O objetivo deste trabalho é apresentar um modelo para análise probabilística de vigas de concreto armado recuperadas à flexão, através da utilização conjunta do método de simulação de Monte Carlo e do método dos Elementos Finitos. Para uma análise da confiabilidade, foram projetadas vigas de concreto armado seguindo as recomendações da NRR 6118:2003. Após, foi considerado que as armaduras tracionadas de flexão sofreram reduções de 10%, 20% e 30% na sua área da seção transversal, sendo, então, feita uma análise da segurança estrutural remanescente. Para o projeto de recuperação das vigas danificadas, estão apresentados os procedimentos do Bulletin 14 da fédération internationale du béton (fib) para o dimensionamento de sistemas de reforço com material compósito colado externamente às estruturas. Assim, a confiabilidade destas vigas recuperadas pôde ser estimada e comparada à confiabilidade das vigas originais. Dentro do processo de simulação, a resposta em termos da carga de ruptura das vigas de concreto armado recuperadas foi obtida através de uma análise numérica não-linear utilizando um modelo de elementos finitos. Devido à importância do deslizamento entre o substrato de concreto e o sistema de reforço estrutural, foram implementados dentro do modelo de elementos finitos, elementos unidimensionais de interface, quadráticos com seis pontos nodais para a captura deste comportamento. As análises probabilísticas através do método de simulação de Monte Carlo usando um modelo de elementos finitos mostraram que se atinge bom nível de segurança no projeto de vigas de concreto armado seguindo as recomendações da NBR 6118:2003. Entretanto, danos nas armaduras tracionadas de flexão podem fazer com que a confiabilidade caía para níveis inaceitáveis. Como solução, o projeto de recuperação estrutural de acordo com o Bulletin 14 da fib fez com que a confiabilidade das vigas recuperadas fosse no mínimo igual à confiabilidade das vigas originais. Assim, a probabilidade de falha das vigas recuperadas foi menor quando comparado à probabilidade de falha das vigas originais. / The objective of this work is to present a model for probabilistic analysis of RC beams rehabilitated for flexure, through the simultaneous utilization of the Monte Carlo method and the finite element method. Initially, three RC beams were designed following the NBR 6118:2003 recommendations. In the next step, it was considered that a reduction of the steel reinforcement area of 10%, 20% and 30% had occurred. Then the procedures for strengthening systems design with externally bonded carbon fiber reinforced polymers (fib, Bulletin 14) were employed for the rehabilitation of the damaged RC beams. Finally, the reliability of the RC beams rehabilitated for flexure could be evaluated and compared to that of the damaged and undamaged RC beams. In the Monte Carlo method, the RC beams failure load was obtained numerically through a nonlinear finite element model. Due to the importance of the slip between the concrete substrate and the external reinforcement, it was introduced in the finite element model a special one-dimensional interface element, with six nodal points and quadratic shape functions. The probabilistic analysis through the Monte Carlo method using a finite element model showed the high reliability attained in the RC beams design following the NBR 6118:2003 recommendations. However, the damage in the internal steel reinforcement can lead to an unacceptable reliability level. As a solution, the design of structural recovery according to the Bulletin 14 produced a reliability level for the RC beams rehabilitated for flexure at least equal to the reliability level of the undamaged RC beams. Consequently, the failure probability of the RC beams rehabilitated for flexure was lower then the failure probability of the undamaged RC beams.

