Response of Beam-Column Rigid Frame Exposed to Localised Fire

Steel Structures are prone to damage and even collapse when exposed to fire. The objective of the present paper is to investigate the effect of fire on the structural behaviour of a steel beam assembled in a moment resisting frame (MRF) with welded connection, numerically using commercially available software ABAQUS. Two different fire scenarios were used for analysis. In the first case, the frame was exposed to a localised fire source acting underneath the centre of the beam, and the same resulted in maximum temperature concentrated at the midspan with large temperature gradient along its ends. The second scenario represented uniform temperature throughout the beam span where the temperature in the beam followed the same time–temperature curve experienced at the beam midspan, similar to the previous case. The maximum temperature in the exposed beam was around 700 °C. A thermal analysis followed by mechanical analysis was performed, where the temperature profile from the thermal analysis was given as input in the structural analysis. Based on the study, it was observed that the recovery of the deflection of beam after cooling was negligible for frames exposed to localised fire. However, for uniform temperature exposure, there was significant recovery of the same.