Store Front Window Span

[XR250]

I am working on designing some light gage for a college addition. I have a 28 t. tall x 12 ft. wide storefront window. It is surrounded on three sides with CMU. At the top, the Arch/Eor is showing a light gage assembly. i put a note on my shops drawing indicating that I assumed the window is spanning horizontally (why wouldn't it?) The Arch has come back and indicated that it is designed to span vertically. I can't believe this is true and, if it was, would there not be significant deflection compatibility issues at the jambs where it runs next to the CMU?

Thoughts?

Thanks

 

[jike]

I assume that are several intermittent mullions shown in the 28 foot height which span 12 feet. What is drawn? I would call a window supplier that the arch has spec'd to discuss how it will be designed.

 

[XR250]

Yes, every 2'-8". I may give them a call.

Thanks

 

[Teguci]

Sounds like they want a curtainwall and not a storefront. At a 28 ft span, you may need to provide an intermediate support. Does the CMU wall span 28 ft? I suggest bracing the curtainwall at the same height(s) that the CMU walls are braced.

 

[XR250]

Yes, storefront, not curtainwall. The section does not show any intermediate bracing.

 

[Teguci]

http://www.conspectusinc.com/downlo...urtain Walls Storefronts Windows 09.12.01.pdf

Max height for storefront = 12 ft.

 

[EngineeringEric]

I think the architect is wrong. The max storefront span is 12ft as Teguci mentioned.

 

[XR250]

Ugh, I meant curtainwall, not storefront - sorry

 

[Teguci]

OK, the Architect is only mostly wrong. We can work with that. At 28 ft the system is just a little longer than what they can handle. Further, you want the bending to match up with the CMU wall (the jamb issue you mentioned). I'd think you have a floor diaphragm at about half that height. I would want to run an HSS across the lobby at that height to brace the vertical curtainwall members back to. The connection at that location would detailed to allow vertical slip but would cut the curtainwall members into 2-14 ft spans and match the bracing for the adjacent walls.

 

[XR250]

Yes, if I was the EOR I would have done it differently. Unfortunately, they dropped the ball on this one.

 

[Ron]

First of all, the maximum height of a storefront is not limited to 12 feet. It depends on the manufacturers extrusion dies and the structural capacity of their mullion configurations, many of which can be internally reinforced in the same manner as a curtainwall section. Both Kawneer and YKK (two major storefront manufacturers in the US) have systems that exceed 12 feet in height.

Your spans may be limited by the storefront or curtainwall sections or by the glass. The glass is generally required to meet the requirements of ASTM E1300.

I just finished a system with all operable openings (automatic doors) framed against TSS and light gage framing in a high wind area.

 

[EngineeringEric]

Hmm good to know Ron, i was told by an architect on a few projects back 12 was their limit. Must have been out of context per a specific manuf.