No-sway collapse of steel frames under fire conditions: A parametric investigation

Fire represents a significant danger for frame structures hosting industrial activities. In this context, the numerical investigation of fire effects and fire induced collapse mechanisms becomes of interest. According to many studies on the topic, two failure modes are identified for a steel frame in fire: An outward (or sway) collapse and an inward (or no-sway) collapse. Above others the failure mode is determined by the following parameters: i) the acting load combination; ii) the typology of the column base restrain and iii) the two interacting mechanical effects of the fire (thermal expansion of the structural elements and thermal degradation of the steel properties). In this paper, a set of nonlinear transient analyses, which take into account for thermoplastic material behavior and geometrical nonlinearities, has been performed in order to understand the influence of different parameters on the collapse mode of the frame.