ASCE 7-05 Gust Effect Factor

[SixkHz]

I'm a Canadian engineer-in-training and I'm working on a glass canopy design for an American project. I've used ASCE 7-05 to calculate seismic loads but this is my first time using it for wind loads.

I have a couple questions regarding the Gust Effect Factor (6.5.8):

1. I've set up a spreadsheet to calculate the gust factor for both rigid and flexible structures. I checked the gust factor for a rigid structure and I got 0.90, which is higher than the optional 0.85 factor listed at the beginning of the section. I read the commentary, and it states that the rigid gust effect factor should typically be 0 to 10 percent lower than the 0.85 factor. I checked my calcs and the equations seem to be correct. Is it possible to have a higher gust factor than 0.85?

2. When determining the flexible gust effect factor, for RB in eq. (6-13a), ? = 4.6*n1*E*B/Vz. I'm just wondering what the "E" term is because I can't seem to find it defined anywhere in the chapter. Is it the elastic modulus of the material making up the structure?

*Note: The canopy is 67 ft long x 64 ft wide x 18 ft tall and I'm designing it as a monoslope free roof.

Any input is appreciated.

 

[WillisV]

Calculated G for rigid structures generally does come out a little lower than 0.85 (like 0.83). Most people just use 0.85 - which is allowed even if somehow your calcs came out higher - thought I would triple check your calcs.

The E was a mistake and deleted in the Errata to ASCE 7.

 

[SixkHz]

Thanks for your help.