectué une tâche auditive à bas-niveau et une tâche auditive mélodique à haut-niveau. Les capacités cognitives verbales et non-verbales ont été mesurées à l’aide des composantes du Wechsler Abbreviated Scale of Intelligence (WASI), un test de quotient intellectuel (QI). Les deux groupes ont obtenu des résultats similaires sur les deux tâches auditives ainsi que sur les mesures de QI. De plus, cette étude a démontré que les habiletés verbales ne permettent pas de prédire la performance sur la tâche auditive à bas-niveau ou sur la tâche auditive à haut-niveau dans les deux groupes. Cependant, les habiletés non-verbales semblent prédire une meilleure perception auditive sur les deux tâches auditives, et ce, pour les deux groupes. Ces résultats soulignent la présence d’habiletés auditives intactes dans un échantillon d’enfants atteints de TSA ayant un QI qui se situe dans la moyenne. De plus, l’étude actuelle met en évidence une relation entre la perception auditive et le raisonnement non-verbal, plutôt que le raisonnement verbal. Ainsi, les résultats de cette étude permettent d’approfondir la connaissance sur les différences individuelles qui existent dans la perception auditive auprès des personnes atteintes de TSA dans les contextes verbales et non-verbales, pour enfin contribuer à une meilleure caractérisation du phénotype du TSA. / Autism Spectrum Disorder (ASD) is often characterized by atypical sensory perception and cognitive profiles. However, previous studies have found mixed findings with regard to auditory processing in ASD. Discrepant findings have been reported in terms of cognitive abilities in ASD. Accordingly, auditory perception and its relation to verbal and non-verbal cognitive abilities in ASD remains poorly understood. The objective of the present research was to examine the association between auditory pitch processing and verbal and non-verbal cognitive abilities in children with ASD, compared with age- and IQ-matched typically developing (TD) children. Participants were 17 children with ASD and 19 TD children, matched on age and IQ. Participants were tested on performed a low-level pitch direction task and a higher-level melodic pitch global-local task. Verbal and non-verbal cognitive abilities were measured using the Verbal IQ and Performance IQ components of the Wechsler Abbreviated Scale of Intelligence (WASI). No group differences in performance were found on either auditory task or IQ measure. Furthermore, verbal abilities did not predict performance on the auditory tasks in either group. However, non-verbal abilities predicted performance on both of the auditory tasks in ASD and TD. This work contributes to a better understanding of sensory processing and cognitive reasoning in children with ASD and typically-developing children. Specifically, these results indicate that tonal pitch-based auditory processing is preserved in individuals with ASD with average IQ. These findings also suggest that auditory perception is related to non-verbal reasoning rather than verbal abilities in both ASD and TD, implying that there may be common perceptual-cognitive profiles in these subgroups of children with ASD that are similar to typical development. Accordingly, this work supports the idea that some individuals with ASD have ‘islets of ability’ amidst their sensory and cognitive difficulties. These results motivate future studies to examine whether similar perceptual-cognitive associations might be observed in a broader sample of individuals with ASD, such as those with language impairment or lower IQ.
74

Havarijní plánování v rámci Integrovaného záchranného systému se zaměřením na činnost policie České republiky / Emergency planning within the Integrated Rescue System with focus on the activities of Police of the Czech Republic

Sázavský, Jan January 2011 (has links)
Subject: Emergency planning within the Integrated Rescue Systém with focus on the activities of Police of the Czech Republic Objective: unify and define the legislation relating to the emergency planning with a focus on the service performance of the Czech Police and implement subsequently relevant legal standards into the tactical exercises "The Island 2011" in order to verify the practical set of principles, mechanisms with the possibilities of their evaluation based on real use. Method applied: research, classification and study of available sources, consultaion with the experts in the subject above, detailed analysis of the carried out exercises. Outcome: Based on the study of legislative norms indicating the framework of activities of individual components of Integrated Rescue Systém, consulting the respective variants of implementation of practical knowledge, as a result, the exercise was designed in order to verify the ability of the police management to manage and control the forces and resources during the performance of the police tasks and also to verify the practical ability of police Officers to perform set tasks and cooperate in the place of intervention with units and relevant agencies. Key words: Integrated Rescue Systém, crisis management, emergency planning, tipical aktivity,...
75

Metodologia para cálculo de perdas técnicas por segmento do sistema de distribuição. / Methodology for calculation of technical losses in each segment of the distibution system.

