Fire Performance of Reinforced Concrete Slabs: Direct Flame Effects

The behaviour of two-way reinforced-concrete slabs exposed to direct fire was investigated in this study. The slabs were exposed to fire for one hour in a gas furnace and the flame-spread area was varied by increasing the number of fire sources from three to six. The slabs were cooled in two different ways: gradual cooling and sudden cooling. The results showed that the flame-spread area had a significant effect on the load-carrying capacity and deflection of the slabs. The load-carrying capacity decreased by 20.68% with gradual cooling and by 33.78% with sudden cooling when the flame-spread area was increased. The deflection at failure increased by 26.3% with gradual cooling and by 33.78% with sudden cooling when the flame-spread area was increased. The ductility factor showed an increase of 12.6% to 50.3 % for gradually-cooled slabs and of 50.3% to 59.6% for suddenly-cooled slabs with an increasing flame-spread area, compared to reference slabs. KEYWORDS: Reinforced solid concrete slabs, Direct fire flame, Thermal flame, Cooling method.