REALISTIC MODELLING OF COMPOSITE FLOOR SLABS UNDER FIRE CONDITIONS Bassam A. Izzuddin1, Member ASCE

Abstract eng:
This paper describes two alternative strategies for modelling the response of composite floor slabs under fire conditions. The first strategy is based on a grillage approximation with 1D elasto-plastic elements, whereas the second strategy employs a more realistic representation based on a newly developed 2D flat shell element. In addition to the modelling of geometric and material nonlinearities, the new 2D shell element incorporates an essential capability of representing geometrically orthotropic slabs, achieved through modifying the Reissner-Mindlin hypothesis. Following a description of the aforementioned 1D and 2D element formulations, a comparative study is undertaken on a composite floor slab subject to ambient and fire loading conditions, where consideration is given to different edge restraint conditions. The study shows that grillage modelling can significantly overestimate the resistance of the composite slab in the large displacement range, particularly in the absence of planar edge restraints. It is therefore suggested that realistic modelling of composite floor slabs using the newly developed 2D shell element is a most effective approach for an adequate response assessment under extreme loading conditions, such as due to fire.

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