Buckling of Trapezoidal Frames Permitted to Sway

The general state of sway of an isolated strut or frame as a whole in the presence of axial compression is resolved to the components of pure-shear sway and no-shear sway. It is the second component of sway only, i.e., the component of no-shear sway, which is the important one for determining the sway buckling loads. It was found that the elastic critical load increases with the increase of the inclination of columns or beams up to a maximum value, and then decreases again. There is a certain inclination of the columns or the beams at which the elastic critical load is maximum. The percentage increase in the critical load and the angle at which the critical load is maximum depend on the geometric properties of the frames as well as the bending stiffness ratios of the frame members; both are bigger in case of hinged base frames than in case of fixed base frames. Curves giving the sway buckling loads and the best proportions of trapezoidal frames to obtain the maximum critical loading capacity are presented.