Joist hangars and drywall screws

[DRP]

The NDS doesn't have a footnoted table for hardened nails, Appendix I does give approximate Fyb values, I'm assuming you were working from memory.

In 11.5.1.1 it reads "Installation requirements to common steel wire nails and spikes, box nails, and threaded hardened steel nails meeting the requirements in ASTM F1667. Nail specifications for engineered construction shall include the minimum lengths and diameters for the nails and spikes to be used.

11.1.5.2 it states "Threaded, hardened-steel nails, and spikes shall be made of high carbon steel wire, headed, pointed, annularly or helically threaded, and heat treated and tempered to provide greater yield strength than for common wire nails of corresponding size"

No such text for hardened screws. The only wood screw I'm seeing in the NDS is one with identical properties to a common wire nail. Yes you can use the formula for mode IIIs and plug in the Fyb of a drywall screw from the manufacturer. This failure mode is the bending of the fastener until the yield point is reached, the weak link isn't the wood it is the bending strength of the fastener. Using the formula I can about guarantee it is going to show the same thing smacking the side of the typical drywall screw is going to show, the screw will not be anywhere near the strength of the nail in this application. If someone on my crew wanted to argue for using a drywall or deck screw in place of a nail I would be happy to put my money down and let the loser pay the engineer.

Edit, you are allowed to predrill for a nail, IIRC up to 70% of diameter, if the replacement nail drops into a small enough screw hole it should be fine

 

[bgingras]

maybe someone already mentioned this, but not only is there an issue with the screws, but what about what it's all attached to? looks like 3/4" sheathing only? also looks like black screws used to attached 2 joists together?

 

[GHRoberts]

The NDS doesn't have a footnoted table for hardened nails, Appendix I does give approximate Fyb values, I'm assuming you were working from memory.

Table 12.3 G comes to mind. But that is only from "memory."

But my point was (and is) that there are approved methods of showing that a fastener is proper. Any AHJ who asks for engineering should not accept a guy swinging a hammer. You either have the math or not.

 

[DRP]

I do agree with you. I was actually proposing the AHJ swing the hammer, but yes the specs trump my demonstration.

If anyone is interested in this, some references, the NDS section on this is here;

http://cobweb.ecn.purdue.edu/~ramirez/CE479/FALL05/CE479WoodDesignNDS01Connections.pdf

The NDS commentary is here;

http://www.awc.org/pdf/NDSCommentaryCompressed/Part11WoodScrewspp133to139.pdf

General dowel equations;

http://www.awc.org/pdf/tr12.pdf

The ESR for Simpson structural screws;

http://www.icc-es.org/reports/pdf_files/ICC-ES/ESR-2236.pdf

These look like they would be interchanges;

http://www.grkfasteners.com/en/selection_guide.htm

http://www.uspconnectors.com/pdfs/18.pdf

The awc connections calc is another good resource. I've set it up here for a wood screw, metal side plate, SPF. Notice the note regarding bending yield strength, set it up for a nail and you will see the same requirement, that is the grade of steel we are talking about at a minimum;

http://tinyurl.com/6ael4z7

While you have the NDS up look at table 10.3.3. notice the strength hits you take for dowel type fasteners (nails and screws) lateral loads in wet wood that subsequently dries. Off Topic, for withdrawal look down at threaded hardened nails... that is where they shine.

I do have an RFI in with FastenMaster re: deck screws, I'll post their response

 

[Daddy-0-]

Screws are fine as installed.....just add a 2x2 ledger underneath. HAHAHAHAHAAH.