The Stability of Weakly Braced Frames

This paper reports an investigation into the buckling of frames with braces whose stiffness is insufficient to prevent sway buckling. Formulae are presented to calculate the effective column length for these weakly braced frames. Threshold stiffness values for the braces are obtained which are just enough to make frame buckle in a non-sway mode. After taking the influence of initial imperfection and lateral loads into account the brace threshold stiffness may be used as a rational basis for classifying sway frames and non-sway frames.