Research toward use of unprotected steel structures

When exposed to fire, steel loses stiffness and strength; to limit this los s of strength and stiffness, external fire protection is provided to the st eel structural members to satisfy required fire resistance ratings. However , the current practice of providing fire protection is based on the behavio r of single elements under idealistic situations; as such, it is conservati ve and does not represent the realistic fire behavior of real structures. R ecently, there has been a spurt of worldwide research activities aimed at m inimizing such fire protection costs. These studies have mainly focused on understanding the realistic fire behavior of complete structures and on dev eloping innovative systems with inherent fin resistance. Feasible solutions are now emerging, in which the external fire protection may be completely removed, in certain situations, without compromising the fire safety of ste el structures. This paper reviews some of the recent developments in this f ield and describes one particular system in some detail. This system uses t he conventional composite slab/steel beam flooring system in conjunction wi th concrete-filled steel tubular columns. Research studies at the United Ki ngdom's Building Research Establishment and the National Research Council o f Canada suggest that it might be possible, through proper design, to elimi nate fire protection for steel in this system.