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Plate washer edge distance on sill plate

Plate washer edge distance on sill plate

(OP)
I am working on a mid-size wood framed structure, 2x6 stud walls and gable roof trusses. It's all single story and in a relatively high wind zone. I have base shear and uplift values on my walls maxing out at around 400 plf. The lateral system is a mix of segmented and perforated shearwalls, the building has multiple wings so shearwalls are all over the place. The uplift is resisted by hurricane ties from roof truss to top plate, top plate to stud, and stud to bottom plate. I prefer to detail the clips to be installed on the inside face of stud for a few reasons: 1) Framers seem to always default to this, I believe so they can come and add the clips on later, you can't really add ties on the outside face of wall once the sheathing is up; 2) Easier to inspect; 3) I feel like it creates a nice couple with the sheathing to help balance out uplift forces on the sill plate.

I currently have it detailed so that the anchor bolts are secured to the sill plate with 3x3x1/4 plate washers with the edge of the plate washer within 1/2" of the interior edge with the hurricane ties as that is the side my uplift forces are designed to travel through, although in reality the sheathing and hurricane ties will likely work together in distributing uplift forces to the sill plate. I'm stealing the 1/2" from SPDWS requirement on walls with combined shear and uplift where they call out a max 1/2" from the edge of the plate washer to the sheathed edge. I am now realizing that the SPDWS requires 1/2" to the sheathed edge on perforated shearwalls and segmented shearwalls with >2:1 aspect ratio, which is a majority of my exterior walls.

Does anyone know of any literature regarding uplift on sill plates outside of the SPDWS recommendations? I see my options as either going to a 4 1/2" plate washer, which I am trying to avoid, or placing the 3" washer edge 1/2" from the sheathing, resulting in 2" from the edge of with the hurricane ties.

Sorry for the long post, thanks in advance for any replies.

RE: Plate washer edge distance on sill plate

I see what you're getting at. One the one hand, if the plate failed on the exterior, you'd still have your designed uplift capacity on the interior. On the other hand, if you fail the bottom plate at the exterior, you may well lose your shear capacity. I like the 4.5" plates. That doesn't seem like much of an ask. Plus you'd dodge any code compliance snags.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Plate washer edge distance on sill plate

Simpson did a tech bulletin on installing truss tie downs on the inside of the wall and they said it changes the failure mode to the connection between the studs and top plates. Without additional hardware the capacity is limited.Link

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