Testing and analysis of catenary action in unprotected steel beams subjected to fire

Abstract

The use of unprotected steel beams in sprinkler-protected office buildings has been increasing in Australia over the past ten years. This has been justified using performancebased assessments, taking into account firstly the high reliability of the sprinkler system and secondly the robust performance of the floor system in fire resulting from the interconnection between the elements of structure. In this context, quantification of the catenary action developed in the steel beams is of interest, and a study of this mode of support has been commenced. Two fire tests have been conducted on steel beams supported in catenary action. A numerical analysis program has been written, based on moment-curvature methods. The material model for steel used in this analysis was that proposed by Poh. This model includes an explicit calculation of creep strain. Experimental and analytical results were compared. Reasonable agreement was obtained for Test 1, but in Test 2 the observed strength was greater than that calculated. Further investigation of this difference will be undertaken