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Re: Differential temperature effect

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Stathis,
Yes, I also agree with Lutz. But I've tried a lot of examples such as
circular tanks, very large plates etc.
But, no results, neither in boundary zones nor in farthermost zones were
close to Timoshenko's formula.
I think that there is a special point in sap2000 to consider the effects
properly.  That's the point I want to capture.

Bulent Deveci



----- Original Message -----
From: "SAP" <epapag(--nospam--at)tee.gr>
To: <seaint(--nospam--at)seaint.org>
Sent: Thursday, February 27, 2003 11:58 PM
Subject: Re: Differential temperature effect


> Bulent,
> I completely agree with James Lutz.
> The Timoshenko formula provides the moment at the clamped edges of of a
> plate that zerors the curvature at this area. In a cylindrical silo wall
> every meridian section (parallel to the cylinder axis) lies on a symmetry
> plane and therefore it does not rotate, so it can be considered
''clamped''.
> The same holds true for infinite plates with no free edges (imagie
pavement
> plates of very large dimensions).
> For that reason the moments along the periphery of the cylinder are
> uniformly distributed and at every point satisfy the Timoshenko
asumptions,
> so they follow his formula. For plates of different shape
>  and finite dimensions the results depend on the boundar;y conditions.
> Therefore one should not expect to get the Timoshenko momments uniformly
> distributed over the plate area.
> Although I am not a SAP user I do not think that there is any problem with
> the program. Temperature gradient is a rather trivial loading case to be
> overlooked by an experienced programer.
>
> Stathis Papageorgiou
> Athens, Greece
>
> ----- Original Message -----
> From: "Lutz, James" <James.Lutz(--nospam--at)earthtech.com>
> To: <seaint(--nospam--at)seaint.org>
> Sent: Thursday, February 27, 2003 8:45 PM
> Subject: RE: Differential temperature effect
>
>
> > Could you describe what you are designing a bit? Sounds like a silo if
you
> > are using ACI 313. The ACI 313 (Timoshenko) formula only computes
flexural
> > stresses in simple plates. It would seem to me that boundary conditions
> > might effect your results in a more sophisticated model. Also,
temperature
> > changes induce membrane forces in plates which would also have an impact
> on
> > the total force experienced in individual elements. What is the relative
> > difference in results from your two methods? Which one is giving you
> bigger
> > numbers?
> >
> > -----Original Message-----
> > From: Bulent Deveci [mailto:bulentdeveci(--nospam--at)superonline.com]
> > Sent: Thursday, February 27, 2003 9:52 AM
> > To: seaint(--nospam--at)seaint.org
> > Subject: Re: Differential temperature effect
> >
> >
> > Lutz,
> > In ACI 313 clause 4.4.9 states that :
> > The thermal effects of hot stored materails shall be considered for
> circular
> > walls or wall areas with total restraint to warping (as at corners of
> > rectangular silos), the thermal bending moment per unit of wall height
or
> > width shall be computed by
> > Mt = Ec*h2*alfa*DeltaT / 12(1-poission)
> > This is the same formula given by Timoshenko.
> >
> > But as for Sap2000, there are two options. One "temperature t" which is
> > constant through the thickness and produces mambrane strains
> > The second, "temperature gradient t3" which is lineer in the thickness
> > direction and produces bending strains.
> > It is obvious that I have to use the second option. But unfortunately,
my
> > results are very far from those I've obtained from the above given
> formula.
> >
> >
> >
> >
> >
> > ----- Original Message -----
> > From: "Lutz, James" <James.Lutz(--nospam--at)earthtech.com>
> > To: <seaint(--nospam--at)seaint.org>
> > Sent: Thursday, February 27, 2003 7:17 PM
> > Subject: RE: Differential temperature effect
> >
> >
> > > I haven't done it, but it looks like it is possible. It wasn't clear
if
> > you
> > > are just modeling a frame or if there are plate elements involved, but
I
> > > think it will handle it either way. It's a pretty powerful program
(once
> > you
> > > figure it out.)
> > >
> > > I think you may have to create a batch input file since the graphical
> > users
> > > interface is limited to more routine kinds of problems as far as data
> > entry
> > > goes. If you have already created a basic model using the GUI, you can
> > dump
> > > it into a text file and edit it to get the stuff you need in there.
> CSI's
> > > manuals aren't the greatest for figuring this stuff out. Good luck.
> > >
> > > -----Original Message-----
> > > From: Bulent Deveci [mailto:bulentdeveci(--nospam--at)superonline.com]
> > > Sent: Thursday, February 27, 2003 8:26 AM
> > > To: seaint(--nospam--at)seaint.org
> > > Subject: Differential temperature effect
> > >
> > >
> > > List,
> > > Does anyone of you have any experience in designing a reinforced
> concrete
> > > structure
> > > having differential thermal conditions with SAP2000 software? I'm just
> > > trying to design a complicated RC structure with nearly 300 C
> differential
> > > temperature and I don't have the chance of insulating it due to the
> > process
> > > of the structure.
> > > I have tried to obtain the bending moments by means of SAP2000
software
> > but
> > > I'm not able to satisfy the results given in some text books such as
> > "theory
> > > of elasticity" by Timoshenko.
> > >
> > > Any comment would be appreciated.
> > >
> > > Bulent Deveci
> > >
> > >
> > >
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