API-650__Seismic Calculation__(E.6.1.4 Dynamic Liquid Hoop Forces)

[Champ58]

In Annex E section E.6.1.4 (Dynamic Liquid Hoop Forces), how do we calculate the value of Y?

(Here, Y = Distance from the liquid surface to analysis point, (positive down), unit: m (ft)).

I don't know how to find out the 'analysis point'. Can anyone please help me with this?

 

[HTURKAK]

Look to E.2 and Notations ; Y Distance from liquid surface to analysis point, (positive down), m (ft).

You are expected to check the stresses for each shell course .

 

[TheEverest]

I am also not clear about the value of 'Y' for Shell#1. In the given example, the value of H = 35.43 ft, so I thought 'Y' also must equal to 35.43 ft, but 'Y' is taken as 34.43 ft (as shown in the figure). Can anyone please clarify this?

 

[HTURKAK]

Nh and Nc can be calculated assuming the calculation point under consideration will be 1 foot above the course bottom level for each course. Nh (hydrostatic hoop force is also calculated for 1 foot ht.

Some people prefer conservatively to check the stresses for each course , at horizontal joint levels..If this is the case, 1 ft shall be free board ht, that is liquid ht for this case = (35.43-1.0)=34.43 ft.

Pls look to the concept of one foot method.

 

[JStephen]

API is not real clear about where the stress should be checked.
If the shell is designed using the 1-foot method, it would make sense to only check it at those same points, but API doesn't actually say that.
Ditto if the variable design point method were used, it would make sense to just check at the variable points.
Most of the time, this doesn't come up since the seismic hoop stresses don't control the design, and you can check at the bottom of the shell course without any penalty.

 

[HTURKAK]

API is not real clear about where the stress should be checked.
If the shell is designed using the 1-foot method, it would make sense to only check it at those same points, but API doesn't actually say that.
Ditto if the variable design point method were used, it would make sense to just check at the variable points.

I agree with you..API does not state explicitly where the stress will be checked. In past,in general i preferred to check at the bottom of the shell course. I have copied and the pasted the snap below from, API 650 11th ed. 2.nd addendum.
App. EC worked example 6.

Apparently The analysis point is, 1 ft high .

 

[TheEverest]

Thank you HTURKAK and JStephen for your replies. This means a lot.