Lateral resisting system problem 2

[Robert216]

I have designed a single story steel frame structure with metal stud infill. I used threaded rod cross bracing to resist lateral loads. The contractor comes back and request that we use shearwall system. I'm having trouble getting the lateral load from the diaphragm (metal deck) into the shearwall without turning the stud infill into a gravity loadbearing system (connection from top of wall to beam to deck). I think one option would be to ensure that all dead load be in place before attaching the sheathing. The only problem is selecting a transfer mechanism from the deflected beam (gravity) to the wall below (lateral stability). Any help on this would be greatly appreciated.

 

[JAE]

I don't recall seeing any lateral collector or axial capacity in most light gage steel double tracks. Even if they did, how could you connect them - never heard of slotted hole connections for screws.

What you might do is require a tube collector to be placed just below the main beam with a gap large enough to accommodate the vertical deflections of the roof beam.

Then, attach the stud wall top track to the underside of the tube. The gap between the tube and the beam would be small enough that any lateral force dragging in from the roof beam would be transfered to the tube via bending in the columns (or you could install some shear plates at each end of the beam/tube to avoid the small column bending).

Then sheath the walls.

You would have to take perpendicular component wind forces from the stud wall into the tube, which would span laterally from column to column. Some additional wind columns might be necessary.

This costs more for the tube, but you save money in not having a slip track, and not having X-braces.

 

[Robert216]

JAE,

Thanks

 

[pcronin]

Check with the Steel Network

http://www.steelnetwork.com/

They have developed gage metal connectors and some can transfer in plane shear into your walls with what they call "stiffclips". They have a decent technical support staff as well.

 

[CFSEng]

Any thought about moment frames or knee-braced frames. Knee bracing can 'easily' be framed around with metal studs

 

[UcfSE]

It seems like installing steel tubes and possible wind columns would cost more than a slip track. You can get a slip track with slotted vertical holes. You would use only one track and the studs get screws in each flange to the track through the slotted holes. Then you can transfer in-plane forces but still have the vertical slip for gravity. They have tested values for the out-of-plane stud reaction on the track as well for up to 54-mil track. You can calculate a value for 68-mil if you need it.

Dietrich Click on deflection connectors, when the pdf opens go to number 4 slotted SLP-TRK.

 

[CFSEng]

Can't speak for all building codes but FBC requires full blocking for wood / metal stud shearwalls. Since you can't attach the sheathing to the track, you would be required to provide either strap or stud blocking below the track for your perimeter sheathing attachment. Wouldn't this put the studs into weak axis bending carrying the shear up into the track? Also, I didnt see any value for in-plane allowable loads. Not sure how strong the track is in-plane transfering shear through the slots

Not saying this wouldn't work, just saying its not a simple load path.

 

[UcfSE]

Correct, there is no inexpensive simple load path. There are alternates.