Fire resistance of composite slabs withp rofiled steel decking: trapezoidal and reentrant numerical simulation

This work investigates the thermal behaviour of composite slabs with steel deck under standard fire conditions corresponding to a fire from the bottom. This composite solution consists of a concrete topping cast on the top of a steel deck. The concrete is typically reinforced with a steel mesh and may also contain individual rebars. The deck also acts as reinforcement and may be exposed to accidental fire conditions from the bottom. This composite solution is widely used in every type of buildings and requires fire resistance in accordance to regulations and standards. Composite slabs need to meet fire-safety requirements according to building codes. The fire resistance is specified by the loadbearing capacity (R), insulation (I) and integrity (E). The fire rating for (R) and (E) is not in the scope of this investigation. The fire rating for insulation (I) is evaluated by two different methods (numerical simulation and simple calculation). Numerical simulation was performed using Matlab PDE toolbox for the thermal effects of standard fire exposure. The fire rating is calculated for 196 different geometric configurations, in order to evaluate the effect of the thickness of the concrete layer and the thickness of steel deck. The fire resistance (I) increases with the thickness of the concrete, according to the results of both methods. The numerical results are also compared with the simplified method proposed by Eurocode, which appears to be unsafe.

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