dead weights and live weight for checking anchor bolts..

[carthago]

While checking anchor bolts Table 3.21 ( up lift loads)

DEAD weights W1, W2 and W3.

My understanding is these are Dead weights only.
Weight of liquid is not included.
Is this correct??

Why not including the liquid weight ???

 

[JStephen]

I assume you refer to Table 3.21 in API-650, Add. 4.

Yes, dead loads only.

One thing that is not clear to me is that if pressure loads exceed the weight of the roof plate, then the entire roof plate should be included in the dead load- but the definitions shown don't include it.

Liquid load is not included here because in order to transfer a significant amount of liquid load to the shell, the shell must move up somewhat. This is possible with an unanchored tank, but not with an anchored tank.

The inclusion of liquid load in the overturning equations in 3.11.2 is a new thing- I think added due to the realization that adding roof uplift drastically increases the overturning moment in many cases.

 

[chicopee]

The way I see this thing, it is very unlikely that a tank filled up (partially or totally) would tip over,therefore, shell and roof weights should only be considered.

 

[JStephen]

When tanks have any substantial amount of liquid in them, they're very unlikely to blow over. And, if tanks are bone-dry, they're not normally pressurized. The typical design check has always been done with the tank absolutely empty. However, this load case requires that uncommon events happen simultaneously. The new addendum recognizes this and allows a part of the liquid contents to be included when evaluating overturn.

 

[carthago]

I am strubecause of the up-lift stry..
So I state my question a bit differently..

Assume a tank with a SELF supporting roof:

by using the following Notation:
Wroof = weight of roof plates.
Wstructures= Weight of structures supporting the roof
Wshell= weight of all tank shell INCLUDING weight of
manholes, plates. Laaders welded on to these shells.

Weight of annular plates and weight of bottom plates NOT included

1/-Are the following W1 , W2 and W3 as defined in
API-650 paragraph 3.21 correct ?

W1= Wshell + Wstructures (corroded)

W2= Wshell + Wstrucures + Wroof (corroded)

W3= Wshell + Wstructures (UNcorroded)

Why not include a fraction of the roof ??


2/-Do we have to include elswere the weight of the products when treating sismic for instance ??

 

[JStephen]

These weights are for use in the net uplift formulas. In the net uplift formulas, they include terms like 0.08th or 8th, and these terms are the weights of the roof plate itself.

When doing seismic design, product weight resisting overturning is included only for the overturning check, but is not included in the anchorage load calculation.