Shear Stud pattern for composite decks

[BoHboH]

Hey everyone, I'm trying to get a gut feel for amount of shear studs (stud pattern) etc cause I have never had to design them. Situation is: 3.5" overall thickness composite decking with light weight concrete; joist are spaced every 4ft. The goal is to get the shear into the joists to transfer it into the building framing down to foundation. I can't seem to find a typical pattern or layout for shear studs. I came up with 3/4" studs at 2ft on center at ever joist. I then had someone recommended I add them in between joists every 16" on center (so instead of 1 row every 4ft at the just the joists there would be 1 row every 16") and that just seems like overkill.

What have you guys seen as typical?

Thanks in advance!

 

[KootK]

Are your joists open webbed steel joists? Or just beams?

Are you going for composite flexural action or transfer of diaphragm shear? Or both?

I don't get the 16" oc thing. Wouldn't that mean welding the studs directly to the decking with no framing below?

 

[BoHboH]

@KootK: they are open web joists.

I care about transfer of diaphragm shear.

Yeah the extra studs make no sense to me either. They basically would only serve as extra 'hold' between decking and concrete.

 

[KootK]

I feel that 2' oc is pretty reasonable. I don't know of a standard.

One thing to consider is that it will be difficult to prevent the studs from providing composite connection for flexure. So your design might benefit from considering both actions (diaphragm / flexure) according to the appropriate load casing.

I'm also not clear on why you would want to transfer shear at every joist. One usually only does that at the particular framing members which function as collectors. And most of your joists are usually not collectors.

Also consider that this setup may induce axial load into your joists. And that would necessitate additional bottom chord bracing to keep them from buckling.

 

[KootK]

They basically would only serve as extra 'hold' between decking and concrete.

That I can kind of sympathize with from the perspective of shear buckling etc. I usually consider the composite rib connection to the deck to be sufficient to brace the concrete. And I'm not even sure that the concrete needs much/any bracing.

 

[BoHboH]

Well, I figured out I have been thinking about this incorrectly; I don't need shear studs on the joists, I need them on the collectors that are supporting the joists. I apologize for the confusion.

 

[KootK]

No worries. If I weren't constantly mimicking the stuff that I see other engineers do, I probably would not have guessed the correct approach on a single thing that I've tried to do in the last two decades. Figuring out what the heck "normal" is in a give space is the challenge, always.