Composite action with hollow core slab
Composite action with hollow core slab
(OP)
Hello engineers,
I have a job where I need to remove a portion of a block load bearing wall in level 1 of a 2-storey building.
The attached sketch explains. To meet the required moment and the deflection limit, I wonder if I can assume a composite action between the steel beam and the slab. To make that work, and given that the compression force will be perpendicular to the hollow cylinders, I am assuming the max. moment resistance will be limited to the compression in the top flange of the slab. i.e. the Neutral axis at the top of the holes. Design the fasteners to meet the required horizontal shear.
All comments will be appreciated.
I have a job where I need to remove a portion of a block load bearing wall in level 1 of a 2-storey building.
The attached sketch explains. To meet the required moment and the deflection limit, I wonder if I can assume a composite action between the steel beam and the slab. To make that work, and given that the compression force will be perpendicular to the hollow cylinders, I am assuming the max. moment resistance will be limited to the compression in the top flange of the slab. i.e. the Neutral axis at the top of the holes. Design the fasteners to meet the required horizontal shear.
All comments will be appreciated.






RE: Composite action with hollow core slab
Your better bet would be to add channels to the CMU wall above the plank if you need to add more steel.
When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.
-R. Buckminster Fuller
RE: Composite action with hollow core slab
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Composite action with hollow core slab
RE: Composite action with hollow core slab
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Composite action with hollow core slab
RE: Composite action with hollow core slab
Yeah, we do. The big difference here is the ability of the hollow core webs to transmit the required horizontal shear up to the top flange, as you've rightly identified. They'll tend to act like small, brittle, unreinforced concrete vierendeel truss webs. Hence my mention of solid grouting the cores above.
Even when the slab is solid, I've always had concerns about the slack between the bolts and the plate. If there's much slip at all, it will take a ton of curvature before the straps will fully engage. A great, although costly, detail that I really like is cored holes in the slab and grouted in place Nelson studs attached to the strap.
If it's an issue of handling weight, could you supply your beam in two halves that get a bolted moment connection in the field? Or use two, stacked beams bolted together at the adjoining flanges?
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Composite action with hollow core slab