Thermal model for charring rate calculation in wooden cellular slabs under fire

Wood is a natural and traditional building material, as popular today as ever, and presents advantages. Physically, wood is strong and stiff, but compared with other materials like steel is light and flexible. Wood material can absorb sound very effectively and it is a relatively good heat insulator. But dry wood burns quite easily and produces a great deal of heat energy. The main disadvantage is the high level of combustion when exposed to fire, where the point at which it catches fire is from 200–400°C. After fire exposure, is need to determine if the charred wooden structures are safe for future use. Design methods require the use of computer modelling to predict the fire exposure and the capacity of structures to resist those action. Also, large or small scale experimental tests are necessary to calibrate and verify the numerical models. The thermal model is essential for wood structures exposed to fire, because predicts the charring rate as a function of fire exposure. The charring rate calculation of most structural wood elements allows simple calculations, but is more complicated for situations where the fire exposure is non-standard and in wood elements protected with other materials. In this work, the authors present different case studies using numerical models, that will help professionals analysing woods elements and the type of information needed to decide whether the charred structures are adequate or not to use. Different thermal models representing wooden cellular slabs, used in building construction for ceiling or flooring compartments, will be analysed and submitted to different fire scenarios (with the standard fire curve exposure). The same numerical models, considering insulation material inside the wooden cellular slabs, will be tested to compare and determine the fire time resistance and the charring rate calculation.

Thermal model for charring rate calculation in wooden cellular slabs under fire

Wood is a natural and traditional building material, as popular today as ever, and presents advantages. Physically, wood is strong and stiff, but compared with other materiais like steel is light and flexible. Wood material can absorb sound very effectively and it is a relatively good heat insulator. But dry wood does bum quite easily md produces a great deal ofheat energy. The main disadvantage is the high levei ofcombustion when exposed to fíre, where the point at which it catches fire is fi-om 200-400°C. After fu-e exposure, is need to determine if the charred wooden stmctures are safe for future use. Design methods require the use ofcomputer modelling to predict the fíre exposure and the capacity ofstructures to resist fhose action. Also, large or small scale experimental tests are necessary to calibrate and verify the numerical models. The thermal model is essential for wood stmctures exposed to fire, because predicts the charring rate as a fünction offire exposure. The charring rate calculation ofmost stmctural wood elements allows simple calculations, but is more complicated for situations where the fire exposure is non-standard and in wood elements protected with other materiais.

Caracterização das comunidades de aves florestais no distrito de Bragança

Com objetivo de caracterizar a comunidade de aves florestais do Distrito de Bragança, fez-se um estudo em quatro locais de características diferentes sob ponto de vista de estrutura e composição de espécies, através de recolha de informação com base nas listas de 10 espécies de Mackinnon e pelo método captura com redes de neblina, para caracterização das biometrias e parâmetros populacionais, de modo a caracterizar a estrutura das comunidades de aves em cada local. A Combinação dos dois métodos possibilitou a captura e identificação de indivíduos de 44 espécies diferentes, pertencentes a 24 famílias distintas. Destas, as mais representativas foram determinadas através do Índice de Frequência das Listas (IFL) e foram Parus major, Erithacus rubecula, Turdus merula e Sylvia atricapilla. Os resultados referentes à riqueza específica, obtidos através das listas de MacKinnon foram analisados com ANOVA não paramétricas (Kruskal-Wallis). Dos quatro locais, a Ricafé mostrou diferenças significativas na variação de número de espécies. Em relação aos períodos de capturas, o segundo quadrimestre teve número de espécies estatisticamente diferentes dos restantes quadrimestres do ano. No Período de Invernada há menor atividade de aves em todos os locais. Pinhal e Tabuado têm pouca diversidade de espécies.