Timber wall stud on steel frame construction

[Enhineyero]

It's quite common to consider timber stud walls as a non-load bearing structure for steel frame construction. Normally, internal timber stud walls have slotted connections on top (to avoid load transfer). However, I haven't seen one for external non-load bearing stud walls (running directly under a steel beam), if you have one I'm interested on seeing it.

Most of the time these external non-load bearing stud walls will have their top plate directly fixed to the flange of the steel beam and that seems to work ok, haven't heard of any issues so far. My guess is that there is very little load to be transferred to the stud wall as most of the dead load deflection have already happened by the time the stud walls get built.

Is it really then necessary to have the slotted connection for the internal walls?

 

[phamENG]

In my part of the world it's pretty rare to use wood studs in a steel frame building. Steel for columns/beams with abnormally high loads in a wood building, perhaps, but a steel frame usually get light gauge steel studs. That said, yes - if it's a non bearing wall it gets a deflection clip. I use them everywhere a stud wall is directly underneath and affixed to the steel beam above it. If you have short, stiff beams and/or you apply the cladding from the roof down it's not going to be much of a problem since the the deflection after installation of the studs below will be minimal. Even in those cases, deflection clips/tracks can be beneficial because the beam is not perfectly straight. Using the clips allows the light gauge stud installer to cut all his studs to the same length, and make up differences with the clips. On longer spans where the beam will not be loaded prior to installation of the wall studs, the calculated deflection can get pretty high and the potential load transfer to the studs is much greater. That may or may not matter much - depends on the size of your studs.

For interior walls, it depends on your detailing. If you're tight to a beam, the same thing as above applies. If it's under trusses, it becomes even more important. If a truss was designed to span freely across a 60ft building but you have a stud wall at 20ft that's tight to the bottom of the truss, you have the potential to support the truss at that point, which could cause stress reversals in the web and buckle members thought to be tension only in the analysis.

 

[Enhineyero]

Thanks phamENG. Most of these projects are commercial in nature. Timber would have been preferred if not for the long clear spans with a small roof to ceiling clearance that the architects want. The loads are relatively small and will not likely cause issues to the studs. Just wondering if we (more particularly the builder) are going into too much trouble in installing deflection clips.

 

[XR250]

The buckling stiffness of the studs likely trumps the bending stiffness of the beam, so any live load and/or live load deflection would technically need some accommodation. Is there a footing or thickened slab under the studs?
I think this is something that typically gets ignored in wood construction (and metal studs in many cases) and does not usually cause an issue.

 

[Celt83]

I've always seen the primary issue with wood infill as it is not a dimensionally stable material and will shrink while the steel framing won't.

The deflection accommodation is much easier with cold form infill as that industry is chock full of tested connection products for it, most details I've seen for wood shoe horn these cold form products in and justify their capacity which usually means any kind of manufacturer warranty for the attachment is now void.

My Personal Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

Open Source Structural GitHub Group:

https://github.com/open-struct-engineer

 

[phamENG]

I know Simpson Strongtie has a connector to brace wood walls to the bottom chord of trusses without creating an unintentional support at midspan. Not sure about walls, though. I suppose you could could come up with something with a deep leg light gauge track that the wood wall rides in, but constructability would be a big concern.

XR250 brings up a really good point about foundations. If the wall is there and in contact with the beam, it's going to take the load and needs a foundation to resist it at the bottom.