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Point Load on Plywood Flooring

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Bobby,

I think that I might have found some things that will point you in the right 
direction, if not give you the information that you need.

APA's "Plywood Design Specification"

The last paragraph of Section 3.8.1 (Shear thru thickness) states:

"Shear-thru-the-thickness values as given in Table 3 shall also be used for 
'punching shear' calculations.  However, no increases in allowable stress 
shall be taken for face grain orientation, glued frame reinforcement, or 
restricted core gaps."

Now, with that, all you have to do is figure out the area resisting punching 
shear.

But, then I looked in PS 1-83:

Table 7 states "Performance Criteria" for concentrated and impact loads.  The 
minimum *ultimate* load for floors is 400 lbs.  Section 4.5.5 states that the 
general provisions of ASTM E661 are to be followed.  I don't have that ASTM 
spec, so I don't know to what area the concentrated load is to be applied.

[I also remember that somewhere there is something about the requirements for 
Index Ratings --- that the minimum span index is good for at least 35 psf for 
roof loads, something else for floor loads, and I believe that there is also 
a concentrated load figure given.]

Anyway, I hope this helps somewhat.

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

Bobby Jenkins wrote:

. > Greetings and Salutations:

. > I have an upcoming project, (residential), with a conventional floor 
. > framing system. The owners have a 700 pound piano supported with three 
. > small legs. The floor framing system will consist of hardwood flooring 
. > over 3/4" plywood, (or equivalent), supported by 2x12 floor joists. As we 
. > can not control the location of the point load, how can we support the 
. > concentrated load of the piano leg?  

. > In the cases, we had limited allowances for movement due to the room 
. > shape and blocking was added to resist the concentrated loads. With this 
. > project, the piano may be anywhere on the first floor.

. > Any thoughts, suggestions, directions will be greatly appreciated.

. > Thanks!

. > Bobby Jenkins, P.E.

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