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Re: Class H

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Paul,
It was a rough day at the office and it was just 8:00
in the morning.  I was feeling very testy towards one
of our large consulting engineering firms who want to be
treated like God but don't want to take any responsi-
bility.
I did make the code examinations and looked for you.
I haven't heard the results yet-- they say approx 3 wks.
Gary


On 11 Jun 2005 at 14:13, Paul Ransom wrote:

> Hey, Gary!
> 
> Rough day at the office? Maybe you got back some BRRAGG scores (I
> completely forgot to go to write the exam. My secretary/wife gave me
> heck for not teling her so she could write it in the schedule).
> 
> Thor's contact suggests that in seismic applications there are
> ductility benefits as a result of reducing the strain-hardening
> effects. I suspect that is a 2 sided sword: 1) when compression
> controls (e.g. global buckling), Class H (stress relieved) will permit
> a lighter section with (presumably) greater ductility in the stress
> relieved regions. 2) a lighter section has less material and therefore
> more deflection and less energy absorbing capacity than a similar
> heavier section.
> 
> Square/rect HSS only benefit from significant residual stress relief
> in the corner regions and, if seam welded, along the seam. Maybe 10%
> of the section area in a 10x10.
> 
> Circular HSS, if cold-formed and seam welded, are evenly stressed
> around the perimeter and not to the same extent as the corners of
> sq/rect HSS. So the benefits will be different.
> 
> It is my understanding that most common size HSS produced in NA these
> days is produced through a die, hot and has only nominal
> "cold-forming" to ensure tolerances. I'm sure that is not the
> universal practice and definitely not for extreme sizes.
> 
> I'm certain that there is a web-site to describe this more completely.
> Also, I'm certain that somebody can point us toward
> documentation/testing/research on materials from current production
> techniques.
> 
> CISCs commentary to S16 is silent on the issue of Class C vs. H, even
> for seismic. However, look at clause 27.5.3. The commentary discusses
> the issue of post buckling fracture but ignores Class C vs. H.
> 
> I have this impression that there may be some corrosion resistance
> benefits to using Class H but I would probably spec a corrosion
> resisting steel before I would hang my hat on that.
> 
> All that said, I have never felt the need to spec Class H and it is
> definitely not mandatory by S16-01.
> 
> Paul
> 
> > From: "Gary Hodgson & Associates" <ghodgson(--nospam--at)bellnet.ca>
> 
> > Re my previous reply. Not the people who replied to your e-mail. The
> > people who always specify Class H are idiots. Gary
> > 
> > On 9 Jun 2005 at 19:56, dave lowen wrote:
> > 
> > > Thank you to all who responded. I believe I thought it was
> > > mandated since every project that crosses my desk requires class H
> > > for compression members.
> > > 
> > > It is certainly not readily available in my neck of the woods.
> 
> > > From: Paul Ransom [mailto:ad026(--nospam--at)hwcn.org] 
> 
> > > > From: "dave lowen" <jatech(--nospam--at)kwic.com>
> > > 
> > > > Can anyone point me to chapter and verse (in Canada) that states
> > > > that HSS compression members must be class H?
> > > 
> > > There is no such requirement. Ummm... if you find one, let me
> > > know...
> 
> 
> -- 
> R. Paul Ransom, P. Eng.
> Civil/Structural/Project/International
> Burlington, Ontario, Canada
> <mailto:ado26(--nospam--at)hwcn.org> <http://www.hwcn.org/~ad026/civil.html>
> 
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