Aneesha Balaji, Praveen Nagarajan and Madhavan Pillai

pp. 183 - 192

Abstract

Fire resistance provisions in Indian codes are prescriptive in nature and provide only tabulated fire ratings for
structural members. Eurocode EN 1992-1-2:2004 suggests simplified methods which include explicit equations for fire resistant
design. The aim of this paper is to familiarize the simplified method, i.e., 500°C isotherm method. The procedure is customized
for Indian conditions and a parametric study is done to determine the fire rating for flexural elements. Fire ratings
recommended in IS 456:2000 is compared with strength criteria by using the 500°C isotherm method. It is also compared by
thermal criteria obtained by heat transfer analysis of finite element model. Through these studies, it is shown that for most
of the cross-sections, the fire rating obtained from the two methods is higher than that given in IS 456:2000 provisions and
the increase in cover has significant effect in increasing fire rating only for lower values of cover to reinforcement. 

Keywords

• 500°C isotherm method
• fire rating
• transient thermal analysis
• tabulated data
• structural elements
• reinforced concrete