Performance of hybrid rebars as longitudinal reinforcement in normal strength concrete

A/though steel is most commonly used as a reinforcing material in concrete due to its competitive cost and favorable mechanical properties, the problem of corrosion of steel rebars leads to a reduction in life span of the structure and adds to maintenance costs. Many techniques have been developed in recent past to reduce corrosion (galvanizing, epoxy coating, etc.) but none of the solutions seem to be viable as an adequate solution to the corrosion problem. Apart from the use of fiber reinforced polymer (FRP) rebars, hybrid rebars consisting of both FRP and steel are also being tried to overcome the problem of steel corrosion. This paper evaluates the performance of hybrid rebars as longitudinal reinforcement in normal strength concrete beams. Hybrid rebars used in this study essentially consist of glass fiber reinforced polymer (GFRP) strands of 2 mm diameter wound helically on a mild steel core of 6 mm diameter. GFRP stirrups have been used as shear reinforcement. An attempt has been made to evaluate the flexural and shear performance of beams having hybrid rebars in normal strength concrete with and without polypropylene fibers added to the concrete matrix

Nonlinear Analysis of Shear Dominant Prestressed Concrete Beams using ANSYS

This study reports the details of the finite element analysis of eleven shear critical partially prestressed concrete T-beams having steel fibers over partial or full depth. Prestressed T-beams having a shear span to depth ratio of 2.65 and 1.59 that failed in shear have been analyzed using the ‘ANSYS’ program. The ‘ANSYS’ model accounts for the nonlinearity, such as, bond-slip of longitudinal reinforcement, postcracking tensile stiffness of the concrete, stress transfer across the cracked blocks of the concrete and load sustenance through the bridging action of steel fibers at crack interface. The concrete is modeled using ‘SOLID65’- eight-node brick element, which is capable of simulating the cracking and crushing behavior of brittle materials. The reinforcement such as deformed bars, prestressing wires and steel fibers have been modeled discretely using ‘LINK8’ – 3D spar element. The slip between the reinforcement (rebars, fibers) and the concrete has been modeled using a ‘COMBIN39’- nonlinear spring element connecting the nodes of the ‘LINK8’ element representing the reinforcement and nodes of the ‘SOLID65’ elements representing the concrete. The ‘ANSYS’ model correctly predicted the diagonal tension failure and shear compression failure of prestressed concrete beams observed in the experiment. The capability of the model to capture the critical crack regions, loads and deflections for various types of shear failures in prestressed concrete beam has been illustrated.

Flexure-shear Analysis of Concrete Beam Reinforced with GFRP bars

This paper gives the details of flexure-shear analysis of concrete beams reinforced with GFRP rebars. The influence of vertical reinforcement ratio, longitudinal reinforcement ratio and compressive strength of concrete on shear strength of GFRP reinforced concrete beam is studied. The critical value of shear span to depth ratio (a/d) at which the mode of failure changes from flexure to shear is studied. The fail-ure load of the beam is predicted for various values of a/d ratio. The prediction show that the longitudinally FRP reinforced concrete beams having no stirrups fail in shear for a/d ratio less than 9.0. It is expected that the predicted data is useful for structural engineers to design the FRP reinforced concrete members.

Mechanical Properties of Rice Husk Ash (RHA) - High strength Concrete

High strength and high performance concrete are being widely used all over the world. Most of the applications of high strength concrete have been found in high rise buildings, long span bridges etc. The potential of rice husk ash as a cement replacement material is well established .Earlier researches showed an improvement in mechanical properties of high strength concrete with finely ground RHA as a partial cement replacement material. A review of literature urges the need for optimizing the replacement level of cement with RHA for improved mechanical properties at optimum water binder ratio. This paper discusses the mechanical properties of RHA- High strength concrete at optimized conditions

Classification of recycled sands and their applications as fine aggregates for concrete and bituminous mixtures

As a result of the drive towards waste-poor world and reserving the non-renewable materials, recycling the construction and demolition materials become very essential. Now reuse of the recycled concrete aggregate more than 4 mm in producing new concrete is allowed but with natural sand a fine aggregate while. While the sand portion that represent about 30\% to 60\% of the crushed demolition materials is disposed off. To perform this research, recycled concrete sand was produced in the laboratory while nine recycled sands produced from construction and demolitions materials and two sands from natural crushed limestone were delivered from three plants. Ten concrete mix designs representing the concrete exposition classes XC1, XC2, XF3 and XF4 according to European standard EN 206 were produced with partial and full replacement of natural sand by the different recycled sands. Bituminous mixtures achieving the requirements of base courses according to Germany standards and both base and binder courses according to Egyptian standards were produced with the recycled sands as a substitution to the natural sands. The mechanical properties and durability of concrete produced with the different recycled sands were investigated and analyzed. Also the volumetric analysis and Marshall test were performed hot bituminous mixtures produced with the recycled sands. According to the effect of replacement the natural sand by the different recycled sands on the concrete compressive strength and durability, the recycled sands were classified into three groups. The maximum allowable recycled sand that can be used in the different concrete exposition class was determined for each group. For the asphalt concrete mixes all the investigated recycled sands can be used in mixes for base and binder courses up to 21\% of the total aggregate mass.

