D4.E.5 Section Classification

Steel sections are classified as plastic (Class 1), compact (Class 2), noncompact (Class 3), or slender element (Class 4) sections depending upon their local buckling characteristics (See Clause 11 and Tables 1 & 2 of CAN/CSA-S16-09, S16-14, or S16-19). The design procedures are different depending on the section class. STAAD.Pro determines the section classification for the standard shapes and user specified shapes.

For channel members, the code gives no indication of flange slenderness classification. Therefore, STAAD.Pro conservatively considers all channel flanges as Class 3 for flexure and thus uses the elastic section modulus for design.