O objetivo da análise estrutural é determinar os efeitos das ações em uma estrutura, com a finalidade de efetuar verificações de estados limites últimos e de serviço (NBR 6118:2003 Projeto de estruturas de concreto). A análise estrutural consiste numa das principais etapas do projeto estrutural de um edifício, pois compreende a escolha dos modelos teóricos, que devem representar adequadamente a estrutura real, e do tipo de análise, com relação ao comportamento dos materiais. Visa-se, com este trabalho, aproximar o meio técnico do acadêmico, e tornar mais acessível a parte da NBR 6118:2003 que trata da análise estrutural. Neste trabalho consideram-se os modelos estruturais mais utilizados, no cálculo de edifícios, e os principais conceitos relativos aos diferentes tipos de análise permitidos pela norma. Em seguida são realizados exemplos de elementos lineares, pelos diferentes tipos de análise, com ênfase na redistribuição de esforços, empregando-se análise linear com redistribuição ou análise plástica. Ressalta-se a importância da consideração de seção T nas vigas e os ajustes necessários quando da consideração de uma envoltória de carregamentos. Tem-se ainda um exemplo de um edifício de oito pavimentos, que visa demonstrar as diferenças nos esforços ou nos deslocamentos obtidos com modelos estruturais distintos / The structural analysis objective is to determine the actions effects in a structure, with the purpose of verifying the ultimate limit states and serviceability (brazilian code NBR 6118:2003 - Design of concrete structures). The structural analysis is one of the main parts of a building structural design, since it involves the choice of theoretical models that represent appropriately the real structure, and the type of analysis due to the materials behavior. This work intends to shorten the distance between design engineers and the academic world, providing a clearer vision of the NBR 6118:2003 structural analysis approach. This work considers the most common structural models used for buildings, and the theory concerning the different types of analysis permitted by the brazilian code. It presents simple examples of linear elements computed by different types of analysis, emphasizing the moment redistribution possibility, either with the linear analysis with redistribution or the plastic analysis. The importance of considering T-beam with moment redistribution is made clear, and lines of direction to consider alternate position of live loads are given. The last example presents an eight store building, and its differences relative to efforts and displacements, obtained by distinct structural models

Most reinforced concrete (RC) structures are continuous in some way, and many of these structures are strengthened using fibre-reinforced polymer (FRP) materials as a routine basis. The problem of how to exploit moment redistribution in FRP-strengthened continuous RC structures is still unresolved. Reduction in ductility has been recognised in such structures. However, FRP-strengthening is introduced as an effective method to enhance the strength and load bearing capacity of RC structures. As a result, design guidelines worldwide employ conservative guidance for design, such that they limit the potential exploitation of moment redistribution in FRP-strengthened members. To date, limited research has been conducted into the redistribution of bending moment in such structures. Previous theoretical studies have not yet led to a reliable and rigorous solution for quantifying moment redistribution throughout the loading cycle. In addition, a wide scatter of moment redistribution percentage findings, from zero to 56%, has been reported in previous experimental studies. This demonstrates the need for further research to effectively characterise the circumstances under which moment redistribution can be relied on, both into and out of FRP-strengthened zones in continuous RC flexural members. This research aims to encourage the use of FRP for strengthening existing RC structures in a more efficient manner. The findings help to better understand restrictions on moment redistribution into and out of FRP-strengthened zones, effect of mechanical anchorage of the FRP on the degree of moment redistribution, and the extent to which moment redistribution can be relied on. A new analytical model, only based on structural mechanics, is developed in this research. A comprehensive set of large-scale structural testing is undertaken to validate the analytical model under various strengthening circumstances. The analytical and experimental results show that moment redistribution can occur into FRP-strengthened zones to full capacity without any limitation, even if the FRP is unanchored. Further, bending moment can also be redistributed out of strengthened zones to a considerable extent (up to 20%), depending on the quantity and stiffness of the FRP, and provided that the FRP is fully anchored. A set of parametric studies is conducted to investigate the effectiveness of different parameters on the level of moment redistribution. The major parameters include compressive strength of concrete, steel reinforcement proportion, steel yield strength, FRP quantity and stiffness, ultimate strain of the FRP, strengthening configuration, load position, beam shape, and curvature ductility. The outcomes demonstrate that it is not only the curvature ductility of FRP-strengthened sections that is important to the capacity for moment redistribution (out of such zones), but also the mode of failure, strength of the other critical zones, the ratio of stiffness between the critical zones, and the loading arrangement. It is concluded that moment redistribution in continuous FRP-strengthened concrete structures should be permitted both into and out of strengthened zones, provided that the criteria for such redistribution are met.