Méffe, André 08 May 2001 (has links)
Este trabalho tem por objetivo propor uma nova metodologia para o cálculo das perdas técnicas de energia e demanda por segmento do sistema de distribuição. As perdas técnicas foram divididas em oito segmentos: medidor de energia, ramal de ligação, rede secundária, transformador de distribuição, rede primária, subestação de distribuição, sistema de alta tensão e outros. Neste último segmento, foram incorporadas as parcelas referentes a equipamentos (capacitores, reguladores de tensão, etc), perdas em conexões, corrente de fuga em isoladores, etc. Desenvolveu-se um sistema computacional, para uso em microcomputador, que conta com dois módulos principais. O primeiro módulo destina-se ao cálculo das perdas técnicas em redes específicas. O cálculo é feito de forma hierárquica, por exemplo, selecionada uma subestação específica, são calculadas as perdas na subestação e em todos os componentes a jusante (redes primárias, transformadores de distribuição, redes secundárias, ramais de ligação e medidores de energia). As perdas técnicas, em termos de energia e demanda, são obtidas por meio de cálculo elétrico específico para os segmentos envolvidos, com a utilização dos dados cadastrais da rede, dados de faturamento e curvas de carga típicas por classe de consumidor e tipo de atividade desenvolvida. Com a aplicação deste módulo para todo o sistema da empresa, ou para uma parcela representativa, obtém-se um índice percentual de perda de energia para cada segmento. Estes índices são transferidos para o segundo módulo, que tem por objetivo efetuar o balanço de energia do sistema. A partir dos dados de energia nos pontos de suprimento, da energia total faturada mensalmente e dos índices de perdas por segmento, são obtidos os montantes de energia de perdas em cada segmento do sistema e uma avaliação das perdas não técnicas. O trabalho ainda apresenta um exemplo de aplicação, em sistema de distribuição real, mostrando os resultados obtidos, e termina apresentando as principais vantagens da metodologia. Os resultados obtidos com a nova metodologia são comparados com os resultados obtidos com outras metodologias. / This work focuses on the development of a new methodology for calculating technical losses within the different segments of the electric distribution system. In order to evaluate technical losses the electrical system was divided into eight segments: energy meter, customer connections, secondary feeder, distribution transformer, primary feeder, distribution substation, high voltage system and another segment that represents other technical losses. The latter comprises losses in equipment such as capacitors and voltage regulators as well as losses in electric connections, isolators, etc. A computational system was developed and it comprises two modules. The first one is intended to calculate technical losses in specific networks. The calculation is made in a hierarchical manner. If a distribution substation is selected for the calculation, the losses in that substation and the losses in all components downstream are calculated. The technical losses, in terms of energy and demand, are obtained by utilizing network topological data, consumed energy data and typical load curves per customer class and activity type. An energy losses index, calculated as a percentage of the supplied energy, is obtained for each segment by applying this module to the entire utility’s power system or in a representative part of it. These values are transferred to the second module, which has the objective of determining the overall energy balance. Technical and non-technical losses, in terms of energy, in each segment are obtained by utilizing the total amount of energy supplied to the system, energy consumed and energy losses indices per segment. This work shows the results obtained by applying the computational tool to a real distribution system. Such results are compared with the ones obtained by using other methodologies, and the main advan ages of this new methodology are outlined.
76

Influência dos propósitos epistêmicos e das ações típicas do professor na promoção da argumentação em aula investigativa de ciências / The influence of epistemic purposes and typical actions of the teacher to promote argumentation in inquiry science class.

