Help settle a bet about the capacity of a wood connection:
We have a beam 2) 2×12 #1 SYP that are fastened together with nails. One of the 2×12’s extends about 2 1/4″ farther than the other and that one 2×12 is supported by 6) 20d nails into a 2)2×6 wood column (#2 SYP) and there is a wood “cleat” underneath the one 2×12 that is nailed. The wood cleat has 2) 20d nails into the 2)2×6 column.
We are trying to ascertin the capacity of the connection.
I think the nail capacity is approximately 185 pounds per nail so roughly the capacity is 8 x 185 = 1480 pounds. The other side of the bet is taking the position that 1) the nail capacity is greater than 185#/nail and 2) the shear capacity is equal to the shear capacity of BOTH 2×12’s together. Remember, only one of the 2×12’s is actually connected to the column with 6) 20 d nails and it is also supported by (bearing on) the “cleat” with 2 nails in it. The other 2×12 stops just short of any support. The 2) 2×12’s are fastened together by an as of yet unspecified nailing pattern but I can’t think of any pattern that would allow for all the shear load to pass into one of the 2×12’s and then have that one board anlone be connected. Sure the bearing capacity of the contact area would be 1907# but the cleat only has 2 nails into it so that doesn’t seem to me that it can be justified.
I see the shear capacity as equal to 2/3 x 1.5 x 11.25 x 90psf =1012.5#. Conceivably this could be increased with a Ch factor equal to 2 for a beam with no splits or checks but I am leery of that with so many nails in it at the end connection. The nailed 2×12 is only lapped over the face of the column by 2 1/4″.
I can not find any justification in the 1997 NDS (the one recognized by our building code) for either a greater nail capacity OR the greater shear capacity.
Is anyone familiar with the NDS justification for either position?
BTW the beam is supporting a storage load.
Your thoughts are appreciated.
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Draw a pix, I'm not going to try to read all that text and draw my own pix.
Are you talking vertical or horizontal shear also.
Sounds like you are busy turning a hack job into a rocket science project and missing the obvious. The end of the two by with only 2-1/4" will split out long before those nails fail in shear, and it is easy to add a couple nails to the block under and/or to get some hardware from Simpson brought into play here.
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No need to get all high and mighty. I realize that finding a solution to the support condition is relatively simple. I am not asking about that. I am looking for an engineering analysis of the code (NDS) allowable capacity. In our particular case, it is going to be helpful toward motivating all to do what is right by being able to demonstrate on paper what the allowable capacity is.
If anyone is familiar with NDS and any provisions that would permit greater nail capacity and/or justification for the total shear being equal to the shear capacity of both the connected/supported piece and the unsupported piece, I would liek to see it.
Thank
PS, I'll try to get a detail posted later.
That sounds like a real half-a$$ed connection that I would find completely unacceptable.
It is!
And it seems to me that it would be incumbent on the original designer to demonstrate the adequacy. Unfortunately that may not be available to me and I want to be sure of my position regarding any provisions in the code that could possibly justify it before I make too big of a stink.
Thanks
Well, why didn't you say so?
It will fail. Don't be shy about raising a stink.
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"We are trying to ascertin the capacity of the connection."
Just load it up until it fails.
An enginering analysis should not cost too much and has more value than our opinions.