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DMA - MSE - Artigos em Livros de Actas Internacionais

Mostrando recursos 1 - 20 de 72

  1. The effect of residual stresses in the lateral-torsional buckling of steel I-beams at elevated temperatures

    Vila Real, P.M.M.; Cazeli, R.; Silva, L.S.; Santiago, Aldina; Piloto, P.A.G.
    When a beam is bent about its major axis it may twist and move laterally, before it reaches in bending. Although the problem, of lateral-torsional buckling of steel beams at room temperature has a well established solution, the same problem at elevated temperature has not. A numerical investigation of the laleral-torsional of buckling of steel I-beams subjected to a temperature variation from room temperature up to 700 °C, with the aim of assessing the effects of the residual stresses in this mechanism of failure, is presented in this page. To this purpose, a geometrically and materially non-linear finite element program, has...

  2. Numerical modelling of steel I-beams with restrained thermal enlongation

    Vila Real, P.M.M.; Lopes, N.; Silva, L.S.; Piloto, P.A.G.
    This paper presents a numerical study of the behavior of steel I-beams with restrained thermal elongation. A geometrical and material non-linear finite element program, specially established for the analysis of structures submitted to finite, has been used to determine the resistance of a beam-column at elevated temperature, using the material properties of Eurocode 3, part 1-2. The numerical results have been compared with those obtained with the Eurocode 3, part 1-2 (1995) and the new version of the same Eurocode (2002).

  3. Thermal analysis in fire-resistance Furnace

    Piloto, P.A.G.; Mesquita, L.M.R.; Pereira, Alexandre Augusto
    Fire resistance rating of building construction elements is defined under fire-resistance test furnace. The geometry and shape of fire-resistance furnaces is not defined by any prescriptive document, being necessary to comply thermally with specified nominal fire curves, such as ISO 834 or hydrocarbon [1,2]. This research work intends to measure temperatures inside furnace volume, using sixteen plate thermocouples to compare average temperature in four planes. Those planes are compared with reference thermocouple which is responsible for controlling furnace operation, see figure 1. Three tests were performed, the first two running with ISO 834, during 45 minutes and the last one running with hydrocarbon curve, during 30 minutes. Experimental results...

  4. Numerical estimation for intumescent thermal protection using one-dimensional IHCP

    Mesquita, L.M.R.; Piloto, P.A.G.; Vaz, M.A.P.; Pinto, T.
    Intumescent coatings are an important group of passive fire protection materials, representing about one third of steel fire protection costs. This insulating system is made of four different chemical compounds that can be classified as: a carbonisation agent, an acid source, a foaming agent and a catalyst. When protecting a steel structure under fire conditions, the intumescent paint is heated, beginning to melt, to bubble and to swell, forming a multi-cellular barrier which decreases the heat transfer from the fire to the substrate. The film behaviour is characterized by an expansion and mass loss, producing a foam char with a geometry that varies from 5 to 200...

  5. Numerical modelling of the behaviour of a stainless steel portal frame subjected to fire

    Lopes, N.; Vila Real, P.M.M.; Piloto, P.A.G.; Mesquita, L.M.R.; Silva, L.S.
    It is known that stainless steel has a better fire performance than carbon steel, which can lead to a growing utilization of this kind of steel in structures. In fact, although more expensive than the carbon steel, structures in stainless steel can be competitive because of its smaller thermal protection need. With the purpose of modelling by Finite Element Method the behaviour of a stainless steel framed structure, without any protection, submitted to fire, has been introduced in the SAFIR program, the material properties of the stainless steel. SAFIR is a finite element program with geometrical and material non-linear analysis, specially developed in the University of Liège for...

  6. Thermal behaviour of reaction intumescent paint used for passive protection of steel structures

    Piloto, P.A.G.; Mesquita, L.M.R.
    Steel structures often need some passive protection measures for the validation of national and international regulations. These regulations present standard and simplified methods for the design of steel structures when exposed to fire conditions. One of this formulae presented in Eurocode 3 has been determined based on simplified hypothesis for material protection behaviour, considering uniform temperature distribution across steel section, constant thermal conductivity and constant thickness for material insulation. This work presents preliminary experimental tests for determining the thermal insulation behaviour (thermal conductivity) as function of the mean insulation temperature evolution [1]. Specimens have been coated and heated with slow heating rate, 800 [ºC/h], and temperatures have been...

  7. Utilização de métodos avançados de cálculo na avaliação do comportamento termomecânico de estruturas metálicas em situação de incêndio

    Piloto, P.A.G.
    Neste trabalho faz-se a modelação numérica do comportamento termomecânico de duas estruturas metálicas sujeitas à acção do fogo utilizando-se para o efeito um programa de elementos finitos para análise não-linear geométrica e material especialmente desenvolvido para cálculo de estruturas em situação de incêndio. O primeiro caso estudado trata uma asna em que o dono da obra apenas permitia a utilização de material de protecção nos banzos e o segundo caso é uma estrutura porticada pertencente a um edifício do tipo comercial em estrutura metálica, para a qual se estudaram vários cenários de incêndio possíveis de modo a definir a situação...