Oliveira, Thiago Luis Silva de 25 November 2016 (has links)
A mediação do professor é fundamental para a construção de argumentos em aulas de Ciências. Nesse sentido torna-se importante estudar as interações discursivas entre professor e alunos. O presente trabalho teve por objetivo analisar como os propósitos e as ações do professor estimulam a argumentação dos alunos em uma aula investigativa de ciências. Para caracterizar a mediação do professor foi utilizada a ferramenta analítica \"propósitos epistêmicos e ações típicas para promoção da argumentação\" de Ferraz e Sasseron (2014) e de Ferraz (2015), enquanto que o layout de Toulmin (TAP) (2006) foi utilizado para identificar os elementos do argumento construídos pelos alunos. Foram identificados dois argumentos contendo os elementos básicos do TAP construídos coletivamente ao longo da aula. Durante a construção dos argumentos, o professor utilizou os propósitos retomar, problematizar, explorar e qualificar. As ações \"retoma dado\" e \"explora ponto de vista\" contribuíram para a construção do elemento dado. A construção da garantia deveu-se as ações \"retoma conceito\", \"retoma informações\", \"explora ponto de vista\" e \"qualifica variáveis, objetos ou fenômenos\". A construção do elemento conclusão foi promovida pela ação \"propõe um problema\". As ações \"qualifica variáveis, objetos ou fenômenos\", \"qualifica explicações ou pontos de vista\", \"retoma informações\" e \"explora ponto de vista\" auxiliaram na construção do elemento refutação do TAP. A maior frequência dos propósitos explorar e qualificar deveu-se ao esforço do professor em promover a avaliação de dados e garantias que os alunos estavam utilizando para a construção de suas conclusões sobre a presença ou não de seres vivos na amostra analisada. / The mediation of the teacher is fundamental for the construction of arguments in science class. Like this it is important to study the discursive interactions between teacher and students. This study aimed to analyze how the teacher\'s purposes and actions stimulate the reasoning of students in an inquiry science class. The analytical tool \"epistemic purpose and typical actions to promote the argumentation\" (FERRAZ; SASSERON, 2014; FERRAZ, 2015) was used to characterize the mediation of the teacher while the Toulmin Argument Pattern (TAP) (2006) was used to identify argument elements built by students. Two arguments containing the basic elements of TAP collectively built along class were identified. During the construction of the arguments, the teacher used the purpose resume, problematize, explore and qualify. The actions \"given recovery\" and \"explores view\" contributed to the construction of the data element. The construction of the warrants was due to the actions \"recovery concept\", \"recovery information\", \"explores points of view\" and \"qualifies variables, objects or phenomena\". The construction element conclusion was promoted by the action \"proposes the problem\". The actions \"qualifies variables, objects or phenomena\", \"qualifies explanations or points of view\", \"recovery information\" and \"explores perspective\" helped in the construction of refutation element of TAP. The highest frequency of the purposes explore and qualify was due to the teacher\'s effort to promote the evaluation of data and warrants that students were using to build its conclusions on the presence or absence of living organisms in the sample.
77

Os acordos de acionistas: uma abordagem comparativa entre os modelos típico e atípico

Abraão, Eduardo Lysias Maia 29 November 2007 (has links)
Made available in DSpace on 2016-04-26T20:26:12Z (GMT). No. of bitstreams: 1 Eduardo Lysias Maia Abraao.pdf: 414016 bytes, checksum: 1d35e6bbf0606c585bbfeb440b39ad28 (MD5) Previous issue date: 2007-11-29 / The present essay provides law practitioners with an opportunity to widely reflect about shareholders agreement in Brazil. It offers subsides that facilitate a better understanding of this institute, while it points out distinctions between nominated or typical and innominated or atypical models. It presents legal subsidies that contribute with the legal-technical analysis that tends to the solution of controversies related to the issue, especially controversies involving shareholders agreements whose purpose is innominated or atypical. It searches to establish the notion of formal and material elements that limit the shareholders agreement framework as typical and/or atypical, trying to differentiate them with the aim of giving them an appropriated legal treatment. It analyzes mixed shareholders agreements, taking into consideration their simultaneous typical and atypical nature, in which case it recommends the methodological segregation of the legal analysis of such agreements. Finally, it realizes that the regulation of certain shareholders agreements under the Brazilian law does not preclude the occurrence of atypical shareholders agreements, whose legal framework is not specific, but instead is based upon general legal guidelines, what implies in a distinct legal treatment thereof / A presente dissertação proporciona aos operadores do direito oportunidade de ampla reflexão sobre os acordos de acionistas no Brasil. Oferece subsídios que favorecem a melhor compreensão do instituto, ao tempo em que ressalta distinções entre os modelos nominado ou típico e inominado ou atípico. Apresenta subsídios jurídicos capazes de contribuir com a análise técnico-jurídica tendente à solução de controvérsias relacionadas ao tema, notadamente aquelas que envolvem acordos de acionistas cujo objeto seja inominado ou atípico. Busca precisar a noção dos elementos materiais e formais delimitadores do enquadramento dos acordos de acionistas como típico e/ou atípico, buscando distingui-los uns dos outros no intuito de conferir-lhes tratamento jurídico próprio. Considera a verificação de acordos de acionistas mistos, sob a ótica da sua natureza simultaneamente típica e atípica, hipótese em que recomenda a segregação metodológica da análise jurídica de tais acordos. Constata, enfim, a realidade de que a regulação de certos acordos de acionistas na lei brasileira não impossibilita a ocorrência de acordos de acionistas atípicos, cujo delineamento legal não é específico, mas fundamentado em diretrizes legais de ordem geral, implicando o seu tratamento jurídico diverso
78