An introduction to ordinary differential equations by computer algebra-systems

We report on an elementary course in ordinary differential equations (odes) for students in engineering sciences. The course is also intended to become a self-study package for odes and is is based on several interactive computer lessons using REDUCE and MATHEMATICA . The aim of the course is not to do Computer Algebra (CA) by example or to use it for doing classroom examples. The aim ist to teach and to learn mathematics by using CA-systems.

Ordinary Differential Equations

Exercises and solutions about ordinary differential equations.

Ordinary People in Extraordinary Times: The Citizenry and the Breakdown of Democracy by Nancy Bermeo

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Dying for the vote : how ordinary people won the right to vote.

Estudia los movimientos sociales para conquistar y extender el derecho al voto entre todos los hombres y mujeres, denominados cartismo y sufragistas. Cumple con los requisitos del currículo nacional inglés para la etapa de 3 de secundaria (key stage 3). Este texto esta preparado para el Schools History Project creado en 1972 para mejorar el estudio de la historia entre estudiantes de trece a dieciséis años. Reconsidera las formas en que la historia contribuye a las necesidades educativas de los jóvenes, y por ello idea nuevos objetivos, nuevos criterios para la planificación y desarrollo del curso, así como de nuevos materiales de apoyo. Requiere nuevos criterios de evaluación y, por tanto nuevos exámenes y, adquirió mayor expansión con la introducción del General Certificate of Secondary Education (GCSE) en 1987.

La atenci??n a la superdotaci??n en el aula habitual = Addressing giftedness in the ordinary classroom

Resumen basado en el del autor

Serviceability behaviour of fibre reinforced polymer reinforced concrete beams

El uso de materiales compuestos de matriz polimérica (FRP) emerge como alternativa al hormigón convencionalmente armado con acero debido a la mayor resistencia a la corrosión de dichos materiales. El presente estudio investiga el comportamiento en servicio de vigas de hormigón armadas con barras de FRP mediante un análisis teórico y experimental. Se presentan los resultados experimentales de veintiséis vigas de hormigón armadas con barras de material compuesto de fibra de vidrio (GFRP) y una armada con acero, todas ellas ensayadas a flexión de cuatro puntos. Los resultados experimentales son analizados y comparados con algunos de los modelos de predicción más significativos de flechas y fisuración, observándose, en general, una predicción adecuada del comportamiento experimental hasta cargas de servicio. El análisis de sección fisurada (CSA) estima la carga última con precisión, aunque se registra un incremento de la flecha experimental para cargas superiores a las de servicio. Esta diferencia se atribuye a la influencia de las deformaciones por esfuerzo cortante y se calcula experimentalmente. Se presentan los aspectos principales que influyen en los estados límites de servicio: tensiones de los materiales, ancho máximo de fisura y flecha máxima permitida. Se presenta una metodología para el diseño de dichos elementos bajo las condiciones de servicio. El procedimiento presentado permite optimizar las dimensiones de la sección respecto a metodologías más generales.

Study of bond behaviour between FRP reinforcement and concrete

El uso de barras de materiales compuestos (FRP) se propone como una alternativa efectiva para las tradicionales estructuras de hormigón armadas con acero que sufren corrosión en ambientes agresivos. La aceptación de estos materiales en el mundo de la construcción está condicionada a la compresión de su comportamiento estructural. Este trabajo estudia el comportamiento adherente entre barras de FRP y hormigón mediante dos programas experimentales. El primero incluye la caracterización de la adherencia entre barras de FRP y hormigón mediante ensayos de pull-out y el segundo estudia el proceso de fisuración de tirantes de hormigón reforzados con barras de GFRP mediante ensayo a tracción directa. El trabajo se concluye con el desarrollo de un modelo numérico para la simulación del comportamiento de elementos de hormigón reforzado bajo cargas de tracción. La flexibilidad del modelo lo convierte en una herramienta flexible para la realización de un estudio paramétrico sobre las variables que influyen en el proceso de fisuración.

