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Re: shell stability

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Daryl,

We thought about it (filling with water would be even more effective). 
However, these options are not viable. 
In the end, the exterior forms with ties to the steel shell appear to do the trick.

Thanks,

--
V. Steve Gordin SE
SGE Consulting Structural Engineers
www.sgeconsulting.com
877-477-4-SGE



h.d.richardson wrote:
Steve,
 
        Is it possible to pressurize it?  Even 1 psi is 144 psf.  Even a small pressure could resist the concrete pressure.  Just a thought.
 
Regards,
 
H. Daryl Richardson
----- Original Message -----
Sent: Wednesday, October 27, 2010 7:43 PM
Subject: Re: shell stability

Alex,

My problem is a large steel tank being used as a form for its own outer concrete shell with welded ties keeping the shell from buckling during the pour.  

Timoshenko's "Theory of Elastic Stability"
was my knee-jerk-reaction reference.  I also looked into Roark (which actually cites Timoshenko's formulas for arches, not shells), as well as Vol'mir's "Flexible Plates and Shells", "Guide to Stability Design" (Galambos), and several designer's handbooks. 

Unfortunately, none of these sources provided a clear-cut solution for a problem at hand.  For example, the Timoshenko's formulas (referenced in Roark) do not appear quite applicable to shallow arches (my case), while other formulas that are applicable to such arches lead to quite paradoxical and seemingly theoretical results.     

I ended up modeling the shell in 3D FEA, evaluating stresses, analyzing the deflected shapes, and still applying the Timoshenko's arch formulas.  The results appear reasonable and corresponding to the field observations.         

Thanks,

--
V. Steve Gordin SE
SGE Consulting Structural Engineers
www.sgeconsulting.com
877-477-4-SGE



Alexander Bausk wrote:
Steve,

Roark's Fomulas for Stress and Strain has and appropriate entry under paragraph 13.5, "Thin Shells of Revolution under External Pressure", as well as Table 13.1.
It also has a calculated example thereto all right.

On 27 October 2010 23:50, Steve Gordin <sgordin(--nospam--at)sgeconsulting.com> wrote:
> Good afternoon,
>
> I am looking for a source of Practical analysis of a
>
> Shallow - Thin - Cylindrical Shell/panel
> under
> Uniform Radial Compression.
>
> The books I have on the subject turn to be of mostly academic value.
>
> Can anyone point me in a right direction?
>
> TIA,
> --
> Steve Gordin SE
>
>
>



--
Alexander Bausk
Civil/Structural design & inspection engineer, CAD professional
MSc Structural engineering, Ph.C. Engineering
http://bausk.wordpress.com
ONILAES Lab at PSACEA
Dnipropetrovsk, Ukraine
Tel. +38 068 4079692
Fax. +38 0562 470263
bauskas(--nospam--at)gmail.com