4. Torsional and flexural-torsional buckling

In the foregoing, we have studied in detail the flexural buckling of compressed structural elements. This type of instability is associated with lateral displacements in a plane of symmetry of the cross-section. This plane is the weak – plane, i.e. the plane of least inertia – for identical support conditions for bending in the two main planes. In general, it cannot be concluded that this is the plane of maximum slenderness, as the applicable buckling curves are not identical for the two possible buckling directions.

In this chapter, we consider another type of buckling instability. It's still a bifurcation instability, but the displacement field that characterizes it includes not only lateral bending displacements, but also torsional displacements. This is known as flexural-torsional buckling. This new instability phenomenon is of the utmost importance when compressed...