Floor Load Distribution 1

[FSB01]

I have a configuration similar to vertical vessel with skirt. My problem is floor load distribution. I need to provide a base that will have sufficient area for load distribution. My problem is to determine how far beyond vessel OD base ring can project? Is there a method to calculate area that I can use based on ring thickness (or vice versa, to determine a thickness based on base ring diameter)?

Thank you

 

[vesselguy]

Suggest you read books such as the ones from Brownell and Young, Moss, Bednar, etc., they will give you detailed derivation that will fully answer your question. Alternatively, if you have Structural Engineer at your office, you can borrow his/her AISC handbook. It does not show you the calcs for a vessel skirt but it does show you the methods for designing typical bearing plates and the priciple can be carried over the vessel base rings.

Why read? Reading and hand calc is over-rated, just buy a vessel design software and you're done.

 

[vesselguy]

FSB01,

Sorry I didn't answer your original question and that is you can have as wide a base ring as you want to spread the load to the foundation/floor. However, you will need to provide gussets to reinforce your steel base ring because if you don't the ring will only have a certain fraction of its width to be effective in passing the load. You will what I mean when you read the books I reference above or in the AISC handbook. If you don't use gussets then I can assure you that you will have a very thick base ring; which does not make sense. Your choice and your money.

 

[FSB01]

It is not as simple as that. Vessel skirt is already calculated, however this is not a skirt, it is just a base plate for load distribution, vessel is not welded to it nor it is bolted. It is just “resting” on it. This is a small but heavy vessel and diameter is not large enough to distribute the load. I am reading the manual, however still didn’t find a solution.

 

[vesselguy]

I was not talking about a skirt. So what you are actually saying is it is am annular bearing ring. This type of design has been used on API storage tanks when the foundation is not a concrete ring but rather a compacted soil base. What you have here is a foundation problem and the problem should be directed to Civil/structural engineer to resolve. Sound like whoever design this vessel did not have the proper allowable bearing pressure data during design.

As far as I know, there is no design book on this but rather use good engineering. A rule of thumb formula to get started on a thickness I've used in the past is for tanks is:

t = 5.169xSqr(W) where W = load in kg/mm with a limitation that the plate width be less than 610mm. Then I would use Roark & Young's formula for plate in bending to double check the case. Of course, I would then get a Civil Structural Eng to verify.

If your project permits, you should provide a flare on your vessel skirt so that you can enlarge the base ring to properly spread the load. That is the proper thing to do and that is how it is done on the mechanical engineering side most of the time. My opionin only, but I feel that using a bearing plate is a cover your butt solution and Senior guys will see right through it.

You're welcome.

 

[FSB01]

As this is portable equipment, bearing plate just what we need. So far, it seems to me that simple cantilever beam calculation for material beyond vessel bottom is required to find bearing plate thickness.
Thank you for the input.

 

[vesselguy]

No worries. Since you mention portable equipment, then I see and understand your situation. It would be so much easier if this site have a facililty to load up a simple bitmap sketch to illustrate what we're talking about. Based on the additional information, then why not make a "portable" (read transportable) skid so you heavy vessel can sit on it. The skid, of course would have a larger footing and can therefore be made stiff enough to spread the load to be under the allowable foundation bearing pressure. Hope this helps.

 

[FSB01]

Skid is what we are working on at the moment (looks like we are on the same track), however, some other limitations are forcing me to use flat plate under the vessel.
I do not how hard would be to adjust forum to upload a sketch, but that would be great help as it is not always easy to explain a problem.