Fire performance of composite columns Made from high and normal strength concrete: influence of thermal and mechanical parameters

Composite structures made from the combination of steel profile and concrete have significant load bearing capacity which depend on the behaviour of the two materials and their interaction, particularly in fire conditions. It is not possible to assess the fire resistance of composite members only by considering the temperature of the steel, because the presence of concrete may contribute greatly to increase the mass and thermal inertia of the member, which improve the fire behaviour of the element. The aim of this work is to develop an efficient Non-linear 3-D finite element model to examine the behaviour of Pin-ended axially loaded composite columns made from High Strength Concrete (HSC) and Normal Strength Concrete (NSC) for different fire ratings of 30, 60, 90 and 120 minutes. Two types of column were selected to investigate the effect of fire, notably HEB profile ranging from 160 to 200 encased with concrete partially or totally (PEC, TEC). These columns were tested under ISO834 fire standard. The critical load has been compared for columns height of 3 m, pinned in both ends. Properties for steel profile and reinforcement were assumed from S275 grade and B500 grade respectively, while C20/25 and C80/95 (NSC; HSC) was assumed for concrete. The results found show that the use of HSC in composite columns reduces the level of fire protection with the regard to NSC.

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