O fomento à implantação e ao fortalecimento dos conselhos escolares é o objetivo visado pelo Programa Nacional de Fortalecimento dos Conselhos Escolares, política criada pelo Ministério da Educação em 2004, tendo como principal instrumento a promoção de formação continuada, por meio da publicação e distribuição de cadernos e da oferta de cursos. O objetivo da dissertação é analisar a implementação do Programa Nacional de Fortalecimento dos Conselhos Escolares (PNFCE) no que concerne ao potencial de contribuição das estratégias e processos de formação de técnicos e de conselheiros para o fortalecimento de todos os segmentos do conselho escolar, com destaque ao segmento dos pais. A pergunta de pesquisa é a seguinte: em que medida os cursos de formação do Programa Nacional de Fortalecimento dos Conselhos Escolares são eficazes para a consecução do principal objetivo do Programa: fortalecer os conselhos escolares? Parte-se do pressuposto que o conhecimento disponibilizado nos cursos de formação para técnicos e dirigentes de sistemas de ensino pode ser determinante para criar uma mudança na escola ou manter a realidade. O trabalho foi realizado a partir de cinco fontes principais: a experiência da autora em um conselho escolar; conteúdos e procedimentos de um curso de formação do PNFCE oferecido por uma instituição de educação superior, do qual também participou a autora; documentos legais e normativos relativos à gestão da educação e ao PNFCE; produção científica sobre o tema dos conselhos escolares e gestão da educação; informações e materiais didáticos e PNFCE, principalmente os doze cadernos do Programa. A política pública estudada, ainda que tenha a finalidade de fortalecer conselhos escolares, apresenta obstáculos que não são condizentes com os objetivos da norma que a criou, a Portaria Ministerial nº 2.896/2004, tendo tais obstáculos sido constatados no processo de implementação. Um dos obstáculos é o fato dos cursos se restringirem aos profissionais da educação. Outro entrave é a distância considerável entre os discursos que proclamam ser a gestão democrática da escola pública, logo, também os conselhos escolares, importantes para a qualidade da educação oferecida pela escola e a realidade que se apresentou no curso estudado, em que a ênfase a determinados assuntos, em detrimento de outros que poderiam empoderar o conselho escolar, pode ser tida como uma forma de condicionar o conhecimento disponibilizado pelas publicações do MEC e que são utilizadas como material didático. Com base no trabalho desenvolvido, foi possível considerar que o PNFCE tem potencial muito limitado para fomentar conselhos escolares fortes e atuantes, uma vez que os conhecimentos que chegam até os conselheiros não são suficientes e adequados a tal finalidade. A democratização do poder de decisão na escola encontra resistências, desde os processos de implementação da política pública até a resistência percebida na escola, que, ao fim ao cabo, pode ser decorrente do (des)conhecimento de direitos e deveres de cada conselheiros escolar. / The support to the implantation and to the strengthening of the scholar councils is the goal to be achieved by the National Program for the Strengthening of the Scholar Councils (PNFCE), politics created by the Education Ministry in 2004, having as its main instrument the promotion of the continued formation, throughout the publication and distribution of notebooks and the courses’ offer. This dissertation’s goal is to analyze the implementation of the National Program for the Strengthening of the Scholar Councils (PNFCE), regarding to the strategies’ potential of contribution and processes of counselor’s and technician’s formation for the strengthening of all scholar council’s segments, highlighti ng the parent’s segment. This research’s question is the following: at what measure the National Program for the Strengtheni ng of the Scholar Counci ls’ (PNFCE) formation courses are effective for the attainment of the Program’s main goal: strengthen scholar councils? It starts from the presupposition that the knowledge made available on the formation courses for technicians and lecture system’s chiefs may be determinant to create a change in the school or keeping the reality. The work has been developed through five main resources: the author’s experience in a scholar council; matters and procedures i n a PNFCE’s formation course offered by a superior education institution, which the author’s been part of as well; Legal and normati ve documents related to education’s management and to the PNFCE; scientific production about the scholar councils’ theme and education management; information and didactic material from PNFCE, mainly the program’s twelve books. The public politics studied, even though it has the goal of strengthening scholar councils, presents obstacles that are not consistent with the goals from the norm that created it, the Mi nistry’s ordi nance # 2.896/2004, having such obstacles been reali zed on the implementation’s process. One of the obstacles is the fact that the courses are restricted to the education professionals. Another barrier is the considerable distance between the speeches that proclaim the public schools’ management is, ergo, the scholar council’s as well, important for the quality of the education provided by the school and the reality that has been selfpresented in the studied course, whereat the emphasis to some subjects, to the detriment of others that might have empower the scholar council, may be perceived as a way to condition the knowledge made available by the Education Ministry’s publications and that are used as didactic material. Based on the work here developed, it has been possible to consider that PNFCE has a very limited potential for the supporting of strong and active scholar councils, once the knowledge that come to the counselors are not enough and fit to such purpose. The democratization of the Power of decision i n schools fi nds resistance, from the public politics’ implementation processes to the resistance noticed in schools, that, at the end of the day, may be resulted from the (un)knowing of rights and duties of each scholar counselor.