Abstract
This paper presents finite element thermal models to evaluate the thermal behavior of composite slabs with steel deck, submitted to standard fire exposure. Composite steel/concrete slabs are a mix of a reinforced concrete layer with a profiled steel deck reinforced by steel bars between its ribs. The resulting transient and non-linear thermal problems are solved numerically with three-dimensional multi-domain finite element models. The models were developed for normal weight concrete and lightweight concrete, and for different steel deck geometries (trapezoidal and re-entrant). The results of the numerical simulations are used to present a new calculation method to determinate the temperatures on the steel deck components and on the rebars and, consequently, to determine the bending resistance of composite slabs under fire conditions.
Highlights
Composite steel/concrete slabs are an alternative construction elements that ensure some advantages to structures, such as the reduction of the self-weight of the structures while speeding up the construction process
In Eq (2), the convection coefficient is αc = 25 W/m2K, the emissivity of steel is εm = 0.7 and the fire emissivity is ε f = 1. This equation represents the amount of energy that arrives to the steel deck by radiation and convection based on the gas bulk temperature, which will be transferred though the slab by conduction
The simplified calculation method used for the load-bearing criterion (R) presented in Eurocode 1994 1.2 [4] can be applied to support composite slabs when exposed to an ISO-834 standard fire [9]
Summary
Composite steel/concrete slabs are an alternative construction elements that ensure some advantages to structures, such as the reduction of the self-weight of the structures while speeding up the construction process. The explicit fire design calculation for composite slabs is not required when the fire requirements are smaller or equal than 30 min and for other fire rating the calculation methods were based on conservative approximations for a safer design procedure This standard was developed to guarantee structural safety according to the fire resistance classes established by ISO 834-1 [9] without the obligation to carry out experimental tests. The numerical models comprise different physical domains with different thermal properties, corresponding to the components of the slab such as concrete, steel deck and rebars. The temperature evolution on the steel deck components and on the rebars is evaluated for all the four different composite slabs with different concrete thickness h1, and subsequently the results are compared with the simplified method provided in the Annex D of Eurocode 1994-1.2. A new formula based on the parametric results is proposed to analytically calculate the temperature of slabs components
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