Inelastic distortional strength of steel beam-columns

Purlins, girts or joists, attached to one flange of steel beam-columns, can provide translational and rotational restraint to the flange and therefore to the member. This flange may be in tension at some locations and in compression at others. When the compression flange, where unsupported, attempts to deflect sideways, failure is likely to occur by either elastic or inelastic distortional buckling. The web, restrained by the tension flange and its attachments, distorts. A non-linear incremental finite element analysis programme has been developed to assess the distortional strength of thin-walled beam-columns of arbitrary open or box crosssection under monotonically increasing static loading. Sweep and camber, loading, restraints, residual stresses and boundary conditions can be prescribed. Output includes the ultimate load, load-deformation diagrams for any node, and the 3-dimensional deformed geometry. For prismatic members, a graphical user-interface defines the problem and presents results. The analyses agree well with reported test results. Examples are presented.