Wind Load on Vertical Tank

[TMEldridge]

I am trying to estimate the wind load's effect on a loading of a ringwall foundation for a vertical steel tank. Tank itself is not anchored to the ringwall (yet). Height to Diameter ratio is 4/9. I've got wind speed for the area and all the tank info available.

 

[IFRs]

You may want to consult ASCE 7, API 650 and/or AWWA D100.

API 650 calculates the 100 MPH wind load or pressure to be 30 PSF on vertical plane surfaces, 18 PSF on projected areas of cylindrical surfaces and 15 PSF on projected areas of conical and double-curved surfaces. For higher winds, ratio by the square of the velocity.

For the fertical cylindrical portion of a tank the force will be 18 * ( V / 100 ) ^ 2 * H * D where H and D are the tank Height and Diameter in feet. The force can be assumed to act half way up the tank or H / 2. The force times the distance is the overturning moment.

For an unanchored tank, API says the tank is stable if the overturning moment from wind pressure is less than 2/3 of the dead load resisting moment.

API calculates the wind uplift load on a foundation as ( 4 * M / D ) - W where M is the wind moment and W is the corroced dead load of the shell and roof plate acting on the shell.

Does this help?

 

[TMEldridge]

Yes this helps very much.

 

[TMEldridge]

One question IFRs... where in API 650 (if it is 650) is that last calc. For some reason I've missed it.