Curtain Wall or Storefront Mullion - C-shape with filler - Bracing 2

[RFreund]

It seems like most manufactures consider a C-shape mullion with a filler piece braced (unbraced length = 0). Is there any technical reference for this? Most seem to base this off of testing (they don't observe LTB of the shape with the filler present). But I believe it is mostly internal testing. Just curious to see what other documents are out there about this. Maybe a AAMA TIR document?

Thanks!

EIT

http://www.HowToEngineer.com

 

[jjl317]

Having a spent a number of years in the exterior cladding industry (including curtain wall and storefront), I feel that these fillers are just examples of the various components used in these systems, that don't lend themselves to a strict theoretical analysis (common in storefront systems like this). Normally, I would not have even considered the "fillers" structurally, and just considered the "C shape", with the fillers along for the ride. The good news is that these systems are typically vetted through full-sized mock-up testing, though trying to justify them via calculations can be a challenge. The only published technical reference that I am aware of that might even remotely touch on this might be from ASCE Structural Journal "Lateral Buckling of Curtain Wall Systems" by Charles Clift and Walter Austin (late 1980's). This is a deep dive (to use a KootK term) in the theory of lateral torsional buckling of curtain wall vertical members, though the systems considered in the analysis are somewhat antiquated, and I am not sure how directly this approach might apply to this case. I did find a free pdf online via a google search. Hope this helps.