API 650 Uplift Loads with Annex F

[EmilianoS87]

API 650 says this

F.8.2 The counterbalancing weight, in addition to the requirements in 5.12, shall be designed so that the resistance
to uplift at the bottom of the shell will be the greater of the following.
a) The uplift produced by 1.5 times the design pressure of the corroded empty tank plus the uplift from the design
wind velocity on the tank.
b) The uplift produced by 1.25 times the test pressure applied to the empty tank (with the nominal thicknesses).

So I believe I have two cases to add up to the Table 5.20b ones.

What are the equations for this two additional cases? I believe are these ones, am I in the right path? what is your experience?

a)[(1.5 * Pi + PWR) * D^2 * 4.08] + [4 * MWS/D] – W1

b)[1.25 * Pt * D^2 * 4.08] – W3

What are the allowable values, on the old 98' standard they gave us some values but know ther are missing.

Thanks for your help.

 

[JStephen]

"U" in those tables is design uplift on the anchor bolts, not uplift on the foundation.
The two cases above are applicable to the foundation, but not to the bolts.
I think the intent is to design for foundation uplift more conservatively than bolt stress.

 

[EmilianoS87]

I understand. Do you belive I need to take into account only the uplift pressure using the PWR to calculate the counterbalancing weight or I also need to take into the account the moment MWS?

 

[JStephen]

From the wording you quoted, I would assume both uplift on the roof and the overturning moment.