CANOPY WIND LOAD

[1prsplmps1]

Greetings; It seems that ASCE7-02 does not cover wind load in canopy trusses (i.e open building). I am working on a steel canopy with cold formed trusses @4'-0" o.c. and spanning 60'-0". If I use a tributary area of 4’x60’=240 sf x (say 20 psf) =4,800# per truss which I believe is tooo conservative. Any suggestions??, thanks..

1prsplmps1

 

[UcfSE]

For open buildings ASCE 7 only covers MWFRS pressures.

That being said, for a 60' truss at 4' o.c., 4800 lbs doesn't sound conservative to me at all, but I'm used to enclosed buildings.

 

[1prsplmps1]

UCFSE: the 4,800# value may be OK for uplift forces but I think is high for horizontal force.

 

[UcfSE]

I agree, I understood what you wrote as being uplift. That does sound high for lateral force. Do they have a large vertical projected area?

 

[1prsplmps1]

UcfSE: the trusses slope is 2:12 therefore 5.0 ft and the elevation at beam/truss bearing. = 30'-0”. You can imagine how critical this height is for this design. Thanks for your interest!!

1prsplmps1

 

[UcfSE]

If you are using the correct procedure for finding your forces by ASCE 7 then just use the numbers you get IMHO. Even though that force seems large it is a 60-foot truss afterall. Are you taking the wind pressure normal to the surface?

 

[1prsplmps1]

Yes, I guess I'll have to bite the bullet..