D14.C.5 Section Classification
The SANS 10162 specification allows inelastic deformation of section
elements. Thus, local buckling becomes an important criterion. 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 11.2 and Table 1 of
SANS 10162-1:2011).
The design procedures are different depending on the section class. STAAD.Pro determines the section classification for the standard shapes and user specified shapes.
Class 4 sections are those with ratios exceeding those listed for Class 3. This classification is a function of the geometric properties of the section. Design is performed accordingly for sections in Class 1, Class 2, and Class 3.
Class 4 sections per SANS 10162-1:2011 are not designed in STAAD.Pro. If a member design is requested for a section of this type, the analysis file will list reason for failure as "Class 4".