Round Clerestory

[wallerdf]

I have a 54'-0" diameter round clerestory right in the center of the roof. It's a good 20'-0" from the edge of the building in all directions. How are others handeling clerestories?

I'm planning on designing it as Other Structures (Chimneys, Tanks, Rooftop Equip and Similar Structures) I'm also less than 60'-0" but if I use GCr = 1.9 (Section 29.5.1) it doesn't seem like I'm taking advantage of the structure being round. Would you use ASCE Figure 29.5-1 for the walls and Section 29.5.1 (GCr=1.5 for uplift) for the roof?

I'm also thinking it might be a little large (too close to the actual building length/width) to really consider it an other structure and that I should just use the regular building wind tables. Now if I do it that way I have a second questions. Would there be an corner and edge zone? I would think there would be no edge zone for the walls and no corner zone for the roof.

Any thoughts.

 

[msquared48]

I would be conservative with the wind here if I were you. Might go so far as to consider ASCE 7-05 6.5.15.1 for a "rooftop structure". However, I would use a factor of .6 or .7 for the shape to reduce the 1.9 factor.

How far above the main roof does it extend?

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[wallerdf]

It sticks up 9'-0".
The references are for the ASCE 7-10. Section 29.5.1 is for rooftop structures. GCr is in place of GCf if your structure is less than 60'-0". Above 60'-0" you would use figure 29.5-1. My thought was to use a combination of the figure (wall pressure) and the section (roof pressure).

 

[MiketheEngineer]

What "nut" architect or wife wants this??

 

[wallerdf]

I've made that comment a bunch over the last few months. I have an elliptical one (180'-0" x 120'-0") on another job. I've definately had to put my thinking cap on how to handle some of these. Like Mike said above, I want to be conservative but I don't want to completely over do it.