The self-compacting concrete (SCC) has been characterized as a great evolution in the concrete technology, being able to fill all empty spaces of the formwork and selfcompacting only by action of its own weight. If steel fibers are added to SCC, without prejudice its properties in the fresh state, new advantages and possibilities of applications will provide concretes more efficient. In this context, a SCC with addition of industrial waste is used, and steel fibers with l/d ratio equal to 50 are incorporated, in a volume fraction of 1%, in order to assess the behavior of reinforced self-compacting concrete beams, with and without the addition of steel fibers, subject to normal and tangential stresses, and compare them with the behavior of conventional reinforced concrete beams. For that, were made reinforced concrete beams of dimensions (12,5 x 23,5 x 132) cm, which were tested by four-point bending, to the 28 days of age. To compare the results, were produced conventional concretes of different compositions, with and without steel fibers. The tests results in the fresh state shown that was possible the obtaining of concrete with self-compacting properties, even with the addition of steel fibers, from a mix already existent of SCC. The addition of the steel fibers to the SCC promoted slight gain in the load capacity of the beam, with lower displacements in the middle span, lower deformations in the reinforcement bars and improved cracking control, compared to the others beams produced with concrete compacted by vibration, with and without steel fibers. / O concreto auto-adensável (CAA) vem se caracterizando como uma grande evolução na tecnologia do concreto, sendo capaz de preencher todos os espaços vazios da fôrma e adensar-se apenas pela ação de seu peso próprio. Se ao CAA adicionam-se fibras de aço, sem prejuízo de suas propriedades no estado fresco, novas vantagens e possibilidades de aplicação proporcionarão concretos mais eficientes. Dentro desse contexto, um CAA com adição de resíduo industrial é usado, e fibras de aço com relação l/d = 50 são incorporadas, em uma fração volumétrica de 1%, com intuito de avaliar o comportamento de vigas de concreto auto-adensável armado, com e sem o reforço de fibras de aço, submetidas às solicitações normais e tangenciais, e compará-las com o comportamento de vigas de concreto armado convencional. Para isso, foram confeccionadas vigas de concreto armado de dimensões (12,5 x 23,5 x 132) cm, as quais foram ensaiadas por flexão a quatro pontos, aos 28 dias de idade. Para comparação dos resultados, foram produzidos concretos convencionais de diferentes composições, com e sem a adição das fibras de aço. Os resultados dos ensaios no estado fresco mostraram que foi possível a obtenção de concreto com propriedades auto-adensáveis, mesmo com adição de fibras de aço, a partir de uma dosagem de CAA já existente. A adição das fibras de aço ao CAA promoveu sensível ganho na capacidade resistente da viga, com menores flechas, menores deformações das armaduras, longitudinal e transversal, e melhorado controle da fissuração, em comparação às demais vigas produzidas com concretos adensados por vibração, com e sem fibras de aço.

[pt] Este trabalho apresenta o desenvolvimento de uma ferramenta computacional gráfico-interativa para a verificação de vigas de concreto protendido com pós-tração aderente ao estado limite de serviço, de acordo com a norma brasileira NBR 6118:2014. A ferramenta é uma extensão (addin) para o Autodesk Robot Structural Analysis Professional , que serve como plataforma de modelagem estrutural. A partir de dados fornecidos pelo usuário através de uma interface gráfica, o programa desenvolvido calcula todas as perdas de protensão que ocorrem ao longo da vida-útil da estrutura, assim como os carregamentos equivalentes à protensão durante este período. O trabalho apresenta os métodos de cálculo tradicionais das perdas imediatas e diferidas, obtidos da NBR 6118, e as modificações que tiveram que ser feitas para permitir um cálculo incremental. Exemplos de utilização do programa e dos cálculos necessários também são apresentados e comprovam, pelos bons resultados obtidos, o acerto na escolha da metodologia escolhida. Como resultado, a ferramenta apresenta duas saídas: uma planilha contendo os esforços e as tensões atuantes na viga ao longo de sua vida-útil e verificações destes valores em relação aos limites estabelecidos para o estado limite de serviço; e o modelo estrutural no Robot apresenta os carregamentos equivalentes da protensão. O usuário pode então adotar estes carregamentos em demais cálculos da estrutura, enquanto a planilha pode ser utilizada para verificar com facilidade se a protensão atende às condições de serviço. / [en] This work presents the development of an interactive graphics computational tool for the verification of prestressed concrete beams with posttensioned bonded tendons to the serviceability limit state stress check according to the Brazilian code NBR 6118:2014. The tool is an add-in for Autodesk Robot Structural Analysis Professionalr, which serves as a structural modeling platform. With data supplied by the user through a graphics user interface, the program here developed calculates all relevant prestress losses that occur throughout the structure s life-cycle, along with the prestressing s equivalent loads during this period. The traditional calculation methods, obtained in the NBR 6118, are presented along with the modifications which had to be implemented in order to allow for incremental loss calculations. Usage examples and the necessary calculations are presented and, through the results obtained, validate the adopted methodology. As results, the program presents two outputs: a spreadsheet containing the resultant forces and stresses and a check of these values with respect to the permissible stresses in the serviceability limit state; and the Robot model presents the prestress equivalent loads. The user may then use these loads in additional calculations. The spreadsheet may be used to easily check if the prestress is sufficient with respect to serviceability conditions.

