In general, wind stability is not a problem with storage tanks; however, if ht/D > 1, the stability should be checked. For an unanchored tank, the overturning moment from wind pressure should not exceed two-thirds of the dead load resisting moment, excluding any tank content, and should be calculated as follows:
MOT < 2/3(WD/2)
where
MOT = Overturning moment from wind pressure (mt)
W = Shell weight available to resist uplift, in tons, less any corrosion allowance, plus dead weight of any portion of roof supported by the shell
D = Tank diameter (m)
For empty, small, high tanks, the resistance to sliding and overturning under the force of wind should be checked. If MOT > 2/3 (WD/2), anchor bolts are required.
If anchors are required, the design tension load per anchor shall be calculated as follows:
tB = (4MOT)/dN — W/N
where
tB = Design tension load per anchor (tons) d = Diameter of anchor circle (m)
N = Number of anchors
Noting that, the anchors should be spaced at a maximum of 3 m (10 ft) apart.
