Distortional Buckling Experiments on Cold-Formed Steel Joists with Unstiffened Holes

Experiments were conducted on cold-formed steel C-section joists with rectangular unstiffened web holes. The presence of holes decreased joist capacity and amplified distortional buckling deformation. Distortional buckling was accompanied by unstiffened strip buckling of the compressed web. When hole depth approached the web depth, sudden flexural buckling of the compressed flange at the hole was observed. Forthcoming direct strength method equations for joists with holes accurately predicted flexural capacity when web hole depth equaled two-thirds the web depth, and was unconservative for larger web holes.