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RE: MISC - Mill Certification/Higher Yield Stress

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Charlie,

I work for company that designs/manufactures communication towers.
After years of designs and certs, we found that 94% of our 36ksi steel
had a yield stress well over 42ksi.  We now use the 42ksi, but monitor
our certs very closely and ensure that we have 42ksi steel.  This is
possible since we do the actual fabrication on site and have much
greater control over our materials than an engineer doing a building
design or some other structure with an independent contractor...  As far
as code support for this decision, I am not sure.  I was not involved in
the decision to use 42ksi yield.....I would suspect that no code support
exists and that it becomes the responsibility of the engineer certifying
the design....

Shawn Wicks Freilinger
Valmont/Microflect Co., Inc.

> -----Original Message-----
> From:	CanitzCF [SMTP:CanitzCF(--nospam--at)aol.com]
> Sent:	Wednesday, December 10, 1997 5:08 AM
> To:	seaoc(--nospam--at)seaoc.org
> Subject:	MISC - Mill Certification/Higher Yield Stress
> 
> Has anyone been involved with a structural steel design in which the
> corresponding mill certification indicated a yield stress greater than
> that
> assumed within your design? For example, you specified ASTM A572 Grade
> 50 and
> the mill certification indicates a 59 ksi yield stress. Does the 9th
> edition
> ASD or the 2nd edition LRFD specifications prohibit the use of the
> higher
> yield stress? Other issues such as serviceability would have to be
> considered
> but I occassionally encounter a situation(such as a field change, User
> revision, etc.) where use of the certified higher yield stress would
> prevent
> replacement/reinforcement of a member.
> 
> 
> 
> Charlie Canitz, PE
> Bel Air, MD
>