Steel Buildings in Europe

Part 7: Fire Engineering 7 - 4 In prescriptive fire regulations, required fire resistance for a building element is expressed in terms of the minimum period of time during which the building element would function satisfactorily while subject to the standard fire. When fire stability requirements are given for single-storey buildings, they usually range from 15 minutes (R15) to 60 minutes (R60), depending on the occupancy class of the building, the provision of sprinklers, the building height and the compartment size. 2.3.2 Compartmentation and building separation Single-storey building must be subdivided into compartments separated by fire walls when the floor area of the building exceeds the allowed maximum compartment size. Limits on the compartment size may be removed by fitting the building with sprinklers. The effects providing compartmentation on property loss is that direct damage is confined to the content of the compartment in which the fire starts, reducing the chances of the fire growing large. As regards the life safety, people in other parts of the building can use escape routes to get out safely without being exposed to the smoke or gases from the fire. When considering fire walls between compartments, fire resistance is generally in the range of REI 60 to REI 120. Fire spread to neighbouring buildings also needs to be prevented. This is achieved traditionally by sufficient separating distances or façade elements with adequate fire resistance. In the French research project Flumilog, a design method has been recently developed to assess the thermal radiant effects of fires in single-storey storage buildings. The method allows calculation of the safe separating distances, taking into account the main characteristics of the building, such as the building content, the type of façade elements and roof, etc. 2.3.3 Fire suppression Sprinklers may be required by national fire regulations. In addition to their obvious effect in the reduction of the fire growth, their use leads usually to a reduction of the fire resistance rating required for the structure. They allow also larger fire compartment sizes. 2.3.4 Smoke control systems National fire regulations may require that smoke control systems are implemented in public buildings, storage building and industrial buildings in order to facilitate escape, by minimising risks of smoke inhalation and injury and to some extend to enable fire-fighters to better see the fire and therefore to extinguish it more speedily and effectively. Smoke control systems help in removing smoke from the fire area, and in limiting the spread of hot gas beneath the roof, which increases the time for the compartment to become smoke-logged, giving people more time to escape safely from the building. This can be achieved by a combination of smoke exhaust systems (mechanical or natural) and screens (which contain the smoke in specific areas).