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Re: MISC - Mill Certification/Higher Yield Stress/Testing

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> From:          CanitzCF <CanitzCF(--nospam--at)aol.com>
> Date:          Wed, 10 Dec 1997 00:07:54 EST
> To:            seaoc(--nospam--at)seaoc.org
> Subject:       MISC - Mill Certification/Higher Yield Stress
> Organization:  AOL (http://www.aol.com)
> Reply-to:      seaoc(--nospam--at)seaoc.org

> 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
> 
> 
>
Charlie,

Others on the list may be able to provide more help with your
specific question.  However, I had an interesting project a few years 
ago evaluating an existing steel structure.  We needed to squeeze a 
little more strength out of a few roof beams to make them work, but 
didn't have the mill tests results like you do.  We had a testing lab 
perform some tests on small samples taken from the beam webs to 
determine the actual Fy (ASTM E8 if I remember correctly).

The problem we encountered, was that the contractor had obtained
the samples by flame cutting.  The flame cutting had an effect on the 
steel which skewed the results and made it hard to determine the 
actual Fy.  It was apparent that the steel yield stress was much 
higher than the 36 ksi we had assumed, so we were ok.  But, if you are 
going to be close, and you ever need to take samples for testing, 
consider sawing or some other method besides flame cutting for the 
sample removal.

Michael Ritter, PE 
Knoxville, TN