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Este trabalho experimental tem como objetivo estudar a ductilidade de vigas retangulares de concreto armado reforçadas à flexão utilizando compósitos com tecido de fibras de carbono. No estudo realizado são apresentados os conceitos clássicos de ductilidade e é proposta uma nova sistemática para obtenção do índice de ductilidade, baseada nas considerações da energia elástica e da energia inelástica. A ductilidade é determinada por meio de um índice energético, que se caracteriza como uma forma mais eficiente para a determinação e análise da ductilidade emelementos estruturais. O programa experimental consistiu no ensaio de sete vigas bi-apoiadas, sendo uma viga de referência e as demais reforçadas à flexão com tecido defibras de carbono. Todas as vigas possuem as mesmas características mecânicas e geométricas e foram dimensionadas de modo a garantir a ruptura por flexão. Aviga de referência, a primeira ensaiada, não foi reforçada e serviu para comparações de incremento de rigidez e resistência após a aplicação do reforço. As vigas reforçadas foram divididas em dois grupos. O grupo A é constituído de duas vigas, reforçadas inicialmente com uma e duas camadas de tecido de fibra de carbono. O grupo B é constituído por quatro vigas que foram reforçadas apósum carregamento inicial. Neste grupo, duas vigas foram reforçadas com uma camada de tecido de fibra de carbono e as outras duas foram reforçadas com duas camadas de tecido de fibras de carbono, correspondendo à mesma área totalde reforço das anteriores. Todas as vigas foram concretadas, instrumentadas e ensaiadas no Laboratório de Estruturas e Materiais da PUC-Rio. Os ensaios das vigas dogrupo B foram realizados com as vigas pré-ensaiadas, reforçadas sob deformação constante e em seguida levadas à ruptura. A deformação foi mantida constante durante a aplicação e o período de cura do reforço. Os resultados obtidos em termos de carga, flecha, momento, curvatura, ductilidade energética e rotação plástica foram analisados. Os estudos realizados mostraram que o reforço com compósitos de fibras de carbono é uma técnica eficaz, que as vigas apresentam ductilidade adequada e que os índicesenergéticos propostos são adequados para este tipo de estudo.
O objetivo deste trabalho é o estudo experimental do comportamento e do desempenho de vigas de concreto armado reforçadas à flexão com tecidos de compósitos defibras de carbono. O programa experimental consiste no ensaio de sete vigas biapoiadas com um vão em balanço. Todas as vigas possuem a mesma seção transversal, armaduras e vãos, dimensionadas de forma que, antes do reforço, o valor do momento positivo máximo seja igual ao do momento negativo máximo. A primeira viga ensaiada não foi reforçada e foi utilizada como viga de referência. As vigas reforçadas foram divididas em dois grupos. No primeiro grupo, três vigas foram igualmente reforçadas nas regiões de momentos máximos positivos e negativos. No segundo grupo, três vigas tiveram sua armadura de reforçoduplicada, em relação às vigas do primeiro grupo, na região de momento máximo negativo. As vigas foram concretadas, instrumentadas e ensaiadas no Laboratório de Estruturase Materiais da PUC-Rio. Para tentar reproduzir a situação real, o carregamento foi aplicado nas vigas reforçadas até atingir cerca de 50% do valor previsto para a ruptura. Neste instante a viga já apresentava diversas fissuras e o ensaio foi interrompido para aplicação do reforço sobcarregamento. Os resultados obtidos para as vigas em termos de deflexão, deformação da armadura, fissuração, modo e carga de ruptura são analisados. É possível verificar um aumento significativo de resistência e rigidez das vigas reforçadas, confirmando a eficiência deste tipo de reforço. A ductilidade avaliada em termos de critérios energéticos aparece como um parâmetro adequado para a análise do comportamento estrutural de vigas reforçadas com tecidos de compósitos de fibras de carbono.
Strengthening Design of Reinforced Concrete with FRP establishes the art and science of strengthening design of reinforced concrete with fiber-reinforced polymer (FRP) beyond the abstract nature of the design guidelines from Canada (ISIS Canada 2001), Europe (FIB Task Group 9.3 2001), and the United States (ACI 440.2R-08). Evolved from thorough cla
"Different strengthening systems have been widely used for many years to retrofit and repair deficient structural members. Reinforced concrete (RC) slabs and beams are commonly strengthened in flexure by externally bonding Carbon Fiber Reinforced Polymer (CFRP) sheets to the bottom side of the member. The CFRP sheets used in strengthening applications have high strength; however, they are brittle materials with low ductility. Basalt Fiber Reinforced Polymer (BFRP) sheets on the other hand have relatively lower strength compared to CFRP, however they have higher ductility. As a result, there is growing interest among researchers and practitioners in combining different types of FRP sheets to produce an enhanced strengthening system in terms of strength and ductility. This study investigates the flexural behavior of RC beams externally strengthened with CFRP sheets, BFRP sheets, and their hybrid combination (CFRP-BFRP). This hybrid system is designed to enhance the properties of composites, where it combines the high strength of CFRP and high ductility of BFRP sheets, respectively. To investigate the behavior of the different strengthening systems, an experimental program was conducted on ten RC beams that were tested under four-point bending. The load versus mid-span deflection data were recorded and used to compare the performance of the strengthened specimens. The test results indicated that all strengthened specimens yielded higher flexural capacity and lower ductility values compared to the unstrengthened control beam. The increase in the flexural capacity of the strengthened beams ranged from 23% to 68% of the control beam. Moreover, the beams strengthened with BFRP and hybrid CFRP-BFRP sheets achieved higher ductility compared with the beams strengthened with CFRP sheets. Thus, it was concluded that the use of a hybrid combination of CFRP-BFRP sheets could achieve the desired increase in the flexural capacity of RC beams with an improved ductility compared to that with CFRP sheets only. Finite element (FE) models were also developed and were able to capture the behavior of the tested beams with a good level of accuracy. The predicted flexural capacity along with the associated mid-span deflection differed by 1% to 10% from the experimental values."--Abstract.
