beam - slab... shear?
beam - slab... shear?
(OP)
Hello guys.
If I have a column supported on a reinf. concrete slab I may have a punching shear problem. I can solve this by making a bigger column cross section dimensions or by making a thicker slab.
What I want to discuss is what happens if I add a beam that is partly integrated with a slab. Does this mean that punching shear of a slab is no longer an issue since shear forces are taken care by a beam? Is there a possibilty of shear along the beam (between the beam and a slab). For this to happen I suspect that deflection of a beam should be huge or that load on a slab is really big.
To make it short - by adding a RC beam bellow a column, we dont have to worry about a slab punching shear any longer? Everything depends on shear resistence of a beam?
If I have a column supported on a reinf. concrete slab I may have a punching shear problem. I can solve this by making a bigger column cross section dimensions or by making a thicker slab.
What I want to discuss is what happens if I add a beam that is partly integrated with a slab. Does this mean that punching shear of a slab is no longer an issue since shear forces are taken care by a beam? Is there a possibilty of shear along the beam (between the beam and a slab). For this to happen I suspect that deflection of a beam should be huge or that load on a slab is really big.
To make it short - by adding a RC beam bellow a column, we dont have to worry about a slab punching shear any longer? Everything depends on shear resistence of a beam?






RE: beam - slab... shear?
RE: beam - slab... shear?
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RE: beam - slab... shear?
RE: beam - slab... shear?
You should use deep beam to support a column above the slab. Try using strut and tie model.
Or you can use transfer slab.
Keep in mind slabs under a concentrated load will be subject to radial positive moments and circumferential negative moments around the downward concentrated load (in contrast to slabs supported by columns).
RE: beam - slab... shear?
RE: beam - slab... shear?
RE: beam - slab... shear?
I would have thought there is still a chance for the column to punch through the slab and beam if the load is a large one?
Please correct me if I am wrong.
Thanks.
RE: beam - slab... shear?
RE: beam - slab... shear?
No....at least not from a 2-way (punching) failure......however, as I pointed out in my post above, there still is the possibility of excessive one-way shears between the slab and the beam (or wall) based on relative stiffness & loads. (Similar to the "beam shear" in the B-B sketch in the OP.)
RE: beam - slab... shear?
What if the beam were a wider and shallower "band" and the critical shear perimterer was wholly within that banded area?
Then we would be back to a punching scenario right?
Thanks for helping me clear up my understanding of the topic.
RE: beam - slab... shear?
RE: beam - slab... shear?
Both punching and beam shear need to be checked when you have a concentrated load on a wide beam, where the critical perimeter is wholly within the beam area (plan).
On a side note, I don't believe extra longitudinal bars help with punching shear capacity (using AS3600). The depth to the steel is the only thing considered, in the case of PT 0.8D is used.
I'm curious how other codes handle it?
Is anyone able to post an excerpt or an explanation of how other codes treat longitudinal steel in a punching shear scenario?
Thanks
RE: beam - slab... shear?
However, it's likely that most slab bands and beams design for appropriate deflection criteria in a scenario like this, won't have punching shear problems.