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RR 22.10.00-3.2 Single Angle Brace Members in AISC 360-16

The engineer now has control over the use of how the provisions of Section E5 are applied to the design of single angle members in compression per AISC 360-16.

Previously, it was assumed that all of the conditions for single angle members were met such that the effects of eccentricity could be ignored and that the effective slenderness ratio may be used. Further, it was assumed that any single angle was an individual member and that the modified slenderness ratio of Cl. E5(a) always applied. These are conservative assumptions and may result in sections that are not the most economical. Therefore, two new parameters have been added which allow the engineer to control the specifics of how single angle members in compression are designed per E5.

For AISC 360-16, single angle members in compression can be designed using a modified slenderness method provided a set of conditions are met for that member. It is left to the engineer to confirm that conditions E5.(1) through E5.(3) are met and to specify this for single angle member using the E5P parameter. Those conditions are:
  • 1) Members are loaded at the ends in compression through the same leg.
  • 2) Members are attached by welding or by connections with a minimum of two bolts.
  • 3) There are no intermediate transverse loads.
If one or more of these conditions are not met, then the E5P 1 parameter value should be assigned to those members.
Note: Conditions E5.(4) and E5.(5) are checked by the program:
  • 4) Slenderness ratio, Lc/r ≤ 200
  • 5) For unequal leg angles, the ratio of leg widths is < 1.7.
The effective slenderness ratio method used for single angles also depends on if those angle members are:
  1. individual members or are web members of planar trusses (in which case, Cl. E5(a) applies - IMM 0)
  2. web members of box or space trusses (in which case, Cl. E5(b) applies - IMM 1)
A message is issued if the E5P or IMM parameter is used with any section type other than a single angle.
Note: The E5P and IMM parameters are only applicable to standard catalog or UPT angles which also are assigned as truss members.
Parent topic: RR 22.10.00-3 Features Affecting the Analysis and Design Engine
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