RESPONSE OF RC FLEXURAL ELEMENTS EXPOSEDTO FIRE

Abstract

Although there may be less probability of occurrence of a fire, but when it occurs, it leaves behind its high impact on a structure is. During a fire event different parts of a structure may get exposed to different level of temperatures which may cause partial damage or total collapse of the structure. A reinforced concrete structure often remains standing after the fire has finished. In case of such partial damage to the structure, it becomes necessary to assess them in order to bring such fire damaged structure in service and to check whether the damaged structure is suitable for retrofitting work or not. For this purpose, an assessment of its residual strength/capacity must be carried out. This study brings out a mathematical model to predict the residual moment capacity of a fire damaged RC flexural element after cooling to ambient temperature. The proposed prediction approach involves 500°C Isotherm and Slice method with or without slip consideration. The incorporation of slip has been introduced by making use of modified strain-compatibility relationship between steel and concrete which accounts for the effect of bond strength degradation between steel rebar and surrounding concrete due p to fire exposure. The role of existence of partial bond has also been studied in great detail. The response of fire damaged RC flexural element has been studied with the perfect bond as well as partial bond condition by making use of finite element analysis based software package ATENA.