At right angle means the screw is loaded in shear rather than tension right?
And that's why screwing in deck boards is good, but not for joists. Use nails for that instead, unless using engineered screws.
So I'd be curious if you'd do the same strength test but with nails: end nailing and toe nailing. After all you did end screws and pocket screws...
I'll add that your "Smashed deck repair hack job" is very interesting... the deck is attached by mortise and tenon joints? I keep reading about ledger boards and joist hangers, so I'm just... surprised? And you replaced posts in hole with essentially deck blocks! Very interesting... Thanks!
Your failures mostly amounted to the joint pulling apart along the glue interface rather than breaking, I suspect adding a transverse retaining pin will make the failures more interesting with significantly higher loads.
Did you consider doing any tests with a retaining dowel or some nails/screws through the mortice and tenon joint?
The transverse pin weakens the tenon and the piece of wood it goes into. If the joint is well designed (so that the glue strength and wood strength are balanced), the tranverse pin only weakens the joint.
