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RE: HSS Section designation

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HSS designations have been used in Canada for as long as I can remember.  I think the first spec was around 1969.
A problem we occasionally have here is that the ASTM A500 class C is often offered as a substitute for our steel grade CSA G40.21 350W.  The problem is that the ASTM spec allows for a tolerance in HSS wall thickness of as much as minus 10 percent, while the Canadian standard requires that the mass of the section not be under by more than 3.5 percent.  ASTM 500 grade C also calls for a minimum yield of only 317 MPa for round sections, versus 350 MPa.   We have to be careful to take these differences into account if American HSS is proposed by the supplier.  In many cases it will be necessary to go to the next size larger wall thickness (say 8 mm instead of 6.4) to be assured of the same strength.
Another issue we run into up here is the difference between class "C" and class "H" sections.  (That's CSA G40.21 class "C", not ASTM A500) "C" sections are made by folding and welding a piece of flat strip.  H sections are made by either folding,welding and subsequently stress relieving or by a seamless extrusion/mandrel process.  (more information is available from CISC
Canadian HSS is normally produced with steel having a yield of 350 MPa (50 ksi), but the class "H" has slightly better compressive resistance in longer columns.  The vast majority is produced and ordered to class "C".  Generally, I design and specify class "C," getting class "H" is a bonus if it happens.
-----Original Message-----
From: Paul Feather [mailto:pfeather(--nospam--at)]
Sent: Tuesday, July 20, 1999 17:41
To: SEAOC List
Subject: HSS Section designation

On recent projects I have switched to specifying pipe and tube sections by the HSS designations in the AISC "Hollow Structural Sections - Connections Manual"
The response I am getting from the fabricator and their suppliers is mixed, but typically they are not familiar with the new designations and/or the specified sections are not readily available.
What are the facts regarding the new HSS sections and designations?  Should we be using the HSS designations or not?  Is the material in the manual available or a premium item?  What is AISC's position?  Is anyone else using the HSS designation, and with what result?
Paul Feather P.E.