Este trabalho analisou o comportamento estrutural de polímeros reforçados com fibra de vidro - PRFV em elementos pré-moldados de concreto, com aplicações específicas em vigas de concreto. Realizou-se um estudo comparativo do comportamento de vigas pré-moldadas reforçadas com armadura convencional, segundo a norma brasileira NBR 6118:2003, e reforçadas com armadura de barras pultrudadas de PRFV, segundo o ACI 440.1R-06. O estudo visa obter subsídios para a aplicação de barras de reforço de PRFV, em relação ao Estado Limite de Serviço - ELS, em obras realizadas em regiões de alta agressividade ambiental. Posteriormente fez-se os mesmos modelos de cálculo em elementos finitos, onde foram comparados e analisados os resultados obtidos com o cálculo prescrito pelas normas. Nem todos os parâmetros da norma americana foram inseridos, uma vez que alguns coeficientes internos que contam com efeitos sísmicos e com a neve estão embutidos nos cálculos. Os resultados obtidos, principalmente no cisalhamento, foram altamente satisfatórios, validando a aplicação do PRFV nas vigas consideradas. / This work studied the behavior of precast beams when subjected to shear stress according to the brazilian standard NBR 6118:2003 reinforced with steel bar compared to the american standard ACI 440.1R-06 when the structural member was reinforced with glass fiber reinforced polymer - GFRP pultruded bars. The goal of this work is to acquire subsidies to apply the GFRP in aggressive environmental sites. Also the same model calculations were performed by using Finite Element Method and compared to the results of the calculation prescribed by the standards. Some parameters indicated in the ACI standard were not followed since they are related to seismic and snow effects. The obtained results mainly in shear loading were highly satisfactory which validates the use of GFRP in the considered beams.

