stiffening rings for API 650 Tanks

[carthago]

Secondary stiffening rings acc. API 650:

Assume that based on D, course heights , thickness, wind speed,.. on calculates:
1/ height of transformed shell= H_transf
2/ H_unstiffened =the height of the Unstiffened shell

lets note:

n < (H_trans : H_usntiffened ) < (n+1)

n= could be equal to 1 or 2 or 3 etc.


If n =0 then no secondary ring is neede.
If n= 1 one secondary ring is need located at
( L =H_transf : 2)from tank upper shell edge.

if n = 2 for instance , two secondary rings are needed
preferably located at ( equally spaced ) at a distance = ( L = H_trans : (n+1) = 3

Well : My question is my understanding correct
is my understanding correct or not ??


Shall the modulus of resistance ( Z) of the ring ( as defined in API be defined on (L) = distance to nearest ring or tank top edge..

Thanks

 

[carthago]

...sorry guys..for the typing errors.

Actually I want to note than the actual european Code EN 14???, the old BS 2425 code or the franch CODRES
have both an example for open and closed tanks..

It the same numerial example in the 3 codes !!
The only difference with API 650 is the facor preceeding the
term H1 = K * t*(t/D)^1.5


but I want to hear your opinion about API 650

Thanks

 

[JStephen]

I think you need to define your H's better. H in the equation is the allowable height, and is not necessarily equal to the actual height of unstiffened shell or the transformed height.

In actuality, it is oftentimes preferable to thicken the shell rather than adding intermediate wind girders.

I read it that H-1 is to the top angle or wind girder, not the other intermediate stiffener. But in the procedure in AWWA D100, it lets you use the distance to the previous girder for the second girder.