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Re: MISC - Mill Certification/Higher Yield Stress

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It is quite common for actual mill yield strength to exceed ASTM minimum 
specified yield strengths.  These days most "A36" steel has yields exceeding 
50 ksi.  I do not believe that AISC currently has an upper limit of yield 
strength but a new standard is being developed for 50 ksi steel with an upper 
limit of 65 ksi for actual yield strength.  Except for high seismic areas 
where yielding is assumed, higher yield strength is usually not a problem.   

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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

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