As vigas mistas de aço e concreto têm sido amplamente empregadas em edifícios e pontes, havendo ampla investigação teórica e experimental a respeito da utilização de perfis laminados e soldados e conectores de cisalhamento compatíveis com esses perfis, como por exemplo, o conector tipo pino com cabeça (stud bolt) e perfil U laminado. No âmbito dos perfis formados a frio, a utilização do sistema misto ainda é incipiente, necessitando de investigações mais aprofundadas a respeito do comportamento estrutural e a adequação dos modelos de cálculo adotados para vigas mistas em perfis laminados e soldados. No Brasil, a ampla disponibilidade de aços planos tem impulsionado o emprego do sistema misto constituído por perfis formados a frio em edifícios de pequeno porte, porém, mediante concepções clássicas, o que não conduz a um aproveitamento mais racional do sistema. Neste trabalho foi investigado um sistema não-convencional de vigas mistas em perfil cartola leve preenchido com concreto, cuja conexão com a laje foi feita mediante duas soluções: conectores do tipo alça em barra chata soldados ao perfil e conectores do tipo alça em barra redonda soldados ao perfil. Foi feita avaliação do comportamento estrutural da conexão aço-concreto, via ensaios de cisalhamento direto (push-out tests), e ensaios em vigas mistas simplesmente apoiadas para avaliação da região de momento fletor positivo. Os conectores de cisalhamento apresentaram ductilidade e resistência compatíveis com as vigas mistas analisadas, e as respostas de rigidez e resistência à flexão para uma condição de interação completa comprovam que a hipótese de plastificação total da seção descreve com precisão o comportamento estrutural do sistema proposto. / The composite steel and concrete beams have been largely applied in buildings and bridges constructions, having also a large amount of theoretical and experimental investigations about the use of hot-rolled and welded shapes and shear connectors that are compatible with these members, as for an example, the stud bolt and channel connectors. In the cold-formed steel sections scope, the use of a composite steel and concrete solution is still premature, what makes necessary a higher degree of a structural behavior investigation and the adequacy of the theoretical solutions proposed, also for the composite steel and concrete hot-rolled and welded shapes. In Brazil, the high availability of steel sheets has pushed the employee of the composite system of cold-formed steel in small and mid-height buildings, however, because of classical conceptions, it doesn\'t lead too a more rational use of the system. It was investigated in this work a non-conventional lightweight composite system formed by hat-shaped beams filled with concrete, witch connection with the slab was done by means of two solutions: arc-shaped connectors in at bars welded too the section and arc-shaped connectors in round bars welded too the section. An analysis was conducted for evaluation of the structural behavior in the steel and concrete interface by push-out tests, and tests in simple two points supported beams for evaluation of the bending strength. The shear connectors showed ductility and resistance compatible with the analyzed composite beams and the stiffness and bending resistance responses for the given condition of full interaction showed that the full section plastification consideration describes with precision the structural behavior of the proposed system.

A substituição do aço pela armadura não metálica objetiva o aumento da durabilidade de estruturas sujeitas à corrosão e a campos eletromagnéticos. Mas, a inserção de um novo material na construção civil demanda especificação de sua composição, comportamento e procedimentos de sua utilização. Este trabalho analisa o comportamento à flexão de vigas de concreto armadas com barras não metálicas. Para esta finalidade foram realizados, uma revisão bibliográfica considerando os trabalhos publicados desde o início das pesquisas até os mais recentes e ensaios dos materiais e de vigas de concreto armado. Os ensaios de determinação das propriedades das barras da armadura não metálica de GFRP (glass fiber polymer – polímero reforçado com fibra de vidro) englobam a determinação do diagrama tensão-deformação e capacidade resistente. As vigas armadas com barras de GFRP foram ensaiadas à flexão em quatro pontos e os resultados comparados com o de uma viga armada com barras de aço CA-50 também ensaiada a flexão. Nos modelos pôde-se perceber a influência das propriedades das barras de GFRP no comportamento geral da estrutura. Por exemplo, as grandes deformações nas barras longitudinais e os deslocamentos dos modelos foram determinados pelo baixo módulo de elasticidade das barras de GFRP. É evidente a necessidade de continuação dos estudos envolvendo barras de GFRP. Estas pesquisas poderão desenvolver meios de se utilizar as propriedades do material em favor do melhor funcionamento da estrutura / Steel reinforcement replacement aims an increase at the durability of structures with corrosion and electrical magnetic problems. But, inserting a new material at the civil construction industry demands specifications of its composition, behavior and procedures for its utilization. This work is a flexural behavior analysis of reinforced concrete beams reinforced with GFRP bars. To make this, a technical literature research was made considering the pioneer until the most recent researches, and components and concrete reinforced beams tests were done. GFRP bars properties tests went from the determination of its strains X stress diagram to its tension resistance. GFRP reinforced beams were submitted to four points flexural tests and the results compared with a CA-50 steel reinforced beam also submitted to the flexural test. The specimens showed the influence of GFRP properties at the behavior of the structure. For example, longitudinal bars large strains and the large displacement of the beam were determined by GFRP bars low longitudinal elastic modulus. Continuing the studies evolving GFRP bars is certainly a need. New researches might be able to design a way to use the composite properties to improve the structure behavior

