Tongue and Groove IBC Nailing Requirement 2304.8

[Yao1989]

I have a question. When designing a 64mm T&G deck, does anyone know why the IBC has this requirement for nailing between planks? It states that for 64mm deck:


2304.8.5.2 Nailing. - Each piece shall be toenailed at each support with one 40d common nail and face-nailed with one 60d common nail. Courses shall be spiked to each other with 8-inch (203 mm) spikes at maximum intervals of 30 inches (762 mm) through pre-drilled edge holes penetrating to a depth of approximately 4 inches (102 mm). One spike shall be installed at a distance not exceeding 10 inches (254 mm) from the end of each piece.

However, for 38mm deck, it only requires:
2304.8.4.2 Nailing. - Each piece of decking shall be toe-nailed at each support with one 16d common nail through the tongue and face-nailed with one 16d common nail.


I find it very hard to understand why a 38 deck only require 1 nail between any 2 given pieces, I would expect that a 64deck maybe require a bigger nail and 2 nails between any 2 given pieces; the nailing specified by code is rather disproportionate to my intuition. In any case, I follow Canadian code, i.e. O86-14, and I could not find this requirement anywhere, so I am not, by code, obligated to follow this. However, I am curious to why the IBC specify such requirement. If anyone can enlighten me to why the nailing requirement between 38mm and 64mm deck is so drastic, I would be very appreciative.

 

[msquared48]

My perception would be that for a 1.5" as oppose to a 2.5" member, there could be more of a warping force generated in the thicker member, hence nails in tension - face or toenails - would be more likely to fail and separate from the supporting joist or beam in tension rather than the bearing generated by the longer 8" course to course nails. In essence the 8" nails help spread any warping force between two or three members, not just one.

Just guessing...

Mike McCann, PE, SE (WA)

 

[Yao1989]

That definitely sounds possible. I was imagining maybe it is diaphragm requirement, but I thought IBC doesn't even recognize T&G as diaphragm.

Still, for such hefty detail to be a code requirement that is so hard to justify by intuition, I would imagine some kind of publication would exist to explain this code requirement.

:S

 

[msquared48]

Have you checked the NDS?

Mike McCann, PE, SE (WA)

 

[Yao1989]

Did a search through NDS 2015 edition. Did not read anything regarding nailing requirements for tongue and groove.

I also thought about the possibility that the nails are required for a "system factor", or "repetition factor" which allows increased capacity by 1.15. Interestingly though, Clause 4.3.9 in NDS 2015, which talks about the Cr factor reads:

"A load distributing element is any adequate system that is designed or has been proven by experience to transmit the design load to adjacent members, spaced as described above, without displaying structural weakness or unacceptable deflection. Subflooring, flooring, sheathing, or other covering elements and nail gluing or tongue-and-groove-joints, and through nailing general meet these criteria".

English is not my first language, but this reads to me that tongue-and-groove joints alone is sufficient to take advantage of the repetition factor, so that crosses out another reason.

 

[KootK]

With the different layups, not all of the boards will make it to supports. So some lateral shear transfer capacity is needed. Comparing 64 to 38, you've got 2.77 times the capacity based on bending but only 2.00 times the capacity for shear transfer. Perhaps the spikes make up the difference. One would think that sizes of the tongues and the grooves of the 64 mm board would be adjusted to eliminate the nailing. Perhaps there's a practical reason why that is not so.

I like Mike's theory too.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.