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Re: Tongue and groove diaphragm

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Will,

The IBC and UBC have tables for both floor (vertical) uniform loading (also
tabular info is based on ability of panels to support concentrated loads), and
for shear loading when wood structural panel floors are used as diaphragms.
Choose the panel thickness based on floor loading and joist spacing; and also
check with floor topping mfrs. requirements for panel thickness based on joist
spacing (some mfrs. require thicker subfloors than code minimums for specific
joist spacings, to avoid or minimize cracking of floor topping under applied
concentrated loads such as foot traffic or wheeled loading such as when moving
appliances or furniture with hand carts), and also with UL or code requirements
for fire-rated floor system designs (if applicable).

After you have selected the required floor panel thickness for the joist
spacing, then determine subfloor nailing to resist the diaphragm design shear
load for your application.  In general, the subfloor sheathing is considered
unblocked for diaphragm design, if T&G wood structural panels are used for most
typical applications, for example when 23/32 in. thick panels are used.
Specifying blocking beneath the T&G joints could be done if required in areas of
high shear near the ends of the diaphragm, or over interior shear walls if the
diaphragm is continuous over these elements (with appropriate nailing, blocking
and connections to transfer shear forces from the diaphragm to the shear walls
below).  When the shear capacity of the unblocked diaphragm is equal to or
greater than the diaphragm design shear, then the blocking can be omitted.  It
is also possible to use stapled continuous sheet metal strips over the T&G
joints to develop a blocked diaphragm; contact the Help Desk at APA - The
Engineered Wood Assn. (help(--nospam--at)apawood.org; or tel. 253-620-7400) for more info on
this application, as well as diaphragm design info and info on wood structural
panels used for floors, and for fire-rated construction.

And yes, it is common to glue the wood structural panels to wood framing with an
elastomeric construction adhesive, to stiffen the floor system, and eliminate or
reduce the potential for floor squeaks.

Good luck; hope these comments help to develop the details for your application.

John Rose
APA (retired)
Tacoma, WA

Will H wrote:

> Thanks, I see that ACI 99 21.7.4 limits the use to minimum of 2.5" for
> diaphragm acting non compositely.
>
> I also found the tables in IBC for T&G vertical load spans.
> Can I just now use the diaphragm tables based on 3/4" plywood for my 3/4"
> T&G for nailing patterns etc. or is there anything else I need to address
> specifically for T&G diaphragms? I understand it is also common to glue the
> T&G floor as well.
>
> >From: "Will H" <haynewp(--nospam--at)hotmail.com>
> >To: seaint(--nospam--at)seaint.org
> >Subject: Tongue and groove diaphragm
> >Date: Fri, 10 Jan 2003 12:05:10 -0600
> >
> >--------------------------------------------------------------------------
> >Your following message has been delivered to the list
> >  seaint(--nospam--at)seaint.org at 10:32:18 on 10 Jan 2003.
> >--------------------------------------------------------------------------
> >
> >
> >
> >I have 3 story buildings (60'x60'plan)which will have tongue and groove
> >floors with 1.5" of lightweight concrete topping. The walls are wood stud
> >with gyp board.
> >
> >I have not worked with T&G before. I am looking for advice on what the
> >standard attachment is and the minimum attachment of the T&G if I consider
> >my concrete to be acting separately as my diaphragm.
> >
> >thanks
> >
> >
> >
> >
> >
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