Storefront is predominantly glass - do I do CMU or steel framing?

[gmoney731]

Hello all,

I am working on a new commercial retail project. Attached is the intended schematic elevation.

When I was first coordinating with the architect (prior to elevations), they mentioned the build would be CMU wall systems.

However, looking at the elevation provided, it seems that I’d have to have steel framing in the front to allow the “glass look”. That steel framing would potentially have to return on both sides to some degree, and that’s where I can transition from steel to CMU.

Is this the correct approach? Or can we do full CMU here?

 

[JLNJ]

There is usually a way to make CMU work, but it won't be as simple as a couple of standard details for punched wall openings.

Architects often default to CMU because it works with their standard wall and roof flashing details. What does your wall section look like? Storefront? Curtainwall? Cavity wall above the glass? Can you sneak a steel column in the corners? Hopefully the columns can be on the CMU centerline. A good architect thinks about these things before you have to.

You might not have much of a shear wall with all that glass. Best to think about the lateral force resisting system as you contemplate the remainder of the wall support.

 

[gmoney731]

Great questions, and thanks for your insight.

I will follow up with the architect to see whether there is actually "wall openings" for this glass, or whether the glass is just for looks, and actually just behind it is the CMU for the MWFRS.

If it's CMU, I'm in great shape for the design. If the glass is meant to be true see-through glass, then the only option I see is steel frame. I will try to see if the CMU works, but per the schematic, they don't even want pilasters at the corners. Perhaps I can convince them that it's necessary?

See the attached schematic for my intent if we have to go steel framing. Do you think something like this, with a spread footing at each column, is reasonable?

If the glass storefront is real, I don't really have any room for lateral x-bracing to help resist shear. All I'll have is columns, the W18 beams, and girts. What other options would I have to help laterally? The storefront elevation is higher than usual, at ~15'...I am assuming the roof will be at ~23-25' - which is pretty high...most stores I've designed are for 18' roof level. If the glass is real glass/opening, then I might also have to consider this partially enclosed, bumping up the wind pressures even more.

 

[jayrod12]

When we have to do these, we turn the columns and beams into a moment frame. Often the top of storefront isn't at the roof beam elevation, so we often cross brace between the girt at top of storefront and roof beam making a far stiffer moment frame.

 

[Stenbrook]

In my experience, it is pretty standard on retail buildings like this to have the back and the two sides as CMU or tilt wall and then the front as steel and infill light guage.

 

[dik]

I'd likely be doing that in structural steel and CFS and surfacing...

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So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik