Shear Walls at Garage Wall Returns 9

[STrctPono]

I rarely design houses and was wondering how to address the shear walls at the return walls around the garage door opening. It seems that this wall is typically as narrow as possible. Say garage door header height of 7ft. Per SDPWS-2005 Wind and Seismic Design Provisions, shear walls should have a maximum h/bs ratio of 3.5:1. What if architect specified that return wall to be say 18"? This is in technical violation of this requirement. What do you do? Go with a Simpson Strong Tie Garage Portal Wall System? Have the Architect redesign the garage area with wider return walls? Thanks for the advice.

 

[kissymoose]

I'm with Celt83, you've been kicked to an engineered design. You might be able to argue that you can keep the prescriptive design of all the other wall bracing and simply engineer a design for this one portal frame. I've found that qualifying and calculating how these IRC provided portals work doesn't work out too well, you're design may differ significantly from a 20" wide wall with 4' pony wall above. Look up medeek here on the forums, he's posted quite a bit about residential portal frame calculations and detailing.

 

[STrctPono]

I'm with Celt83, you've been kicked to an engineered design.

Bummer. Oh well. I will try to run through a full design and see what I can come up with. Not sure what to use for the EI of a wood shear wall when analyzing it as a portal frame. I guess I can do some research.

I had zero experience with this a few days ago and you have all given me a lot of food for thought. Thanks!

 

[phamENG]

You can't really get a good EI value for it. As Celt83 mentioned, a wood shear wall assembly's deflection is non-linear. Best bet would probably be to take the deflection listed in that APA white paper and put it in the AWC's SDPWS equation 4.3-1 for shear wall deflection. You'll have to look up the deflection values for the kind of hold-down they used - I know Simpson publishes them for the HDUs but I'm not sure about the straps embedded in concrete. Put in other data from the test setup description and then you can back out the apparent stiffness of the assembly. Run it again with the hold down you plan to use and the wood species, etc. and you can probably get pretty close.

It's a place to start, at least.

 

[ChiefInspectorJ]

Howabout this:
Have a cantilevered stem wall as high as possible.
Use simpson moment connectors at base of built up stud columns. or self adjusting rods.
Double sheath 2x6 SS SYP wall or lamstuds with 3/4" plywood- nailed and glued.
Then top off with 16" lam beam across to king studs also sheathed with walls.
Add straps at 45 degrees at door opening edges.

All this might cost more than prefab units.

 

[radiocontrolhead]

Chief,

Are we making stuff up now?