Wind Loading on Elevated Structure on Open Framing

[jgeng]

Does anyone have suggestions on how to deal with wind loading on an elevated enclosed structure supported on open framing? ASCE 7 does not seem to address this case?

 

[ishvaaag]

I don't know in ASCE-7 but in my view the bottom would be treated as the roof, each as its respective height. For the open framing quite likely one would use full wind push with almost 0 shadowing of the force, for its shape and height. Some account of the overall slenderness might be required for a more proper portrait of the dynamic effects on relatively slender structures. Curiously this approach would be entirely definible in Spain within the older sixties load's code; sometimes wanting to be precise one loses general applicability.

This would be the end of most cases. Other issues to check for more complicated cases would be wind vortex shedding, aerodynamic effects, maybe a set of time history analyses based on some measured or thought to be realistic set of forces. Specialty wind tunnel houses will deliver state of the art loadings, computational fluid dynamics seems not to be reliable enough at the time being.

 

[vmirat]

I have a similar situation right now. I'm designing a canopy that is rectangular in plan (40'x46') with a 3 foot vertical fascia, height to soffit is 16 feet. The roof deck is at the top of the fascia panel and the soffit is at the bottom, so it's a rectangular box 3 feet high supported on four columns. Very much like your basic gas station canopy.

I decided to use ASCE 7, Figure 6-20, but only cases A and B. It seems Case C is accounting for the decrease in suction on the leeward side of a sign or wall. Since my structure wouldn't have this condition, I ignored Case C.

 

[Teguci]

Consider Figure 6-21 "Chimneys, Tanks, Rooftop Equipment and Sim" or Figure 6-23 "Trussed Tower" in ASCE 7