| Name: | Description: | Size: | Format: | |
|---|---|---|---|---|
| 5.44 MB | Adobe PDF |
Authors
Advisor(s)
Abstract(s)
A madeira, ao longo de séculos, tem sido um dos materiais mais utilizados pela humanidade,
especialmente na engenharia e construção de edifícios. Apesar do surgimento de
regulamentações mais rigorosas no projeto, na construção e na segurança contra incêndio, a
utilização da madeira continua a ser um material que exige critérios bem definidos, uma vez
que é de utilização muito atrativa e abrangente. A madeira é um material cujas propriedades
variam significativamente sob diferentes condições de humidade, temperatura e carga
aplicada. É por isso, um material vulnerável a alterações quando exposta a elevadas
temperaturas, como as que ocorrem em situações de incêndio. Quando a madeira é exposta ao
fogo, as suas propriedades degradam-se progressivamente, levando à carbonização do
material. Este processo de carbonização, embora crie uma camada protetora que isola o núcleo
interno da madeira, resulta na diminuição da secção resistente, comprometendo, assim, a
resistência ao fogo dos elementos construtivos. A avaliação do comportamento da madeira sob
tais condições pode ser feita através de ensaios experimentais, utilização de modelos analíticos
e, mais recentemente, através de modelos numéricos. Os modelos numéricos oferecem uma
vantagem significativa, especialmente quando há dificuldades na realização de testes
experimentais ou quando as aproximações dos métodos analíticos não são suficientes. Esses
modelos permitem uma verificação mais detalhada, alargada e paramétrica de diferentes
elementos construtivos sob diferentes condições, inclusive sob a ação do fogo. Nesta
dissertação, exploram-se temas para a investigação de modelos construtivos em madeira leve,
com placas de gesso e com cavidades internas: o estudo das propriedades dos materiais
envolvidos, a ação do fogo, a interação do fogo entre os elementos construtivos, e as
metodologias utilizadas na avaliação da resistência ao fogo. A avaliação da resistência ao fogo
incluí uma revisão das normas europeias, os eurocódigos, e a literatura científica relevante.
Numa primeira fase deste trabalho, desenvolveram-se seis modelos numéricos construtivos em
madeira leve, divididos em dois grupos: os modelos com cavidade interna sem isolamento e os
modelos com as cavidades preenchidas com isolamento. A validação dos resultados é baseada
na análise da evolução das temperaturas, e na aplicação do critério de isolamento térmico
conforme a norma EN 1363-1. Numa segunda fase, obtiveram-se os tempos de resistência ao
fogo dos modelos. Com base nas diferentes simulações, compararam-se os resultados e
verificou-se que o tempo de resistência ao fogo diminui no grupo dos modelos com cavidade
vazia, em relação ao grupo de modelos com a cavidade preenchida com isolamento. Também,
é possível aferir que dentro do mesmo grupo de modelos, o tempo de resistência ao fogo
diminui, quando se utilizam parafusos de aço para fixar a placa de gesso à madeira. Por fim,
aplicou-se um método de cálculo simplificado, obtido experimentalmente, por Frangi et. al, na
análise da resistência ao fogo de elementos construtivos de madeira protegidos A comparação
de resultados com os obtidos numericamente, demonstrou que a equação simplificada é
conservadora, uma vez que o rácio calculado foi sempre próximo nos diferentes modelos
desenvolvidos deste estudo.