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-06-20T17:31:50Z No. of bitstreams: 1 amandacristinabastoscosta.pdf: 631086 bytes, checksum: f8501a7a04122b69c61f6508938e9d52 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-07-13T15:24:49Z (GMT) No. of bitstreams: 1 amandacristinabastoscosta.pdf: 631086 bytes, checksum: f8501a7a04122b69c61f6508938e9d52 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-07-13T15:25:02Z (GMT) No. of bitstreams: 1 amandacristinabastoscosta.pdf: 631086 bytes, checksum: f8501a7a04122b69c61f6508938e9d52 (MD5) / Made available in DSpace on 2016-07-13T15:25:02Z (GMT). No. of bitstreams: 1 amandacristinabastoscosta.pdf: 631086 bytes, checksum: f8501a7a04122b69c61f6508938e9d52 (MD5) Previous issue date: 2012-08-31 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Este estudo se propôs a realizar uma análise acerca da concepção de participação social no contexto das políticas educacionais durante o período do bloco no poder do governo de Luís Inácio Lula da Silva. Para isso, utilizamos uma política educacional específica no que diz respeito ao incentivo à participação no ambiente escolar. Trata-se do Programa Nacional de Fortalecimento dos Conselhos Escolares lançado em 2004 e que proclama como objetivo central o fortalecimento da formação e da consolidação dos Conselhos Escolares como forma de promover uma participação ativa dos cidadãos nas escolas. Nesse sentido buscamos compreender o conteúdo da participação social a partir dos seguintes objetivos: caracterizar os fundamentos da formação social brasileira que marcam as orientações políticas e ideológicas acerca da participação na educação; identificar a correlação de forças sociais, as disputas de poder e os projetos societários que contextualizam as diferentes perspectivas de participação formuladas na recente história educacional brasileira e analisar o conteúdo da participação expresso pelas políticas educacionais a partir dos cadernos do Programa Nacional de Fortalecimento dos Conselhos Escolares, do Ministério da Educação. Com base no materialismo-histórico utilizamos como metodologia a análise documental, por entender que tais documentos apresentam intencionalidades, interesses específicos e atuam no sentido de intervir diretamente na sociedade. Para a construção dessa análise, buscamos compreender a participação social na filosofia clássica nas origens do liberalismo baseado em Locke e Rousseau e em sua crítica às formulações de democracia e Estado de Marx e Engels e posteriormente de Gramsci e Poulantzas. Logo depois, procuramos compreender a participação, mais especificamente, na formação social brasileira a partir do processo de inserção tardia ao modo de produção capitalista até os anos do neoliberalismo. Nesse último período articulamos o processo de reestruturação produtiva ao contexto de formulação das políticas públicas para a área educacional, demarcando a participação no nível da pequena política além de suas especificidades no bloco do poder de Lula em relação ao de FHC. Confirmamos essas questões ao analisarmos o material fornecido pelo PNFCE, onde destacamos a participação como ponto central no novo padrão de sociabilidade e que expressa o programa político do neoliberalismo da Terceira Via. Seu objetivo é de estabelecer uma estratégia de consenso e coesão sociais, sem proporcionar a construção de um nível de consciência política elevada. Nesse sentido, seu conteúdo nega um projeto contra-hegemônico da classe trabalhadora. / This study aimed to execute an analysis on the social participation design in the context of educational policies during the period of the power bloc of the government of Luiz Inacio Lula da Silva. For this, we used a specific education policy regard to the encouragement of the participation in the school setting. This is the National Program for the School Boards Strengthening released in 2004 and it proclaims as its main objective the strengthening of training and consolidation of School Boards as a way of promoting active participation of citizens in schools. In this respect we tried to comprehend the content of social participation on the bases of the following objectives: to characterize the ground rules of the Brazilian social formation that highlight the political and ideological regarding to the educational participation, to identify the social forces correlation, the power struggles and corporate projects that contextualize the different participation perspectives issued in the recent Brazilian educational history and analyze the contents of participation expressed by the educational policies from the National Program for Strengthening of School Boards guide book, the Departament of Education. Based on the historical-materialism we used as methodology the documental analysis, understanding that these documents present intentions, specific interests and act to intervene directly in the society. For this analysis construction, we seek to understand the social participation in classical philosophy of the origins of liberalism based on Locke and Rousseau and his their critique of democracy and rule formulations of Marx and Engels and later Gramsci and Poulantzas. Soon after, we sought to understand the participation, more specifically, in the Brazilian social development from the process of late introduction of the capitalist production mode until the neoliberalism years. In this last period we articulated the process of productive restructuration to the context of public policies for education formulation, pointing out the participation on the level of the small politics beyond its specificities on the Lula’s power bloc related to FHC. We confirmed these questions by analyzing the material provided by National Program for the School Boards Strengthening, where we emphasize the participation as a central point in the new pattern of sociability and that expresses the political program of the Third Way neoliberalism. Its goal is to establish a strategy of consensus and social cohesion, without allowing the construction of a high level of political consciousness. Accordingly, its contents denies a counterhegemonic project of the working class.