  8. New proposals for the design of steel beam-columns under fire conditions

    Lopes, N.; Vila Real, P.M.M.; Silva, L.S.; Piloto, P.A.G.; Franssen, J.-Marc
    The possibility of having, in parts 1-1 and 1-2 of Eurocode 3, the same approach for the design of beam-columns and for lateral-torsional buckling, was investigated by the authors in previous papers using a numerical approach, where it was concluded that those assumptions could be made. In the present paper a new approach for lateral-torsional buckling has been used with the formulae for the design of beam-columns at elevated temperature based on prEN 1993-1-1 combined with the formulae from prEN 1993-1-2. In both cases the results obtained are much better than the current design expressions, when compared with those obtained in...

  9. Influência das imperfeições na temperatura crítica de vigas sujeitas à encurvadura

    Mesquita, L.M.R.; Piloto, P.A.G.; Vaz, M.A.P.; Vila Real, P.M.M.
    Neste trabalho é apresentada uma aplicação da técnica de Moiré para a medição de campos de tensões. O caso em estudo consiste na medição do campo de deslocamentos na superfície de um provete sob tracção, possuindo um furo passante no seu centro. As redes são obtidas por impressão laser num papel especial. A replicação da rede na superfície do provete é feita por um processo térmico com pressão controlada. Foram ensaiados provetes de alumínio. A rede registada na superfície do provete foi fotografada em diferentes fases do ensaio, estas fotografias são tratadas num programa de processamento de imagem. Os valores obtidos experimentalmente são comparados com os valores...

  10. Metodologia para projecto mecânico de moldes para injecção de plásticos

    Piloto, P.A.G.; Caleiro, C.
    O projecto de moldes para plásticos pode ser optimizado, recorrendo a metodologias de cálculo assistidas por computador. Este tema abrangente utiliza vários domínios científicos do conhecimento, nomeadamente estudos reológicos, térmicos e estruturais. Neste artigo é apresentada uma metodologia de projecto que tem como objectivo a obtenção de peças em plástico sem defeitos e de Óptima qualidade. A previsão do campo de pressões e de todo o estado do fluido não Newtoniano é o indicador primeiro destes fenómenos. A transposição destes resultados para um programa de elementos finitos de análise termo — estrutural possibilita uma análise do comportamento desta ferramenta. Durante...

  11. A simple model for lateral torsional buckling resistance of steel I beams under fire condition – comparison with experimental results

    Piloto, P.A.G.; Vila Real, P.M.M.
    When a beam is bent about its axis of greatest flexural rigidity it may twist before it reaches its strength limit state. This flexural stability limit state is most commonly referred to as lateral torsional buckling of a beam. The twisting of the beam occurs when the compression flange becomes unstable as a result of its being subjected to flexural induced axial stresses. Lateral torsional buckling is of importance when the compression flange is laterally unsupported as is often the case in continuous beams, cantilever beams, frame beams and frame columns. The aim of this work is to develop a simple model, i. e., an...

  12. Lateral torsional buckling of steel i beams in case of fire: experimental evaluation

    Piloto, P.A.G.; Vila Real, P.M.M.
    In this paper, experimental tests on lateral torsional buckling of steel I Beams under fire conditions are presented. The beam, spans varies from 0.5 to 6.5 [m] length and the temperature was risen up to 600 [ºC]. The initial conditions of the steel beams were measured. The residual stress state was characterized by the hole drilling method, using specific strain gauges, The geometric imperfections was measured by means of a laser beam and the cross section of the beams was dimensionally controlled. The methodology to the thermo-mechanical load was first heat the beam and let it expand for controlling the...

  13. Encurvadura lateral de vigas submetidas a elevadas temperaturas: comparação numérica

    Piloto, P.A.G.; Vila Real, P.M.M.
    Embora o fenómeno de encurvadura lateral seja bem conhecido à temperatura ambiente, o mesmo não acontece para situações de temperaturas elevadas. Assim é necessário validar com resultados numéricos e/ou experimentais o estudo deste fenómeno para que seja possível utilizar modelos simplificados em normas, como do caso do Eurocódigo. Neste artigo será feita uma comparação numérica com vários programas de elementos Mitos, nomeadamente o Cosmos/M, o ANSYS 5.5 e o SAFIR, este último desenvolvido na Universidade de Liège para análise de estruturas sujeitas à acção do fogo. Para tal será necessário recorrer a modelações de geometria e de material com comportamentos não...

  14. Análise numérica de vigas "I" de aço em situação de incêndio, sujeitas à flambagem lateral. Contribuição para a validação de uma proposta de revisão do Eurocode 3 - parte 1.2.

