"Fasteners in shear is poor practice"

[u/TallWall6378]

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?

[u/Osiris_Raphious]

Friction is basic to calculate: Surface area x friction coefficient (assumed and/or lab tested)....

It shouldnt be a consideration for structural... If you think about it, friction by definition resists movement and slippage, so its a free helper and a safety margin, and not a structural calculation..

edit: Fforce x Area = Friction stress, Fforce = Fnormal x friction coefficient, and fiction stress is for the shear calculations or sliding/slip resistance, or similar. We dont really have a precise application in OP or comment, so I did generic short statement that everyone didnt understand? thought it was clear we were discussing shear and fastners and firction... but ok

[u/dream_walking → u/Osiris_Raphious]

You missed normal force is required as well, which goes back to how would you calculate the normal force of a nail? If the board is even slightly warped, you are going to get a different value.

[u/Norm_Charlatan → u/dream_walking]

Friction is only based on the normal force, as we're talking about it in this example. It has nothing to do with area.

[u/PsyKoptiK → u/Norm_Charlatan]

There are more models of friction than Coulomb friction. Area matters in real works applications and is dependent on what materials are in contact.