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Este estudo apresenta uma análise numérica de lajes mistas através do Método dos Elementos Finitos (FEM) utilizando o Matlab (PDE Toolbox) e compara os seus resultados com os valores obtidos através dos métodos simplificados da norma EN 1994-1-2.
A comparação entre os métodos analíticos e numéricos tem como objetivo analisar o comportamento e a influência dos novos parâmetros, bem como a resposta térmica dos quatro perfis de lajes mistas com o intuito de compreender a evolução temporal nos elementos estruturais durante a exposição ao fogo.
O método de solução requer a caracterização dos materiais a temperaturas elevadas. O modelo de interface adicional inclui uma resistência térmica entre a placa de aço e a cobertura de betão, representada pelo efeito da camada de ar que geralmente se cria durante os testes experimentais.
O principal objetivo deste trabalho é determinar a resistência ao fogo por isolamento de lajes mistas com uma plataforma de aço colaborante ao comportamento do betão de peso normal; o tipo de aço escolhido foi o S350 quando submetido a uma curva de fogo padrão ISO-834.
Esta investigação apresenta uma análise da resposta térmica do conjunto e do desempenho de 4 componentes intervenientes na resistência mecânica para avaliação do critério R (todas as partes da placa de aço: flange inferior, intermédia e flange superior e os varões de reforço nas lajes mistas).
Este estudo compreende dois modelos trapezoidais (Cofraplus 60 e Polydeck 59s) e dois modelos re-entrantes (Multideck 50 e Bondek) com diferentes espessuras de h1. No total, foram realizadas 80 simulações para a validação e elaboração do estudo paramétrico, utilizando os modelos numéricos desenvolvidos para propor novos propostas e coeficientes (Proposta I, II, III e IV) para estimar a temperatura dos componentes presentes no critério de carga (R) e também a estimativa do tempo de resistência de isolamento (I) em comparação com o modelo proposto no Anexo D do Eurocódigo 1994-1.2.
This study presents a numerical analysis of composite slabs by the Finite Element Method (FEM) using MATLAB Partial Differential Equations Toolbox (PDE Toolbox) and compares the results with those obtained using the simplified methods of EN 1994-1-2. The comparison between the analytical and numerical methods aims to analyse the behaviour and the influence of the new parameters, as well as the thermal response of the four composite slab profiles, to understand the temporal evolution in the structural members during fire exposure. The solution method requires the characterisation of the materials at elevated temperatures. The additional interface model includes a thermal resistance between the steel plate and the concrete cover, defined by the air layer effect that usually occurs during experimental tests. The main objective of this work is to determine the fire resistance by insulation of composite slabs with a steel platform collaborating to the behaviour of normal weight concrete (NWC); the type of steel chosen was S350 when subjected to a standard ISO-834 fire curve. This research analyses the thermal response of the assembly and the performance of 4 components used in the mechanical analysis to assess the fire resistance R (all parts of the steel deck: Lowe flange, Web, Upper flange and the reinforcing bars in the composite slabs). This study comprises two trapezoidal models (Cofraplus 60 and Polydeck 59s) and two re-entrant models (Multideck 50 and Bondek) with different thicknesses of h1. In total, 80 simulations were performed for the validation and elaboration of the parametric study, using the developed numerical models to propose new proposals and coefficients (Proposal I, II, III and IV) to estimate the temperature of the components present in the load-bearing criterion (R) as well as in the estimation of the insulation resistance time (I) in comparison with the model proposed in Annex D of EN 1994-1-2.
This study presents a numerical analysis of composite slabs by the Finite Element Method (FEM) using MATLAB Partial Differential Equations Toolbox (PDE Toolbox) and compares the results with those obtained using the simplified methods of EN 1994-1-2. The comparison between the analytical and numerical methods aims to analyse the behaviour and the influence of the new parameters, as well as the thermal response of the four composite slab profiles, to understand the temporal evolution in the structural members during fire exposure. The solution method requires the characterisation of the materials at elevated temperatures. The additional interface model includes a thermal resistance between the steel plate and the concrete cover, defined by the air layer effect that usually occurs during experimental tests. The main objective of this work is to determine the fire resistance by insulation of composite slabs with a steel platform collaborating to the behaviour of normal weight concrete (NWC); the type of steel chosen was S350 when subjected to a standard ISO-834 fire curve. This research analyses the thermal response of the assembly and the performance of 4 components used in the mechanical analysis to assess the fire resistance R (all parts of the steel deck: Lowe flange, Web, Upper flange and the reinforcing bars in the composite slabs). This study comprises two trapezoidal models (Cofraplus 60 and Polydeck 59s) and two re-entrant models (Multideck 50 and Bondek) with different thicknesses of h1. In total, 80 simulations were performed for the validation and elaboration of the parametric study, using the developed numerical models to propose new proposals and coefficients (Proposal I, II, III and IV) to estimate the temperature of the components present in the load-bearing criterion (R) as well as in the estimation of the insulation resistance time (I) in comparison with the model proposed in Annex D of EN 1994-1-2.
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Resposta térmica Lajes mistas de aço-concreto Resistência ao fogo Betão de densidade normal Modelo numérico Eurocódigo 4 MATLAB Incêndio padrão