Punching shear verification of concrete walls

[Refaatfaraj]

Dear colleagues

Could someone point me to how the punching shear verification can be done for the indicated walls in the attached capture? The intended punching verification at the raft foundation level.
Or in this case the punching shear verification can be ignored?

Knowing that:

- I am using EC2 (the control perimeter at 2d). So the answer is Yes. Then how does control perimeter calculate?

Any help will be appreciated

Refaat

 

[KootK]

I think that punching shear would apply here just as it would with above grade walls.



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.

 

[Klitor]

http://www.eng-tips.com/viewthread.cfm?qid=412803

Control perimiter as equivalent column with dimensions dx1.5d

 

[Refaatfaraj]

Hi KootK & Klitor

Thank you a lot for your response.

IMHO that the challenge of this issue how shall we consider the overlapping between the control perimeter from grade walls and basement walls?
Because they are working as group to resist the punching shear stress.

As you can see in the attached capture from EC2 . The control perimeter is totally different.

I am trying to simulate this situation in the software by columns replacing the walls. But even that isn’t the accurate situation because the software is treated with each element (column) separately.

Or do you have another suggestion?

Would you please to point me to any reference or software can do the situation more exact?

Your help will be highly appreciated

Refaat

 

[KootK]

I'm not sure what you mean by "grade walls". Can you elaborate? You've got a few situations to consider and will need to exercise some judgment to figure out which are most appropriate:

1) For very long walls, punching shear basically reverts to one way shear checks.

2) For short walls, under gravity loads, two way punching shear checks may be sensible.

2) For any wall acting as a shear wall, it may be prudent to consider the wall rocking over in flexure and delivering it's load only at the wall tip as punching of the compression zone. Three sided critical perimeter.

This design guide tackles some related issues although not yours specifically: Link





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.

 

[Refaatfaraj]

Hi @KootK


Thank you a lot for your explanations .


May I know if I have to subtract the total force in the wall from the uplift soil reaction inside the control perimeter ? for example

Ved = 22000 KN ( the total force in the wall ) .

Wall length = 7 m , wall thickness = 0.30 m , d =0.825 m , soil pressures under the raft foundation = 200 KN/m2 and the control perimeter according to EC2 = 2d .

Perimeter length = a + 4 *d = (7000)+(4* 825) = 10300 mm

Perimeter width = b + 4*d = (300)+ (4*825) = 3600 mm

The area of perimeter = 10300*3600 = 37.080 m2

The uplift soil reaction = 200*37.080 = 7416 KN

Then the net force which is should be used in the punching shear verification under the wall = 22000-7416 = 14584 KN.

Do you agree with me for this approach ?

Best Regards
Refaat