Open Structure with obstructed flow

[MAeng]

Hi -

I'm designing a canopy with is open on 3 sides but not on the side where it's added to the existing building. Since the existing building is there, I feel this should be looked at as an open building with obstructed flow since in this one direction the wind cannot be considered free flow and there will be a resultant uplift when the wind hits the existing building wall. Any thoughts on this? Am I looking at this correctly?

 

[hokie66]

Yes. If the canopy or awning is low relative to the existing building, the pressure will be predominately down. But as the height approaches the height of the existing, uplift will control.

 

[slickdeals]

ASCE 7 has tables for this kind of a scenario.

 

[msquared48]

If the canopy is not permanently attached to the building, you may also be required to design it as if the building were not there. I would look at both conditions.

Mike McCann
MMC Engineering

 

[MAeng]

I should say it a new roof structure connected to the end of an existing building and that the new structure has no side walls. The structure is wood joists and plywood and is supported on steel frames (since there are no shearwalls). I'm looking at this as a "flexible" structure and using the "obstructed flow" uplift values (which are pretty high) because of the existing building. Does this make sense?

Thanks for your replies.

 

[hokie66]

Yes, it does to me. The pressures on the canopy with the wind blowing normal to the existing building will be higher than without the building there.