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Re: Simpson wall anchors

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at 06:42 PM 2/16/99 -0800, you wrote:

>>Do you just consider that the plywood and joist are tied together and
>>essentially form a composite?

        I do, except that I don't just "consider" it on faith, but ensure
that it works that way by adding enough additional nails from plywood to
joist beyond the strap to take care of the shear along the faying surface
that the strap nails generate by their action. These nails are in addition
to what nailing for diaphragm shear requires, and enough width of sheet must
be provided to absorb these nails and the strap length too. Treat yourself
to a free-body diagram or two as a check.

        This concept accepts that the sheet is acting in direct tension as a
splicing medium. You can look up plywood strength values in the APA Plywood
Design Spec and find out if the breed of plywood you are using can handle
this splice stress and diaphragm stresses simultaneously. I think I know
what you will find, and it will amaze you how much stronger plywood is than
the closest allowable nailing pattern's strength. But you have to impose
sheet layout and dimension demands to make this scheme viable, and then be
prepared to show why recent code prescriptives against using diaphragm
sheathing for multiple purposes should be waived. One argument could be that
the first 3/8 inch of the floor sheathing serves as the diaphragm, and the
top 3/8 serves as the splice. Isn't it a pity that latter-day code revisors
are forcing engineers into becoming Philadelphia lawyers?

>>or do you use longer nails?

        I would do this as a supplement, but not as a replacement for
developing composite action by extra nailing beyond. Simpson's short nails
are short versions of Common Nails; no difference in wire diameter. Extra
length goes clear through the flange of the TJI and looks untidy. The straps
have holes for Common Nails, with rare exception. Verify all that in the
catalog.(I have capitalized Common Nails because of the holy regard in which
they are held in the Los Angeles area.)

Charles O. Greenlaw  SE    Sacramento,CA
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