Cutting off the top or bottom?
You would need two 0.75" x 4" plates
Steel is about 10 times as strong as wood
A 9.5" deep beam is 5.6 times as strong as a 4" deep beam
A 3.5" wide deep beam is 2.3 times as strong as a 1.5" wide beam.
2.3*5.6 is about 13, so the steel is right on the money
But the wood will fail before the steel reaches its capacity because of the load share. They don't share load according to strength, they share load according to stiffness.
And I apologize on the ratio, A36 steel is 7 times as strong as an LVL with Fb of 3100 psi
Screws transfer toad they don't carry load
Right. But they only transfer, they don't carry. The steel and wood carry
Not quite. Two MC4x13.8 will match the strength and stiffness
But that's 5" wide
It doesn't match the strength and stiffness. It's close to the strength, but stiffness is only 60%
I'm trying to match what is there
I would sister the channel on one side and a plate on the outside
Or a custom shape. I can design a custom shape as an additional service if you're interested
I see. I think you need a custom shape then. It's the only way to match the strength and stiffness of what is there now
Do you have any other questions for me on this topic? If you could rate my answer, I would appreciate it.