Steel and Composite Structures

This chapter examines structural fire engineering considerations that are specific to steel, which is a common construction material. First, thermal and mechanical properties of steel at elevated temperatures are discussed. Second, failure modes specific to steel structures (e.g. connection brittleness) are examined. Lastly, pertinent analysis techniques for structural fire engineering applications involving steel structures are presented. Notably, tensile membrane action theory is covered in depth, which is a mechanism that provides thin slabs with large load-bearing capacity, resulting from large vertical displacements, where induced radial tension in the centre of the slab (due to the large deflection) is resisted by a peripheral compression ring. Also, the performance of structural steel connections under fire conditions is closely examined. In the event of a fire, the global frame response is closely linked to the behaviour of such connections. When excessive axial and rotational deformations occur at high temperature, the connections need to be robust enough to provide structural integrity.