Is there a back to back channel fastening pattern?

[see_gen_notes]

I know that there is a nailing pattering for built up wood beam. I'd like to know if there's a similar pattern/ standard for back to back channels to be used as beams.

 

[dik]

Are you talking steel channels... if so, I use 1-1/2" long fillet welds spaced at 12" on the compression side and at 18" on the tension side...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[see_gen_notes]

I'm using aluminum channel but I assumed that the connection would be same if not similar. I'm trying to avoid welding as I am building channel frames and then fastening them together in the field. I'm currently debating on weather I want to do two rows of fasteners when my channel is only 4" or do a staggered offset.

 

[dauwerda]

you definitely don't want to weld it if it's aluminum.

 

[Tmoose]

Using aluminum makes the channels only about 1/3 as stiff as steel, and probably much more expensive.

The modulus of elasticity of the wood is probably no better than 1/3 that of aluminum.

I'm wonder what properties need to be matched in your composite beam.
I suspect some kind of adhesive might be helpful or even necessary for real composite action.

 

[EdStainless]

The other issue to watch when fastening Al is the risk of galvanic corrosion.
If there is any risk of moisture reaching this you really need to take special care.

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P.E. Metallurgy, consulting work welcomed

 

[see_gen_notes]

@EdStainless they plan to fully insulate the area, spray foam an all. So there shouldn't be any moisture. On a slightly different note, my guy says he needs to run a conduit through all of my joists and beams. Is there such thing as a stiffener plate that I can put around the opening to transfer the load?

 

[Tmoose]

For floor joists there are rules about safe plumbing/electrical hole locations and size to not compromise bending stiffness and strength.