Required bracing stiffness on lateral buckling strength for H-shaped beams with bracings

Lateral bracings are usually set to upper flanges of H-shaped beams in moment resisting frames, and then the stress of the braced flange may become tensile. If the bracings are connected to the tensile flange of H-shaped beams, its lateral buckling strength is more increased than that without bracing. The bracing connected to a tensile flange must restrain torsion to increase the lateral buckling strength of the beams. In this paper, the elastic lateral buckling load of H-shaped beams is developed with the energy method, and the relationship between the lateral buckling load and bracing rigidity is clarified. Bracing rigidities are lateral and rotational rigidities. The required bracing rigidity is suggested from two equations of the elastic lateral buckling load. Next, large deformation analyses are performed using ABAQUS with version 6.8, and the elasto-plastic lateral buckling behaviour for H-shaped beams with lateral and rotational bracings is presented. Also the buckling load is related with lateral and rotational bracings. Finally, the lateral buckling load for H-shaped beams with the required bracing rigidity is estimated with the modified equivalent slenderness ratio, and the elasto-plastic buckling stress is compared with the buckling curve for the Japanese standard code.