O objetivo da análise estrutural é determinar os efeitos das ações em uma estrutura, com a finalidade de efetuar verificações de estados limites últimos e de serviço (NBR 6118:2003 Projeto de estruturas de concreto). A análise estrutural consiste numa das principais etapas do projeto estrutural de um edifício, pois compreende a escolha dos modelos teóricos, que devem representar adequadamente a estrutura real, e do tipo de análise, com relação ao comportamento dos materiais. Visa-se, com este trabalho, aproximar o meio técnico do acadêmico, e tornar mais acessível a parte da NBR 6118:2003 que trata da análise estrutural. Neste trabalho consideram-se os modelos estruturais mais utilizados, no cálculo de edifícios, e os principais conceitos relativos aos diferentes tipos de análise permitidos pela norma. Em seguida são realizados exemplos de elementos lineares, pelos diferentes tipos de análise, com ênfase na redistribuição de esforços, empregando-se análise linear com redistribuição ou análise plástica. Ressalta-se a importância da consideração de seção T nas vigas e os ajustes necessários quando da consideração de uma envoltória de carregamentos. Tem-se ainda um exemplo de um edifício de oito pavimentos, que visa demonstrar as diferenças nos esforços ou nos deslocamentos obtidos com modelos estruturais distintos / The structural analysis objective is to determine the actions effects in a structure, with the purpose of verifying the ultimate limit states and serviceability (brazilian code NBR 6118:2003 - Design of concrete structures). The structural analysis is one of the main parts of a building structural design, since it involves the choice of theoretical models that represent appropriately the real structure, and the type of analysis due to the materials behavior. This work intends to shorten the distance between design engineers and the academic world, providing a clearer vision of the NBR 6118:2003 structural analysis approach. This work considers the most common structural models used for buildings, and the theory concerning the different types of analysis permitted by the brazilian code. It presents simple examples of linear elements computed by different types of analysis, emphasizing the moment redistribution possibility, either with the linear analysis with redistribution or the plastic analysis. The importance of considering T-beam with moment redistribution is made clear, and lines of direction to consider alternate position of live loads are given. The last example presents an eight store building, and its differences relative to efforts and displacements, obtained by distinct structural models

This work aims to investigate the flexural behaviour of continuous hybrid reinforced concrete T-beams (HRCT). The investigations consist of three parts; the computational part, the experimental part and the finite element analysis. The computational part included two parts, the first one is developing an analytical programme using MATLAB software to investigate the moment-curvature behaviour of HRCT-beams and to design the experimental specimens. This was followed by the experimental part, where six full-scale reinforced concrete continuous T beams were prepared and tested. One beam was reinforced with glass fibre reinforced polymer (GFRP) bars while the other five beams were reinforced with a different combination of GFRP and steel bars. The ratio of GFRP to steel reinforcement at both mid-span and middle-support sections was the main parameter investigated. The results showed that adding steel reinforcement to GFRP reinforced concrete T-beams improves the axial stiffness, ductility and serviceability in terms of crack width and deflection control. However, the moment redistribution at failure was limited because of the early yielding of steel reinforcement at the beam section that did not reach its moment capacity and could still carry more loads due to the presence of FRP reinforcement. The second part of the computational part included the comparison between the experimental results with the ultimate moment prediction of ACI 440.2R-17, and with the existing theoretical equations for moment capacity, load capacity, and deflection prediction. It was found that the ACI 440.2R-17 design code equations reasonably estimated the moment capacity of both mid-span and middle-support sections and consequently predicted the load capacity of the HRCT-beams based on fully ductile behaviour. However, Qu's and Safan's equations underestimated the predicted moment and load-capacity of HRCT-beams. Also, Bischoff's and Yoon's models underestimated the deflection at all stages of the load for both GFRP and HRCT- beams. For the numerical part, a three-dimensional finite element model has been developed using ABAQUS software to examine the behaviour of HRCT-beams. The experimental results were used to validate the accuracy of the FEM, where an acceptable agreement between the simulated and experimental results was observed. Accordingly, the model was used to predict the structural behaviour of continuous HRCT-beams by testing different parameters.

