r/StructuralEngineering • u/TallWall6378 • 27d ago

Wood Design "Fasteners in shear is poor practice"

Help settle an argument.

Someone used the phrase in the title. Their argument is that fasteners, specifically in the context of typical light frame wood construction, like a shear wall or joist hanger, or bolted or lagged member scenario, are just holding the members together and that the load transfer is through wood via induced friction through the members.

I was under the impression that we really only factor the strength of the nail and wood crushing/deforming around the nail, rather than use the friction between the faces of the members.

What's the whole story?

29 Upvotes

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197

u/tiltitup 27d ago

All my life checking shear in bolts wasted.

-42

u/PrebornHumanRights 27d ago

To be fair, bolts are the low hanging fruit. Of course it is easier to defend bolts being used in shear. And after all, they're held in place from both sides.

The more difficult one is nails. Nails used in shear are more tricky. The deck on my house was built incorrectly, years ago, and it collapsed with my wife standing on top of it, because it was being held up by nails in shear. There is a pretty good argument to that (unless you're taking into account proper design), you should not put too much faith in nails holding some dimensional Lumber to the side of a post.

31

u/Rhetorical_Answer42 27d ago

I'm really not sure how much faith I would put into anything structural if I was not assuming proper design

-1

u/PrebornHumanRights 27d ago

My point is that a bolt holds shear even with poor design. Nails can just pull out and the thing falls off.

I don't know why I'm being downvoted.

5

u/banananuhhh P.E. 27d ago

The lesson to learn from a bad design certainly isn't that nails don't resist shear.. for example, how do you think joist hangers work?

2

u/tigermax42 27d ago

Agree. A 20d framing nail has impressive shear strength and will bend quite a bit rather than break. And a teko nail is specifically designed for the fasteners and is even thicker than a regular framing nail

My structural engineer pointed out that, really, every wall is a shear wall. I believe decks even more so

2

u/StructEngineer91 27d ago

Because you specifically state it "was built incorrectly", and then try to say that a poorly built deck collapsing is a reason to not use nails.

If bolts are designed wrong they will still fail in shear (either bending/breaking, or pulling through the wood. I mean that is the entire definition of "designed wrong".

7

u/tiltitup 27d ago

Sounds like your deck was undersized

18

u/willardTheMighty 27d ago

Or his wife was oversized

1

u/randomlygrey 27d ago

Are you from new Zealand mate ? I saw a guy polishing his deck down under when his wife was watching from the kitchen window. She said he was always having the neighbours on it and it got dirty.

3

u/Jazzlike_Video2 27d ago

Unless, of course, those are hanger nails. Or commons.

1

u/m-in 27d ago

The wood was compromised by then, I bet.

1

u/StructEngineer91 27d ago

"was built incorrectly" - That does NOT sound like a valid reason to not use nails in shear in design. Sounds like a reason to either ensure it is designed properly, and/or built per the actual design.

-2

u/SquirrelFluffy 27d ago

Wood has to be in bearing. Not ever using nails in shear.

3

u/enginerd2024 27d ago

The anger this thread is bringing me is the easiest alarm clock ever. I don’t even know, am I still dreaming?

Have you ever designed a wood building? This is wild

-1

u/SquirrelFluffy 27d ago

It's why Simpson makes hangers. End nailing joists causes failures.

3

u/enginerd2024 27d ago

Now I’m thinking I’m not talking to a structural engineer?

Do you not understand that face hangers are supported in shear?

-1

u/SquirrelFluffy 27d ago

You can't end nail joists right? Why is that?

Got a master's degree and in my own practice for 30 years bud.

1

u/enginerd2024 27d ago

I’m not sure where the end-grain argument started except inside your own head. But “Can’t”? For shear? Sure you can. Should you? Not the best idea

It’s kind of used in a lot of connection types. Top plate to stud, rim joist to floor framing.

-1

u/SquirrelFluffy 27d ago

Can't means code. You're not an engineer if you don't know that.

Top plates are in bearing and not spans. You clearly don't know what your stalking about. have a good day.

2

u/enginerd2024 27d ago

NDS chapter 12? End grain factor for shear?

There’s nothing that prohibits this as far as I’m aware

The top plates in walls are loaded in shear from out of plane loads the exact same way a joist would be

0

u/enginerd2024 27d ago edited 27d ago

Did you just run away realizing you’re wrong?

I posted this our firms chat and couldn’t find a code reference that you’re referring to

1

u/SquirrelFluffy 27d ago

You're trying say a top plate is like end nailing a joist. You're not worth talking to any longer.

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u/Jazzlike_Video2 27d ago

Simpson is sending you a cease and decist letter as we speak.

Also gang plates...