Rectangular Tank Design Flat Plate Ratio Inconsistencies

[milen_d]

Hey Guys, i am working on designing a rectangular tank. I am using the Pressure Vessel Handbook by Megyesy and also Roarks Formulas for Stress and Strain. When determining alpha and beta from the H/L ratio, i am seeing different values for a and b between the PV handbook and Table 11.4 Case 2d on page 505. For example, @H/L=1 in PV a=0.022 and b=0.16; @H/L=1 in Roarks a=0.040 and b=0.2. The inconsistencies are present at all ratios. Am i looking at the correct tables? Is there something i am missing? Thanks!

 

[AWDMIKE]

While I've never designed a rectangular tank, I would look into something developed for industry while at the same time referring to those books.

If you can't find anything in any tank standards, have a look at API Bulletin 2V Design of Flat Plate Structures.

 

[robyengIT]

see also (google) : "Kleinlogel rahmenformeln". From site "archive.org" you can download a copy. See from pag 359 of PDF file (it's in german language but you can easily understand formulas)

Here in english :

https://kupdf.com/download/kleinlogel-rigid-frame-formulas_58a67b946454a7cd3fb1e8dd_pdf

 

[milen_d]

@AWDMIKE, thanks man. I will check it out as soon i get a copy. Hopefully there will be something on this ratio in there.

@robyengIT: thanks for the suggestion, i downloaded the book however it seems to have nothing to do with tank design. I suppose it can be useful if you use the cantilever beam method to determine wall thickness, however that theory's results are a bit too liberal. Either way it has nothing to help answer my initial question. The Height/Length ratio is one of the factors that determines material thickness for the tank walls. It is associated with stress and strain on a rectangular plate.

 

[AWDMIKE]

I took a closer look at your post and wanted to reply again.

My version of Megyesy (12th Edition), page 213, references two documents, one is a publication and the other is a Timoshenko textbook.

I'll attach the publication herein. It's very old, from 1936, and to my knowledge cannot be purchased anymore.

The other file I cannot attach but I'm thinking it's available on the internet somewhere. In any case when I first read your post I wasn't certain whether the two loading cases you were comparing were the same.

The case in Megyesy says "under hydrostatic pressure" so I'm thinking it's either Case 2 (all four sides simply supported) or Case 8 (three sides simply supported and one side free - maybe when you have an open top tank without a stiffener on top) in the "Stress and Deflection of Rectangular Plates" document.

If I look at Roark's (I have the fourth edition hard copy) for a flat plate, all four edges simply supported, with a distributed load varying linearly along the length (not varying along the breadth), I see the exact same numbers in Roark's as I do in Megyesy's for a/b = H/L of 1.0 to 4.0. Therefore I can conclude the case in Megyesy's is the same as Case 2 in the "Stress and Deflection of Rectangular Plates" document.

You didn't mention which edition of Roark's you had, but I have here a digital copy of the 7th edition. If this is the same edition which you have, Table 11.4, Case 2d is for a rectangular plate with three sides simply supported, and one free, which is not the same as what's in Megyesy's table. To compare apples with apples, you would need to look at Roark's Table 11.4, Case 1d, which is for a rectangular plate with four sides simply supported, with a uniformly increase load along the length. There you will see the same numbers between Roark's and Megyesy's books.

Hope this helps.