Ribbon Window Framing 4

[SEH2010]

I am currently working on a project that is a 2 story office building. The exterior wall will be a metal panel system with a ribbon window at each floor. Column spacing is 24'-8".

My question is, what is the most practical way to frame the wall to support the window and cladding for lateral and gravity loads? My initial thinking was steel channel framing braced back to the structure at the floor and roof level and a HSS spanning from column to column below the window on the first floor.

I have attached a preliminary section for help.

Thanks in advance.

 

[JAE]

I think your light gage studs could be used to cantilever up and down from the floor-beam system.

Keep in mind that your WF floor beam along the deck edge has very little torsional stiffness so you also would need to supply diagonal kickers from the WF bottom flange up to the underside of the deck to prevent beam twist.

If the light gage studs can't perform (in your case the distances are small so probably no problem), then you could add vertical steel channels or angles spaced between studs (perhaps every other or every third/fourth stud) to take the loads into the floor.

 

[Ron]

Agree with JAE...in addition, note that the sunshade system will create a moment at its connection that you'll have to deal with. Further, the curtain wall system can be internally reinforced by a significant amount to help with the wall (check with the curtain wall mfr....they have stiffening channels that are placed inside the aluminum sections for reinforcement.

Watch the connection between the steel studs and the curtain wall...that can be an issue if you have high wind loads.

 

[Lion06]

I provided a similar detail on a 9-story mixed use building recently. We didn't have the ability to add kickers because of limited floor-to-floor heights. I provided a channel welded to the bottom of the WF. Along the sides where the spandrel had no supported beams I added small WF beams at like 10' max to cut down the span of the channel. The connection detail of the section to column was a simple shear connection from WF to column and an angle on the top flange of the WF and the underside of the channel. The angles had horizontal slotted holes to allow simple beam rotation, but the connection was needed to take out the torsion.

 

[Lion06]

I also ensued to say that the channel was needed for strength, but was needed more for the deflection of the studs. The angle of twist is obviously highest at the center so the studs have a small deflection near the ends and it gets very large at the center.

 

[Galambos]

there is a ton of information on this topic in AISC's Design Guide 22: Facade Attachments to Steel-Framed Buildings.

Hopefully, you are a member and can download it for free!