Afin de prolonger leur durée de vie et d'assurer la sécurité des usagers, les structures en béton peuvent nécessiter un renforcement au cours de leur durée de service. La technique de renforcement par collage externe, en surface, de composites renforcés de fibres de carbone, de verre ou d'aramide à l'aide de résines durcissant à température ambiante est largement employée pour son efficacité et sa facilité de mise oeuvre. Toutefois l'utilisation à la fois de fibres synthétiques et de matrices polymères produit un impact écologique non négligeable. L'objectif de ce travail de recherche est d'examiner la possibilité d'utiliser des fibres de lin pour le renforcement externe de structures en béton. Les propriétés mécaniques spécifiques et le bilan environnemental avantageux des fibres de lin en font une alternative intéressante aux fibres de verre. Cependant leur origine naturelle conduit à une plus grande variabilité des propriétés, à un comportement en traction non linéaire et une sensibilité accrue à l'humidité. Les principaux objectifs du travail de thèse portent ainsi sur la sélection des matériaux et la mise en oeuvre les plus adaptés, sur l'évaluation des performances du matériau et de son adhérence au support béton et sur une évaluation de la durabilité des propriétés du système. Dans une première partie expérimentale deux méthodes de mise en oeuvre du renfort à fibres de lin (stratification au contact et collage de lamelles rigides) sont développées et caractérisées. Des observations tomographies X confirment la bonne imprégnation des fibres et la cohésion des composites. Les essais de traction révèlent un comportement en traction bilinéaire comme décrit dans la littérature, avec des propriétés d'effort par largeur de bande comparables aux composites de renfort à fibres de verre. La caractérisation des interfaces composite/béton menée par tests de cisaillement à double recouvrement confirme une bonne adhérence qui se traduit par une rupture cohésive dans le substrat béton. La nature des fibres ne semble pas influencer le comportement de l'interface. Les systèmes de renforcement à fibres de lin sont donc capables de reprendre des efforts transmis par cisaillement de façon comparable aux matériaux de renfort à fibres de verre. Dans une deuxième partie des essais exploratoires de durabilité ont ensuite été menés pour vérifier la pérennité des propriétés de ces deux composites de renfort dans un environnement de service. Un vieillissement accéléré artificiel en enceinte climatique est mis en place tandis que des composites à fibres de lin stratifié au contact sont exposés pendant un an à l'environnement extérieur. Un second vieillissement hygrothermique à 70°C est mené pendant 4 semaines. Les dégradations des propriétés des composites à fibres de lin sont comparables à celles de certains composites de renfort à fibres de verre. Malgré la nature hydrophile des fibres de lin, les premiers essais ne montrent pas de dégradations des propriétés qui rendraient le composite impropre à une utilisation comme renfort extérieur de structures en béton / To extend their life and ensure the safety of users, concrete structures may need strengthening during their service life. The technique of strengthening by external bonding of composites carbon, glass or aramid composites using polymer that are cured at room temperature is widely used for its effectiveness and ease of implementation. Yet the uses of both synthetic fibers and polymer matrices have a significant environmental impact. The objective of this research is to examine the possibility of using flax fibers for the external strengthening of concrete structures. Their high specific mechanical properties and positive environmental balance make them an interesting alternative to the glass fibers. However, they also present a larger variability in properties, a non-linear tensile behavior and high sensitivity to humidity. The main objectives of this thesis involve the selection of the materials and the most suitable implementation, the evaluation of the materials’ performances and adherence to concrete support and a sustainability assessment of those properties. In a first experimental section, two methods