Steel Buildings in Europe

Part 7: Fire Engineering 7 - 3 Regarding fire service operations, it is commonly accepted that fire-fighters should not enter a single-storey building because of fast fire growth. Usually they are forced to fight the fire from outside, covering neighbouring walls with water. Hazard in this case for fire-fighters is then reduced to zero in the event of structural collapse since it occurs at a level of temperature at which fire- fighters can not withstand (provided that the progressive collapse, in the case of compartmented buildings, and the collapse of the structure toward outside do not occur [5,6] ). In the event of, at the beginning of fire, they need to enter within the building to rescue people, they cannot last within the building after the heat flux is more than 7 kW/m², which is also very far for the risk of collapse of the structure. For these reasons, an increase of the intrinsic fire resistance of single-storey buildings is unnecessary. However, the overall stability of the structure and the stability of fire walls need to be accurately considered, to avoid any progressive collapse. A single-storey building undergoes progressive collapse when local failure of the heated part of the structure leads for the failure of adjoining cold structures. In addition, to provide a safe situation to fire-fighters located around the building, the structure of single-storey building (including façade elements) must collapse towards the inside of the building. Many National Regulations have taken into account previous remarks for industrial single-storey buildings as well as for public buildings by not requiring any fire resistance rating for such works but introducing specific safety requirements in terms of overall structural behaviour and concentrating requirements on egress facilities and early fire detection and/or suppression. With regards to other single-storey buildings with relatively low fire loads, the risk of life in the event of fire is reduced as egress of occupants and fire-ground operations are straightforward. 2.3 Main requirements of current fire regulations 2.3.1 Fire resistance of structural members Despite the comments above, fire resistance ratings are sometimes required for the structure of single-storey buildings [7] . The fire resistance is expressed as the time during which a building element can withstand exposure to fire without losing its function (load-bearing elements or separating element). Usually, building elements are classified using three performance criterion:  The load bearing capacity, R , which is the ability for a load-bearing element to resist a fire without losing its structural stability  The integrity, E , which is the ability of a separating element, when exposed to fire on one side, to prevent the passage through it of flames and hot gases  The insulation, I , is the ability of a separating element, when exposed to fire on one side, to restrict the temperature rise on the unexposed face below specified levels (in general a average value of 140°C).