Abstract
Conventional fire resistance assessments of reinforced concrete (RC) structures often overlook the cooling phase, despite its critical role in real fire scenarios where material degradation continues beyond peak temperatures. This study evaluates the residual load-bearing capacity of RC columns subjected to fire, incorporating both heating and cooling phases. Through a comprehensive numerical investigation using SAFIR software, the effects of key parameters including fire duration, column height, cross-sectional geometry, boundary conditions, and concrete mix design are examined. Results show that larger sections and fixed-end supports enhance post-fire structural performance. High-performance concrete reinforced with date palm fibers (HPCDPFS) demonstrated superior thermal resilience, retaining up to 57 % of its initial strength at 650 °C, compared to 39 % for standard concrete. While steel reinforcement exhibits partial strength recovery after cooling, concrete suffers irreversible thermal damage, particularly under thermal shock, resulting in an additional 33 % strength reduction. These findings highlight the necessity of accounting for the cooling phase in performance-based fire design and support the adoption of fiber-reinforced HPC for improved fire resilience in RC structures.