Composite Action?
Composite Action?
(OP)
Got another project where I have to analyze some steel bar joists for additional load. There is metal deck over the joists and a 4" total thi kness slab over that. The 22 gage deck is composite with the concrete and the deck is welded to the joists. There are no shear studs.
In the analysis of another engineer a few years ago, he apparently assumed that the bar joist, deck and concrete were all working together in partial composite action, modeling the joist as a W section with the transformed section of a partially composite beam with nominal shear studs.
Personally, I have a real problem with assuming any composite action for the steel bar joist assembly, as one would have to rely on the weld between the 22 gage decking and double top chord angle of the joist. If the decking was 16 gage, I would have to think about it a little harder. Just a little. My feeling here may create a huge problem for the client.
How do others feel about this?
In the analysis of another engineer a few years ago, he apparently assumed that the bar joist, deck and concrete were all working together in partial composite action, modeling the joist as a W section with the transformed section of a partially composite beam with nominal shear studs.
Personally, I have a real problem with assuming any composite action for the steel bar joist assembly, as one would have to rely on the weld between the 22 gage decking and double top chord angle of the joist. If the decking was 16 gage, I would have to think about it a little harder. Just a little. My feeling here may create a huge problem for the client.
How do others feel about this?
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com






RE: Composite Action?
RE: Composite Action?
It's been a couple of years since I looked at it. But, I seem to recall that the method of transferring shear between concrete and joist was not usually related to studs. I remember seeing one with a deformed top chord and another that relied on friction.
My point being only that using composite action for that system may not as unreasonable as it first sounds.
RE: Composite Action?
RE: Composite Action?
Puddle welds without weld washers and inspection are not reliable for design.
RE: Composite Action?
RE: Composite Action?
Nothing like stirring up the pot for a little fun, eh?
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com