PV Elite: Design of basering Tower in Module Bolted to Structural Steel during sea shipping

[mechmania]

Dear All,

I am designing Packed tower (ID:8.5 ft, TTL: 78 ft Skirt Length: 10.5 ft DP: 1050 PSIG/FV and DT: 175 deg F)

This project concept is Modular Design (Dictated by Client) So this Tower be in Module. Tower base will be bolted to Structural steel.

Since it being in module during the Sea shipping this will travel verically and combined loading of WIND and G-loading will govern the design. I was able to add G loading and Combined requirement in PV Elite, but HOW DO I TELL PV ELITE THAT THIS TOWER IS NOT ON CONCRETE FOUNDATION AND INSTEAD ITS ON STEEl.
I can not zeroed out value of F'c and Fc..it won't allow me to do that?

Also because of this combined loading during sea transport my PV elite shows Basering thickness to be 5" which i think is very hi. What modification i can make?

Best regards
Mechmania

 

[gr2vessels]

Check the Seismic loading page, it is an input data at the bottom of input page. Also, click the seismic data page and click the F1, help page. You will get all the details explained, including advice on use.
gr2vessels

 

[marty007]

Will the tower be laterally supported in the module anywhere other than at the base ring? If so, this would dramatically reduce the moment needing to be resisted at the anchors. I doubt your software would provide an option to analyse this, but it would likely be worth the time to do some hand calculations.

Cheers,
Marty

 

[StoneCold]

mechmania
Can the tower really travel vertically? I have a hard time believing that will work out. Most module designs have a framework outside of the vessel. Then the vessel would be attached along the sides of the vessel to the structural steel. That might be better than a bottom mount with a skirt, and it might work out better if you have to ship it on it's side.

my 2 cents.

Regards
StoneCold

 

[mechmania]

@ gr2 vessels: I figured out that in Base ring input Tab, on bottom right you have to select the Option " Use the skirt stress to determine the concrete stress for the simplified methot?"...this essentially means base ring is supported on structural steel and not on concrete foundation.

@marty007 : Yes tower will be supported laterally in the structure by support brackets and tied to structural steel around it.How would I hand calculate the load that I need to give it to structural engineer so that it can be transferred to Structure. I am not sure about HandCalculation..If you can throw some guide line regards to it...it would be learning session for me

@ StoneCold: Since Tower is in Module and hence it will travel vertically.

regards,
Mechmania

 

[marty007]

It's time to go back to a free-body diagram.

What you have is essentially a vertical column that has a fixed support at the bottom (moment and force support) and is simply supported at multiple other points along the height of the column. The force applied to the column is continuous over the height and is related the the lateral acceleration multiplied by the vessel mass (the pressure boundary section would likely have a much higher mass than the skirt).

Unfortunately solving such a situation could be ugly by hand (multiple supports means you'd be dealing with deflection along the column to determine the forces on each lateral support).

This type of situation could be modeled in software that is typically used for pipe stress analysis, such as CAESAR.

In reality, as long as the column has lots of lateral supports along its height, then the moment on the base support would likely be very small. The forces on the skirt would likely just be the vertical weight and a portion of the shear load. (it's the moment that is probably leading to your 5" thick base ring).

 

[mechmania]

Dear all,

I have follow up question.

Now i am in process of optimizing Base ring thickness!

PV Elite Calculates base ring thickness based on Jawad & Farr Eq 12.12
t base ring = Base ring Width * (3* Sc/S)^0.5

This Still gives higher base ring thickness of 3.5"

I checked Eugene F. Megyesy (PV Handbook..Edition 13)and on Page 81 it says that, above Jawad and Farr formula for Basering thickness is without any Gusset plate consideration.

For base ring with Gusset plate :
t base ring =(6Mmax/S)^0.5
And with this my thickness reduces to 1.45"

So my question is ...

Why PV Elite does not take in to account the Gussets when calculating Base ring thickness when gussets are specified?

Which formula governs the Base ring thickness?

Regards,
Mechmania