of implementation of the flax fiber reinforcement are developed and characterized: by wet lay-up and by bonding of pre-hardened. Tomography observations confirm the good fiber impregnation and cohesion of the composites. The tensile tests show a bilinear tensile behavior as described in the literature, with stress per width at failure comparable to glass fibres strengthening systems. The characterization of composite/concrete interfaces is conducted by double overlap shear tests and confirms a good adhesion which results in concrete failure before the failure of the reinforcement system. The nature of the fibers does not appear to influence the shear behavior of the interface. For glass or flax wet lay-up systems, failure can occur with failure of the composite. Flax fiber reinforcement systems can take up the forces transmitted by shear in a manner comparable to glass composites. In the second part, sustainability tests were conducted to ensure the sustainability of the properties of these two composite reinforcements in a service environment. An artificial accelerated aging test in a climatic chamber is set up while wet lay-up flax fiber composites are exposed to the external environment during a year. A second hydrothermal aging test is conducted for 4 weeks at 70°C. The degradations of the properties of the flax composites are comparable to those of some glass reinforcement composites. Despite the hydrophilic nature of the flax fibers the first tests show no degradation of properties that would make the composite unsuitable for an external reinforcement of concrete structures

Dans le domaine de la construction, le béton armé est un matériau le plus couramment utilisé pour construire des bâtiments, des ponts…Avec sa grande histoire, il y a un très grand nombre d'ouvrages qui se retrouve dégradé pour de multiples raisons tels que les accidents routiers, l'évolution de trafic, les modifications de chargement dans les bâtiments ou les actions climatiques… Pour résoudre ces problèmes, deux possibilités principales s'offrent aux maitres d'ouvrage : la reconstruction ou la réparation. La reconstruction est une solution intéressante mais coûte très cher et ne peut pas être appliquée pour tous les ouvrages (ouvrages historiques …) La deuxième solution est donc souvent utilisée pour maintenir les ouvrages dans un bon état de service. Une des méthodes de réparation couramment utilisée consiste à l'application de matériaux composites pour renforcer les structures béton armé. Les coûts relativement acceptables et la mise en oeuvre rapide en font une solution technique de plus en plus appréciée. La technique de renforcement par matériaux composites se traduit par l'encollage de tissu ou de plats réalisés à partir de fibres de carbone ou de verre sur un support en béton. Ces types de matériaux ne sont pas d'origine naturelle, leur production provoque de forts impacts sur l'environnement et de plus, ces matériaux ne sont pas dégradables à leur fin de vie. Donc pour répondre à la question du développement durable qui demande que tous les domaines respectent l'environnement, un nouveau matériau écologique pouvant remplacer ces matériaux dans le renforcement de structure béton armé est toujours demandé. La fibre de Lin est un matériau d'origine naturelle qui présente de bonnes propriétés mécaniques. A l'heure actuelle, la fibre de Lin est appliquée dans plusieurs domaines : l'automobile, le sport, … Dans le domaine génie civil, avec ses bonnes propriétés mécaniques, la fibre de lin peut être utilisée dans le domaine du renforcement des structures béton armé en substitution des fibres courantes (fibre de carbone, fibre de verre…) Le but de cette thèse est l'évaluation de la capacité d'utilisation des fibres de Lin dans le renforcement de poutres béton armé. L'étude se focalisera au cas de renforcement au cisaillement qui n'est pas bien documenté dans la littérature, sui sera comparé avec le renfort par des fibres de carbone. Le programme expérimental est réalisé sur des tests de flexion 3 points avec la charge approche de l'appui pour avoir un fort effort tranchant dans la zone intéressée sur des poutres rectangulaires et des poutres en T. Les poutres sont