Neste trabalho foi desenvolvida uma plataforma computacional para análise via método dos elementos finitos de estruturas de concreto armado convencional e reforçado com fibras de aço. A ferramenta numérica desenvolvida foi obtida por meio do acoplamento do programa FEMOOP, denominado solver com o pré e pós-processador GiD. Esse acoplamento foi possibilitado por meio da programação de um conjunto de arquivos denominados arquivos de customização, responsáveis pelo trabalho conjunto dos programas. Utiliza-se uma única interface gráfica com caixas de diálogo vinculadas ao código do solver, responsáveis por aplicar as condições de contorno do problema, tipo de análise, e aplicação dos materiais nos seus respectivos elementos finitos. Para a representação do concreto, foram implementados elementos finitos planos isoparamétricos quadrilaterais e triangulares e para as armaduras elementos finitos isoparamétricos unifilares lineares e quadráticos representados por meio do modelo discreto. Para o comportamento do concreto, foi considerado um modelo elástico não-linear com comportamento isotrópico até o limite de ruptura, acoplado a um modelo de amolecimento linear na tração. As fissuras são representadas pelo modelo de fissuração distribuída do tipo rotacional. Como critério de resistência para o concreto podem-se usar o modelo de Ottosen ou o modelo de Willam e Warnke de cinco parâmetros implementados na plataforma. Especificamente para considerar a presença de fibras de aço descontínuas na matriz de concreto, é utilizado o critério de ruptura proposto por SEOW e SWADDIWUDHIPONG (2005), que é uma alteração no meridiano de tração do critério proposto por Willam e Warnke. Para o concreto reforçado com fibras de aço fissurado considera-se o trecho pós-fissuração proposto no modelo de tração de LIM et. al (1987). As armaduras têm seu comportamento descrito através de um modelo elasto-plástico bilinear. A interação entre as armaduras e o concreto foi considerada como de aderência perfeita. Como se trata da modelagem de um material com comportamento não-linear, foi implementado para resolução das equações de equilíbrio o método de Newton-Raphson. Por fim, a plataforma final obtida foi avaliada por meio da simulação de vigas de concreto armado convencional e reforçado com fibras de aço disponíveis na literatura, que confirmaram a eficiência das implementações efetuadas. / In this work a computational platform for the analysis of reinforced concrete structures reinforced or not with steel fibers has been developed. This tool is based on the finite element method and has been obtained by the coupling of FEMOOP, denominated solver, with the pre and post-processor program GiD. The coupling has been possible by programming a set of customization files responsible for the communication between the two base programs. A single graphical interface with particular dialog boxes which are linked to the solver facilities is used to apply the boundary conditions, type of analysis, and material properties in the finite element model. For the geometrical representation of concrete elements, plane isoparametric quadrilateral and triangular finite elements have been implemented, while for the steel reinforcement bars, discrete isoparametric truss finite elements with linear end quadratic interpolation have been used. In order to model the mechanical behavior of concrete materials, a nonlinear isotropic elastic model together with a tension softening linear model has been adapted. Cracks are represented through a rotational smeared crack model. Both Ottosen and 5 parameters Willam-Warnke models can be used as the strength criterion of concrete. A failure model proposed by SEOW and SWADDIWUDHIPONG (2005), based on an adaptation of the Willam-Warnke model where a modification of the tension meridian is introduced, is used to consider the discontinuous steel fibers dispersed into the concrete mass. The post-cracking behavior of the steel fiber reinforced concrete considers the tension model proposed by LIM et. al (1987). The steel rebars have their behavior described by a bilinear elastoplastic model. A perfect bond between concrete and the reinforcing bars is assumed. For the solution of the nonlinear equations the Newton-Raphson method is used. The developed computational platform has been evaluated through a set of numerical simulations of tests performed in conventionally reinforced and steel fiber reinforced concrete beams available on the literature. These simulations confirm the efficiency of the current implementation.

