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Re: Nail connection factors

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Dennis Wish, where are you?

Alexander Sasha Itsekson wrote:

 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=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 clinched.4.  Any other thing that I should consider in designing this joint such as predrilling of nail holes, close attention to edge distances etc? Thanks in advance,Sasha Itsekson, SE