A simplified approach for evaluating equivalent fire resistance under design fire exposures

This paper presents an energy based approach for estimating equivalent fire resistance of structural members under design fire exposures. The approach is based on the principle of equivalent energy and estimates equivalent fire resistance by equating the total energy transferred from a design fire to that transferred by a standard fire exposure. The proposed approach is validated by comparing predictions from the proposed approach with those obtained from existing time equivalent methods, empirical formulae and non-linear finite element analysis. Based on the results, a correlation between equivalent fire resistance and maximum design fire temperature has been developed and is validated for RC beams. It is shown that the proposed method provides a reliable estimate of time equivalency and hence facilitates rational fire design.