Essa pesquisa apresenta um estudo da composição de concreto reforçado com fibras de polipropileno e objetiva avaliar seu comportamento estrutural em um tipo de painel alveolar de parede fina. A adição de alto teor de fibras de polipropileno ao concreto modifica algumas de suas propriedades mecânicas, conferindo ao compósito maior resistência à tração, resistência à flexão, resistência ao impacto e tenacidade. Inicialmente foram realizados ensaios de caracterização do compósito, sendo eles: consistência, resistência à compressão axial, módulo de elasticidade, resistência à tração por compressão diametral, resistência à tração na flexão e tenacidade. Estudou-se o comportamento de todas essas propriedades mecânicas para os teores de fibras de polipropileno de 0, 1 e 2% em volume de concreto. Com intuito de estudar o comportamento mecânico dos painéis alveolares de parede fina pela adição de fibras, foram realizados ensaios de carga concentrada e flexão. Este estudo foi realizado para os teores de fibra de 0 e 2%. Foram produzidos dois tipos de corpos de prova, ambos com seção transversal de 300 mm x 140 mm, e comprimentos de 600 mm e 1200 mm, para cada teor de fibra e respectivamente para os ensaios de carga concentrada e flexão. Para os ensaios de caracterização, não houve indícios de resultados significantes da adição dos teores de fibras 1 e 2% para a resistência à compressão e módulo de elasticidade. Já os ensaios de consistência, resistência à tração e tenacidade, apresentaram resultados expressivos, principalmente para o teor de fibra de 2%. Para os ensaios nos corpos de prova no painel quanto à carga concentrada, observou-se aproximadamente dez vezes maior capacidade de carga, cinco vezes maior capacidade de deslocamento e sete vezes maior resistência à punção. Os ensaios à flexão no painel apresentaram tensões resistentes pouco menores para os corpos de prova do painel contendo 2% de fibras. Conclui-se então que as propriedades do material cimentício com elevado teor de fibras são apropriadas para aplicação em painéis alveolares de parede fina. No entanto, é necessário melhorar a trabalhabilidade da mistura, pois devido às pequenas espessuras das paredes do painel, o adensamento do material não foi realizado de forma satisfatória. / This research presents a study on the composition of polypropylene fiber reinforced concrete and intents to evaluate its structural behavior in a type of thin-walled hollow core panel. The addition of high content of polypropylene fibers to the concrete modifies some of its mechanical properties, giving the composite greater split tensile strength, flexural strength, impact strength and toughness. Firstly, characterization tests of the composite were performed: consistency, compressive strength, modulus of elasticity, split tensile strength, flexural tensile strength and toughness. It was studied the behavior of all these mechanical properties for the contents of polypropylene fibers of 0,1 and 2% by volume of concrete. In order to study the mechanical behavior of the thin-walled hollow core panels by the addition of fibers, were performed concentrated load and flexural tests. This study was performed for fiber contents of 0 and 2%. Two types of specimens were produced, both with a cross section of 300 mm x 140 mm, and lengths of 600 mm and 1200 mm, for each fiber content and to be tested respectively for the concentrated load and flexural tests. For the characterization tests, there was no evidence of significant results arising on the addition of the fiber contents 1 and 2% for the compressive strength and modulus of elasticity. The tests of consistency, tensile strength and toughness presented significant results, especially for the fiber content of 2%. The flexural tests on the panel showed slightly lower tensile strengths for specimens containing 2% fibers. It is then concluded that the properties of the high fiber cementitious material are suitable for application in thin-walled alveolar panels. However, it is necessary to improve the workability of the composite, because due to the small thicknesses of the panel walls, a satisfactorily consolidation of the material has not been achieved.

