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# RE: curved wood sw

• To: <seaint(--nospam--at)seaint.org>
• Subject: RE: curved wood sw
• From: "Avik Ghosh" <avikg(--nospam--at)borm.com>
• Date: Mon, 9 Apr 2007 16:53:16 -0700

Title: Message
Interesting idea.  I would expect load values to be less than regular shearwalls since there is an added eccentricity.

Here are some more questions, (but no answers from me):  Since shearwall values are typically based on testing, it would be interesting to see how someone would test a curved wall.  Testing would have to represent actual design scenarios.  How would the roof/floor diaphragm distribute the load along the wall?    Would it be along one axis or radially along the length of the wall?

If assumed along one axis, then the wall is potentially loaded out of plane to the sheathing along certain segments of the wall and one would have to detail for that. This means that along certain segments of the wall, the edge nailing into the sill plate may try to act like holdowns therefore causing the sill plate to bend about it's weak axis (unless a Simpson MAS like strap is used at each stud or the wall is double sided).  I would guess that the loading distribution to the nails would also be uneven along the length of wall if this type of loading is considered.

If loading is assumed radially along the length of the wall, then a test jig that can simulate this radial motion would have to be used.  I don't know how practical that is.

These are some challenges that I would think a curved shearwall would pose that perhaps someone has done testing and has answers for.

-Avik

-----Original Message-----
From: Robert Kazanjy [mailto:rkazanjy(--nospam--at)gmail.com]
Sent: Monday, April 09, 2007 4:20 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: curved wood sw

David-

There was a thread on this topic back in May '06 but not much useful info in it.

I am not aware of any technical papers on the subject...maybe APA can shed some light on the subject.

At the time, I asked the OP

>>>>>>>>>
How "curved" is your shear wall?  Radius of curvature?  10'  100'   1000'?   Building approx foot print?

Could you "linearize" the problem? That is, could each 8' or 16' segment be considered "straight"?

IMO the key to your design solution is a diaphragm that is quite rigid in both directions, esp in the location where the shear wall attaches to the diaphragm.

<<<<<<<<<

Addtionally, a top & bottom plate that "encompasses" the wall curvature would be very helpful....ie a very wide plate made of engineered wood or plywood.

a few years ago I made a curved (~12' radius) raised platform....... really a box beam about 12" wide, 16" deep & ~ 20 feet long.

I skinned it (sides) with relatively thin material (door skin), the curved top & bottom plates were cut from 3/4" plywood, 3/4 ply vertical ribs were placed ~ 16" o/c

The resulting assembly was incredibly rigid

Not exactly a shear wall.....but pretty close.

cheers
Bob

On 4/9/07, David Topete < dtopete(--nospam--at)gfdseng.com> wrote:

Does anyone have any info on curved shearwalls of wood construction?  The structure is single-story, but I will likely need holdowns, depending on what "length" of wall I use.  Is there a minimum radius maybe?  Any help is appreciated.  TIA.

David A. Topete, SE