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Nail connection factors
- To: <seaint(--nospam--at)seaint.org>
- Subject: Nail connection factors
- From: "Alexander Sasha Itsekson" <sasha(--nospam--at)engstruc.com>
- Date: Thu, 19 Dec 2002 15:29:16 -0800
Happy Holidays to
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
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=1.25. 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 embedment.
3. Using 16d
nails connecting two 2x members the provided embedment is 1.5 inch <
12*0.162=1.944. Can I use Cd=1.0 if I specify that the nails are to be
4. Any other
thing that I should consider in designing this joint such as predrilling of nail
holes, close attention to edge distances etc?