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RC Slab punching check

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Message 1 of 7
rodainnajjar1229
2304 Views, 6 Replies

RC Slab punching check

Dear Sir
kindly find attached file.
i have to check punching for slabs but i have problems:
for example : slab no.209
see( pic 1): for case S75 we have Q=1783.91kn
but we i check shear in model ( pic 2)
Q=3130-2287=843 KN
and when we calculate shear stress ( to take into consideration shear forse +portion of unbalanced moment by eccentricity of shear ) =1.53 mpa but in robot more than this see (pic 3)

Best Regards

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6 REPLIES 6
Message 2 of 7

The value of Q includes the unbalanced moment so it is expected to be larger than the difference in axial forces from the columns. The later value should be displayed as Maximum punching force after you select S75 on the list of varification points.

 

punching force.PNG

 

Could you attach your hand calculations (1.53 MPa) please? That would help in investigating this situation. Thank you.



Artur Kosakowski
Message 3 of 7

Kindly find attached file

Message 4 of 7

Thank you. I'll try to have a closer look at it. Mind that bending is approx. 244 kNm (162.65 + 81.8).

 

bending2.PNG



Artur Kosakowski
Message 5 of 7

kindly find attached file

Message 6 of 7

As far as I can see the difference is in the way the critical perimeter is calculated. Robot reduces it due to the nearby opening.

 

For slabs Robot assumes the rectangular stress distribution.

 

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

 

 



Artur Kosakowski
Message 7 of 7

@Artur.Kosakowski Is it fine to release the moments at bottom of column if it is connecting to a raft slab? The unbalanced moments in the column will be removed then and will transfer only axial force for punching check, but still I'm skeptical with Q(admissible) value calculation in RSA 2023. Do you have any background of RSA punching figures please? Does RSA takes "effective depth" of slab in in control perimeter calculation as per EC2 6.32?

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