renforcées par des tissus de lin bidirectionnels et unidirectionnels et par différentes configurations de renforcement. Les normes de calcul ACI, FIB, CSA, CNR-DT… recommandées pour calculer des structures avec des renforts de carbone et de verre dans le renforcement au cisaillement sont appliquées afin de vérifier leur efficacité dans le cas d'un renforcement par fibres de lin. Enfin un modèle numérique est étudié par la méthode des éléments finis pour reproduire le comportement des poutres renforcées par fibre naturelle afin d'étudier les paramètres qui jouent un rôle important dans le renforcement au cisaillement des poutres béton armé par fibre de lin. Les résultats montrent que le renfort par fibre de Lin présente des effets significatifs dans le renforcement au cisaillement de poutres béton armé (augmentation de la résistance de cisaillement de 10% à 33%). Le renfort par fibres de Lin présente une capacité mécanique équivalence à celle de fibre de carbone dans le renforcement au cisaillement de poutres béton armé et un potentiel dans le renforcement de structure béton armé. Les résultats du modèle numérique par la méthode des éléments finis traduisent un comportement similaire à ceux enregistrés lors des essais expérimentaux / In the field of construction, concrete is the most common material used to construct buildings, bridges... With its great history, there are a large number of structures that is found degraded for many reasons such as road accidents, changes in traffic, load changes in buildings or climate action ...To resolve these issues, two main options available to project owners: the reconstruction or repair. Reconstruction is an interesting solution but is very expensive and cannot be applied to all structures (historical works ...). The second solution is often used to keep the structures under service conditions. A repair methods commonly used is the application of composite materials to strengthen reinforced concrete structures. The relatively acceptable cost and rapid implementation make this technical solution increasingly appreciated. The Flax fiber is a natural material which has good mechanical properties. At present, the flax fiber is applied in several areas: automotive, sports ... In the civil engineering field, with its good mechanical properties, flax fiber can be used in the field of building Reinforced Concrete structures substitution of regular fibers (carbon fiber, fiberglass ...) The aim of this thesis is the evaluation of the ability to use flax fibers in strengthening reinforced concrete beams. The study will focus on a case of shear reinforcement that is not well documented in the literature; it will be compared with the reinforcement with carbon fibers. The experimental program was carried out on 3-point bending tests with the support of load approach for a strong shear in the area concerned on rectangular beams and T-beams. The beams are reinforced by bidirectional flax fabrics and unidirectional reinforcement and different configurations. The calculation standards ACI, FIB, CSA, CNR-DT ... recommended to calculate structures with carbon reinforcements and glass in building for shear strengthening are applied to ensure their effectiveness in the case of a reinforcement flax fibers. Finally, a numerical model is being studied by the finite element method to reproduce the behavior of beams reinforced with natural fiber to study the parameters that play an important role in shear strengthening of concrete beams reinforced with flax fiber. The results show that the reinforcing flax fiber has significant effects in the shear reinforcement of reinforced concrete beams (increase in shear resistance of 10% to 33%). The reinforcement by flax fiber has a mechanical capacity equivalent to that of carbon fiber in the shear reinforcement of reinforced concrete beams and potential in strengthening reinforced concrete structure. The results of the numerical model by the finite element method reflect a behavior similar to those obtained during the experimental tests. The model also valid flax fiber capacity comparable to that of carbon fiber in the shear strengthening of reinforced concrete beams

No description available.

