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# Hi Gourile, thanx for the very conc

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## Hi Gourile, thanx for the very conc

(OP)
Hi Gourile, thanx for the very concise and clear bit of info.

Do you want to go on further on lift force and drift forces?. Just for the fun of detail?

So drift pushes stuff along the wind. Lift pushes stuff perpendicular to the wind in horizontal direction right?

Gust is the dynamic portion of wind pressure. When we change that to static it is like increasing the steady portion by a factor of around 1.5 to 2?. Am I right?

### RE: Hi Gourile, thanx for the very conc

You are quite right about the drift and lift. Drift, is sometimes called drag, but the idea is the same. The gust is the dynamic effect. The velocity is considered as a sum of a mean velocity, with the gustiness,i.e
v=v0+.5v0sin(2.pi.t/60)
This is a normal formula of wind velocity 'v' with a mean velocity of 'v0' and a maximum gustiness of 1/2 mean velocity for a return period of 1 minute (60 seconds). The amounts of course, may vary from region to region. You better check with your local design code. API RP2A, is an approved code around the US. The dynamic effect becomes important when you deal with welded connections in your tower, as a few cycles may cause a fatigue on the welds. If your connection are all bolted, you may consider the maximum velocity of 1.5v0 to check for members individually, but not for the whole tower. Please don't hesitate to write to me if you needed more info.

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