ABSTRACT
A beam which is bent in its stiffer principal plane may buckle out of that plane by deflecting laterally u and twisting </>, as shown in Figures 7.1 and 7.2b. These deformations are interdependent. For example, a twist rotation (j> of the beam cross-section will cause the in-plane bending moment Mx to have an out-of-plane component Mx(j> as shown in Figure 7.3a, which will cause lateral deflections u. Conversely, lateral deflections u will cause the moment Mx to have a torque component Mxu' as shown in Figure 7.3b, which will cause twist rotations <j>.
