Evaluation of CSA S16-14 asymmetry parameter for singly-symmetric beams

The provisions in the Canadian design standard S16, Design of Steel Structures, for determining the lateral–torsional buckling capacity of unequal-flange I-shaped beams employ an asymmetry parameter, βx, that is a function of the cross-sectional shape. It has been observed that the approximate equation for this parameter in the standard can be highly inaccurate in some cases. A study was completed to compare the approximate values of βx to the exact solutions for 16 312 singly-symmetric I-sections and 188 standard WT-shapes from the CISC Handbook of Steel Construction. It is concluded that the current standard provides extremely variable results, but is generally conservative for use in design, with the exception of T-sections, as long as the larger flange is in compression. Recommendations for adoption into the next edition of the standard are provided.