Punching shear

[mammut]

Hey,
I would highly appreciate any help in the following issue:
Reinforced slab is supported by round column. And there is load bearing wall on the top of the slab (see an image)
For example Eurocode 2 doesnt give any guidance how to take that wall in to a count when calculation the slab for punching shear (for example - how it affects the punching perimeter)?
At least i could not find anything..
Thanks in advance..

 

[KootK]

I think that it would be appropriate to treat the wall as a load source that does not otherwise affect the punching shear capacity. Most of its load will likely be delivered to the slab well away from the punching shear perimeter.

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.

 

[Lomarandil]

Agreed. I wouldn't take it to affect the perimeter (not in a way that we can quantify reliably).

If anything, you may be able to account for some load transferring more or less straight from the wall to the column and bypassing the punching shear just like some bearing pressure helps directly under the column in a footing. But don't get too aggressive there.

----
The name is a long story -- just call me Lo.

 

[mammut]

Hi KootK,
Thanks for an answer!

One important thing I forgot to mention ~98% of the load that goes to column comes from wall.

Then the question would be - what if the wall is directly over the column?
I guess - if in that case wall thickness is the same or bigger than column diameter - we could assume that there is no risk of punching ??
And second question - what if it's "almost" directly over the column?

Best Regards

 

[mammut]

Hi Lomarandil
Thanks for your answer!

Comparison with the footing seems very logical.
But anyhow its a bit different situation - so I wonder is there some design guides that addresses situation like this.

Best Regards

 

[KootK]

Then the question would be - what if the wall is directly over the column? I guess - if in that case wall thickness is the same or bigger than column diameter - we could assume that there is no risk of punching ?? And second question - what if it's "almost" directly over the column?

I'd recommend a process along these lines:

1) Do whatever analysis/judgment work is required for you to feel comfortable that you know the path by which the load in the wall makes its way to the column with a reasonable degree of accuracy, be it through the slab outside of the joint or by direct compression strut action at the joint.

2) Design punching shear to suit #1

3) Design your wall, also, to suit #1. If you think that all of your wall load is getting transferred to the column right near the punching shear perimeter, then your wall design will be significantly affection by local stresses in that area.

4) Take whatever "belt and suspenders" measures you feel are appropriate to cover any uncertainty that you have regarding the load path that you established in #1







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.