How to calculate thickness of thin sheel for radial buckling?

[Losty]

Hi Guys,

i got a situation where a thin shell (open ended) of 1300 mm dia X 950 mm length is subjected to a uniform external pressure on outer cicumference say, 1500 KPA ....

How can i calculate the safe thickness of the shell for buckling ??

The material of the sheel is steel.


Thanks in advance.

Losty

 

[jimzpe]

Check out Roark's Formulas for Stress & Strain and the ASME. The methods require few iterations due to the mode of failure. Think there's a software solution still out there, I have it and have verified it's accuracy. Not on that computer right now so I don't know the name.

 

[jimzpe]

Need to add (forgot in last post) that you should not be supprised to see "very low", calculated allowable pressure values. These low pressures (verses the expected high internal pressures) are correct.

 

[JStephen]

The ASME B&PV Code covers this in Section VIII.

The Roark formulas and ASME assume the shell is stiffened at the ends. If one end is actually free, no stiffeners at all, I know of no solution. This is a situation that occurs in storage tanks.

The different tank codes also include provision for wind loading on cylinders, which is essentially an external pressure problem, and also include requirements for the top stiffener.

Be careful using the Roark formulas, as they give the buckling pressure, not the allowable pressure. And that buckling pressure is not necessarily a minimum buckling pressure, either.

 

[jimzpe]

JStephen, thanks for infilling the unmentioned / forgotten items from my posts. Roarks does give recommended factors for allowable vs. buckling pressures - you just need strong glasses (magnifying type) to read the small printing.

 

[PEStructural]

I have a similar situation right now on a steel tank with external pressure. Where in Roarks does it talk about the allowable stresses?

Thanks!

 

[Losty]

I found it on the Rorak's Book .....

I looked at 4th edition ...and its on page 690, chapter 14, Elastic Stability.

Thanks for your help guys ...

Losty