COMPOSITE BEAMS WITH PARTIAL FIRE PROTECTION

This paper presents the results of a theoretical investigation into th e effectiveness of a novel way to significantly reduce the fire protec tion cost to a composite beam. In this method, only the steel lower fl ange and a fraction of the steel web ave protected. The effectiveness of a partially protected composite beam is assessed by comparing its p lastic moment capacity with that of a fully protected beam subject to both the standard fire exposure and design fires. The parametric time- temperature curves in Eurocode 1 are used to determine the time-temper ature relationships of design fires. A finite element analysis compute r program for hear transfer is used to evaluate the temperature field in the composite cross-section. The plastic moment capacity is calcula ted by dividing the composite cross-section into many small blocks and summing their contributions. Partial protection is suitable for situa tions where the protection is applied along the steel profile. Results fr om this study indicate that the total fire protection cost may be reduced considerably due to more than 50% reduction in the protected s urface area, despite similar material costs. (C) 1998 Building Researc h Establishment. Published by Elsevier Science Ltd. All rights reserve d.