overturning stability for a fixed roof tank

Question

overturning stability for a fixed roof tank

69020211 (Petroleum)

(OP)

5 Dec 10 00:08

Hi all,

I am going to calculate the OVERTURNING STABILITY for a fixed rood storage tank (supported roof).
In section 5.11.2 (API 650, edition 11), we see:

MDL = moment about the shell-to-bottom joint from the weight of the shell and roof supported by the shell

can anyone tell me how I assume the weight of roof supported bye the shell?

we have roof plates and roof structures ( rafter+girders+column).

Thanks all

JStephen (Mechanical) · Answer 1 · 2010-12-05 01:33:37

Normally, you're designing the roof structure along with the rest of the tank, so you pull those numbers off your roof structure design.

If you know the geometry, figure the loading on each rafter is equal to the spacing between rafters (which varies along the length) times the plate weight plus the rafter weight, and treat the rafter as a simply-supported beam with trapezoidal loading.

If you're checking for stability, try doing the calculation without including the roof weight. If it passes like that, it won't matter what the roof weight is.

69020211 (Petroleum) · Answer 2 · 2010-12-05 02:23:15

JSteph

I got it. but I think i have to calculate the detail information of rafter, girder and column.

many thanks again

CarlosTank (Mechanical) · Answer 3 · 2011-04-02 16:28:15

Hello fellow I sum 50% of the last rafter (support for the shell) and weight of roof plate support for this rafter.

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overturning stability for a fixed roof tank