Effect of sustained service loading on post-fire flexural response of reinforced concrete T-beams

This paper presents the effect of sustained service loading at elevated temperatures on the residual flexural response of reinforced concrete (RC) T-beams after exposed to elevated temperatures of 700 and 900°C (1292 and 1652°F) for 3 hours and then cooled in air. Two beams were subjected to a constant simulated service loading equal to 22.6% of undamaged (unheated) flexural strength, while the counterpart beams were exposed to fire without any applied sustained load. The test results showed that the bottom (tension) steel reinforcements in all fire-exposed beams had experienced the peak temperatures that were higher than a critical value (593°C [1099°F]) before the post-fire static test. The post-fire static test results showed that the sustained loading has a detrimental effect on the post-fire flexural response of RC beams. The effect was more pronounced on the post-fire stiffness and ductility than on strength. In the paper, simplified finite element models for predicting the temperature response and post-fire load-deflection relationships of fire-exposed RC beams are also described.