9 - Lateral-torsional buckling of deep beams

Abstract

Lateral–torsional buckling is the name commonly associated with instability of the “plane form of bending” of deep beams. When such a beam is loaded in the plane of greatest flexural rigidity, small inplane deformation occurs. In this pre-buckled state, the beam typically undergoes deflection caused by inplane bending, extension, and possibly inplane shear. When the critical load is reached, the beam deflects out of that plane and undergoes combined deformation involving both out-of-plane bending and torsion. This chapter discusses two sets of examples of such buckling analysis. The first set of examples involves straight forward examples of pure, constant bending in the pre-buckled state. The second set of examples, which includes complex examples are cantilevered beams, some of which have a more complicated pre-buckled state depending on the loading. Here the lateral–torsional buckling of a pinned-pinned beam—subjected to loads—is considered to produce constant planar bending deformation in the pre-buckled state. First, a straight beam is considered that is much stiffer in one flexural plane than in the other. A thin strip-like beam fulfills this condition. After that comes Vlasov correction. Finally, a small amount of initial curvature is introduced and its effect on the lateral—torsional buckling is determined.