Design of a Rectangular Tank compared to a Cylindrical Tank 6

[IgorTC]

Hi,

For a back of the envelope type of calculation, I am trying to design a small tank that is going to need to fill as much space as possible. That space has a square cross section:

I went through this very useful paper and used the formula in:

http://www.gowelding.com/pv/square.pdf

that seems to fit with the asme code 13.

I am getting wall thicknesses for a square tank or a square tank with rounded corner that are very large compared to thicknesses I would get from a simple cylindrical tank using thin walled approximation (which is satisfied in my case).

Is this because the shear stress appears in the square or square with round corners configuration and it is not there in the cylindrical configuration ? why the large difference ?

I have read this very informative stress :

http://www.eng-tips.com/viewthread.cfm?qid=154686&page=1

and I assume I am seeing the same difficulties somehow.

Thanks in advance,

Igor.

 

[TGS4]

Flat plates resist pressure through bending, which is relates to stress via the thickness and the moment of inertia (sigma = Mc/I). Round vessels resist pressure through membrane tension via the radius and thickness (sigma = Pr/t).

So, very different "Mechanics of Materials" mechanisms here. Note that at the extreme a square vessel will become "round" under pressure - resisting pressure through tensile membrane action seems to be a "natural" state...

 

[JStephen]

This is exactly the reason why practically every tank of any size is round. Ditto for piping, aircraft fuselages, balls, balloons, and perhaps some other applications.

 

[BarryEng]

Have a look at Blogett (welding design), one of the Lincoln series of books.

There is a section (worked examples) on circular tanks & rectangular tanks (with & without rib reinforcement).

I agree with the comments of the last two threads.

 

[IgorTC]

BarryEng,

Thanks. I may to consider a more complex design and rib reinforcement might be part of it.
Do you know have a place where I can order it on the interweb ?

Igor.

 

[BarryEng]

Yes I can give you a ref (I will find it later).
It is very expensive if you only want this one bit of info. I will see if I can post the bits that you require.

Have you tried a local university, technical college or library for the book? They may allow you to copy a page or two. See how you go, & I will find the info.

Try this site for the book: -

http://www.amazon.com/Design-Welded-Structures-Omer-Blodgett/

 

[IgorTC]

BarryEng,

Thanks.

Amazon has the 1966 and 1976 editions, are those examples in there or should I be looking for a newer version ?

Igor.

 

[DSB123]

BarryEng,
The Blodget book from Lincoln Welding is very cheap. The expensive part can be the cost of shipping dependant on where in the world you live. I am sure the cost of the book you refer to cost me only around $20 about 5 years ago.

 

[MJCronin]

Folks...

http://www.amazon.com/Design-Welded-Structures-Omer-Blodgett/dp/9998474922

http://www.alibris.com/search/books/qwork/1604721/used/Design of welded structures.

Sadly, Blodgett is no longer in print, according to some websites.... IMHO, structural engineering is now officially dead in America

-MJC

 

[LSThill]

Team Member & MJCronin (Mechanical)

Solutions to Design of Weldments

https://ssl.lincolnelectric.com/foundation/item.asp?prodnum=D810.17&PID=16

8 ½” x 11” Paperback

This design brochure represents a collection of the most frequently encountered design problems experienced by Mr. Blodgett. The text gives sample problems and a solution recommended by Mr. Blodgett. Typical topics include: circumferential welds in torsion, longitudinal shear on 8 sided section, shock loading, and distortion. 78 pages.

Cost $3.50

Design of Welded Structures

https://ssl.lincolnelectric.com/foundation/item.asp?prodnum=DWS&PID=16

Cost $22.00

Design of Weldments
By Omer W. Blodgett, design consultant
This reference handbook describes in detail design techniques for creating machine designs in arc welded steel. Much of this material has had no previous publication. Theoretical analysis, problem-solution examples and case history studies explain how to design machine components for manufacturing economies and improvement of product performance through efficient use of steel’s excellent physical properties.
Since its publication, this book has become a standard reference manual for design problems in welded metal products.

Design of Weldments includes 8 sections dealing with ‘Weldesign,’ a system that reduces weight and cost and improves production.
464 pages, 8 ½” x 11”, 923 illustrations, nomographs, charts.
Cost $15.00

Take the course and get the book's