Research Toward Use of Unprotected Steel Structures

Abstract

When exposed to fire, steel loses stiffness and strength; to limit this loss of strength and stiffness, external fire protection is provided to the steel structural members to satisfy required fire resistance ratings. However, the current practice of providing fire protection is based on the behavior of single elements under idealistic situations; as such, it is conservative and does not represent the realistic fire behavior of real structures. Recently, there has been a spurt of worldwide research activities aimed at minimizing such fire protection costs. These studies have mainly focused on understanding the realistic fire behavior of complete structures and on developing innovative systems with inherent fire 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 steel structures. This paper reviews some of the recent developments in this field and describes one particular system in some detail. This system uses the conventional composite slab/steel beam flooring system in conjunction with concrete-filled steel tubular columns. Research studies at the United Kingdom's Building Research Establishment and the National Research Council of Canada suggest that it might be possible, through proper design, to eliminate fire protection for steel in this system.