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Cantilever 2nd story shear wall to 1st floor

Cantilever 2nd story shear wall to 1st floor

Cantilever 2nd story shear wall to 1st floor

(OP)
Designing a conventional wood framed 2-story duplex.  The client desires to have one side of the 2nd story cantilevered 2-feet over the 1st story.  At the edge of the 2’ cantilever is supporting both wall and roof load.  2x12 floor joists @ 16” are facilitating the cantilever.  

I have never detailed this before, but just at guess my thought is to double up the 2x12 rim and transfer the roof/2nd story shear via the floor diaphragm to the 1st story shear walls.  My question and concern is how is to overcome moment/overturning?  

Also, on that 2nd story cantilevered shear wall line, I have limited width for shear walls (read H:V <2).  Is it possible to use something like a Simpson shear wall on a cantilever?  Again, I am at the same loss as to how to transfer the chord forces.

Thanks for your help!    

RE: Cantilever 2nd story shear wall to 1st floor

If you provide solid blocking between the joists over the inner wall then this will stop the joists rolling over.

The return walls can be used to help resist the push/pull at the ends.

As for the simpson shear wall, you need to go back to first principles and calculate the additional bending in the cantilever from the push/pull under overturning.

csd

RE: Cantilever 2nd story shear wall to 1st floor

This is done all the time.  I would use at least dbl 2x12 or 4x12 @ the ends of the upper level shearwalls.  Fasten/strap the end of the shearwall to dbl or 4x.  Back @ the lower level walls, attach an upsidedown PHD with threaded rod thru top plates to HD post below. Agree with csd72 about the Strong-Wall.

RE: Cantilever 2nd story shear wall to 1st floor

Three ways of handling this come to mind:

1. Size the rim joist to handle the couple induced by the overturning moment in the shearwall. Calcs out best when you have a lot of short shearwalls at the cantilever. The heavy rim joist distributes the overturning forces to a lot of cantilevered floor joists which transfer the forces back to the bearing wall.

2. Install beams (or double/triple/+ joists) at the shearwall ends to transfer the loads back to the wall. Works best when you have a longer shearwalls.

3. Distribute the holdown loads to the cantilever joists under the wall according to displacement under load - zero at the approximate center of the wall and some maximum value at the ends, varying linearly in between.

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