Column supported on a slab - punching shear

[gmd255]

im from Europe so I use Eurocodes (I believe ACI has similar control).
Lets say we have a column on a slab that is supported by walls (green lines in pictures).
Eurocodes give us 3 options for control perimeter (punching shear):

1. column is in the middle of a slab,
2. column is on / close to the edge of a slab,
3. column is at / close to corner of a slab.

Im asking what happens to a control perimeter when column is close to walls that supports a slab. Should I draw/use a control perimeter for punching shear as a combination of above options because its not 100% corner/edge column? Im talking about a bottom column in the last picture. The column is to close to the walls to use OPTION 1, but I think if I consider that control perimeter (punching shear of a slab) can appear right next to walls it is OK?

 

[DETstru]

The way I see it is you have two potential failure modes:

A. The column punches through the slab. Similar to how you have shown it in your last sketch. The result would be a big hole in the slab.

B. The wall/slab connection fails. this would be most likely at the corner. In this case, the wall below punches through the slab and the column/slab connection stays intact.

See my sketches.

 

[gmd255]

DETstru thank you!

I agree with 1. I think I have to calculate a control perimeter as you draw it and use it in a punching shear control.

Well in case 2. thats a slab shear control not a punching shear right?

 

[DETstru]

Correct. Case B is just slab shear.