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Punching Shear of slab meeting a lengthy column

Punching Shear of slab meeting a lengthy column

Punching Shear of slab meeting a lengthy column

My case is as follows
Three floor beams are meeting at a column(225x1000 mm) at one of it's edge as given in the figure attached. I wish to know whether the other end of the column will susceptible to punching failure of the slab and if so how to determine the punching perimeter of that zone
thanks in advance

RE: Punching Shear of slab meeting a lengthy column

I am not sure what building code you are designing to, but the Eurocode addresses the issue of punching shear at the ends of walls (similar to your situation).
I have yet to see anything in the ACI that addresses this situation.

Decon/Jordahl's punching shear program takes this into account.

Page 11/28 of this attachment has some information as well

RE: Punching Shear of slab meeting a lengthy column

Thanks slickdeals. I am using ECs

RE: Punching Shear of slab meeting a lengthy column

I think another tricky part here is to assess what the load on the tip (punchable area) of the column is as a percentage of the total load on the column. It's likely that a lot more of the load goes to the stiffer beams on the back side of the column, so you may not have an issue at all.

RE: Punching Shear of slab meeting a lengthy column

Adding a couple of 25M bot bars into the wall extending into the slab helps a lot, too.


RE: Punching Shear of slab meeting a lengthy column

Would agree that the Eurocode equations won't necessarily apply to this case when you have beams. Also don't think the 1,000 mm is too lengthy. I can see studrails being an overkill in this situation based on my judgment.

RE: Punching Shear of slab meeting a lengthy column

I think it's a good call for OP to be looking into this. The moment connection to the columns is likely to be a lot stiffer than the torsion stiffness of those spindly 225 X 550 beams. There's no safety concern with the beams in play but you'll not have a happy owner if the nose of that wallumn ends up popping through somebody's tiled floor.

My guess is that the moment connection between column and slab will take the form of a vertical couple like this:

- The beams providing slab hold down.
- Wads of compression at the nose of the column.

So yeah, my instincts run the same as OP here. I'd go with the Euro provisions because, well.. I'm not sure there is anything else. Some manner of reasonable C-perimeter around the nose. And the integrity bars that dik mentioned. If things do crack up, that should keep ti from getting too far out of hand.

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: Punching Shear of slab meeting a lengthy column

thanks all

Are you referring to a one couple of bent up bars over the column or just one couple of bottom bars anchored down to the column. What would be more effective??

Yes. It is hard to apply Euro codes directly to this situation. Yes it is also true that the length of the column also matters as you can't say at what threshold value of column length would the punching is going to critical.

When working out a reasonable C-perimeter, 2d perimeter distance can be drawn around the nose of the wallumn to the front and sides. But how would it be when it is approaching to the back side(beam side)??

RE: Punching Shear of slab meeting a lengthy column

The following documents may help:

Eurocode 2 doesn't specify a distance from the wall tip to consider the control perimeter but the German and Austrian national annexes, as well as MC2010, specify a distance of 1.5*d. An appropriate reduction of the control perimeter length should also be used to take into account load eccentricity. MC2010 does this using a ke reduction coefficient of 0.75.

RE: Punching Shear of slab meeting a lengthy column

Thanks a lot avscorreia

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