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RE: History of Fy in A36

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This is a problem that crept up over time.  As the tendency of steel manufacturing evolved from ore to recycled steel, there was a noticeable steady increase in yield strengths.  This then became the marketing impetus to move to the dual standard in the 90's.  I recall in 1988 canvassing various steel suppliers what the difference was between Gr 36 and Gr 50 steel.  It was then that I found that some fabricators had no price differential.

The mill test reports in the late 70's showed A36 steel Fy as 45 to 50 ksi.  This made sense when you consider developing a standard deviation and assurance of a Fy minimum of 36 ksi steel throughout a rolling.  The exercise is similar in developing the f'cr for concrete where you develop a standard deviation for concrete strength. 

Many steel fabricators maintain records for several years.  I know of older firms that have project files from the '20's.  These records could be researched to establish trends.

This would be a good University research project funded by AISC. 

Regards,
Harold Sprague
KL&A

-----Original Message-----
From:	Stan J [SMTP:hawneng(--nospam--at)wac.com]
Sent:	Monday, June 01, 1998 6:41 PM
To:	seaoc(--nospam--at)seaoc.org
Subject:	History of Fy in A36

We are now all well aware of the problem of A36
steels with yields closer to 50 ksi than to
36ksi.  While most of us were oblivious to this
problem until Northridge; when did this problem
actually develop?  Had strengths of supplies
gradually crept upwards over the decade before
Northridge?  Was there a sudden dramatic change
during the 70's?  Does anyone have info that could
be useful in predicting reasonable upper limits on
Fy based upon time in which the steel was erected.





Thanks
Stan Johnson, PE,  This, of course, can be a tough
one to explain to the layman.  How do you tell a
building owner that their steel may be too
strong?!

BTW:  My problem does not involve 50ksi columns vs
36 ksi beams and strong column weak beam criteria;
but instead, evaluating a section for compactness
criteria.

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