Composite slim floor stainless steel beam construction exposed to different fires

Nonlinear 3-D finite element models have been developed to investigate the structural behaviour of unprotected simply supported composite carbon steel and composite stainless steel beam constructions under fire conditions. The nonlinear material properties of carbon steel, stainless steel, composite slim concrete floor and reinforcement bars were incorporated in the models. The interfaces between the composite beam components were also considered allowing the different components to retain its profile during the deformation of the composite beam. The finite element models have been validated against published fire tests. The time–temperature relationships, deformed shapes at failure, time–vertical displacement relationships, failure modes and fire resistances of the composite carbon steel and composite stainless steel beams were evaluated by the finite element models and compared well against the fire tests. Furthermore, the variables that influence the fire resistance and behaviour of composite stainless steel beams comprising different stainless steel grades, load ratios during fire and fire scenarios were investigated in parametric studies. The study has shown that composite slim floor stainless steel beam construction offers a considerable increase in the fire resistance and better structural fire behaviour compared with traditional composite slim floor carbon steel construction. The fire resistances of the composite stainless steel beams obtained from the finite element analyses were compared with the design values obtained from the Eurocode 4 for composite construction at elevated temperatures. It is shown that the EC4 predictions are quite conservative for the design of composite slim floor stainless steel beam construction heated using different fire scenarios.