O concreto reforçado com fibras (CRF) corresponde a um material compósito formado principalmente por cimento hidráulico, agregados miúdo e graúdo, água e fibras descontínuas. A principal finalidade do reforço no concreto com fibras é o aumento da capacidade resistente pós-fissuração do compósito, que reflete no ganho de tenacidade. Tradicionalmente, as fibras de aço, por possuírem elevadas rigidez e resistência à tração, são as mais utilizadas para o reforço do concreto, enquanto que as fibras sintéticas são adotadas para controle de fissuração por retração plástica do compósito. A macrofibra polimérica se trata de uma fibra sintética estrutural que se difundiu no mercado brasileiro nos últimos anos, possuindo pouca pesquisa a respeito de seu desempenho como elemento de reforço no concreto. Diante disto, nesta pesquisa foi avaliado o uso da macrofibra polimérica na composição de concreto para fins estruturais, sendo analisado o comportamento mecânico de duas matrizes de concreto reforçado com fibras, uma convencional e a outra de alta resistência, com diferentes teores de fibra de aço e de macrofibra polimérica. Para isto, foram determinados o abatimento e a massa específica de cada concreto no estado fresco. No estado endurecido, foram realizados ensaios de absorção de água, índice de vazios, massa específica, resistência à compressão, Barcelona, tenacidade à flexão em prismas e tenacidade à punção em placas. Nas misturas com maiores teores de fibra não foi possível se obter a trabalhabilidade desejada, mesmo com a adição de superplastificante. Em alguns concretos, a macrofibra polimérica e a fibra de aço tiveram desempenhos equivalentes com relação à absorção, índice de vazios, resistência residual no Estado Limite Último (ELU) dos prismas e tenacidade das placas. O acréscimo do teor de macrofibra polimérica provocou alterações não significativas no valor do índice de vazios, da resistência residual em prismas e da tenacidade em prismas e placas. Foi encontrado uma equivalência entre os valores de tenacidade do concreto com menor teor de fibra de aço e do concreto com maior teor de macrofibra polimérica para a maioria das misturas. A macrofibra polimérica apresentou uma eficiência menor do que a fibra de aço quando utilizada no concreto destinado a pisos industriais. Além disso, o acréscimo do teor de macrofibra polimérica provocou pequenas alterações na espessura do piso industrial. / The fiber reinforced concrete (FRC) is a composite material mainly composed of hydraulic cement, fine and coarse aggregates, water and discontinuous fibers. The main purpose of the reinforcement in the concrete with fibers is the increase of the post-cracking resistant capacity of the composite, which reflects in the toughness gain. Traditionally, steel fibers, due to their high stiffness and tensile strength, are the most used for concrete reinforcement, while synthetic fibers are used to control the plastic shrinkage cracking of the composite. The polymeric macrofiber is a structural synthetic fiber that has spread in the Brazilian market in recent years, with few researches regarding its performance as a reinforcement element in concrete. Therefore, the use of the polymeric macrofiber in the concrete composition for structural purposes was evaluated in this study and the mechanical behavior of two fiber reinforced concrete matrices, one conventional and the other with high strength, with different contents of steel fiber and polymeric macrofiber, was analyzed. For this, the slump and the specific gravity of each concrete in the fresh state were determined. In the hardened state, water absorption, voids, specific gravity, compressive strength, Barcelona, flexural toughness in prisms and punching toughness in plates tests were performed. In the mixtures with higher fiber contents it was not possible to obtain the desired workability, even with the addition of superplasticizer. In some concretes, the polymeric macrofiber and the steel fiber had equivalent performances with respect to the absorption, voids, residual strength at Ultimate Limit State (ELU) of the beams and toughness of the plates. The increase of the polymeric macrofiber content did not cause significant changes in the value of the voids, residual strength in prisms and toughness in beams and plates. An equivalence of the toughness values of the concrete with lower content of steel fiber and the concrete with higher content of polymeric macrofiber was found for the majority of the mixtures. The polymeric macrofiber was less efficient than the steel fiber when used in concrete for industrial floors. In addition, the increase of the polymeric macrofiber content caused small changes in the thickness of the industrial floor.

