Composite slabs with reinforced concrete and cold-formed profiled steel deck are very popular and reduce the building construction time. The steel deck acts as a permanent formwork to the

The fire resistance of composite slabs with steel decking, in Europe, is usually defined using simple calculation models provided by the Eurocode EN 1994-1-2. For assessing the methodology of these simple calculation methods, a new advanced calculation method is presented, using the software ANSYS. The numerical model is first validated with experimental data reported on bibliography and then a parametric analysis is conducted to better understand the effect of the load level on the composite structure under fire. The validation of the simulations consisted of three different models: the first model considers perfect contact between the steel deck and the concrete topping, and the two following models consider the existence of an air gap between these materials, acting as a thermal resistance on the temperature field through the thickness of the slab. The numerical results show good approximation to the experimental results, mainly when using the non-perfect contact model, reaching 3.88% and 16.91% of difference with respect to the insulation and load-bearing criteria, respectively. Based on the validation models, a parametric study is presented, modifying the load level from 10% up to 75%. New simple calculation models are presented to define the fire resistance of composite slabs, considering the load level, and the debonding effect between the concrete and the steel deck.

Este trabalho tem como objetivo examinar a eficiência do reforço estrutural utilizando Compósitos Reforçados com Fibra de Carbono (CRFC), avaliando o aumento da resistência de vigas biapoiadas de concreto armado. Para isto, vigas de concreto armado receberam a implantação de camadas de CRFC, para que fossem verificadas as diferenças de deformações, as mudanças nos valores de carga de ruptura e os modos de falha destas vigas. Foi feita a previsão das cargas de ruptura das vigas reforçadas por meio do método de dimensionamento utilizado. As vigas foram rompidas em laboratório pelo ensaio de flexão a quatro pontos até o seu colapso. Os ensaios experimentais comprovaram a efetividade deste método de reforço estrutural. No que concerne os resultados, foi possível perceber que a utilização do reforço estrutural com CRFC foi capaz de aumentar a resistência das vigas em até 34%. Além disso, observou-se que a implantação do CRFC pode mudar significativamente a ductilidade da viga reforçada. Para mais, a utilização dos incrementos de ancoragem mostrou um aumento de até 42% na carga última e aumento na deformação de tração de até 102% em relação a viga de referência, dando origem a um maior aparecimento de fissuras.

SummaryDouble‐stud light steel frame (LSF) walls provide an enhanced insulation performance when exposed to fire conditions. However, the behavior of different configurations of such assemblies under fire is not well understood. Thus, this study aimed to assess the fire resistance of non‐load‐bearing double‐stud LSF walls subjected to ISO834 standard fire. The walls were lined with one or two type F gypsum plasterboards on each side, using cavity uninsulated or insulated with ceramic fiber. The experimental tests revealed that a wider cavity slows the heat transfer through the cross‐section, delaying the temperature rise on the unexposed surfaces. The use of ceramic fiber insulation substantially increases the fire resistance of the wall and when the cavity is partially filled with this material, if the blanket is placed towards the exposed side, enhanced insulation fire resistance is achieved. Based on the finite element method, a numerical validation was conducted using a special hybrid approach that used experimental temperature values inside the cavities or insulation blankets. This approximation was essential to improve the numerical results. Also, the employment of an air layer, located at specific regions of the models, helped to improve the numerical results, introducing an extra thermal resistance. A new simplified approach was proposed based on the improved design model available in the literature, and the results obtained are consistent with the experimental results. The predicted insulation fire resistance of the numerical and simplified methods agreed well with the experimental results and useful information is supplied to support further numerical and experimental studies.