Problem Description

There is an error in accounting for additional moments when designing single angle sections as per AISC 360-16. The error has been found to occur under the following circumstances
a. profile is a single angle
b. section is checked as per AISC 360-16 against a list of load cases
c. the section is subjected to axial compression in some and axial tension in some other cases

In such cases the program is failing to account for additional moments due to eccentricity of compression force as outlined in the section E5. Moreover in situations when all the load cases result in compression, the program is calculating eccentric moments on both legs instead of just calculating it on the connected leg.

This may result in incorrect calculation of the stresses frbw and frbz when checking as per equation H2-1 and the member may consequently be under designed or overdesigned.

Workaround

No workaround is available as of now for this defect.

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Solution

The defect is addressed and a fix is available in STAAD.Pro CONNECT Edition V22 Update 12 (22.12.00.142).