Local buckling study of flanges and webs in I-shapes at elevated temperatures

Local buckling in floor beams has been one of the important observations in several fire events in steel buildings such as World Trade Center Tower 7 and large-scale fire experiments such as Cardington in UK. Utilizing three dimensional finite element methods for complex geometry and nonlinear behavior of such connections, local buckling of the web followed by the buckling of the lower flange is observed to occur in early stages in fire, which causes instability to the floor system, and a reduction in the connection strength. To fully capture the behavior of floor systems, one needs to be able to predict such buckling behavior of the beam. This paper contributes to such knowledge by investigating the local buckling of floor beams at elevated temperatures using nonlinear finite element models. The results are compared to AISC provisions of plate buckling under ambient and elevated temperatures.