Modelling concrete slabs subjected to localised fire action with OpenSees

Purpose: Reinforced concrete slabs in fire have been heavily studied over the last three decades. However, most experimental and numerical work focuses on long-duration uniform exposure to standard fire. Considerably less effort has been put into investigating the response to localised fires that result in planarly non-uniform temperature distribution in the exposed elements. Design/methodology/approach: In this paper, the OpenSees for Fire framework for modelling slabs under non-uniform fire exposure is presented, verified against numerical predictions by Abaqus and then validated against experimental tests. The thermal wrapper developed within OpenSees for Fire is then utilised to apply localised fire exposure to the validated slab models using the parameters of an experimentally observed localised fire. The effect of the smoke layer is also considered in this model and shown to significantly contribute to the thermal and thus thermo-mechanical response of slabs. Finally, the effect of localised fire heat release rate (HRR) and boundary conditions are studied. Findings: The analysis showed that boundary conditions are very important for the response of slabs subject to localised fire, and expansive strains may be accommodated as deflections without severely damaging the slab by considering the lateral restraint. Originality/value: This work demonstrates the capabilities of OpenSees for Fire in modelling structural behaviours subjected to non-uniform fire conditions and investigates the damage pattens of flat slabs exposed to localised fires. It is an advancing step towards understanding structural responses to realistic fires.