Ce travail porte sur l'étude du comportement mécanique d'une console courte en béton armé renforcée par collage de tissus en fibres de carbone et en particulier sur l'influence du nombre de couches de tissus en fibres de carbone, du type du renforcement, de l'orientation des tissus composites, du type de tissus en fibres de carbone. Les résultats montrent que la performance de la console n‘augmente pas linéairement en fonction de l'épaisseur de la plaque composite. Il existe une épaisseur optimale de tissus en fibres de carbone. Dans le cas du renforcement sur les deux faces du béton, il existe un nombre de couches optimales. Dans le cas du renforcement par bandage, l'épaisseur de matériaux composites plus intéressants est de trois couches. Par contre, la résistance de la console renforcée dépend fortement de la surface renforcée. Les résultats montrent également que le comportement d'une console renforcée peut être présenté en trois phases: la phase élastique globale, la phase de la propagation de fissures et la phase de l'ouverture des fissures diagonales. Le renforcement de la console permet d'augmenter considérablement la résistance ultime de 20 à 82% et la rigidité de la console. Les ruptures des consoles renforcées peuvent être résumées en cinq modes. En se basant sur les résultats obtenus et les modèles existants, la résistance ultime de la console renforcée et non renforcée a été estimée et analysée. Un modèle basant sur lа théorie de l'endommagement a été développé dans ce travail. L'effet de fatigue sur le comportement et sur la résistance ultime de la console courte renforcée a été également étudié dans ce travail. / This study deals with mechanical behaviour of strengthening reinforced concrete corbel by bonding carbon fibre sheet and in particular the influence of the number of layers of carbon fiber fabric, the type of strengthening, the orientation of the composite fabric and the type of carbon fiber fabrics .The results show that the performance of the corbel does not increase linearly with the thickness of the composite plate. There is an optimum thickness of the carbon fiber fabrics. In the case of strengthening on both sides of the concrete, there are an optimum number of layers. In the case of fully wrapped strengthening, the most interesting thickness of the composite is three layers. However, the resistance of the strengthening reinforced concrete corbel depends strongly on the bonded surface.The results also show that the behavior of strengthening corbel can be presented in three phases: the overall elastic phase, the phase of crack propagation and the phase of the opening of diagonal cracks. Strengthening the corbel can significantly increase the ultimate strength from 20% to 82 % and the stiffness of the corbel. The failure of the strengthening corbel can be summarized in five modes.Based on the results obtained and the existing models, the ultimate strength of the strengthening corbel or without strengthening, was estimated and analyzed. A model based on damage theory has been developed in this work. The effect of fatigue on the behavior and ultimate strength of the reinforced concrete corbel has also been studied.

Nickel based superalloys are currently being investigated for high temperature applications in advanced steam power plant operating at temperatures of 700˚C and above. Three nickel-based superalloys Inconel 617, Inconel 625 and Nimonic 263 alloys, which are of primary interest for boiler technology components such as furnace walls, superheater tubes, header and steam pipes, etc and for steam turbine technology components such as HP &IP cylinders, rotor forgings, casing and valve chest, blading, etc., have been evaluated for long and short term creep performance. Creep deformation processes occurring at high temperatures and stresses lead to the evolution of microstructures in the form of precipitation, precipitate coarsening and recovery effects. The deterioration in mechanical properties as a result of this microstructural change has been evaluated by hardness testing. This work discusses the microstructural evolution occurring in alloys in samples that have been creep exposed at a series of temperatures from 650°C to 775°C and for durations from 1000 to 45,000 hours using advanced FEGSEM, TEM, XRD and phase extraction techniques. The fractions and morphology of different phases, their locations during exposure to higher temperatures and probable creep fracture mechanism in these alloys are illustrated and discussed.

Master of Public Health - MPH / Introduction According (UNAIDS/WHO, 2011a) globally, 34.0 million [31.4 million–35.9 million] people were living with HIV at the end of 2011 out of which 80% live in Sub Saharan Africa. In absolute terms, the burden of HIV increased by 354% between 1990 and 2006 (Ortblad et al, 2010). The prevalence of HIV in Zambia stands at 14.3% in the age group 15 to 49 years. Having realized that HIV/AIDS is no longer a health issue alone Zambia embarked on the multisectoral response initiative which allows many stakeholders to play their role. In order to coordinate this multiplicity of stakeholders the government of Zambia created the National HIV/AIDS/STI/TB Council (NAC) with the core mandate to coordinate the national HIV/AIDS response agenda. In turn, the NAC created the Provincial (PATF) and District AIDS Task Forces (DATF) as decentralized structures through which to coordinate the response at provincial and district levels respectively. However, DAFT is not coordinating the response to HIV/AIDS epidemic effectively but the reason for the ineffective coordination has not yet been described. Aim The aim of the study is to explore factors which impact on the capacity of Lusaka DATF to coordinate an effective and sustainable local HIV/AIDS response. Methods A descriptive qualitative research was undertaken using purposive sampling methods. Data collection methods included a Document Review, Key Informant Interviews using semi structured interview guides, Focus Group Discussions and Field Notes. Results The study has found that the following factors promote effective coordination of DATF stakeholders and their activities at local level: recognition of the DATF by stakeholders as a formal structure which is enshrined within the institutional framework of the government; joint planning and resource mobilisation for activities by stakeholders particularly around national commemoration days such as World AIDS Day and the National VCT day and holding of stakeholder forum meetings to share experiences and lessons learnt. The study has also established that the following factors are responsible for preventing the DATF from coordinating effectively include: DATF does not exist as a legal entity enshrined in any Act of Parliament No. 10 of 2002 which created the NAC; there are multiple reporting channels for local stakeholders instead of having only one reporting framework through the DFATF; inadequate stakeholder forums; lack of memoranda of understanding between the DATF and stakeholders; weak technical capacity of the DACA due to factors such as lack of a training programme; inadequate joint planning and resource mobilisation plans and efforts; poor understanding and different interpretations of the of the concept of coordination by different stakeholders; weak feedback mechanisms from the DATF secretariat to stakeholders; and multiplicity of DATF guidelines by different partners which have at times contradicted each other. Poor political, civic and technical leadership engagement has been identified as key inhibiting factors.

