Axially loaded fustra 1

[Paquale]

I would like to calculate the potential loading effect on a thin walled frusta (truncated conical shell)i.e. deflection maximum stress etc

I have found an equation in "Roarks Formulas" but the results I'm getting are unbelievable.

Can anybody help?

 

[Bbird]

If you run a finite element analysis (FEM) you could compare the result with that from Roarks formulas. The truncated cone should be very easy to set up by the polar coordinate system in a modern package.

Many young engineers are not taught classical theories but can develop a good skill in the understanding of a complex structure through testing it with computer software.

 

[ishvaaag]

Then you may try

Formulas for
Stress, Strain and Structural Matrices
Walter D. Pilkey
Wiley Interscience
Chapter 20

You may find also something in

Stresses in Plates and Shells 2nd edition
Ansel C. Ugural
Mc Graw Hill
Chapter 12

Estructuras Laminares
J. Courbon
Editores Técnicos Asociados S.A.
Barcelona 1981

=
Voiles Minces
J. Courbon
Eyrolles
Paris

Laminas de Hormigón
A. M. Haas
ietcc
Madrid
Capítulo 3

=
Thin Concrete Shells
John Wiley & Sons
New York, London

Don't fail to ask google in a variegated number of ways, plus of course make FEM models.

 

[prex]

Can you be more specific on the type of loading?
Roark has formulae for conical shells subject to end loads: these give rise to local bending effects that of course exist, but might be unimportant in your situation.
If you have internal pressure only the calculation is quite simple: use the formula for a cylinder where the radius is the local curvature radius (normal to wall) of the cone.

prex

http://www.xcalcs.com

Online tools for structural design

 

[JWB46]

Have a look at API RP2A WSD under 'conical transitions'. (NB It's not uncommon to get high secondary bending stresses in this type of structure.)

Hope this helps.

 

[Paquale]

In Reply To PREX

I have a 4.5m base diameter, 5 Degree angle at the base of the cone and a 1.6m top diameter. The base of the shell is welded to a cylinder and the top will have a flange welded. This will support some metal work totaling 2.5 Tonnes.

My experience tells me that there should be no problems with this but "Assumptions" lead to larger problems. I therefore have been trying to calculate the reaction of the cone to the loading to professionaly address this issue in my design.

 

[prex]

You should be concerned only with compressive longitudinal stress in the conical skirt wall (though your load doesn't seem very high). The longitudinal stress is practically the same as for a cylinder as cos&[ignore]alpha[/ignore]; is very close to 1 for &[ignore]alpha[/ignore];=5°.
BS5500 and EN13445, but also ASME VIII, have methods for checking the stability of cylindrical walls.

prex

http://www.xcalcs.com

Online tools for structural design