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RE: Mill tests

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Title: RE: Mill tests

Ooops! Forgot about the mill cert vs. minimum specified yield part of your question.

Mill certs can vary from the minimum specified yields for many reasons. In some cases, the whole heat of steel may be at a higher yield strength. In other cases, variations occur in a heat with multiple shape sizes 9smaller shapes get more rolling, which drives up the yield for that shape. There are other reasons as well that I'll omit for simplicity sake.

To accomodate the needs of the seismic designer, we've addressed material overstrength issues with an Ry factor in the AISC Seismic Provisions. Multiply Fy by Ry and you get an average yield stress (called Fye) for the grade of steel. For example, Ry = 1.1 for ASTM A992 (50 ksi W-shapes); Ry = 1.5 for A36 W-shapes.

Seismic Provisions and Supplement No. 1 are freely available for download here:

    http://www.aisc.org/documents.asp?mode=docdetail&doc=188
    http://www.aisc.org/documents.asp?mode=docdetail&doc=153

The grades for which a value of Ry is given will be expanded in Supplement no. 2, which is forthcoming.

Charlie

-----Original Message-----
From: Jason Kilgore [mailto:jkilgore(--nospam--at)leok.com]
Sent: Monday, December 11, 2000 1:34 PM
To: seaint(--nospam--at)seaint.org
Subject: Mill tests


We had a project where A501 (hot-rolled) pipe was specified for handrail
supports for a stair.  The handrail was 36" high.  UBC code requires a 200#
point load at any location, so 1.5" I.D. pipe was required.

The fabricator wanted to use 1.25" I.D. pipe in A500 Gr. B, which AISC lists
as having a Fy of 42,000 psi.  The fabricator claimed that ASTM lists it as
46,000 psi.  He then sent me a copy of the mill test report, which indicated
a Fy of 63,000 psi.  The steel was cross-certified for A53, but nothing that
would result in such a high yield.

Which is correct - 42ksi or 46ksi?
Is it common for steel to test out that much higher than spec?

----
Jason W. Kilgore
Leigh & O'Kane, L.L.C.
jkilgore(--nospam--at)leok.com
(816) 444-3144



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