Stud Shear Wall for Steel Frame

[RG88]

I am working on a single story conventionally framed steel building. The roof system will be standard barjoist framing supported on wide flange beams. Due to some architectual limits on the placement of internal columns (which subsequently limits 'K' bracing placement) and the client's desire to keep the framing & connections simple as possible, I have run into an issue that I haven't really seen before. Has anyone ever used steel stud framing (curtain walls) as a shear wall for structural steel framing? I have not seen this before and the architect is asking that I do my homework on why it cannot be done before he reworks the interior framing to place the braced frame where I feel it should go.

I have worked on similiar structures with exterior masonry shear walls and other 'stud skinned' steel framed structures with braced frames, but this project cannot have braced frames in the exterior walls. The next location for an internal braced frame parallel to this exterior wall is pushing the limit for using the roof diaphragm to transmit the shear back to the interior braced frame. In other 'stud skinned' steel framed buildings, I have been able to use the roof diaphragm to transmit the shear to an internal frame and resrict the drift of the exterior wall within allowable limits.

I am aware of the moment resisting frame option, but I would prefer to use that as a last resort because of the difficulty in obtaining easily constructed connections between HSS columns and wide flange beam sections. Also the dead load on this particular exterior wall is very small so uplift becomes another issue with moment resisting frames. It might help to understand my dilemma by knowing that this is design build and the client is a steel erector with their own thoughts; however, they cannot find any past projects that disagree with my position...that it is not an acceptable or documented practice to use steel stud curtain walls to brace a steel frame structure. The studs are not infill so they are on the outside of the steel framing. The exterior columns are of course inset from the studs so K bracing on the exterior will eat up valuable space and will send the architect into a fit. I have also worked with CFSM on residential projects and am versed in developing shear panels with those members, but this idea of using the steel stud framing as a shear wall for the frame just doesn't sit well with me. I am open to any references or ideas that others may have.

 

[jheidt2543]

You might try calling the Technical Services Dept. of a couple of the stud manufacturers, like Ceco or Bostwick. They should have a good handle on what has been used around the country.

 

[AlohaBob]

I've done it often. IBC now gives design values for steel stud shearwalls. The frame columns help resolve end forces rather than try to load the steel studs for this purpose. The panels carry shear while the columns carry the axial loads of overturning. Just detail the loadpaths so the members work as designed.

I've used rolled shape braces within walls and just infilled with lite gage framing. It is often a happy solution.

 

[jcox]

When you infill with lite gage framing, do you design the brace for out of plane bending? I'm sure that its probably not that big of a deal, I was just wondering what steps you use in the design.

 

[RG88]

I believe jcox has brought up a good point. I don't know that out-of-plane bending would be an issue as much as the moment applied about the long axis of the column. I design the diagonal bracing as a column and design the connections to keep the loading along the centerline of the brace to mitigate buckling.

In my particular application I cannot brace along the outside wall because of windows. Normally I would use HSS sections and brace diagonaly from a beam-column to a column-baseplate. On this project, I am curious if the non-load bearing curtain wall can be designed as a shear wall with light gage strap X bracing between windows. The wall is outside of the column line so the rake angle for the roof deck would function as a the collector/connection between the stud wall and the steel framing. The studs are on the outside of the steel framing because of the parapet extension above the roof deck. I have worked with structures like this before without the studs acting as the primary shear resistance mechanism, but I had the advantage of bracing the next internal parallel frame and keeping the deck plane torsional drift and subsequently in-plane exterior wall drift to allowable limits.

 

[AlohaBob]

You can use lite gage strap bracing. The connections are tedious though. Eccentricity is easily brought into the problem to make construction easier. Be mindful of local overstresses. I mean at the brace plate end stud connection. Welding connections can help. I use a piece of rolled C section bolted to the floor to resolve the base tension.