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RE: A 36 steel vs A992

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Bob,

I presume that the topic is for W shapes.

The changes were on 2 fronts.  Creating design formulas to properly account
for steel overstrength, and making the appropriate changes to the ASTM spec.
Back in the old days we did not properly account for the REAL overstrength
in steel in our design.  Ever since the Nucor Yamato plant came on line in
the 80's with their electric arc furnaces the shape market moved rapidly to
steel that was both 36 ksi and 50 ksi (dual certified).  Even before that,
steel mill test reports often showed yields of 50 or 60 ksi for steel
specified as 36.  And it still met spec. because we focused on minimum yield
strength.

The failures in moment frames of the Northridge earthquake showed the
problems of material overstrength.  The overstrength issue then were
addressed in all types of steel design.

Today's designs use the A992.

You don't really need to be tight with the fabricators, but you do need to
stay current with what is happening with materials.  There was a time when
welding was not practical, because of the variability in steel carbon
content A6 steels prior to the 1940's.  But fabrication process forced the
mills to drop carbon content and the A36 spec was born.  We learn, we
evolve, and we change.  There was also a time when all we had was 3,000 psi
concrete, and twisted rail bar.

Regards,
Harold O. Sprague

> -----Original Message-----
> From:	Robert M. Hanson [SMTP:Bob(--nospam--at)KappaEngineers.com]
> Sent:	Tuesday, January 08, 2002 2:27 PM
> To:	seaint list
> Subject:	A 36 steel vs A992
>
> List,
> I would like to get some opinions on the A36 and A992 issue in seismic
> zone 4 from some of the steel folks. The fabricators are in general are
> providing the A992 when notes indicate A36 steel for all but most channels
> and angles. My question is in regard to strength calculations for bracing.
> The yield for A992 vs. A36 can have dramatic effects in connection design.
> Are you day to day steel folks using A992 yield for strength calculations?
> Seems like one would need to be tight with the fabricators at front end to
> see what is being provided.
> Thanks in advance,
> Bob Hanson, SE
> Carson, Calif.

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