Fire Resistance of Reinforced Concrete T-Beams with Circular Web Openings

The flexural performances of a solid reinforced concrete (RC) T-beam and three RC T-beams with circular openings subjected to the ISO-834 standard fire were experimentally studied. The failure mode, fire resistance, time-deflection curve, and mid-span deflection recovery of the RC T-beams were analyzed by considering the factors such as the bottom chord depth and the stirrup status (refers to whether the stirrups were cut off when drilling). The results showed that the fire resistance of the RC T-beam with a 220 mm bottom chord was almost the same as that of the solid beam and both failed in ductile modes; however, the fire resistance of the RC T-beam with a 100 mm bottom chord was 18.9% lower than that of the solid beam and failed in a brittle mode. Whether the stirrups of the pure bending section were cut off when drilling had little effect on the fire resistance of the RC T-beam. Numerical simulations were also validated to study the mechanical properties influenced by the bottom chord depth. Finally, a simplified method of high precision was proposed to deduce flexural capacities of RC T-beams with circular openings under fire.

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