La tesis se enmarca en la caracterización, a nivel material, de la fractura del hormigón reforzado con fibras de acero (SFRC) bajo solicitaciones de tracción y cortante, y sobre la determinación de parámetros que representan la tenacidad del material sometido a esos dos modos de carga. Asimismo, se han realizado ensayos hasta rotura por cortante de elementos estructurales a escala real, los cuales se han analizado utilizando formulaciones existentes en distintos códigos de diseño.El comportamiento a tracción uniaxial del hormigón reforzado con fibras de acero se caracteriza utilizando cilindros entallados, elaborados con hormigones de resistencia normal y alta, con y sin fibras de acero. La metodología se extiende también para testigos extraídos de elementos de mayor tamaño. Los resultados se utilizan para definir parámetros de tenacidad y resistencia equivalentes de post-pico utilizables para representar el comportamiento del material y para un posible diseño estructural. Además, se desarrolla un estudio paramétrico experimental, que considera diferentes variables del ensayo y forma de probetas, para definir una configuración confiable del ensayo. Se analizan los modos de rotura observados y se evalúa la respuesta tensión-ancho de fisura. Asimismo, se propone una relación tensión-apertura de fisura característica para el diseño y análisis estructural. El comportamiento a tracción uniaxial se compara también con el de flexión y tracción por compresión diametral.La fractura por cortante se estudia a nivel material, en hormigones de resistencia normal y alta, con y sin fibras de acero, utilizando la configuración de cortante directo denominada push-off. Se analizan el modo de rotura y la respuesta tensión-desplazamiento. Además, se definen parámetros basados en la tenacidad y tensiones equivalentes de cortante para una posible utilización en el diseño estructural.Con el fin de obtener resultados que validen la utilización de las fibras de acero como refuerzo de cortante y al mismo tiempo estudiar la fractura por cortante a nivel estructural, se han realizado ensayos a escala real sobre vigas de sección rectangular y en T. Se analizan las respuestas carga-flecha y carga-ancho de fisura de vigas rectangulares de hormigón reforzado con fibras de acero variando su altura y de vigas T variando las dimensiones del ala. Los resultados obtenidos experimentalmente se utilizan para verificar la aplicabilidad de los métodos de diseño existentes en el caso del hormigón reforzado con fibras de acero. Además, se presenta una propuesta para el diseño a cortante basada en la respuesta tensión-desplazamiento relativo obtenida a partir del ensayo push-off de cortante directo. / The thesis deals with the characterization of the failure of steel fiber reinforced concrete (SFRC) in tension and shear, on the material level, and the determination of parameters that represent the toughness in these two modes of failure. Tests have been performed on large-scale beams failing under shear failure, which have been analyzed using existing design code formulas. The toughness parameters determined from the material are used in the design against such failure.The uniaxial tensile behavior of SFRC is characterized using notched cylinders of normal and high strength concretes, with and without steel fibers. The methodology is also extended to cores extracted from large elements. Results are used to define toughness parameters and equivalent post-peak strengths to be used for representing the material behavior and for possible structural design. Furthermore, a parametric study considering different test variables and specimen shape is carried out in order to define a reliable test configuration. The observed modes of failure are analyzed and the stress-crack width response is evaluated. Also, a characteristic stress-crack width response is proposed for structural analysis and design. The uniaxial tension behavior is also compared with that of flexural and splitting-tension.The shear failure is studied using the direct shear push-off test configuration, in normal and high strength concretes with and without steel fibers. The mode of failure and the stress-slip and stress-crack opening responses are analyzed. Toughness parameters and equivalent shear strengths based on the test results are defined for structural design.In order to provide results for validating the use of steel fibers as shear reinforcement and for studying shear failure at the structural level, full-scale tests on rectangular and T-beams were performed. The load-deflection and load-crack width responses are analyzed and compared with results of plain concrete beam tests. The experimentally-obtained results are used to evaluate the applicability of existing design methods for steel fiber reinforced concrete. Furthermore, a proposal for shear design based on the shear stress versus slip relationship from the push-off shear test is presented.

