Composite beam with gap between concrete and steel

[DKLA]

Hi,
I am designing a composite beam with a 5/8" gap between concrete and top of steel beam.
I have 8" concrete slab. I am considering the following factors in design:
1. Bending of studs; and
2. slippage of concrete vs. steel.

Any other things I should consider?

Thanks

 

[rowingengineer]

I don't really understand, what is in the gap, if noting, are you relying on the studs to take the compression too? a sketch would be nice, because i can think of a lot of things if it is the case above.

Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that them like it

 

[DKLA]

I have a waterproofing layer (bituminus+mirror drain). Total thickness is 0.5".
Compression is a good point.

 

[rowingengineer]

I still don't understand, but here is a few things just for fun: punhcing shear if the stud is too long,Flange bending for the beam, rusting of the exposed stud due to the cervice created.

Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that them like it

 

[DKLA]

I have attached a sketch. This should help.

 

[mobe]

DKLA,
This looks a bit dodgy, mate. I think that with the other parameters you have to consider with composite design, like loads in construction phase prior to full design loads, propping issues & costs for shear studs etc. that unless this a huge job I would design as non-composite. I also think that the gap between the concrete & the top of the beam is not covered in your average design info. If this is metal deck permanent shuttering is the stud a special or could it be out of its normal design zone? Too many ifs. Ignore the composite action as it could be argued this is not truly composite & you may have a deflection issue.

 

[rowingengineer]

is there any reason the water proofing layer needs to extend so far over the beam?

Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that them like it

 

[apsix]

As RE said, why not overlap the WPM 25mm or so with the flange, leaving a strip of concrete in contact with the beam.

I'd be interested to know why corrosion of the beam is not an issue when protecting the slab with a WPM is required.

 

[DKLA]

Thank you for all your input.
A few clarifications/improvements to the detail:
1. Create pockets of concrete around the stud by starting and the stopping the mirror drain. Bituminous layer will run continuous.
2. Water seepage to floor below is major concern.
3. False work will be provided which will be adequately shored between beams.
4. Check studs for combined shear and bending.

Any other input?
Thanks in advance...

 

[rowingengineer]

Probably not the way I would do it, I would have considered using a difference system of water proofing, given the control of construction needed to ensure the water proof membrane is not harmed.

Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that them like it