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Re: Steel Modulus and Strength

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Thanks for the clarification.

My original post was only to determine what values to use as defaults for
the software. I will use 29000ksi, 60ksi and 40ksi.

I appreciate the other info......

jim
----- Original Message -----
From: Roger Turk <73527.1356(--nospam--at)compuserve.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Wednesday, July 26, 2000 5:39 AM
Subject: Re: Steel Modulus and Strength


> It doesn't make any difference because *we* don't know the strength of the
> concrete in the structure.  The specified strength is the 28-day strength
of
> laboratory cured concrete cylinders.  Strength of in-place field cured
> concrete is only required to be 85 percent of the laboratory cured
cylinders.
>
> 40 years ago when I was in school, E for steel was 30,000 ksi.  Then it
was
> changed to 29,000 ksi;  prestressing strand is 28,000 or 27,000, and it
> doesn't make any difference.  These values are just *averages* and an
> approximation of the modulus of elasticity up to the proportional limit.
>
> BTW, strut theory for concrete has been in used since early in the 20th
> century.  Any concept that gives the "right answers" is valid, even it the
> concept is "wrong."  (Take the Whitney stress block.)
>
> A. Roger Turk, P.E.(Structural)
> Tucson, Arizona
>
> Jim Korff wrote:
>
> >>Great...
>
> So why do we bother with specifying concrete strength of  3000 psi.....we
> could just say 2900 psi....or 3100 psi....or somewhere in between......if
it
> doesn't make any difference anyway.....
>
> All I'm after is a default value to use a in a design software
> program.....(oops....it's one that originated in Europe.....where they
still
> seem to think about the structural mechanisms)...so if anyone has a
logical
> suggestion (29msi vs 30msi)....I would certainly appreciate it.....
>
> flippant answers certainly don't add anything.....
>
>
> jim
>
> A few years ago some "professors" would be upset at the notion of strut
and
> tie mechanisms......<<
>
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