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D8.A.2.2 Section Classification

The IS 800: 2007 specification allows inelastic deformation of section elements. Thus local buckling becomes an important criterion.

Steel sections are classified as Plastic, Compact, Semi-Compact, or Slender element sections depending upon their local buckling characteristics.

This classification is a function of the geometric properties of the section as well as nature of the load applied to the member. The design procedures are different depending on the section class.

STAAD.Pro is capable of determining the section classification for the standard shapes and design the section for the critical load case accordingly. The Section Classification is done as per section 3.7 of IS 800:2007 and Table B2, for Outstanding and Internal Elements of a section.

For the criteria for being included in those classes, refer to section 3.7.2-(a) – (d) of the code.

Slender Sections

STAAD.Pro is capable of designing I-Sections with slender webs for IS 800:2007.

The IS:800-2007 code does not provide any clear guidelines about what method should be adopted for the design of slender section. The "Flange Only" methodology is used where it is assumed that flexure is taken by the flanges alone and the web will resist shear with adequate shear buckling resistance. This method requires that the flanges be non-slender elements (i.e., on the web is a slender element) to qualify for a valid section for design. If any of the flange elements become slender, the design will not be performed and a warning message is displayed in the output.