Boundary Nailing For Unblocked Floor Diaphragm

[2meterman]

I'm designing a basement with an adjacent garage so that the wall is completely backfilled and also has a potential wheel load as a surcharge on the basement wall.

My calculations show that the reaction at the top of the wall is 550 lbs horizontal. I've looked through my NDS books and all the values I find for blocked or unblocked diaphragms are for wind and seismic loads.

Does anyone know where I can find tables or values for blocked/unblocked diaphragms that are for dead loads. Or is there a method I am missing for just calculating the shear capacity of the nails and sheathing. The floor is using Engineered Lumber (I-joists) but I don't think that will have an affect on the diaphragm loads.

I'm assuming that the published values for wind and seismic have been increased by the load duration factors. Do I just divide the published values by the duration factors?

Any input would be greatly appreciated. If I can't get big enough diaphragm values then I guess I'll have to design
a beam in the top portion of the wall to resolve the horizontal loads.

Thanks in advance for everyone's help.

 

[Lion06]

I may be mistaken, but I don't think the values for diaphragms can be calculated by a rational method. I believe they are based on testing.
Try looking in IBC, I haven't looked at it in a while, but I don't remember the values being specified for seismic or wind only.

 

[samdamon]

APA report #138 ("Plywood Diaphragms") has a note on page 2 saying that tabulated shears (for wind and seismic loading) can be reduced 25% for "normal" loading. The chart this note refers to provides allowables for blocked diaphragms.

The copy I have is dated 2000 and is based on the older 97 NDS.
Check with the APA to see if they have a newer version,

http://www.apawood.org

 

[2meterman]

I just had another idea. All the tables refer to roof and wall diaphragms. The thicknesses of the sheathing only go up to 19/32.

My situation is for a floor diaphragm using 23/32 sheathing. Has anyone seen a table or report that covers floor diaphragms w/ 23/32 sheathing?

 

[ChipB]

2meterman,
The published values should be reduced by 25%. In other words, if the tabulated value is 400 plf, you would use 300 plf, then, if you decide to classify the load as permanent, C_d=0.9 and now your value is down to 270 plf.

Also, look at your bolts from the wall to your sill plate. I believe I already had a thread on this.

Can you tie the top of your wall into the garage slab, and carry the tensile forces across to the opposing garage wall? If you do this, you'll need to you the "at rest" pressure of 60psf equivalent fluid weight for your wall design.

 

[PMR06]

Two ideas that don't directly answer your original question, but may help:

Can you dowel the garage slab into the walls or pour it over the wall?

Can you devise a detail in which the floor joists drag strut the wall load into the floor diaphragm?

BTW, Where is the load going once it is in the adjacent floor diaphragm?