Which type of steel structure is most prone to buckling under load?

The column frame is particularly susceptible to buckling under load because its primary function is to transfer axial loads. Columns are designed to carry compressive forces, and when these compressive forces exceed a specific limit known as the critical load, it leads to buckling. This instability often occurs before the material reaches its tensile or compressive strength because of the geometry and slenderness ratio of the columns.

In a column frame structure, these vertical members (columns) can be relatively slender compared to their height, which increases their likelihood of buckling when subjected to compressive forces. The slenderness effect means that as the height of the column increases with a constant cross-section, the risk of buckling under load becomes greater.

Other types of frames, like portal frames and truss frames, are generally designed to distribute loads more effectively through triangulation or rigid frames, which helps to mitigate the chances of buckling. Shear frames are also designed to resist lateral loads, minimizing the risk of failure due to buckling. Hence, while buckling is a concern for all structural elements under certain loading conditions, column frames specifically face a heightened risk due to their structural properties and load-bearing functions.