O círculo de eranos: a experiência da educação do campo ou como os contextos podem gerar

RESUMO: Estamos a vivenciar dois fatos paradoxais: de um lado, uma organização da escola instituída que gera a autoconservação das práticas do professor e, do outro, tendências nos plano científico e do discurso político que apelam ao retorno ao ator - que reconhece o professor como sujeito de seu saber e fazer. Foi neste contexto que se realizou a pesquisa subjacente a esta tese sobre a formação docente num projeto de escolarização que se fundamenta numa perspetiva de educação popular contra-hegemónica, edificada, no Brasil, como ‗educação do campo‘. Buscou-se compreender a vivência docente, suas perceções e aprendizagens. Desenvolveu-se a investigação a partir das questões: é possível, no contexto atual de mudanças sociais direcionadas ao processo cada vez maior de individuação docente, a formação em democracia participativa numa experiência de educação popular? Como ela se estabelece? O que ela nos ensina? A metodologia assentou na observação participativa das reuniões de planeamento, avaliação e replaneamento dos(as) professores(as) e coordenadores, numa proposta local de educação do campo - do Programa Nacional de Educação na Reforma agrária. As reuniões e escolarização ocorreram em Ilhéus/Bahia/Brasil, durante os anos de 2005-2006. As referências teóricas para a análise empírica do material coletado foram: a perspetiva da reflexão-ação emancipatória de Carr e Kemmis (1998), que compreende as instituições educacionais criadas por pressões sociais e políticas; e a conceção de emancipação desenvolvida por Freire e por Habermas, assente na ação comunicativa/dialógica. Para a análise utilizou-se o método da Análise Crítica de Discurso (ACD), cuja principal referência foi Fairclough. Nas narrativas das reuniões percebeu-se o desenvolvimento de uma polidez positiva – atos de fala que demonstram o falante desejando estabelecer o consenso com ouvinte; assinalada por estruturas modais que direcionaram para a abertura de relacionamento e participação mútua entre professores(as) e coordenadores do projeto. O conteúdo manifesto das falas amparou-se numa perspetiva de educador que se constrói na prática, e, ao mesmo tempo, a constrói, mas que, entretanto, necessita de aportes teóricos críticos no processo de embate epistémico entre os saberes da vida quotidiana concreta e os saberes científicos. A função interpessoal foi expressa pela arquitetura dialógica, permitindo um processo de construção mútua de escola e professores(as). Pode-se afirmar que a prática analisada indica que nestes tempos, de controlo intenso das instituições escolares, de competição, de solidão, é obviamente necessária a organização coletiva de professores (as), de movimentos sociais e universidades, amparados e financiados por ordenamentos legais (conquistados pela população), para consolidar e ampliar projetos críticos de escolarização, mudando, reciprocamente, escolas e professores(as). ABSTRACT: We are experiencing two paradoxical facts: the organization of the established school which generates the self-preservation of teaching practices and, on the other hand, there is a political and scientific trend that claims the return of the ―actor‖ – the teacher being the subject of his knowledge and actions. It was therefore in this context, that the underlying research for this Thesis was conducted. It concerns to the teacher training in an educational project which is based on the perspective of a counter-hegemonic and popular education available to people at the Brazilian countryside – also called ―Field Education‖. We searched the understanding of the educational experience, its perceptions and learning. The investigation was developed from two fundamental questions: Is it possible to have the experience of a popular education system in a functioning democracy, at the light of the recent social changes that lead to a greater individuation? How is it established? What can we learn from it? The methodology was settled on the participant observation of the planning and evaluation meetings of teachers and coordinators of the National Education Program in the Land Reform in Brazil. These meetings occurred in Ilheús- Bahia- Brazil during the years of 2005-2006. The theoretical references to the empirical analyses of the material collected were: the perspective of the reflection – action emancipative of Carr & Kemmis (1998), which comprehends the educational institutions created by social and political pressures; and the conception of emancipation developed by Freire and Habermas, which is settled on the communicative-dialogical action. For the analysis it was elected the method of Critical Analysis of Discourse (CAD),which main reference was Fairclough. During the account of the meetings it was noticed the development of a positive politeness – which reveals the desire of the speaker to reach an agreement with the listener, signalized by modal structures that directed to an open and participative relationship between teachers and coordinators of the project. The manifest content of the speeches was sustained by the educator perspective, which is built on the daily practice. However, it needs some basic theoretical contributions to the epistemic struggle between concrete ordinary life and the scientific knowledge. The interpersonal function was expressed by dialogical architecture, allowing a mutual process of construction that involves the school and the teachers. The practice analyzed indicates that, more than ever, due to the massive control of the institutions, the extreme competition and solitude, the collective organization of the teachers, the social movements and the universities is necessary. They should be supported and financed by legal systems to consolidated and amplify important education projects, bringing necessary changes for schools and teachers reciprocally.

Global models for concrete realities

This paper intends to analyze the evolution of the Ecomuseums from their early appearance in the seventies until the present, emphasizing the characteristics which make them unique and different from all the other museums. This analysis will be used to show the Japanese landscape on ecomuseums and how the ecomuseum evolution might be a reference at internatioal level.

Japan ecomuseums: global models for concrete realities

The present document intends to analyze the different ecomuseums visited and studied in Japan trying to describe the reality of Japanese ecomuseology. From the descriptions of Japanese ecomuseums extrapolate the main features to build a model that is a possible reference for the XXI century ecomuseums.