Light gauge exterior wall studs on 3-story office building

[MJC6125]

I'm working on 3-story office building with composite steel floor structure and light gauge steel stud exterior walls with brick veneer and punched openings (max opening width = 14'). Most of my experience with steel framed buildings are 2-story or shorter structures. So, I'd like to get the opinions of others on a couple items. See elevation view below for reference.

1. The plan is to balloon frame the exterior stud walls (studs bypass the floor slab and steel structure). Is this what you would typically do for a building like this? Can all of the exterior studs be supported vertically at the foundation and just clipped off with slip clips at the levels above? Or would you need to support the studs vertically at any of the upper levels for any reason? A couple things to note are that this is Seismic Design Category B (so seismic shouldn't be a big issue) and the overall wall height from the first floor is 44'.

2. We have brick veneer that exceeds the 30' max height limit per the ACI 530 prescriptive requirements, so I believe a shelf angle will be required. Would you weld this shelf angle back to the light gauge steel stud framing or back to the steel superstructure? If it is attached to the steel superstructure, deflection limits on the edge beams would have to be much more stringent. Would you ever consider not providing the shelf angle and letting the brick stack 44'? I know I've seen some posts on this website that allude to that, but I imagine it's not the industry standard.

3. Any good references for these types of details and this condition are much appreciated.

 

[structSU10]

I prefer to attach shelf angles to the structure. It looks like you have some bands of brick above those large windows - those will require a shelf angle / hanger system to support those I would imagine - or of tube frame in the plan of the walls with a shelf angle.

I have gone taller than 30' with brick, it really comes down to proper control joint details. It looks like you have 'piers' of brick on either side of the windows. if the window details accommodate the brick movement, and you have a joint at the edge of window, you could probably push it to the taller wall.

 

[DaveAtkins]

I recommend bringing the floor system out to the outside face of the steel studs. The studs would go from floor to floor, with a deflection clip at the top of each stud where it connects to the floor above. Use a steel angle (not sheet metal) for the pour stop at the edge of the floor system, and weld the brick veneer relief angle to this pour stop.

DaveAtkins

 

[phamENG]

I second DaveAtkins recommendations. Don't exceed the 30' if you can avoid it. One of the reasons is due to flexibility of the structure. Lateral drift (even under wind loading) can exceed what the bed joints can accommodate without excessive cracking.

You might as well run the self angles at every floor given the number and size of window openings. If the architect complains, tell him to use lipped brick to hide the angle. Also, make sure the angles are galvanized with field repair after welding!

 

[XR250]

As a recovering LGS engineer, I would take DaveAtkins advice.