Tipicidade, antijuridicidade e culpabilidade nas infrações tributárias

Cunha, Arlindo Felipe da 28 May 2010 (has links)
Made available in DSpace on 2016-04-26T20:30:11Z (GMT). No. of bitstreams: 1 Arlindo Felipe da Cunha.pdf: 1605255 bytes, checksum: fe2313c08ab21c68bbe23b60bb371b22 (MD5) Previous issue date: 2010-05-28 / The theme infringement tax is understudied by national doctrine. Most existing work part of the study of sanction, thereby relegating to a background the infringement, as if this were the order and logic of the system. The explanation for this order of study showing the idea placated in spatial planning national responsibility for infringement is straightforward. Until proved otherwise the taxpayer is always guilty and undeserving of the penalty. However, this idea is not backed by legal in the current constitutional development. The goal of this work is to study the infringement taxation based on school finalist adopted by the current Penal Code, which shows more fair when the imposition of capital punishment. For the theory finalist culpability is not psychological, but regulatory compliance, is therefore not illicit element and Yes assumption. Guilt as a normative pure enables you to identify and note the various causes of exclusion of anti judicially and guilt, as well as where extinction. In that order of idea the constitutional principles that protect the taxpayer should not be studied in sanction and yes on guilt, as a mechanism for identifying the true nature of the infringement and as a parameter to the imposition of the penalty. That is why we started the analysis of the theme based on study of tribute from financial law and the principle of solidarity, many with administrative power. Subsequently, discussed their legal status, the subsidiary application of the principles and institutes criminal law, the typical, anti judicially and guilt. Is understanding pacific in criminal law that punishment itself will never solve the problem of crime, which must be resolved by a fairer social policy. The same can be said with respect to taxation, the sanction concealment itself will never solve the problem of tax collection, only a fairer tax policy is that be aware the contributor of the need to contribute to the maintenance of the State. To paraphrase Cezar Roberto BITENCOURT, typical, anti judicially and culpability are such interrelated ways that each element of the infringement (offence) presupposes the previous. The Division of infringement (offence) on three aspects, for the purposes of assessment and 4 valuation typical, anti judicially and guilt, eases and streamlines the application of law, securing against arbitrariness and contradictions which often could occur. This tripartite division of valuation enables a final result appropriate and fair / O tema infração tributária é pouco estudado pela doutrina nacional. A maioria dos trabalhos existentes parte do estudo da sanção, relegando a um segundo plano a infração, como se esta fosse a ordem e a lógica do sistema. A explicação para esta ordem de estudo provém da ideia pacificada no ordenamento nacional de que a responsabilidade pela infração é objetiva. Até prova em contrário, o contribuinte é sempre culpado e merecedor da sanção. No entanto, tal ideia não encontra respaldo jurídico no atual ordenamento constitucional. O objetivo do presente trabalho é estudar a infração tributária com base na escola finalista adotada pelo atual Código Penal, que se mostra mais justa quando da imposição da pena. Para a teoria finalista a culpabilidade não é psicológica, mas normativa, assim, não é elemento do ilícito e sim pressuposto da pena. A culpabilidade como normativa pura permite identificar e ressaltar as várias causas de exclusão de antijuridicidade e culpabilidade, bem como de extinção da punibilidade. Nessa ordem de ideia, os princípios constitucionais que protegem o contribuinte não devem ser estudados na sanção e sim na culpabilidade, como mecanismo de identificação da verdadeira natureza da infração e como parâmetro para a imposição da sanção. Por isso é que começamos a análise do tema com base no estudo do tributo sob a ótica do direito financeiro e do princípio da solidariedade, contrapondo com a potestade administrativa. Posteriormente, analisamos o seu regime jurídico, a aplicação subsidiária dos princípios e institutos de Direito Penal, a tipicidade, a antijuridicidade e a culpabilidade. É entendimento pacífico no Direito Penal que a pena em si nunca irá resolver o problema da criminalidade, que deve ser solucionado por uma política social mais justa. O mesmo se pode dizer com relação à sonegação fiscal, a sanção em si nunca irá resolver o problema da arrecadação tributária, somente uma política tributária mais justa é que conscientizará o contribuinte da necessidade de contribuir para a manutenção do Estado. 2 Parafraseando Cezar Roberto BITENCOURT, tipicidade, antijuridicidade e culpabilidade estão de tais formas relacionadas entre si que cada elemento posterior da infração (delito) pressupõe o anterior. A divisão da infração (delito) em três aspectos, para fins de avaliação e valoração tipicidade, antijuridicidade e culpabilidade -, facilita e racionaliza a aplicação do direito, garantindo a segurança contra as arbitrariedades e as contradições que frequentemente poderiam ocorrer. Essa divisão tripartida da valoração permite um resultado final adequado e justo
79

