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Abstract(s)
Uma situação de incêndio carateriza-se como uma ocorrência de fogo não planeada que é prejudicial tanto para os seres vivos como para as estruturas. No caso de estruturas de alumínio, o risco de perda das propriedades do material é enorme podendo originar o colapso da estrutura. Assim, torna-se fundamental a análise térmica deste material no desenvolvimento da proteção para garantir a segurança das estruturas em caso de incêndio. Neste trabalho, para além do estudo de perfis em alumínio não protegidos sob ação do fogo, também é pertinente a mesma abordagem, no entanto para soluções de proteção em caso de incêndio. As placas de gesso e a lã de rocha são as soluções abordadas neste trabalho. A análise térmica de perfis requer o conhecimento das propriedades dos materiais, tanto do alumínio como os respetivos isolamentos. As curvas nominais de incêndio são fundamentais para simular o desenvolvimento da temperatura do fogo ao longo do tempo. As equações e os métodos de transferência de calor para aplicação são também importantes para o posterior cálculo da variação da temperatura. O cálculo da variação da temperatura em função do tempo, da secção transversal de perfis em alumínio será realizado tanto por meio de métodos analíticos (Método simplificado proposto pelo Eurocódigo 9 Parte 1-2) como por métodos numéricos (Método de Elementos Finitos), sendo os mesmos comparados numa fase final. Os métodos de cálculo revelaram-se concordantes no caso dos perfis não protegidos e apresentaram divergências no caso dos perfis protegidos. O fator de massividade para perfis protegidos foi reajustado de forma a aproximar as curvas até cerca de 2700 segundos. A partir deste instante, conclui-se que as cavidades de ar, presentes nas seções retas dos perfis, apresentam influência na temperatura final e que os efeitos das mesmas não constam na equação simplificada proposta pelo Eurocódigo 9 Parte 1-2. Apurou-se também, que para os perfis não protegidos quanto maior o fator de massividade maior é o gradiente térmico do perfil. E para os perfis protegidos quando maior a secção reta transversal, maior é a resistência térmica do perfil.
A fire situation is characterised as an accidental occurrence of fire that is harmful to both living beings and structures. In the case of aluminium structures, the loss risk of the material properties is enormous, which can lead to the structural collapse. Thus, the thermal analysis of this material becomes essential in the development of protection to ensure the safety of structures in case of fire. In this work, in addition to the study of unprotected aluminium profiles under the fire action, the same approach is also relevant. However, for protection solutions in case of fire, gypsum plasterboards and rockwool insulation are the solutions addressed in this work. The thermal analysis of profiles submitted to fire requires knowledge of the material properties of both aluminium and its protection. Nominal fire curves are fundamental to simulate the development of fire temperature over time. The heat transfer equations and methods for application are essential for subsequent use in the calculation of the temperature variation. The calculation of the temperature variation depending on the time of the cross-section of aluminium profiles should be performed both by analytical methods (simplified method proposed by Eurocode 9 Part 1-2) and numerical methods (Finite Element Method), these methods should be compared in a final stage. The calculation methods shown to be concordant in the case of unprotected profiles and presented divergences in the case of protected profiles. The massivity factor for the protected profiles was changed to approximate the curves until about 2700 seconds. From this time instant, it was concluded that the air cavities present in the cross-section profiles have influence on the final temperature and that they are not included in the simplified equation proposed by Eurocode 9 Part 1-2. It was also found that for the unprotected profiles, the greater the massivity factor, the greater the thermal gradient of the profile. And for protected profiles, the larger the cross-section, the greater the thermal resistance of the profile.
A fire situation is characterised as an accidental occurrence of fire that is harmful to both living beings and structures. In the case of aluminium structures, the loss risk of the material properties is enormous, which can lead to the structural collapse. Thus, the thermal analysis of this material becomes essential in the development of protection to ensure the safety of structures in case of fire. In this work, in addition to the study of unprotected aluminium profiles under the fire action, the same approach is also relevant. However, for protection solutions in case of fire, gypsum plasterboards and rockwool insulation are the solutions addressed in this work. The thermal analysis of profiles submitted to fire requires knowledge of the material properties of both aluminium and its protection. Nominal fire curves are fundamental to simulate the development of fire temperature over time. The heat transfer equations and methods for application are essential for subsequent use in the calculation of the temperature variation. The calculation of the temperature variation depending on the time of the cross-section of aluminium profiles should be performed both by analytical methods (simplified method proposed by Eurocode 9 Part 1-2) and numerical methods (Finite Element Method), these methods should be compared in a final stage. The calculation methods shown to be concordant in the case of unprotected profiles and presented divergences in the case of protected profiles. The massivity factor for the protected profiles was changed to approximate the curves until about 2700 seconds. From this time instant, it was concluded that the air cavities present in the cross-section profiles have influence on the final temperature and that they are not included in the simplified equation proposed by Eurocode 9 Part 1-2. It was also found that for the unprotected profiles, the greater the massivity factor, the greater the thermal gradient of the profile. And for protected profiles, the larger the cross-section, the greater the thermal resistance of the profile.
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Keywords
Análise térmica Perfis em alumínio Curvas de incêndio Proteções de incêndio Thermal analysis Aluminium profiles Fire curves Fire protections