Diagonal Versus Orthogonal Ribs in Stability of Steel I Beams

The paper presents the numerical study of the stability of steel beams for various slenderness ratios of the web and various types of stiffening ribs. FEM analyses employing fine meshes of shell elements are conducted. Stability response of beams with transverse orthogonal ribs and longitudinally stiffened web is compared with the stability of beams with diagonal ribs. The latter ones demonstrated remarkably higher resistance to local instability of the web and astonishingly higher resistance to global instability. By the way of next numerical examples the torsional stiffness of beams with various rib configurations was evaluated. High torsional stiffness provided by diagonal ribs explained high global buckling load.