Deformabilidade de ligações viga-pilar de concreto pré-moldado / Deformability of beam-column connections in precast concrete structures

Ferreira, Marcelo de Araújo 22 February 1999 (has links)
No presente trabalho é abordada uma metodologia analítica para o cálculo de deformabilidades de ligações típicas de concreto pré-moldado, levando-se em conta os mecanismos básicos de deformação na ligação. Foram estudas duas ligações típicas viga-pilar de concreto pré-moldado. A primeira ligação é uma ligação com almofada de elastômero e chumbador. É apresentado um desenvolvimento analítico para o cálculo da deformabilidade ao cisalhamento da ligação. Também, é abordado um procedimento para a determinação da resistência ao cisalhamento. Foram realizados ensaios de cisalhamento, de flexão e torção nessa ligação, onde foram variados a geometria da almofada e o diâmetro do chumbador. A segunda ligação é uma ligação resistente à flexão com chapas soldadas. É apresentado um desenvolvimento para o cálculo da deformabilidade à flexão da ligação. Foram realizados dois ensaios de flexão alternada em um protótipo com ligações soldadas e um protótipo monolítico, o qual serviu de referência para avaliar a rigidez da ligação. Os valores calculados da deformabilidade ao cisalhamento, para os protótipos com almofada de elastômero e chumbador, foram, em média, 23% superiores aos valores experimentais. Todavia, este equacionamento não se aplica ao caso de uma ligação com almofada com um fator de forma maior do que 5. As resistências ao cisalhamento calculadas corresponderam a valores entre 96 a 100% em relação aos valores experimentais. A ligação com chapas soldadas apresentou uma rigidez à flexão da ordem 83% da rigidez da ligação monolítica. O valor calculado para a rigidez à flexão secante foi 5% superior à rigidez apresentada pela ligação ensaiada. O momento máximo de cálculo da ligação, estimado com base na rigidez calculada, foi 6% superior ao momento de ruptura. A partir dos resultados experimentais, demonstrou-se que, através da utilização de procedimentos analíticos para a determinação das deformabilidades, pode-se obter uma boa estimativa para os valores experimentais, constituindo-se assim em uma alternativa viável e em uma ferramenta de grande potencial a ser explorado para o projeto das ligações de concreto pré-moldado. / This thesis discusses an analytical methodology to determine the deformability of beam-column connections for precast concrete structures, considering the basic mechanisms of deformation in these connections. Two typical beam-column connections it was studied. For the first one, which consists of a connection with bearing pad and dowel bars, is presented an analytical development to determine its shear deformability. In addition, it is discussed a procedure to determine its shear resistance and some tests, which include shear, bending moment and sprain about beam axis, are also reported, where it were used different parameters to the bearing pad geometry and to the dowel bar diameter in the connections. For the second connection, which consists of a moment resistant connection with welded plates, is presented an analytical development to determine the connection flexibility. In order to evaluate the flexibility behaviour of the connection, two tests are reported. In the first one was used a rigid connection, which was used as a stiffness reference. As a result, the theoretical shear deformability, calculated to the prototypes with bearing pad and dowel bars, presented 23% more than the experimental results. Therefore, this calculus was not applied for pads with shape factor bigger than 5. The predicted shear resistance suited to values between 96 and 100% in relation to experimental values. The stiffness response of the resistant moment connection suited about 83% of the rigid connection stiffness. The theoretical secant stiffness of the connection it was 5% bigger than the experimental response. The predicted ultimate bending moment it was 6% bigger than moment crack of connection. Based on the analysis of the results, it was demonstrated that, the employ of analytical developments to determine deformabilities in the precast concrete connections is viable and provides good estimated values. In other way, the use of those analytical developments together with available procedures consist on important design tools to be applied for the precast concrete connections.
80

