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canopy wind loads

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I have designed way too many of these things, and had numerous discussions on seaint with people about canopy wind loads....  What I end up doing is if the structure is free standing, like at a gas station or a picnic pavilion, is use ASCE 7-02 wind loads on open roof structures for the uplift load. Yes, this is only for monoslope roofs but that is all we have to work with. If it has a decent slope in the roof or a parapet or large fascia, I do apply a lateral wind load- I model it as a freestanding sign above grade and use the proper ASCE coeff.
 
Now if it is a canopy connected to a building, where wind loads will hit the face of the building, then go up and hit the underside of the canopy, I conservatively model this as an overhang. The wind pressures will be much higher then you would get if you did as above. However, my and other engineers' opinion that I have discussed this with is that the canopy is attached and is an overhang, and will capture extra wind pressure that is hitting the face of the wall and travelling upwards into the canopy. Here, the canopy is "trapping" the wind pressure.... I may reduce this load if it is a very small canopy and there are "escape routes" to the sides to relieve this pressure. But canopies such as at the front of a supermarket, strip center, mega-lo-mart, etc., I model them as overhangs....
 
ASCE does allow use of other pressure coefficients from other sources and texts, I believe there is a list in ASCE somewhere. There were some very useful charts, especially for open structures, in the back of a book at one of my previous companies, which I made copies of but cannot find at the moment: Wind Effects on Structures: Fundamentals and Applications to Design
by Emil Simiu, Robert H. Scanlan... There are used copies of this on the internet.
 
Just be careful if the charts/diagrams say the pressure coefficients were derived from uniform flow tests.....

 
HTH,
Andrew Kester, PE
Structural Engineering Consultant
Lake Mary, FL