Simplified approach to estimating the elastic lateral-torsional buckling capacity of steel beams with top-flange loading

It is well-known that the lateral-torsional buckling capacity of a wide-flange beam is lower when transverse loads between brace points are applied to the top flange instead of at the shear centre. Although top-flange loading is commonplace, the load height effect can often be neglected due to lateral restraint provided by the loading mechanism itself; however, there are several common cases for which it must be considered in design. This paper provides the research background to the current provisions in CSA Standard S16 to account for the load height effect and proposes an effective length method that expands on these provisions to reduce their conservatism, while maintaining a simplicity appropriate for use in design. Employing a large and diverse database of steel shapes, the proposed method is compared with a comprehensive variety of other design approaches and available numerical and experimental data.