Differences in inelastic properties of steel and composite beams

Abstract The inelastic behaviour of continuous steel and composite beams in which strain-weakening occurs due to local and lateral buckling is compared both theoretically and experimentally. While the required rotation capacity of composite beams is larger than that of equivalent steel sections, other factors offset this greater ductility requirement. The available rotation capacity is shown to be particularly sensitive to the proportion of the depth of the steel section that is in compression and the lateral slenderness ratio in the negative moment region. This behaviour is explained theoretically and illustrated in seven tests on steel and composite beams. The substantial benefits to be gained in available ductility by using semi-rigid end connections in continuous composite beams are also demonstrated.