Buckling of Members Having Open Sections

Abstract

Many flexural members are braced by other elements of the structures in such a manner that they are constrained to deflect only in the plane of applied transverse loads, e.g. slab-beam floor systems are extremely rigid in their own plane and the beams can deflect only in a plane perpendicular to the slab. The horizontal and rotational displacements are prevented by the floor system. On the other hand there are numerous instances where the members have no lateral support or bracings over their lengths and members can buckle in lateral direction under transverse loads. Similarly open column sections having only one or no axis of symmetry e. g. a channel section, and T-section or an angle section when subjected to axial compression; simultaneously undergo lateral displacement and rotation. This type of failure occurs because of low torsional rigidity of such sections. Further, in such sections, the critical load lies between the critical load for the torsional mode and that of pure flexural mode. A pure flexural mode exists when the centroidal axis coincides with shear centre axis. Therefore, a member subjected to an axial compressive force can also undergo lateral buckling.