Résumé:
Composite structures made from the combination of steel profile and concrete have a significant loadbearing capacity which depends on the behaviour of the two material components and their interaction, particularly in fire conditions. This work includes two parts, notably the thermal and mechanical behaviour of the composite column under compression and combined compression and bending. The aim of the first part is to develop an efficient non-linear 3D finite element model to investigate the behaviour of pin-ended axially loaded composite column made from high strength concrete and normal strength concrete at different fire rating classes. The fire behaviour of the columns was tested according to ISO-834 standard fire. The results show that the use of HSC reduces the level of the fire protection with the regard to NSC. NSC in composite structures accommodates higher deflections than HSC, which is safer in case of fire accident. In the second part of this work, the Fire performance of partially encased composite columns (PEC) subjected to eccentric loading is studied. Numerical and analytical methods are used to evaluate the load bearing capacity of PEC composite columns under combined compression and bending moment. The parametric study includes the buckling length, the load eccentricity, the fire exposure time and the fire scenario. It is found that the analytical results agree well with those of the numerical method, particularly for higher fire rating classes (R60-R90-R120). The results show also that the PEC composite column loaded by an axial compression resists better to fire than the composite column subjected to an eccentric loading.
