Wood joinst with nails loaded in shear 1

[StructFton]

Hi All,

I am evaluating a wood joist joint that involves loading some common wire nails in shear. Basically the joint is simple, involving nails driven through a spandrel joist, and into the end grain of a floor joist (see attached). Typically, I have used joist hangers for this application in the past...however this time I am getting some resistance to this idea which is why I am evaluating the attached joint.

I want to determine the # of nails required, and I am designing the joint to CSA O86-01. The most relevant clause is 10.9.4 'Lateral resistance' of spikes and nails; however, this clause is for 'lateral' resistance for nails driven perpendicular to the grain, while my joint involves nails driven parallel to the grain (of the floor joists) and the forces are acting vertically.

My questions are:

1) Any suggestions if I am using the correct clause to calculate the capacity in shear for the nails?
2) If so, what is the penetration of the nail supposed to be into the joist?
3) Is this joint even allowed, and thus I should push back with the joist hangers? I don't want to do this just if I am not familiar with different types of wood joints.

Thanks

 

[Lion06]

I think that's a bad detail. You will get very little capacity out of that. I'm not familiar with your design code, but using the NDS you multiply the values you get for side grain by 0.67 to account for the end grain.

 

[StructFton]

Thanks for the post. I agree the detail is not ideal.. we have the same end grain factor in the canadian code. My question is two part...1) is the the detail fundamentally flawed (not just a matter that I won't get much capacity out of it), and 2) does the clause I list even cover the arrangement of this detail.

Look forward to any comments

 

[Lion06]

I don't have your code, but in the NDS, we would get the capacity for a nail driven perpendicular to grain and apply the end grain factor of 0.67 so that seems reasonable to me. Read the commentary for your end grain factor to see exactly how it is applied, but I would imagine it is the same as the NDS.

There is nothing fundamentally wrong with the detail, I just don't like it much.

 

[msquared48]

Personally, I never, but never, rely on end grain nailing for any loads. Use the side-nail joist hangers, or Simpson A35's.

Mike McCann
MMC Engineering

 

[hokie66]

Agree with Mike. Never depend on nails into end grain. So yes, I think the detail is fundamentally flawed.

 

[StructFton]

Hi All,

Thanks for the input. I will go with my first thoughts and push back with joist hangers

thanks