As mentioned in the 1997 HSS Specification, producers are able to make A500 steel close to the minimum end of the tolerance of -10% for the plates used to produce HSS. As a result, the 1997 Specification captured this as a change to the design wall thickness to determine appropriate capacities for Hollow Structural Sections (HSS).
This is in effect for some time after the 12th edition (3rd edition LRFD in 1999), and is included in the 13th edition (2005 AISC Specification). It should have been used after 1997, but users of the old 9th edition (the "last" edition of ASD at the time) may have missed this information.
As a result, HSS columns and axially loaded members in the 1997-2005 time frame might not include this reduction in the original designs. If the column can be checked successfully including the 0.93 t[sub]des[/sub], that would be the ideal situation.
Specifying HSS, Stine, Modern Steel Construction, July 2005.
Note the nomenclature for HSS/TS changed circa 1990 (Stine).
