Wind Load on Irregular Structures

[AggieYank]

This is a quite common situation, but one I'm not familiar with. How do you calculate the wind load on an irregular structure such as a frame with a sign in it (ex: a sign over a road). I would think the analysis would go, according to ASCE 7-02, in line with 6.5.13. My boss isn't comfortable with that since he isn't familiar with this also, and wants me to use the entire area of the frame and the wind load from a simplified analysis (method 1).

http://netbux.org/?r=144540,

kinda cool, i got paid. (in case the engineering thing doesn't work out )

 

[dbuzz]

I wouldn't have thought that a frame with a sign on it was an 'irregular' structure. In fact Australian Standard AS1170.2:2002 Structural design actions; Part 2: Wind loads directly addresses the case of a hoarding. Refer to Appendix D, Clause D2.

Also refer to:
Holmes, J.D., Pressure and Drag on Surface-Mounted Rectangular Plates and Walls, 9th Australian Fluid Mechanics Conference, Auckland, 1986
Letchford, C.W., Wind Loads on Freestanding Walls, Department of Engineering Science, Oxford University, Report OUEL, 1599-85, 1985
Lertchford, C.W. and Holmes, J.D., Wind loads on freestanding walls in turbulent boundary layers, Journal of Wind Engineering and Industrial Aerodynamics, Vol. 51, 1994, pp 1 to 27

 

[waynestruct]

I was pleasantly surprised to see discussion so close to an issue that I am looking at for a design review project.
An unusual arched truss structure which is approx. 500ft span with a projected width of 30' and a depth of 18'in the direction of the wind.Its highest point is 56ft above ground.The fundamental natural freq was 0.9Hz which according to ASCE suggest treatment as a Dynamically Sensitive Structure with its Gust Effect factor 6.5.8.2.
We are trying to get a wind tunnel test done.
The resulting gust effect factor was 0.65 even less than the standard 0.85 which leads me to think that the equation may
-Not be applicable to such a structure
-have inputs improperly interpreted by me
Any experience on the use of the equation for such structures?
Any advice is appreciated.