Timber Deck to Steel Beam Top Flange Nailer

[marinaman]

What has been your experience fastening heavy timber decking to double 2x6 nailers? 3" heavy timber T&G decking has a fastening pattern required by AITC 112-93 as one 60d face nail per timber plank support and a 40d toe nail per plank at the support. If the double nailers are SYP No.2 2x6's atop the steel beam top flange, bolted to the top flange, have you guys had any difficulty with splitting of the 2x6 nailers when fastening the heavy timber decking? The decking must be in a mixture of simple and two span continuous layup (due to architectural constraints) and can not be random layup. I am pre-drilling the holes thru the timber decking.

 

[structuresguy]

Well, the first thing I would worry about is the fact that a 60d nail, at 6" long, will not drive flush thru a 3x6 plank and double 2x nailers. It will be 1/4" too long.

Beyond that, I would worry about splitting if all the nails will be located along a straight line. I would try to stagger them side to side, across the width of the 2x6 nailers.

 

[SlideRuleEra]

40d and 60d nails in 2x6 SYP would cause a (splitting) problem in SYP. Two suggestions to try:

1. Cut or grind the points off every nail. A blunt nail will cut its way thru wood instead of acting like a wedge to split it. Withdrawal resistance is reduced... but may?? be an acceptable compromise.

2. Use 2x6s of a (less dense) wood species that is not as likely to split.

For "General Observations of the Nailing of Wood" see:

http://www.fpl.fs.fed.us/documnts/fpltn/fpltn-243.pdf

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[marinaman]

Thanks Structuresguy. I had realized in my NDS that the 60d nail was too long, even though the code mandates the 60d face nail, and I have completed the calcs for a 50d facenail, simply to get a shorter nail. The code also requires a 40d toenail at each board support. It seems to me that what is going to have to happen, where planks butt end to end at a support, is that the 50d face nails and the 40d toe nails can not be aligned along the same nailer grain, or the grain will split....and also, the planks will need to be pre-drilled for the face nail and the toe nail.

Does this sound like what you guys have done before?

 

[msquared48]

Ever thought of predrilling the decking and the double 2X nailer and using wood screws instead of the spikes?

Mike McCann
MMC Engineering

 

[structuresguy]

My personal feeling is that the wood code is giving you prescriptive fastening for non-engineered design. I think that you should be able to engineer a connection solution that is applicable to your particular structure and loading and use that instead of the spikes. I have used 2x6 T&G planking here in FLorida many times, and I have never used spikes that size, and never had an issue with any building department. I design a nailing pattern that works for my shear and uplift, and use that. This, IMO, is why we have engineers. Otherwise, contractors could just use all the code prescriptive design and we would not be needed.