4
Wwater = - [pi]R3[UPSILON]
3
where
Wwater = weight of water, lbs
R = inside radius of sphere, feet
[UPSILON] = density of seawater, lbs/ft3
4
thus
Wwater = - [pi] (7.5)3 (64.0) = 113,100 lbs.
3
The weight of the sphere (neglecting penetrations) is calculated by
Wsp = 4[pi](r)2 (tsp ([UPSILON])
where
Wsp = weight of sphere, lbs
r = mean radius of sphere, inches
[UPSILON] = density of steel, lb/in.3
Thus
Wsp = 4[pi](91.0)2 (2.0)(0.283) = 58,900 lbs.
Assume that the penetration reinforcements and entranceway, etc., add
another 10,000 lbs of dead weight load to the structure. Thus the total
dead weight load to be sustained by the cylindrical support skirt is
Wtotal = 113,100 + 58,900 + 10,000 = 182,000 lbs.
(5) Support Skirt Compressive Stress.
The average compressive
stress in the support skirt is given by
Wtotal
[sigma]comp = ------------
[pi]Dsts
[sigma]comp = compressive stress, acting longitudinally in the
support skirt, psi
Ds = mean diameter of skirt, inches
ts = thickness of support skirt
Wtotal
solving for ts
ts = ---------------------
[pi]Ds[sigma]comp
and arbitrarily*
setting [sigma]comp = 2,000 psi
182,000
ts = ------------------- = 0.241
[pi](120.0)(2000.0)
set ts = 0.25 inches.
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