Steel Buildings in Europe

Part 7: Fire Engineering 7 - 38 5.6.1 Fire walls To limit the fire spread to a neighbouring compartment from the fire compartment, a solution that requires the building to be subdivided into independent compartments can be achieved by implementing one of the following construction details:  Two independent fire walls (such as sandwich panels, prefabricated panels, etc.) each fixed to an independent structural frame (see Figure 5.15 (a)). In this case, when one structure and its fire wall collapse during a fire, the fire cannot spread to the neighbouring structure, which remains stable and fire protected by the second fire wall  A single fire wall inserted between both structures. This fire wall can be a self-stabilized wall and fully independent. The fire wall can be also fixed at its top to both structures by means of “fusible” ties (see Figure 5.15 (b)) which, in case of fire near the wall, releases the connection to the ‘hot’ structure (usually when a temperature from 100 to 200°C is reached in bolts) without causing any damage to the wall (it one remains attached to the steel structure located on the ‘cold’ side) and the stability of the neighbouring cold structure. Self-stabilized walls are commonly used in practice. However during a fire, this solution can be dangerous for people (occupants and firemen) because they collapse away from the fire as a consequence of thermal bowing effect. So, they should be used only if their behaviour has been evaluated by advanced calculation model taking into account second order effects. Moreover, where spacing from the self-stable wall to the neighbouring steel structure is not sufficient, it is important to make sure that the fire wall can bear the force which may be induced by the movements of the building due to the thermal elongation of the roof structure (beams and purlins) due to the increase of temperature in the cell with the fire. As an alternative to the previous solutions, it is possible to insert the fire wall into the steel structure of the single-storey building as illustrated in Figure 5.15(c). Such wall can be either perpendicular to the steel frame or parallel to the steel frame. Several solutions can be then considered: fire wall inserted into a line of columns, fire wall attached to columns or fire wall moved from a line of columns. For these solutions, adequate measures must be implemented to avoid the collapse of the wall as a result of significant lateral displacements of the steel structure. These measures concern:  The attachment of fire walls to the steel structure  The fire protection of the steel structure near fire walls,  The roof system above fire walls  The bracing system.