Effect of lateral and rotational restraint for bracings on lateral buckling load for h-shaped beams under moment gradient

The bending moment of Hie beam is varied along the member under Hie dead load and lateral seismic load, and then the stress of the upper flange whh Hie lateral bracings become compressive or tensile. Therefore the lateral bracings connected to flange need to have Hie lateral and rotational rigidity to prevent the lateral buckling of the beams when the upper flanges have the tensile stress. In this paper, Hie elastic lateral buckling load of H-shaped beams under moment gradient is developed whh the energy method, and Hie relation between Hie elastic lateral buckling load and Hie required rigidity is clarified. Next, the elasto-plastic lateral buckling moment is evaluated using the modified slenderness ratio with the elastic lateral buckling load.