API 650 Add4 ( Uplift pressure on roof due to wind )

[dharmeshajoshi]

Before Add 4 of API 650 was introduced we used to take horizontal force acting on the roof which is equal to 15 lbs/ft^2. But Add 4 of API 650 says there is an uplift pressure of 30 lbs/ft^2 acting on the roof due to wind.

Such high uplift pressure 30 lbs/ft^2 can occur from inside the tank.

I do not understand how there will be vertical wind pressure acting on the roof.

Can someone tell if it is possible to have such high uplift force on the roof due to wind?

 

[DSB123]

dharmeshajoshi,
All tanks located outside are subjected to uplift due to wind. You really need to read some wind literature to familiarise yourself with the effects of wind on structures.

 

[carthago]

We have the same effect on roofs for steel structures..as I understood this due to the suction acting on the roof