API 650 Wind Moment

[richissa]

Hi,

I am trying to calculate the wind moment applied on vertical tanks based on API 650.

Per API 650 sec 5.2.1.k ([18 lbf/ft2][V/120]2) on vertical projected areas of cylindrical surfaces and ([30 lbf/ft2][V/120]2) uplift on horizontal projected areas of conical or doubly curved surfaces.

Any suggestions on how to calculate the Moment once the wind pressure is determined?

Thanks in advance!

 

[fegenbush]

Please look at Figure 5-27 of API 650. The moment is the force multiplied by the centroid of that force.

 

[JStephen]

API-650 actually uses two different moments. One is about the edge of a tank, and is used to determine if the tank must be anchored. The other is the moment about the centerline, and for that moment, the roof vertical load cancels out.

The wind pressures calculated are used on the projected areas of the tank to calculate the moments.

 

[SKY302]

1)Horizontal Wind force on the cylindrical surface = Fs = D x H x PWS.
2)Vertical Wind force on the conical surface = Fr =Pi()/4* D^2 X PWR.
3)Overturning moment about the shell-to-bottom joint from horizontal + vertical wind pressure Mw= Fs*H/2+Fr*D/2

 

[richissa]

Can you please define PWS and PWR.

Thanks!

 

[fegenbush]

PWS = Pressure of Wind on the Shell
PWR = Pressure of Wind on the Roof