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Re: Proportional Limit, A36 Plate

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Charlie Carter agrees with you.  

The 10 percent figure comes from "Strength of Materials", by S. Timoshenko
(originally published 1930), Third Edition, reprinted 1957. 
At that time we were dealing with A7 steel, which I took to yield at 30
ksi.  The reference gives a range of 25 to 30 ksi for proportional limit.

I aimed for an average and, as an attempt at being conservative, arrived at
10 percent less than yield.  

Using the proportional limit equal to yield makes the design of this stack
look better.

Fountain

----------
> From: Paul Feather <pfeather(--nospam--at)san.rr.com>
> To: seaint(--nospam--at)seaint.org
> Subject: Re: Proportional Limit, A36 Plate
> Date: Tuesday, May 15, 2001 7:42 PM
> 
> Fountain,
> 
> My understanding has always been that the proportional limit is
essentially
> the yield point for steel with Fy <= 65 ksi.  Higher strength low alloy
and
> quenched and tempered steels require use of the 2% offset rule.
> 
> What is the permissible tolerance in the ASTM spec for A36 plate? It
would
> seem reasonable to me that as soon as you use the A36 classification you
> should be confident that the product meets minimum spec. Where do you get
> the 10% figure from? If you are specifying the product there should be
mill
> certs stating the material properties for comparison.  If you are working
> with existing steel and the application is that critical, can you have a
> sample tested?
> 
> Paul Feather
> ----- Original Message -----
> From: "Fountain Conner" <fconner(--nospam--at)pcola.gulf.net>
> To: <seaint(--nospam--at)seaint.org>
> Sent: Tuesday, May 15, 2001 2:36 PM
> Subject: Re: Proportional Limit, A36 Plate
> 
> 
> >
> >
> > Can I count on the *yield* for A36 plate being over 36ksi, or can I
assume
> > the proportional limit as equal to *yield*?  My only reference leads me
to
> > suspect that the proportional limit for steel could be as much as 10
> > percent below yield.
> >
> > There's a reason for this exercise -- I'm checking a stack per ASME
> > STS-1-1992 (the latest according to ASME website).  If the proportional
> > limit is significantly less than yield, my allowable bending stress
will
> be
> > lessened substantially.
> >
> > Thanx,
> >
> > Fountain
> >
> > ----------
> > From: Charlie Carter <carter(--nospam--at)aiscmail.com>
> > To: 'seaint(--nospam--at)seaint.org'
> > Subject: RE: Proportional Limit, A36 Plate
> > Date: Tuesday, May 15, 2001 1:51 PM
> >
> > >Does anyone have a "ready" number for the proportional limit for A36
> > plate,
> > >from 3/16" to 1/2" thick?
> >
> > Fy for ASTM A36 steel plate is 36 ksi up to and including a thickness
of
> > 8".
> > Above 8" thickness, it is reduced to 32 ksi.
> >
> > Charlie
> >
> >
> >
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