    Cazeli, R.; Vila Real, P.M.M.; Valdir, P.; Piloto, P.A.G.
    O presente trabalho documenta as análises numéricas de vigas “1” de aço sujeitas ao fenómeno da flambagem lateral, em situação de incêndio, tendo por base os resultados obtidos do programa SAFIR. O SAFIR é um programa de elementos finitos que faz a análise não-linear geométrica e do material, especialmente desenvolvido para o estudo de estruturas sujeitas à acção do fogo. Os resultados obtidos por esse programa são comparados aos resultados obtidos pelo método simplificado de dimensionamento apresentado na parte 1-2 do EUROCODE 3. Esse último modelo conduz a níveis de segurança que dependem do Índice de esbeltez reduzido dos elementos...

  15. Numerical and experimental evaluation of lateral torsional buckling of beams at elevated temperatures

    Piloto, P.A.G.; Vila Real, P.M.M.; Franssen, J.-Marc
    When a beam is bent about its greatest flexural resistance axis it may twist and move laterally, before it reaches its strength limit. Although this problem of lateral torsional buckling of steel beams at room temperature is well known, the same problem at elevated temperature is not. This paper summarises the results obtained iii the scope of a research project entitled “Lateral buckling of steel I beams under fire conditions”, where a set of 120 experimental and numerical tests were performed on IPEIOO beams, submitted to temperature varying from 20 °C to 600 GC, to validate a new proposal for the...

  16. The influence of lateral bending restrain in numerical and experimental evaluation of lateral buckling resistance design moment of steel I beams at elevated temperatures

    Piloto, P.A.G.; Vila Real, P.M.M.; Franssen, J.-Marc
    The numerical and experimental determination of the buckling design moment of steel I beams is influenced by the type of support and load restrain during the mechanical and thermal load. As a result of beam temperature rise the axial movement will be allowed and the type of load and support restrain will be compared from fully to unrestrained state. For this study a simple supported beam is bent about its axis of greatest flexural rigidity. Taking into account the geometric and material imperfections, the beam may twist before it reaches its strength limit state. This flexural stability limit state is most...

  17. A simple model for the lateral–torsional buckling of steel I-beams under fire conditions: numerical and experimental validation

    Vila Real, P.M.M.; Piloto, P.A.G.; Franssen, J.-Marc
    When a beam is bent about its greatest flexural resistance axis it may twist and move laterally, before it reaches its strength limit. Although this problem of lateral-torsional buckling of steel beams at room temperature is well known, the same problem at elevated temperature is not. This paper summarises the results obtained in the scope of a research project entitled “lateral buckling of steel I-beams under fire conditions”, where a set of 120 experimental and numerical tests were performed on IPE 100 beams, submittted to temperatures varying from 20 °C to 600 °C, to validate a new proposal for the...

  18. Numerical modelling of the fire resistance of steel I-beams with restrained thermal enlogation

    Vila Real, P.M.M.; Silva, L.S.; Lopes, N.; Piloto, P.A.G.
    In this paper the influence of the restrained thermal elongation in the behaviour of steel I— beams being part of a frame has been studied. In fact there is a significant difference between the case of a beam acting as a single element free lo exhibit axial thermal elongation or being pan of a frame where the stiffness of the remaining strucure contributes with some restraint to the free elongation of the beam. A numerical study of the behaviour of steel I-beams subjected to fire and a combination of axial force and bending moments has been presented. A geometrical and material non-linear...

  19. Influência dos constrangimentos na temperatura crítica de vigas sujeitas à encurvadura lateral

    Mesquita, L.M.R.; Piloto, P.A.G.; Vaz, M.A.P.; Vila Real, P.M.M.
    Quando uma viga sem constrangimentos laterais se encontra sujeita a um carregamento mecânico e é simultaneamente submetida ao efeito de temperaturas elevadas, pode ocorrer instabilidade por encurvadura lateral torsional devido à diminuição da capacidade resistente. São determinadas as equações diferenciais de equilíbrio para a encurvadura lateral e as respectivas condições de fronteira de elementos sujeitos a restrições e a temperaturas elevadas. São apresentadas análises não lineares de geometria e material, realizadas no programa ANSYS, em vigas de aço IPE220 de diferentes comprimentos, sujeitas a um estado de flexão uniforme, correspondente a graus de utilização de 40 % e 60%. É analisado o efeito da rigidez da restrição axial no...

  20. Numerical modelling of lateral torsional buckling for partially encased steel beams at elevated temperatures

    Piloto, P.A.G.; Mesquita, L.M.R.; Ramos Gavilán, A.B.
    Partially encased beams are composed structural elements widely used for industrial and commercial buildings with increasing significance. Composite beams may be designed for service load conditions without the collaborative contribution of slabs. Instability problems may occur because concrete may not have the age to resist and also because the concrete may slip over steel, crack or crush. Lateral torsional buckling is an instability phenomenon that may occur in these situations. This paper presents a material and geometric non linear finite element model for determining lateral torsional buckling resistance of partially encased beam without encasement reinforcement in fire conditions. The steel part...

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