Part 1: Architect’s Guide 1 - 46 Composite steel-concrete construction In composite construction, the combined properties of steel and concrete can increase the fire resistance to cold and fire. Figure 6.3 Composite construction For I or H columns, the composite section consists of a complete coating, or more often a filling, between the web and flange, as shown here. For tubular columns, the section is rendered composite by filling the tube with concrete. The weight of the columns is significantly increased, but the performance can achieve a resistance of R180. Composite steel-concrete design is also effective in providing the floor beams with significant fire resistance. Placing structure outside the envelope An external structure is only exposed to flames projecting from openings and from burning parts of the building. Contact with the ambient air also helps to cool it down. Positioning the structure outside the building can avoid the need for fire protection. 6.2.5 Active fire protection methods When dynamic fire protection devices are used (detection, alarms, smoke extraction, sprinklers) or if there is human intervention to put out the start of a fire (extinguishers), these are called ‘active’ methods. Smoke detection Signs Smoke extraction extinguishers Sprinklers Figure 6.4 Active fire protection methods
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