Sprintlyftet är ett vanligt lyft som används på byggarbetsplatser idag för att montera betongbalkar och det används dessutom när betongbalkarna hanteras i fabriken där de tillverkats. Allt fler prefabricerade byggelement tillverkas och det leder till att lyftens kapacitet behöver säkerställas. I den här studien provades kapaciteten experimentiellt i ett specifikt lyft, sprintlyftet. Det är ett lyft som Abetong använder till sina betongbalkar. Det som under studien kontrollerades var om betongbalkarna idag klarar mer än vad de gjorde vid motsvarande provning för 42 år sedan. En jämförelse mellan provningar som gjordes av Abetong år 1975 och den här studiens provning visar att sprintlyften som används idag klarar av mer last än vad provningarna från 1975 gjorde. Förklaringen till det är främst att kvalitén av betongen har utvecklats under åren. / The sprint lift is a common lift used on construction sites today to mount concrete beams and it is also used when the concrete beams are handled in the factory where they were manufactured. More and more prefabricated building elements are manufactured and this means that the lifts capacity needs to be ensured. In this study, capacity was experimentally tested in a specific lift, the sprint lift. It is a lift that Abetong uses for its concrete beams. What was checked during the study was if the concrete beams today manage more than they did in the corresponding test 42 years ago. A comparison of tests made by Abetong in 1975 and this study's test show that the sprint lift used today is capable of more load than what the 1975 tests did. The explanation for this is primarily that the quality of the concrete has developed over the years.

The ability to adjust structural response to external loading and ensure structural safety and serviceability is a characteristic of Smart Systems. The key to achieving this is through the development and implementation of smart materials. An example of a smart material is a Shape Memory Alloy (SMA). Reinforced concrete structures are designed to sustain severe damage and permanent displacement during strong earthquakes, while maintaining their integrity, and safeguarding against loss of life. The design philosophy of dissipating the energy of major earthquakes leads to significant strains in the steel reinforcement and, consequently, damage in the plastic hinge zones. Most of the steel strain is permanent, thus leading to large residual deformations that can render the structure unserviceable after the earthquake. Alternative reinforcing materials such as superelastic SMAs offer strain recovery upon unloading, which may result in improved post-earthquake recovery. Shape Memory Alloys have the ability to dissipate energy through repeated cycling without significant degradation or permanent deformation. Superelastic SMAs possess stable hysteretic behavior over a certain range of temperature, where its shape is recoverable upon removal of load. Alternatively, Martensite SMAs also possess the ability to recover its shape through heating. Both types of SMA demonstrate promise in civil infrastructure applications, specifically in seismic-resistant design and retrofit of structures. The primary objective of this research is to investigate experimentally the performance of concrete beams and shear walls reinforced with superelastic SMAs in plastic hinge regions. Furthermore, this research program involves complementary numerical studies and the development of a proposed hysteretic constitutive model for superelastic SMAs applicable for nonlinear finite element analysis. The model considers the unique characteristics of the cyclic response of superelastic materials.

No description available.

Corrosion of steel reinforcement has been identified as one of the major problems facing many existing reinforced concrete structures including bridges. The exposure to aggressive environmental conditions such as those with high concentrations of chloride ions due to the use of de-icing salt in cold regions or high concentrations of carbon dioxide due to increased greenhouse gas emissions, accelerate the initiation process of corrosion. As corrosion initiates, the structural performance in terms of load-carrying capacity, ductility, and service life deteriorate over time. Coupling the effect of reinforcement corrosion with service loads may further weaken the structural performance of reinforced concrete bridges due to the presence of transverse load-induced cracks. Accordingly, a research program was conducted to evaluate the structural performance of reinforced concrete beams subjected to coupled effects of service loads and reinforcement corrosion. The research project consisted of combined experimental and numerical investigations. The experimental phase consisted of tests of nine small-scale beams and six large-scale beams. The beams were designed, constructed, instrumented, and loaded under a four-point load test. The primary test variables were the applied corrosion current density, level of corrosion, and level of sustained loading as percentage of beam ultimate capacity (0% Pu, 40% Pu, and 60% Pu). The corrosion level of steel reinforcement was quantitatively assessed using gravimetric weight measurements and three-dimensional laser scanner technique. Test results indicated that failure of corroded RC beams was brittle due to premature rupture of corroded steel bars, which was attributed to the development of localized corrosion at the sections with flexural cracks in beams. Furthermore, it was found that beams subjected to higher levels of service loads, experienced further reductions in ultimate load capacity and ductility. In addition, tensile tests were used to evaluate the effect of corrosion on the mechanical performance of steel bars retrieved from the corroded beams. It was found that the tensile strength of corroded steel bars, based on nominal sectional area, was reduced with the increase of corrosion levels. In contrast, the tensile strength, based on minimum sectional area, was not influenced by the non-uniform distribution and localization of corrosion. In fact, there was a slight increase in strength with the increase of corrosion levels. The numerical phase consisted of finite element analyses of beams using DIANA FE analysis software. A simplified approach was implemented to introduce the damage induced by corrosion into two-dimensional nonlinear FE models, based on the experimental testing of corroded beams and corroded steel bars. The analyses were reasonably accurate in predicting cracking patterns, residual load capacity, residual ductility, and failure modes of corroded beams. Subsequently, the validated model was used to conduct a parametric study on the level of service loads, level of corrosion, strength of concrete, and tensile reinforcement ratio. It was found that the FE model of corroded beams was strongly influenced by the level of service loads, level of corrosion, and tensile reinforcement ratio.

