Browsing by Author "Leite, Pedro A. S."
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- Fire design of wood connections loaded in shearPublication . Fonseca, Elza M M; Leite, Pedro A. S.The main objective of this work is to compare the fire resistance between wood-steel-wood (W-S-W) and wood-wood-wood (W-W-W) connections, both joined by steel dowel fasteners, in double shear. The analytical and design procedures follow simplified equations presented in Eurocode 5, part 1-1 and 1-2. A computational methodology, based on finite element method, was also implemented to produce two dimensional thermal simulations, which permits to verify the heating effect through the dowels fasteners or steel elements through the connection in study. Different cross-sections will be identified, considered as the most relevant parts, to compare the temperature distribution in the studied connections. According to the fire exposure, a thermal and transient effect will happen and a char-layer appearing in the exposure side of the connections. The measured quantity of the charred area permits to identify the lost structural material in the studied cross-sections. The charring rate will calculate and compared with the constant value proposed by the Eurocode 5, part 1-2. There are typical values for the charring rate of wood between 0.5-1.0mm/min according to Eurocode 5, part 1-2. However, as a general conclusion and additional information to help designers and professionals, the number of fasteners increases with the applied load, lower dowels diameters have higher effect in the number of fasteners, at fire exposure the steel fasteners bring the heat to inside the connections, and different wood densities affect the thermal behaviour and the charring rate evolution. The charring rate permits to quantify the lost layer thickness and the fire resistance of the connection, dependent on the chosen material density.
- Fire safety of wood-steel connectionsPublication . Fonseca, Elza M M; Silva, Lino; Leite, Pedro A. S.The main objective of this work is to present different analytical and computational methods which permit the safe design calculation of the wood-steel connections, under fire conditions. Wood is an anisotropic, heterogeneous and porous material and its behaviour varies with temperature. The increase of temperature influences the progressive degradation of wood properties. During fire exposure, it is need to determine if the charred wood connections are safe in use. Design methods require the use of analytical methodologies and computational modelling to predict the fire exposure and the components capacity to resist to this action. In this work, the authors present studied cases, that will help professionals to analyse wood-steel connections and focus the type of information needed to decide whether the charred elements are adequate or not to use. For the same wood-steel connections, different insulation materials will be analysed to compare their behaviour and determine the fire resistance in time domain.
- Wood Connections Under Fire Conditions Protected with Gypsum Plasterboard Types A and FPublication . Fonseca, Elza M M; Leite, Pedro A. S.; Silva, LinoThe wood behavior varies with temperature, which has a negative effect, be-ing verified by progressive properties degradation. After fire exposure, it is possible to measure the wood char layer and the remaining resistant cross-section area. Based on numerical models and analytical equations, it is pos-sible to study the protection level of wood connections, during fire exposure, and evaluate wood and steel dowels temperature fields in conjunction. The main objective of this work is to verify the fire resistance of unprotected (W-W-W) wood connections and compare the results with protected connections using gypsum plasterboard. According Eurocode 5, part 1-2 the connections could be protected by the addition of wood paneling, wood-based panels or gypsum plasterboard type A, H or F. To obtain conclusions according the application of different type of gypsum plasterboard in the designed W-W-W connections in different densities material, numerical models were building to verify the level of protection in fire action. Design methods require the use of analytical methodologies and computational modelling to predict the fire exposure and the components capacity to resist to this action. Results of the temperature field in the studied connections under fire will be presented, with the measured char layer in unprotected members and comparing the protected efficiency with different types of gypsum plasterboard.