Yes / This paper reports the testing of 11 reinforced concrete (RC) two-span beams strengthened in flexure with externally bonded carbon fiber-reinforced polymer (CFRP) sheets. The beams were classified into two groups according to the arrangement of the internal steel reinforcement. Each group included one unstrengthened control beam. The main parameters studied were the position, length, and number of CFRP layers. External strengthening using CFRP sheets was found to increase the beam load capacity. All strengthened beams exhibited less ductility compared with the unstrengthened control beams, however, and showed undesirable sudden failure modes. There was an optimum number of CFRP layers beyond which there was no further enhancement in the beam capacity. Extending the CFRP sheet length to cover the entire hogging or sagging zones did not prevent peeling failure of the CFRP sheets, which was the dominant failure mode of beams tested.

[pt] Este trabalho apresenta um estudo experimental sobre a redistribuição de momentos em vigas contínuas de concreto construídas em aduelas pré-moldadas, com juntas secas, e protendidas com cabos sintéticos externos. Para tanto foram ensaiadas quatro vigas contínuas, com dois vãos iguais, sendo uma monolítica e as demais em aduelas pré-moldadas. Todas as vigas têm a mesma seção transversal tipo I, com dois vãos, altura da seção de 30 cm, largura do flange e espessura da alma igual a 30 cm e 10 cm, respectivamente. A viga monolítica tem relação 1/dp (vão/altura) igual a 18,75 e nas vigas em aduelas os valores desta relação foram entre 12,5, 18,75 e 25. As vigas são protendidas com dois cabos sintéticos externos com traçado poligonal. Os cabos utilizados são feitos com fibras sintéticas de alta resistências (2700 MPa) e alto modulo de elasticidade (126000 MPa) conhecidas comercialmente como Kevlar. O objetivo deste estudo é examinar a redistribuição de momentos em vigas contínuas com sistemas construtivos diferentes e com diferentes relações 1/dp frente à utilização de cabos sintéticos. Os resultados mostram que a redistribuição de momentos em vigas em aduelas pode ser obtida a partir de uma viga monolítica semelhante e que o comportamento da redistribuição de momentos nas vigas em aduelas é pouco influenciada pela relação l/dp. / [en] An experimental investigation on the behavior of continuous segmental concrete beams, prestressed with external aramid tendons, was carried out. Four beams were tested; one was monolithic and the others were constructed in precast dry- jointed segments. All the beams had the same overall dimensions, with two spans and an I section 30 cm high, flange width of 30 cm and web thickness of 10 cm. The 1/dp span/section height) ratio was 18,75 for the monolithic beam and 12.5, 18.75 and 25 for the segmental beams. The beams were post-tensioned with two external aramid tendons, which are made of high strength (2700 MPa) high modulus (126000 MPa)Kevlar 49 yarns. The main objective was to study the moment redistribution in the post-cracking stage. Test results have shown that the moment redistribution in segmental beams can be obtained from a similar monolithic beam and that the moment redistribution is only slightly affected by the 1/dp.

No description available.