NDS Toenail Conx. Subject To Lateral and Withdrawal Loads

[codySTR]

I've dug myself into a deep hole of confusion on a topic that is probably very routine and simple: How do you apply the NDS equations to check a toenail connection subject to both withdrawal loading and lateral loading?

Instead of a sketch of this situation, refer to to the 3D image in figure 1 in the AWC Design Aid 2 document here: Link

The particular connection I'm designing/checking is as depicted in the link. I have a 2x6 DF-L parapet stud toe-nailed to a 2x6 wall bottom plate (in the structure there is also a knee brace to brace the parapet stud, but that is not important). The toe-nail connection is subject to 120 lb uplift/withdrawal and 65 lb shear/lateral. Both forces are small, I realize, but I want to understand the correct application of the NDS provision.

I thought I'd start with NDS Section 12.4.2, which covers Combined Lateral and Withdrawal Loads for Nails and Spikes. However, based on the definition of variable "alpha", this seems to pertain to the situation where the fastener is loaded at an angle to the wood surface. Does that apply in my case? Would I simply find the angle of the resultant measured relative to the vertical stud axis? Or relative to the horizontal plane of the main member (wall bottom plate)? It doesn't seem right to do this based on the definition for "alpha". Thoughts?

 

[phamENG]

Alpha won't be from the toe nail angle, if that's what you're asking. You'll take your shear and your uplift and combine them to get a single resultant force, as determine the angle of that force. That's your alpha. Adjust your Z' for the lateral loading (considering all factors including the toe nail factor) based on alpha and you'll be good.

 

[codySTR]

pham: Right. To clarify, I was not thinking I'd need to find the angle of the toe-nail itself, but rather the angle of the resultant relative to _____. Is (blank) the vertical stud axis parallel to the uplift force, the horizontal sill plate axis parallel to the applied lateral load, or ...? This confuses me because the given definition of alpha is the "angle between in the wood surface and the direction of the applied load, degrees". But what is the "wood surface" in my case? This determines the angle alpha. And furthermore NDS Figure 12F shows the force at an angle to the wood surface (true to the definition of alpha) in a configuration different than what happens with the combined withdrawal and lateral loading on the toenail connection I have. Does equation 12.4-2 still apply?

 

[phamENG]

Ah...I see your confusion now. Notice that the result of that section is Z'[sub]α[/sub], not W'[sub]α[/sub]. Z is your lateral, W is your withdrawal. So it's the angle between your resultant and a purely lateral load - I'd use the sole plate wide face as my "wood surface".