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RE: HSS Section designation[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: "'seaint(--nospam--at)seaint.org'" <seaint(--nospam--at)seaint.org>
- Subject: RE: HSS Section designation
- From: Paul Meyer <PMeyer(--nospam--at)HASimons.com>
- Date: Wed, 21 Jul 1999 09:05:56 -0700
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 http://www.buildingweb.com/cisc/index.html
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.
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