Slat-band chains are used as conveyors by the food industry, breweries and bottling plants. The operating conditions require abrasion resistance and strength which are at the limit of the capabilities of the current material of choice, cold worked type 430. In an unconventional way of strengthening this material, Mintek developed a process in which the cold worked material is aged between 450°C and 500°C. The present work aims to elucidate the strengthening mechanism, using type 430 stainless steel containing 16.42% Cr and 0.036% C, in the cold-rolled condition (38% reduction in area), with and without prior solution heat treatment. The Cr-rich precipitate α" may form in the 450°C to 500°C range (due to the miscibility gap in the Fe-Cr system), resulting in the increased hardness and lowered ductility. Mossbauer studies confirmed that the α", at this composition and temperature, forms through the process of nucleation and growth. Hardening due to α" precipitation was only observed after aging for 64 hours or more, however. After increasing the dissolved interstitial content by solution heat treatments (in the vicinity of 900°C), increases in Vickers hardness of 30-50 kg/mm2 could be obtained after only 8 minutes at 475°C. This hardness increase corresponds to an increase in tensile strength of more than 100 MPa. The increased hardness does not appear to be caused by strain aging, and presumably results from fine carbide or nitride precipitation. Solution treatment at 930°C also introduced some martensite (α') into the microstructure, which raised the hardness of the unaged cold worked material. Overaging of the carbide and nitride precipitates was observed at 475°C, but not at 450°C, probably due to the lower diffusion rates at the lower temperature. No averaging of the α" precipitates occurred, for aging times up to 2072 hours. Samples aged for selected periods of time at 475°C had low impact strengths - even well before the formation of α" - and revealed predominantly cleavage fracture with some ductile fracture areas, mostly at grain boundaries. Both impact strength and lateral expansion indicated that embrittlement accompanies the increased hardness obtained by aging. Calculation of critical crack lengths from the impact data, however, revealed that a maximum flaw length of 0.8 mm, for specimens solution treated at 880°C, could be tolerated before catastrophic failure. Since it is not expected that flaws of that size would exist in the as manufactured links, fatigue will probably determine the lifetime of the chains, although the lower K1c values indicate that less crack propagation will be tolerated before brittle fracture. During the aging treatment, the strength may be lowered by recrystallisation of the coldworked material. Transmission electron microscopy (TEM) revealed the start of recovery, but no recrystallisation. Some large precipitates (around lμm in diameter) were present. These were identified, through their diffraction patterns, as M23C6; these carbides were present in both aged and unaged material and hence represent precipitates which had not dissolved during the initial solution treatments. The α" precipitates- and the presumed newly formed nitride and carbide precipitates - were too fine for detection by TEM. Potentiodynamic testing of the treated material in a 0.5M H2SO4 solution indicated that, although the probable hardening mechanisms imply localised Cr depletion of the matrix, the general corrosion resistance and passivation behaviour were not affected. It is concluded that the strength of the chain may be increased markedly by short-term heat treatments at 475°C, with lowered toughness, but with no decrease in corrosion resistance. Martensite, work hardening, and precipitation of carbides and nitrides all contribute to the final strength, with α" formation only becoming significant after longer aging times. / Dissertation (MEng)--University of Pretoria, 2013. / Materials Science and Metallurgical Engineering / unrestricted