Residual load bearing capacity of reinforced concrete frames after fire

Abstract

Estimating the residual strength of fire-exposed reinforced concrete (RC) structures is of great importance in determining whether the cooled structure is safely functional or immediate repair is needed. This paper describes the results of experimental and numerical investigations on fire and post-fire structural responses of a 2-story moment-resisting RC frame test specimen. The lower story of the test specimen, which was subjected to service loads, was heated for 60 minutes in accordance with the ISO-834 standard fire test. The test specimen exhibited a satisfactory structural performance during the fire course and considerably recovered much of its pre-fire deflection state when cooled. To investigate the re-serviceability and residual load bearing capacity of the cooled test specimen, a destructive cyclic vertical loading was conducted. A detailed 2D finite element model was developed as well. By comparing the test and analysis results, it was found that due to the fire damage the test specimen lost 30% of its load bearing capacity. The proposed numerical modelling approach in this study predicted considerably well the post-fire residual strength of the test specimen.