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Nail connection factors

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answers are keyed to your questions:

1) Yes. The 7-day load duration factor is for construction loads and applies
to fasteners as well. See NDS Table 2.3.2. 

2) The clinching increase only applies to double-shear nailed connections.
There's more background on this in the 1997 NDS Commentary section 12.3.3.

3) No. As stated above, the clinching provision only applies to double-shear
nailed connections, so using 1997 NDS you'd have to take the penetration
reduction if it's less than 12D. However, in the 2001 NDS, the connection
provisions have been revised and the penetration depth factor is no longer
required for calculated values since all six yield modes are used to
determine design values for dowel-type fasteners (i could provide more on
this in a separate thread if anyone is interested).

4) I think someone responded that you would be adding additional moment to
the rafter with this type of connection. There are adjustment factors in
AF&PA's Wood Frame Construction Manual (WFCM) for One- and Two-Family
Dwellings, 2001 Edition Tables 3.26A-H (which are also incorporated in the
2000 IRC Tables R802.5.1 (1-8)) to account for that if you haven't already
done so.


Buddy Showalter, P.E.


From: Alexander Sasha Itsekson=20
To: seaint(--nospam--at)
Sent: Thursday, December 19, 2002 2:29 PM
Subject: Nail connection factors

Happy Holidays to everybody,
The architect in his wisdom decided to replace ceiling tie joists with =
the collar ties at the midheight of the pitched roof. The pitch is 4:12 =
and the roof rafters and collar ties are 2x8's.
Anybody who tried to design the rafter to tie connection knows that it =
is difficult to put enough fasteners in the joint to resist the tie =
tension. In this case I have around 2500lbs of tension.
I have a few questions:
1. The table 3.5 of the NDS'97 Structural Connections Supplement =
lists Construction loads and doesn't list roof live load as a typical 7 =
day duration load to be used with the C_sub_D=3D1.25. Can I still use a =
25% increase in allowable shear values for my fasteners for the =
connection at roof framing design?
2. I remember from way back when that if one specifies clinched =
nails, then one can use a 100% increase in allowable shear value. I =
looked through NDS and the only reference that I could find is a 100% =
increase when used in a double shear application. Don't we get an =
increase capacity due to the fact that the nail withdrawal is not an =
issue in lateral nail loading or is it just equivalent to a 12D =
3. Using 16d nails connecting two 2x members the provided embedment is =
1.5 inch < 12*0.162=3D1.944. Can I use Cd=3D1.0 if I specify that the =
nails are to be clinched.
4. Any other thing that I should consider in designing this joint =
such as predrilling of nail holes, close attention to edge distances =
Thanks in advance,
Sasha Itsekson, SE

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