The resistances of steel I-section monorail beams to lateral buckling are difficult to assess because monorails are often not well restrained against twisting. Monorails are supported at intervals along the top flange, but are free along the bottom flange, except at supported ends where vertical stiffeners may restrain the bottom flange. The buckling resistance is increased by the loading which generally acts below the bottom flange and induces restraining torques, but it is not common to take advantage of this. The buckling resistance may also be increased by any restraints against lateral deflection and longitudinal rotation of the top flange at internal supports, but it is difficult to quantify their effects without analysing the distortion of the monorail web. This project analyses the influence of restraints on the elastic lateral buckling (without distortion) of monorails loaded at the bottom flange, and shows how this might be accounted for in design.
Trahair, NS 'Lateral Buckling of Monorail Beams', Research Report R883, School of Civil Engineering, University of Sydney, 2007.