Section classification (Beams: AISC 360)

Tekla Structural Designer
2021
Tekla Structural Designer

Section classification (Beams: AISC 360)

Cross-section classification is determined using Table B4.1 (360-05), or Tables B4.1a+B4.1b (360-10 and 360-16).

At every cross section there are two classifications for each element in the section (flange or web) - one for axial compression and one for bending (flexure).

If axial compression does not exist (0kip or tension), the axial classification is not applicable. If bending is not present about both axes then the flexure classification is not applicable.

For axial compression the web and flanges are classified as either Compact or Slender (360-05), or as either Non-slender or Slender (360-10 and 360-16). The worst of the two is the resultant axial classification.

For bending both the web and flange are classified as Compact, Non compact or Slender and the worst of the two is the resultant flexural classification.

All unacceptable classifications are either failed in check mode or rejected in design mode.

Note that Tees and Angles (single and double) that are slender in their flexural classification are permitted.

Classification for plated beams

Since built-up (plated) beams allow for asymmetric sections, the general approach in flexure classification for all built-up beams is:

  • under major bending the compression flange is classified (both flanges are classified if double curvature exists, and the worst case is reported)

  • under minor bending both flanges are classified

  • under biaxial bending, major and minor bending are considered independently and the worst case is reported

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