Experimental and analytical study on post-fire residual flexural behavior of corroded reinforced concrete beams after various cooling methods

To study the flexural behavior of corroded reinforced concrete (RC) beams after various cooling methods, a series of tests were carried out on twenty-four RC beams. The study delved into the effects of corrosion degree (5 %, 10 %, and 15 %), fire exposure time (60 min, 90 min, and 120 min), and cooling methods (natural cooling and water cooling) on the flexural performance of the beams. The results indicated that during the cooling phase, beams subjected to water-sprayed cooling exhibited a faster cooling rate and more pronounced surface cracks in comparison to beams undergoing natural cooling. All beam specimens showed flexural failure mode, but it should be noted that water-spraying cooling may induce brittle failure in beams post-fire. The descending segment of the load-deflection curve for failed specimens with over-reinforcement was steep, indicative of poor ductility. The peak load of the specimens decreased by 36 % from unexposed to 120 min of exposure. Notably, the impact of fire exposure time on peak load was more pronounced than that of the corrosion degree. In terms of cooling methods, the flexural capacities exhibited a more significant decline in beams subjected to waterspraying cooling compared to those under natural cooling, with a reduction of 42 %. The residual flexural capacities of corroded RC beams were predicted using a simplified analytical model incorporating heat transfer analysis and cross-section analysis methods. The predictions demonstrated excellent agreement with the experimental results. The conclusions can provide theoretical guidance for fire rescue after exposure to fire.