Mitigation of fire-induced progressive collapse of steel framed structures using bracing systems

Abstract

This paper investigates disproportionate collapse resistance of braced steel frames exposed to fire. The influence of type, number and location of bracing systems on the global collapse is studied. The results show that using braces can enhance the fire-induced collapse resistance by 1 hour. For a single-compartment fire, the collapse can be prevented by using either horizontal or vertical braces. The presence of vertical braces at interior bays is essential to prevent collapse. It is necessary to use a combined horizontal and vertical bracing to prevent collapse for interior multi-compartment fires. For multi-compartment fires at corner, fire protections are required for the perimeter columns to prevent global collapse. Slabs have beneficial influence on the collapse resistance which can be resisted by a tensile ring around the perimeter of the heated slab, and also by tensile yield lines extended to the frame edge. It is suggested to ensure the fire partition at corner regi on to avoid fire spread to adjacent compartments since spreading of corner fires are more dangerous than that of interior fires.