Este trabajo de investigación presenta un estudio sobre el comportamiento de los puentes de dovelas de hormigón con pretensado exterior y juntas secas conjugadas, centrándose en el estudio de la respuesta a solicitaciones de flexión y cortante combinados, en servicio y en rotura. Se evalúa, asimismo, la posibilidad de sustituir total o parcialmente la armadura convencional de las dovelas tras la inclusión de fibras metálicas en el hormigón.Para ello se realizaron ensayos sobre paneles, para evaluar la resistencia de las juntas conjugadas, y ensayos de vigas con distinto grado de pretensado sometidas a flexión y a cortante. Tanto de vigas como de paneles, se fabricaron dos series paralelas, una realizada con hormigón convencional y otra con hormigón reforzado con fibras de acero. Tanto los resultados obtenidos en estos ensayos, como los de los ensayos encontrados en la bibliografía, se han comparado con la variada formulación existente para evaluar la capacidad resistente de las juntas secas conjugadas propuesta por distintos investigadores y normativas.De entre todos los modelos de junta estudiados, todos ellos basados en el Método de los Elementos Finitos, finalmente se han puesto a punto dos modelos para estudiar la transmisión de cortante entre juntas conjugadas. Un modelo elaborado con elementos tipo junta a los que se les confiere un comportamiento de rozamiento coulombiano y que modeliza la junta (y sus llaves conjugadas) con su geometría. Otro modelo de junta plana que modeliza el comportamiento medio de la junta en la zona de llaves con elementos tipo junta dotados de un modelo de comportamiento de rozamiento cohesivo. Estos modelos de junta han sido calibrados y aplicados al estudio de los ensayos. El primer modelo de junta ha sido aplicado al estudio de los ensayos de paneles. Los dos modelos de junta han sido aplicados al estudio de los ensayos realizados sobre vigas, de los que se ha realizado un completo análisis no lineal en teoría de segundo orden, incluyendo el comportamiento no lineal de los materiales. El modelo de junta plana ha sido usado en el estudio de dos ejemplos de puentes, uno isostático y otro continuo.De todo lo anterior se han extraído conclusiones referentes al modelo de análisis, a la resistencia de las juntas, al armado de las dovelas y al comportamiento global de este tipo de estructuras. / This work presents a study of the behaviour of segmental concrete bridges with external prestressing, focussing on the response under combined flexure and shear, in the service and ultimate limit states. The possibility of replacing entirely or partially the conventional reinforcement of the segments through the incorporation of steel fibres in the concrete is also evaluated.Tests have been performed on panels to evaluate the resistance of castellated dry joints, and on large-scale beams with different levels of prestressing for evaluating the response under flexure and shear. The tests were conducted on conventional and steel fibre reinforced concretes. The results obtained in these tests, as well as those found in the literature, have been compared with several design formulas for evaluating the load-carrying capacity of dry castellated joints. The formulas that gave the best predictions have been identified and used further in the analysis of bridge girders. Two models have been used within the framework of the Finite Element Method for simulating the transmission of shear along joints between match-cast segments. In one of the approaches, the geometry of the joints (and the shear keys) is represented with interface elements with Coulomb frictional behaviour. In the other approach, the global behaviour of the key zone of the joint is represented by flat interface elements with cohesive frictional behaviour. These joint models have been calibrated using the results of the experiments. A complete analysis was performed taking into account the geometric nonlinearities and the non-linear behaviour of the materials. The flat joint model has been used in the study of two bridges, one simply supported highway bridge and another five-span highway bridge.The results of the experimental and numerical analyses have led to significant conclusions regarding the modelling of the keys, load-carrying capacity of the joints, reinforcement detailing in the segments and the global behaviour of segmental structures with dry castellated joints.

Studies on the behavior of steel fiber reinforced concrete (SFRC) and slurry infiltrated fibrous concrete (SIFCON) to impact loading have started in recent years. Using these relatively new materials, higher values of tensile and compressive strength can be obtained with greater fracture toughness and energy absorption capacity, and therefore they carry a considerable importance in the design of protective structures. In this thesis, computational analyses concerning impact loading effect on concrete, steel fiber reinforced concrete (SFRC) and slurry infiltrated fibrous concrete (SIFCON) are conducted by the aid of ANSYS AUTODYN 11.0.0 software. In the simulations, the importance of the concrete compressive and tensile strengths, and the fracture energy, together with the target and projectile erosion parameters, were investigated on the response of concrete target and projectile residual velocity. The obtained results of the simulation trials on concrete, SFRC and SIFCON have been compared with the experimental outcomes of three concrete, two SFRC and two SIFCON specimens in terms of deformed target crater radius, depth volume and striking projectile residual velocities. The simulation analyses have shown that, compressive as well as tensile strengths of the concrete, SFRC and SIFCON specimens are of great importance on the crater volume while erosion parameters have a significant effect on the projectile residual velocity. Simulation outcomes possess a higher accuracy for concrete simulations when comparisons are made with available experimental results. This accuracy deteriorates for SFRC and SIFCON specimens. It was further concluded that related material tests of the specimens must be available in order to obtain higher accuracy.