Análise experimental e numérica de ligações viga mista-pilar com cantoneiras de alma e assento - pavimento tipo e ligações isoladas / Theoretical and experimental analysis of beam-to-column composite connections with bottom and web angle - typical floor and isolated prototypes

Bessa, William Oliveira 08 December 2009 (has links)
Esta pesquisa apresenta um amplo programa experimental de ligações viga mista-pilar com cantoneiras de alma e assento, incluindo protótipos isolados e ligações inseridas num pavimento tipo constituído de laje pré-moldada com vigotas e lajotas cerâmicas. Os objetivos do trabalho foram avaliar os efeitos da fissuração da laje no comportamento da ligação (rigidez inicial e momento resistente), o acréscimo da taxa de armadura secundária e os detalhes propostos para a ancoragem das armaduras longitudinais. Nos ensaios experimentais foram analisadas as rotações das ligações, deslocamentos e deformações nos elementos. Para o estudo teórico, tomou-se como referência o Método das Componentes do EUROCODE 3 e 4. Paralelamente, um estudo numérico para ligações mistas foi desenvolvido com o objetivo de incluir a laje de concreto, as armaduras longitudinais e transversais, além da não linearidade física e geométrica na análise por elementos finitos. De acordo com os resultados, a condição prévia de fissuração da laje mostrou-se menos relevante que a continuidade das vigas na direção do eixo de menor inércia do pilar, no que se refere à determinação da rigidez inicial e resistência das ligações mista inseridas num pavimento tipo. A metodologia de modelagem numérica foi capaz de representar de forma satisfatória os mecanismos plásticos e os estados limites últimos da ligação. / This research presents an extensive experimental study of the structural behavior of the beam-to-column composite connections with bottom and web angle, including isolated prototypes and typical floor with slab made of precast joist with lattice and bricks. The objectives were to evaluate concrete slab cracking effects in the composite connections behavior (initial stiffness and resistant moment), the secondary steel ratio increase and the proposed details for the longitudinal steel bars anchorage. In the experimental tests, it was analyzed the connection total rotation, the displacements and deformations in the connection components. The theoretical study was developed based on EURODODE 3 and 4 methodologies. Besides, a numerical study was developed with the purpose of including the concrete slab modelling, the longitudinal and transversal steel bars, and the geometrical and material non-linearity in the finite element analysis. According to the results, the beam continuity through to the column minor axis showed to be more important than the concrete slab previous cracking, for the initial stiffness and resistant moment composite connections behavior in the typical floor. The numerical models represented satisfactorily the plastic mechanism connection and the ultimate limit states.

Page generated in 0.0421 seconds