Fibre-reinforced polymer (FRP) composites are used to strengthen reinforced concrete (RC) structures. A large amount of research now exists on this. This book brings together all existing research into one volume.
"The demand for strengthening of aging reinforced concrete (RC) structures are continuously rising. Carbon fiber reinforced polymers (CFRP) are the most widely used externally bonded-reinforcing (EBR) materials for strengthening and retrofitting of RC structural members. The use of high strength galvanized steel mesh (GSM) strengthening material has recently gained some acceptance. However, Both CFRP and GSM have high strength but have low ductility. Recently developed aluminum alloys (AA) have high ductility and some desirable characteristics that may overcome some of the shortcomings of CFRP and GSM. Combining AA with CFRP and GSM will result in a hybrid material with balanced strength and ductility. Therefore, the major aim of this research is to develop a hybrid ductile and strong retrofitting system by combining AA plates with GSM and CFRP laminates to strengthen RC beams in flexure. A comprehensive experimental program was carried out to determine the tensile strength and the bond strength of the hybrid system. Fifteen-coupon specimens were tested for tensile strength, six specimens of concrete prisms for bond strength and 25 T-beam specimens for flexural strength under a four-point loading. Results showed an increase in the flexural capacity of the strengthened specimen ranging from 10% to 77% compared to the control beam and a decline in ductility of 13% to 59% compared to the un-strengthened specimen. Furthermore, analytical models based on ACI 440.2R-08 guidelines were employed to capture the flexural behavior of the tested specimens. Experimental results correlated well with the analytical predictions in a range of 30% of the experimental values. The study concluded that the newly proposed hybrid systems are promising systems for the improvement of the flexural behavior (strength and ductility) of RC beams."--Abstract.
The first textbook on the design of FRP for structural engineering applications Composites for Construction is a one-of-a-kind guide to understanding fiber-reinforced polymers (FRP) and designing and retrofitting structures with FRP. Written and organized like traditional textbooks on steel, concrete, and wood design, it demystifies FRP composites and demonstrates how both new and retrofit construction projects can especially benefit from these materials, such as offshore and waterfront structures, bridges, parking garages, cooling towers, and industrial buildings. The code-based design guidelines featured in this book allow for demonstrated applications to immediately be implemented in the real world. Covered codes and design guidelines include ACI 440, ASCE Structural Plastics Design Manual, EUROCOMP Design Code, AASHTO Specifications, and manufacturer-published design guides. Procedures are provided to the structural designer on how to use this combination of code-like documents to design with FRP profiles. In four convenient sections, Composites for Construction covers: * An introduction to FRP applications, products and properties, and to the methods of obtaining the characteristic properties of FRP materials for use in structural design * The design of concrete structural members reinforced with FRP reinforcing bars * Design of FRP strengthening systems such as strips, sheets, and fabrics for upgrading the strength and ductility of reinforced concrete structural members * The design of trusses and frames made entirely of FRP structural profiles produced by the pultrusion process
Few decades ago, there were no guidelines for torsion design of reinforced concrete (RC) beams. Hence, many existing beams in older buildings have a lack of adequate torsional strength since they were not properly designed for torsion. One way to regain/rehabilitate adequate torsional strength is through application of externally bonded carbon fiber reinforced polymers (CFRP). To date, American Concrete Institute (ACI) code, as well as other building codes, do not have recommendations or provisions for strengthening RC beams for torsion using fiber-reinforced polymer (FRP) composites due to the inexistence of conclusive experimental and analytical data. Of the very limited works on this behavior, the majority of the focus has been devoted to experimental works. Realistic spandrel beams in a building that lack torsional strength were modelled in this research, and strengthened to examine various behaviors such as load capacity, deflection, torque, twist, crack propagation, ductility, and failure modes. For this purpose, six RC beams were tested: four reference beams and two strengthened beams were used to observe additional capacity through the use of carbon fiber-reinforced polymer (CFRP) sheets. To strengthen the beams, one layer of sheets was completely wrapped around them. Results show an additional torsional capacity of 63% and 178% relative to their respective reference beams. Through strengthening, modes of failure of the beams changed from brittle torsion-dominated failure to shear-flexure failure in both beams. The study also included crack pattern and ductility of test beams. Cracks became smaller in width and more evenly distributed across the torsion-loaded area, and torsional ductility was enhanced by 266% and 165% respectively. Flexural ductility was also greatly enhanced by more than five folds. Finally, using ACI 318-14, ACI 440.2R-02, and available formulae in the literature, the beams were analyzed and the respective values were compared.