Thesis (M.S.)--Mississippi State University. Department of Civil Engineering. / Title from title screen. Includes bibliographical references.

A special problem in many reinforced concrete structures built in the 1970s and earlier is the lack of continuity between elements. Continuity is a characteristic of structures essential to preventing collapse. Therefore, in extreme loading conditions such as loss of a column support due to terrorist attack or if earthquake or other extreme actions occur, the structures could be vulnerable to collapse. The study reported here focused on two structural discontinuities in existing reinforced concrete structures, discontinuity in bottom reinforcement in beams (horizontal discontinuity) and poorly detailed lap splices in columns (vertical discontinuity). The objective of this study was to develop rehabilitation methods using CFRP to provide continuity of reinforcement in existing structures. To develop the rehabilitation methods, two separate experimental studies were conducted using beam and column specimens. CFRP materials were applied to the bottom or side face of a beam and anchored using CFRP anchors or U-wraps to provide horizontal continuity in bottom reinforcement and tested under dynamic loading. After CFRP rehabilitation, the ductility of the bottom reinforcement and large rotational capacity of the beam were realized. CFRP materials were also applied to the lap splice region in square and rectangular columns which exhibited a brittle splice failure as-built. After rehabilitating the columns using CFRP jackets and anchors, the failure mode changed from a brittle splice failure to yield of column reinforcement, and the strength and deformation capacity were improved under both monotonic and cyclic loading. Based on the results of beam and column tests, design guidelines for CFRP rehabilitation were proposed. Horizontal and vertical continuities can be provided through the use of CFRP for rehabilitating existing reinforced concrete structures that were designed prior to the introduction of codes that require continuous reinforcement along members and between adjacent members. The vulnerability of such structures to collapse can be reduced through rehabilitation. / text

Fiber reinforcement is being widely used in concrete tunnel linings these days. Using fiber reinforcement can save not only cost, but also labor and time spent on construction. However, many owners hesitate to incorporate fiber reinforcement in tunnel lining due to lack of experience with and knowledge of the behavior of fiber reinforced concrete (FRC) In this study, fiber reinforced concrete was made with various kinds of fibers such as steel fiber, macro-synthetic fiber and hybrid fiber (a blend of macro-synthetic fiber and glass fiber). Many experimental tests were performed to investigate the compressive, flexural and shear behavior of fiber reinforced concrete. In addition to the structural capacity of FRC, the distribution of fiber reinforcement inside the concrete matrix was investigated. Test results of these experimental tests were thoroughly examined to compare and quantify the effects of fiber reinforcement. Next, the test results were used to generate axial force-bending moment interaction diagrams based on current design approaches. In addition, the current design approaches were modified to estimate the accurate and exact value of bending moment. Fiber reinforcement clearly improved the structural performance of tunnel lining. The post-peak flexural and shear strength was significantly influenced by the type and amount of fiber reinforcement. / text

Tiriamajame darbe nagrinėjami tempiamieji plieno plaušu armuoti gelžbetoniniai elementai. Atliekama teorinių skaičiavimo metodų literatūros apžvalga. Darbe gauti nauji eksperimentiniai tempiamųjų plieno plaušu armuotų gelžbetoninių elementų deformacijų duomenys. Iš bandymo rezultatų eliminuojamas betono susitraukimas. Patikslinami Eurokodo 2 ir Model Code tempiamųjų elementų deformacijų skaičiavimo metodai, įvertinant plieno plaušo įtaką. Liekamieji įtempiai apskaičiuojami taikant empirinį metodą. Atliekama teorinių ir eksperimentinių rezultatų palyginamoji analizė. Darbo pabaigoje pateikiami pagrindiniai rezultatai ir išvados. / In this Master Thesis investigation of steel fiber reinforced concrete members subjected to tension is performed. Literature survey on theoretical investigation methods of steel fiber reinforced concrete is done. New experimental data of steel fiber reinforced concrete members subjected to tension is obtained. Concrete shrinkage is eliminated from experimental data.Eurocode 2 and Model Code strain calculation methods of members subjected to tension are adjusted to steel fiber reinforced concrete members. Residual stresses calculated using empirical method. Comperative analysis of experimental and theoretical results is done.