Strength of slender concrete-filled steel box columns incorporating local buckling

Abstract

Composite columns have seen a significant resurgence in their use over the last decade. This has resulted in the use of very thin-walled steel sections, which are susceptible to local buckling. Furthermore, these members have been applied in jump-start construction in the basement of tall buildings where slenderness effects may be dominant. The interaction between local and global buckling therefore needs to be investigated. This paper presents a method for incorporating local buckling in assessing the global buckling load of concrete filled steel columns. A parametric study is then undertaken to consider the effects of column slenderness, plate slenderness, steel yield strength and concrete compressive strength on the behaviour. The overall buckling loads of these columns are then compared with the buckling loads when local buckling is neglected. A series of design charts are then established to determine the reduction factor for global buckling caused by local buckling of the steel section. This reduction factor is then shown to be useful in augmenting existing international specifications such as Eurocode 4.