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Re: Load Paths

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Bill Allen, S.E. wrote:

I was in my reading room and re-reading the October, 2004 issue of Structure Magazine when I ran across a Simpson ad for the StrongWall (p.6). See: Provoked by the title “Imagine the Possibilities”, I had two thoughts which are totally unrelated to any Simpson product:

Based on the image referenced above:

   1. How does the in-plane shear load get to the shear walls?
   2. How is out of plane bracing provided for the shear wall on the
      second floor?

I am interested in any (and all) comments.


T. William (Bill) Allen, S.E. (CA #2607)


Consulting Structural Engineers <>

V (949) 248-8588




F (949) 209-2509

I am not sure that out-of-plane forces are as much a concern as most of us have debated in the past. The last time we had this discussion was when I posed it on a home I was doing where I had 14-foot plate heights in the great room and there were questions about the calculation of wind loads on the walls and their effect on the panel design. I think we need to look back historically on this in areas where homes are designed to reasonable wind gusts (not considering open areas off lakes and oceans but the typical 70-90 mph wind load with Exposure C in the 97 UBC). Historically, this has not been a problem as we have not been able to identify damage to one or two story single and multi-residential structures subjected to wind normal to the walls. In a simple sense, these walls are braced by interior partitions that are perpendicular to the wall subject to out-of-plane forces. On a two story structure, you consider the movement of the diaphragm that acts at the top of a wall in tension or compression out-of-plane. Again, I don't think we have attributed much damage to this in most areas of the US unless the you are in an area subject to hurricanes and other high wind regions.
This might not answer your question, but maybe the following will ad to it.

Simpson now has a narrow full metal shearwall similar to the Hardy Panels. I received a newsletter from Simpson two days ago that describes the panels - intending to be used where there was not a sufficient area for a conventional or hybrid shearwall (such as the Strongwall). Again, the issue of out-of-plane forces on light-weight structures may be treated as we have treated the design of carpenter trusses in the past - prescriptively :>)

Seriously, I don't think that out-of-plane forces are a problem due to the redundancy of interior partitions that help control diaphragm movement. I also believe that sheathing and exterior finishes - especially metal lath and stucco - must be considered as part of a "system of construction materials" that work together and is not actually a "sum of their parts."

I know this does not answer the question, but if you know of a situation where specific damage was caused because the walls failed in buckling (out of plain) then I would be interested in reading the opinions of others about it.


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