Effect of transient creep on fire induced instability in steel framed structures

This paper examines the influence of temperature-induced transient creep on the onset of instability in steel framed structures subjected to fire exposure. A comprehensive numerical model is developed in ABAQUS to trace the overall response of a steel framed building under fire exposure, specifically taking into account the transient creep strain that develops at elevated temperatures. The developed model is applied to conduct a parametric study on a ten-story braced steel framed building under different fire exposure scenarios. The effect of critical parameters such as the intensity and duration of fire exposure and the extent of fire spread in the building (number of compartments or floors burning) on high-temperature creep deformations that develop in the steel framed structure is evaluated. Results from the parametric study indicate that the high-temperature creep governs the stability of steel framed buildings under severe fire conditions. Fires with moderate to high fire severity (peak fire temperature exceeding 800 °C and burning for 2 h or more) are found to be more critical from the perspective of transient creep, as large creep deformations develop in steel members from exposure to high temperatures for a sustained duration. Simultaneous burning of multiple compartments in a single story is found to have the highest influence on the stability of the steel framed building, due to the high level of transient creep strains resulting from high stress levels that develop in the steel members.