Effect of air-gap on response of fabricated slim floor beams in fire

Fabricated slim floor beams are produced by welding a steel plate to the bottom flange of an I-shaped steel section. During their fabrication, an air-gap is induced between the welded steel plate and the bottom flange. Previous studies have shown that the presence of this air-gap has an influence on their thermal behaviour in fire. Though the presence of this air-gap has an influence on their thermal performance, no investigations have yet been conducted to analyse its effects on their structural response. This study investigates the influence of the air-gap on structural response of fabricated slim floor beams in fire. Finite element modelling is performed to predict their response at elevated temperatures which is validated by replicating the experimental data from the literature. A sensitivity study is then conducted using the validated analytical method to study the effects of the air-gap presence and its size on their response in fire. Results obtained show that the presence of the air-gap has a significant influence on their structural response and enhances their fire resistance (in this case by approximately 15%). The size of the air-gap, however, has no significant influence on their structural response in fire. As the presence of the air-gap is found to be helpful and beneficial, findings from this research can be used to develop similar designs for structural members as an efficient and inexpensive way to improve their response in fire.