Flat Head with Stiffeners

[steris]

I'm designing a Section VIII Div 1 vessel where one end has a flat rectangular head with stiffeners (reinforcement ribs) welded to it. I'm going down this route versus a thicker flat head mainly for cost reasons. I've looked through UG-47 and UW-19 however all the references are to staybolts and I'm not sure those sections are applicable to my vessel. Am I wrong about this? Are there any sections of the code that cover this type of construction or is this an U-2(g) situation? Is there a way to apply appendex 13 to this? Are there any good design references I can use for this?

I've check out a few other posts that tangentially cover this but they didn't quite answer the question:
thread794-141734
thread794-93914

Any help would be greatly appreciated!

Best,
Steris

 

[muld0020]

I'm not exactly certain of your design, but some general direction would be.

If you have a "head" (end caps) then UG34 governs for circular and non-circular sections. These formulas calculate stress, but do not consider deflection. I think depending on your design U-2(g) could be used.

I would be inclined to use Appendix 13 if you are looking at a rectangular section with end caps, since there are clear examples. However, you should read 13-1 for the scope of that paragraph and the applicability of U-2(g). If your design doesn't fit then U-2(g).

 

[steris]

Hi Muld -

Thanks for the input! I don't think that UG-34 would apply because of the reinforcement bars. I think that I may be able to apply something similar to Appendix 13 Fig 13.2(a) sketch 5. Even though that sketch is for a rectangular shell with radius-ed corners, the construction is similar to what I want to do. I've attached a picture of the configuration I'm looking to achieve. The head is under internal pressure on the non-reinforced side and it is welded to the shell around the perimeter.

Thanks for the help!
-Steris

 

[muld0020]

That looks like a lot of stiffeners relative size. You might want to look at "T" bars or Angles where you get more stiffness for less cost with better moment of inertia relative the neutral axis than flat bars.

Looks like if you already have the 3D model you are on the road to U-2(g). It should suit you better for this design.

 

[steris]

FEA is always an option but I just wanted to make sure that there are no standard rules for addressing a construction like this. Intuitively, I feel like this should be a standard design covered by rules in Section VIII - especially given it's similarity to constructions covered in Appendix 13.

 

[Karloss12]

Sounds like Appendix 13 with mixed parts of sketch 1 and 4.

When designing a rectangular vessel to Appendix 13 you are always left with rectangular holes in each end (like you describe.

Sounds like all you need to do is disect and combine the equations for sketch 1 and 4 for use in designing the end head.

 

[MEngg07]

Steris,

Yes, exact figure is not available but you can use figure (10) from Appedix 13, which is alomost same as your requirements