Structural behaviour of Reinforced Concrete (RC) columns under fire

Abstract

The paper presents a numerical study on the response of RC columns under fire. The numerical studies deal with both: during fire (fire rating) scenario and after fire (residual) scenario. The results highlight the importance of Load-Induced-Thermal-Strains (LITS) for predicting the Fire Rating (FR) of RC columns. The predicted temperature variation across the cross-section and axial deformation of column with time are in good agreement with the experimental measurements available in literature. The importance of considering cooling phase of fire for evaluating the behaviour of RC columns has been emphasized. Because of the peak temperatures occurring during the cooling phase and the additional damage due to cooling, the column may also fail during cooling period. The effect of exposure duration on the residual axial load carrying capacity of RC columns has also been discussed. The presented numerical studies using 3D fully-coupled thermo-mechanical model for simulating the behaviour of axially loaded RC columns during the complete fire hazard situation, shows its capabilities to realistically account for different strain components and damage components occurring during different phases of fire hazard (viz. heating-phase, cooling-phase & residual-state). The model uses temperature dependent microplane model for concrete and classical von-Mises plasticity models for reinforcing steel.