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Re: A 36 steel vs A992

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Robert:

A992 steel has tighter requirements imposed on it.  It has (if I recall
correctly) a limit on the ratio of yield strenth to ultimate strength.
A992 steel should be a much better product to use for seismic situations.

A36 is a much less tight spec.  As I understand it, it only requires a
minimum yield strength along with a rather loose requirements for chemical
content.  As a result, most A992 steel will likely be able to be dual
certified as A36 steel.  Obiviously, this would mean that while you are
designing using 36 ksi for the yield strength, you could actually be
getting steel with yield strengths above 50 ksi.  Thus, your structures
yield mechanisms could be greatly altered.

This particular issue is why the AISC Seismic provisions use a modified
yield stregth (Fy*R) for design calculations.  The "R"-factor takes into
account the possible varience in the yield strength for the different
steels.  That is why the "R"-factor for A36 steel is higher than for A572
since the A36 spec is generally the least tight of them all.  This also
helps deal with the trend that most steel today is typically dual
certified (i.e. both A36 and A572/A992).

HTH,

Scott
Ypsilanti, MI


On Tue, 8 Jan 2002, Robert M. Hanson wrote:

> 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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