Beam to steel beam connection with wood spacer

[jeffhed]

I have a project where a new aluminum beam is framing into an existing steel beam (perpendicular). The aluminum beam is fastened to the steel beam with an angle clip on each side of the beam. There is an existing 1/2" thick wood siding exterior that was going to be removed at the beam connection points and the new beams fastened directly to the steel beams. Apparently they have installed the clips over the top of the wood siding and the addition is competely installed and now the inspector is questioning the discrepancy. Before my connection worked fine. Now I am a little unsure how to analyze the connection. The wood will crush a lot easier than the steel or aluminum and has weakened the connection (trying to figure out exactly how much). If I transform the wood to steel, it is non existent compared to the steel and since it actually would increase the steel thickness a small amount it would increase the connection capacity so that way doesn't seem correct. If I transform the steel to wood then the calculations will look at bearing failure in the wood which can really only happen in the 1/2" wood siding so that doesn't seem completely correct either. The third option seems to be to calculate the capacity in the 1/2" wood by itself but this feels a little too conservative becuase I won't be able to get the connection to work in the 1/2" thick wood. In my mind the screws are almost cantilevering from the steel beam through the wood since the wood is so much softer than the steel but maybe this is also too conservative. But thinking of it this way also makes me concerned that wind pressures and fatigue could be a problem? Has anyone looked at something similar to this before (I'm sure someone has)? What is the correct way to analyze the connection to determine how much weaker the connection is? It's almost like a double shear problem but load is only on one side.

 

[CANPRO]

A sketch would help. What is the load in the connection? Is it mostly dead or live load? Shear, axial, moment? What is this new aluminium beam supporting? I have a bunch more questions, but I think a sketch would answer most of them.

 

[jeffhed]

I have attached the detail showing the new aluminum beam connecting to the steel beam.

 

[jeffhed]

I have attached the same detail with a red line showing roughly where the wood spacer is.

 

[CANPRO]

its almost impossible to read the text or see the details in the sketches. I think if you attach a clearer sketch with some loads shown, you will get some helpful responses.

 

[structSU10]

AISC has info on filler plates for bolts (J5.2). I don't know if it really is applicable to TEK screws, and the wood may be too compressible, but anything over 1/4" needs the shear capacity reduced for the bolts.

Also, how do you deal with galvanic corrosion between the steel and aluminum?

 

[jeffhed]

Sorry,
I guess the snipping tool didn't use a very high resolution, but it didn't look that bad on my screen. This one should be clearer. As far as galvanic corrosion goes, the aluminum and steel will be powder coated and/or painted and the steel is painted so they are not in direct contact.