Structural response of a MRF exposed to travelling fire

In this study, structural response of a seismically designed steel moment-resisting frame subjected to travelling fire is investigated. This is to determine the structural strength of a generic frame designed for an extreme load when subjected to fire as another extreme load in addition to quantifying the effect of travelling fire size on its collapse behaviour. In this study, using the concept of travelling fire, and calculating the thermal field applied to structural elements, a generic frame was examined against a family of fires travelling across its first floor. In this regard, the resolved far-field gas temperatures dependent on the distance to the centre of fire were considered in order to calculate the temperature at the unprotected steel members. Analysis results revealed that fire size can deeply affect the total collapse time of a frame so that by reducing the fire size to a half or a quarter, collapse time increases by 19% and 62%, respectively. It was also suggested that columns of such structures should be designed against travelling fire considering the effect of load redistribution by which axial forces of columns might be doubled compared to the nominal loads applied to them prior to fire