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
Solved! Go to Solution.
Solved by Artur.Kosakowski. Go to Solution.
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.
Could you attach your hand calculations (1.53 MPa) please? That would help in investigating this situation. Thank you.
Thank you. I'll try to have a closer look at it. Mind that bending is approx. 244 kNm (162.65 + 81.8).
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.
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@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?