<div>Several truck fires have occurred in recent years involving bridges with reinforced and prestressed concrete components. If the fire burns for a significant period of time (15 minutes or more), bridge inspectors and engineers must determine if the exposure to elevated temperature has reduced the strength and serviceability of the concrete components. Little guidance is available, however, correlating the results of field inspections with the actual condition of the reinforced/prestressed concrete elements. This dissertation presents the results of a research program conducted to develop rational guidance for inspectors and engineers to evaluate concrete bridge elements after a fire event and help them make informed decisions regarding the future status of the bridge. <br></div><div><br></div><div>The research program includes tests on portions of a reinforced concrete deck and three full-scaled AASHTO Type I prestressed girders acquired from a decommissioned highway bridge. In addition, six pretensioned concrete prismatic beam specimens with varying levels of prestress were fabricated and tested. The specimens had cross-sectional dimensions of 8 in. by 8 in. and were designed to simulate the bottom flanges of common I-shaped prestressed concrete bridge girders. The deck specimens and four (of the six) concrete beam specimens were subjected to elevated temperatures using radiation-based heaters. Two (of the six) prismatic specimens built in the laboratory were subjected to a hydrocarbon pool fire test conducted in the field for using approximately 135 gallons of kerosene. The concrete temperature profiles and the deformations of the specimens were measured using thermocouple trees and displacement transducers, respectively. Concrete samples were also cored and examined using various methods (DSC and SEM) to correlate microstructure degradation (microcracking, dehydration of C-S-H, decomposition of calcium hydroxide, etc.) with the measured temperatures through the depth of the specimens. <br></div><div><br></div><div>To evaluate the residual loading-carrying capacities of prestressed concrete girders after being subjected to fire, a hydrocarbon pool fire test was performed on two decommissioned AASHTO Type I girders in the field. Load tests were then conducted on the prestressed girders under both ambient and post-fire conditions. After structural testing, material tests were also conducted on concrete cores taken from the girders to evaluate the post-fire concrete microstructure alteration. Furthermore, three-dimensional finite element models were developed to predict the residual load-carrying capacities and overall structural responses of prestressed concrete bridge girders after being exposed to fire. Results from the numerical models generally agree favorably with experimental observations and provide insights into the behavior of the specimens. A parametric study was performed using the benchmarked finite element models to expand the database and establish design recommendations further. Capacity influence lines for load-carrying capacities and structural stiffness were developed and discussed.</div><div><br></div><div>Based on the results from this research, guidelines for the post-fire assessment of prestressed concrete bridges are included in this dissertation along with a step-by-step checklist. Bridge inspectors can infer the extent of damage to prestressed concrete bridge girders in the event of a fire and develop a post-fire assessment plan cognizant of the findings. In most cases, no more than 1.0 in. of the concrete from the exposed surface undergoes material damage / deterioration due to loss of CH, cracking, and spalling. The impact on the strength of prestressed concrete girders is relatively minor based on experimental results. Their initial stiffness, however, will likely be reduced. <br> </div><br>