Wood has been one of the most widely used materials by humanity for centuries, especially in engineering and building construction. Despite the emergence of more rigorous regulations for design, construction and fire safety, the use of wood remains a material that requires well defined criteria as it very attractive and comprehensive use. However, wood is a material whose properties vary significantly under different conditions of moisture content, temperature, and applied loading conditions. It is therefore a material vulnerable to changes when exposed to high temperatures, such as those that occur in fire situations. When wood is exposed to fire, its properties progressively degrade, leading to charring. Although this charring process creates a protective layer that insulates the inner core of the wood, results in a reduction in the crosssection, thus compromising the fire resistance of structural elements. The assessment of wood behavior under such conditions can be carried out through experimental tests, the use of analytical models, and, more recently, through numerical models. Numerical models offer a significant advantage, particularly when experimental tests are difficult to carry out or when the approximations of analytical methods are insufficient. These models allow for a more detailed, expanded and a parametric verification of the different wooden structural elements under different conditions, including under the fire action. In this dissertation, different topics are explored for the investigated of wooden light constructive models, with gypsum plasterboard and with internal cavities: the study of the material properties involved, the fire action, the fire interaction between the constructive elements, and the methodologies used to evaluate fire resistance. The fire resistance assessment includes a review of European standards, Eurocodes, and relevant scientific literature. In the first step of this work six structural models were developed, divided into two groups: the structural models with empty cavities and the models with cavities filled with insulation. These models will be analyzed numerically. The validation of the results is based on the analysis of the temperature evolution and the application of the thermal insulation criterion according to standard EN 1363-1. In the second phase, the fire resistance of the models was obtained. Based on the different simulations, the results were compared, and it was found that the fire resistance time decreases when comparing the models with empty cavities to the group with filled cavities. It is also noticeable that within the same group, the fire resistance time decreases when steel screws are used to fix the plasterboard to the wood. Finally, a simplified calculation method was applied, obtained experimentally by Frangi et al. for fire resistance analysis of constructive wooden elements protected by gypsum. Comparison of results with those obtained numerically demonstrated that the simplified equation is conservative, since the calculated ratio was always close in all different developed models in this study.
Wood has been one of the most widely used materials by humanity for centuries, especially in engineering and building construction. Despite the emergence of more rigorous regulations for design, construction and fire safety, the use of wood remains a material that requires well defined criteria as it very attractive and comprehensive use. However, wood is a material whose properties vary significantly under different conditions of moisture content, temperature, and applied loading conditions. It is therefore a material vulnerable to changes when exposed to high temperatures, such as those that occur in fire situations. When wood is exposed to fire, its properties progressively degrade, leading to charring. Although this charring process creates a protective layer that insulates the inner core of the wood, results in a reduction in the crosssection, thus compromising the fire resistance of structural elements. The assessment of wood behavior under such conditions can be carried out through experimental tests, the use of analytical models, and, more recently, through numerical models. Numerical models offer a significant advantage, particularly when experimental tests are difficult to carry out or when the approximations of analytical methods are insufficient. These models allow for a more detailed, expanded and a parametric verification of the different wooden structural elements under different conditions, including under the fire action. In this dissertation, different topics are explored for the investigated of wooden light constructive models, with gypsum plasterboard and with internal cavities: the study of the material properties involved, the fire action, the fire interaction between the constructive elements, and the methodologies used to evaluate fire resistance. The fire resistance assessment includes a review of European standards, Eurocodes, and relevant scientific literature. In the first step of this work six structural models were developed, divided into two groups: the structural models with empty cavities and the models with cavities filled with insulation. These models will be analyzed numerically. The validation of the results is based on the analysis of the temperature evolution and the application of the thermal insulation criterion according to standard EN 1363-1. In the second phase, the fire resistance of the models was obtained. Based on the different simulations, the results were compared, and it was found that the fire resistance time decreases when comparing the models with empty cavities to the group with filled cavities. It is also noticeable that within the same group, the fire resistance time decreases when steel screws are used to fix the plasterboard to the wood. Finally, a simplified calculation method was applied, obtained experimentally by Frangi et al. for fire resistance analysis of constructive wooden elements protected by gypsum. Comparison of results with those obtained numerically demonstrated that the simplified equation is conservative, since the calculated ratio was always close in all different developed models in this study.
Description
Keywords
Wood Gypsum Insulation Fire Resistance Madeira Gesso Isolamento Resistência ao fogo