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D1.A.10.2 Compression

Design of the members subject to compression is performed per chapter E of AISC 360-16.

All the cross-section profiles described in section 1A.10 are considered for compression.

The design compressive strength is calculated based on the applicable limit states of flexural buckling, torsional buckling, and flexural-torsional buckling modes as per Cl.E.1.

The nominal compressive strength, Pn , shall be the lowest value obtained based on the applicable limit states of flexural buckling, torsional buckling, and flexural-torsional buckling. In general, Table.E1.1 is followed for the choice of applicable sections/clauses for the various cross section shapes.

Limit States

Following limit states are checked for flexure per Equations E3-1, E3-2, and E3-3 for without slender elements:
  • Flexural buckling about X axis
  • Flexural buckling about Y axis
  • Flexural buckling about U axis (for unsymmetrical shapes only)
  • Flexural buckling about V axis (for unsymmetrical shapes only)
  • Flexural-torsional buckling
Flexural-torsional buckling is checked per Equations E4-1, E4-2, and E4-3, E4-4, E4-7. Note the following:
  • Check no performed for solid rect or circ bars, thin-walled rect or circ hollow sections, double-channel face-to-face (only when channels are connected by full weld or tension bolts), or single angles with compact long legs.

The gross area is used for members with non-slender elements whereas the effective area, Ae, is used for slender elements. The effective width of a slender element of any section other than round HSS is calculated for each limit state of compression as per eq. E7-2 or eq. E7-3 depending on the condition mentioned in the specification. The effective area (Ae ) for a slender HSS round section is calculated as per cl. E7.2.


The design parameters that affect compression are:
  • LEG
  • LZ
  • LY
  • LX
  • KZ
  • KY
  • KZ
  • SNU
  • CSP

Slenderness Limits

The code does not mandate the maximum slenderness limit for members in compression. However, the program will check against a maximum slenderness ratio (L/r) which is specified using MAIN parameter whose default value is 180. The length considered to calculate the compression slenderness will be the full member length.