Columns are vertical compression members designed to resist the combined effects of axial forces and bending moments. Bending moments in columns may occur due to lateral forces from wind and earthquake loads, as well as load eccentricities and column imperfections. The lateral deflections that occur due to bending cause additional secondary bending moment as a result of greater load eccentricity. The magnitude of secondary bending moments classifies a column as slender or short. The secondary moment of a short column is small, with the load carrying capacity ultimately determined by cross-sectional strength. Slender columns, however, experience significant secondary bending moments and the load carrying capacity is greatly influenced by the length and loading conditions of the member, as well as cross-sectional strength. AS3600 – 2009 ‘Concrete Structures’ classifies a column as short if Le/r ≤ 25 for a braced column (lateral side-sway prevented).