Fire resistance of steel-framed multi-storey buildings

Temperatures in unprotected steel elements of a building rise rapidly under fire conditions. These increases in steel temperatures are accompanied by sharp reductions in strength and stiffness. Consequently, regulatory authorities require fire protection to structural steel elements to achieve a required fire resistance with the intention of ensuring the stability of the steel structures under fire conditions. This paper provides a brief description of the developments in the fire resistance of steel framed multi-storey buildings, specifically the investigations undertaken at the UK's Building Research Establishment. The design of steel frames in multi-storey buildings for fire resistance is moving away from the traditional prescriptive method of fulfilling the requirements of building regulations to being performance based, ie. based on the understanding of the fire behaviour, the structural behaviour and requirement under fire conditions. This paper concludes with the suggestion that fire protection to steel beams in most multi-storey steel framed buildings may be eliminated, The reason is that the floor slabs have inherently sufficient load carrying capacities via the mechanism of tensile membrane action at large deflections.