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Re: plywood diaphragm restrained fdn wall

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Are you looking at a full 10' of backfill on the 10' wall?  If the fill is 9' or less, then I would think it would compare equally with a 9' wall with 9' of fill, with respect to the lateral forces.
I used a similar approach recently to compare reinforcing requirements in a residential 10' foundation wall with less fill than a 9' wall with 9' of fill.  By comparison with the 9' IRC wall, the 10' wall was "acceptable" with the lesser fill amount.
Jim Wilson, PE
Stroudsburg, PA

Joe Grill <jgrill(--nospam--at)> wrote:
I am working on a foundation for a residential structure for a co-worker in our office.  I took the opportunity to try to set it up on Risa3D as we are trying to minimize the CMU (here most fdn walls are CMU) thicknesses.  By the way, this morning the local axes display miraculously worked (don?t know what I was doing wrong yesterday).  Due to the depth of the foundation he will probably still have to use 12? CMU and use the floor diaphragm as restraint at the top of the wall. 
If a person assumed a rectangular box basement with the same fill on opposing sides then the diaphragm/floor assembly will be in compression, and in my case about 500 plf to the diaphragm.  The floor joists will be perpendicular to this direction so I will suggest he install some blocking at some spacing to get nailing into the diaphragm.
I guess this is another one of our questions regarding the IRC code.  The IRC would allow this for a 9? high basement wall with no further consideration in the floor diaphragm.  He has 10? walls.  Will the plywood diaphragm take this magnitude of compression?  It seems that historically it will.
Any comments?
Joseph R. Grill, P.E. (Structural)
Shephard - Wesnitzer, Inc.
Civil Engineering and Surveying
P.O. Box 3924
Sedona, AZ  86340
PHONE (928) 282-1061
FAX (928) 282-2058