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Wind action at duct bend

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Pawel27

Structural
Joined
Nov 18, 2008
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PL
I am interested in how to apply wind action at duct bend (see green colour in attachment). In case of straight duct line I use "Pressure distribution of circular cylinders" according to EN 1991-1-4 from section 7.9. You can see also this pressure distribution in attachment (section A-A).

I do not know how pressure distribution apply at bend area. Maybe it can be neglected.
 
 https://files.engineering.com/getfile.aspx?folder=abd21767-9d32-4f0e-a96a-0b74b060a0e5&file=Wind_action_at_bend.png
How big of a duct are you talking about here? Is it 24 inches? Or 10 feet. I've seen large ones for air supply and exhaust at power plants.
 
I'd say unless you want to do a wind tunnel analysis to use the same pressure across your entire cross section.
 
The duct will act similar to a smokestack. The bend creates a potentially turbulent condition as wind is shed around the vertical duct and will act like wind blowing along a roof ridge on the horizontal section. They will collide!

Consider an airfoil brace in the bend.
 
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