wind load on gate

huangyhg

wind load on gate
i need to calculate the wind loads on an operable gate that is located in an otherwise solid wall of a building. the gate has aluminum tubes on all four sides with 1" vertical pickets at about 5"c/c.
does anyone know of a reference for this condition or have an idea of how to calculate the loads?
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i'd just use the area of the gate times the wind load from asce 7-05.  some debris could hang up in the pickets and create a solid area for wind.
you (theorectically) would have some wind "blow through" the slots in the gate - in the 4.0 inch clearance between each 1" picket - but consider that the eddy losses and whipping around the sqquare edges and corners of the very-definitely-not-aerodynamically-shapped square "box" (in plan view) would mean the true effective air resistance is very, very close to the a flat plate, hinged at one end.  (or a flat plate, rolling open on tracks - even less resistance).
you get extra "area" with the top and bottom bars, and decorations on the bars, and on the end pieces.  
if you want to get "about right" znd don't want a conservative answer, try a plate hinged at one side, then take credit for 7/16 to 1/2 of it being "open" - rather than the 20% open that you'd expect from the geometry.   
pressure point would still be at the centroid of the area: unless you want to also assume that the wind "at top of plate" is significantly greater than "wind at bottom of the plate" which is greater than "wind at ground level" - which is zero.  then you could figure that the real pressure point from the wind will always be above the calculated center of area of the plate.
you need to model this so that you can get the latch or pin reactions for their design.  as noted, use asce 7 and consider it as a lattice structure of sorts. as jedclampett noted, consider it solid or nearly so, since when you get design winds, you're also likely to trap debris against it.
if you are using a pin to latch the gate in place, check the bending on the pin as well.  
jed makes a good point about the debris.  based on that though, you would also have to consider impact from wind blown debris...  don't know where the required limit would be on that.
mike mccann
mmc engineering
i would design it as free standing wall or sign.
never, but never question engineer's judgement