Structural performance of long-span composite truss and beam systems in fire

Composite truss and composite beam systems have recently been widely applied in long-span multi-storey floor construction. In a fire resistance design according to BS5950 Part 8, two alternative calculation approaches, a limiting temperature method and a moment capacity method, are used to assess the fire resistance of composite structures. The in-fire performance of the structures and insulation materials are required to satisfy a limiting strain level and a simple deflection criterion during the structure’s specified fire resistance period. However, it is difficult to estimate the deflection of long span structures at elevated temperatures, due to the significant thermal effects on both the materials and structural mechanics. This project uses the Sheffield FE package ‘Vulcan’ to investigate numerically the in-fire performance of two types of long span structure which are passively protected against fire.