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Re: [SEAOC] Yield strength of structural steel shapes

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>It appears that there is a difference of yield strength for structural steel
>(Fy) between Mill Cert and results of lab coupon tests.  Anybody know if
>there are test data showing the relationship between the two?  Which number
>do you suggest for evaluation the capacity of an existing structure?

Presumably the mill certs refer to an ASTM standard. The ASTM standard
provides minimum acceptable properties for compliance with the standard.
Actual data may exceed the minimum by 10% or 15%, sometimes more.
Constructional steel supplied to a more restrictive standard (higher
mechanical properties) may be sold as conforming to a less restrictive
standard, provided all the chemical and meahanical ranges are met. The
actual difference is a statistical thing. Sometimes mill certs are simply
certificates of compliance stating that the material is warranted to meet
the minimums specified by the applicable ASTM standard. In that case your
labs tests will always exceed the certs, provided the material conforms.

If your lab tests show less than the ASTM standard, you have non-conforming
material, and your structure may be in technical violation of regulatory or
contract requirements. If your lab tests show greater than the ASTM
standard, use the ASTM properties for evaluation, since you don't know
whether your test results apply to all the steel of the structure. In any
event use the minimum of the ASTM standard or the lab tests, and report any
non-conformance to your client.

Christopher Wright P.E.    |"They couldn't hit an elephant from
chrisw(--nospam--at)        | this dist--"   (last words of Gen.
Voice phone (612)933-6182  | John Sedgwick, Spotsylvania 1864)