Hello,I have exported the load cases from a STAAD model to a foundation model in a previous version CE.09.03.0014, then I have an update of the software to version V9.5.0.62. With the previous version I got the following values for punching shear checking. (Shear forces per meter)
Now, with the updated version V9.5.0.62, the same model fails for punching shear and the results are expressed in shear stresses. These values seem to be incorrect.
In both cases, there is no way to see the procedure how was punching shear checks done. Find below StaadFoundation file.
.Silo_Found.sfa
We are looking into this and will get back to you soon.
Hello Kris, have you taken a look on this?
Joselin, apologies for the delay.
The punching results from both versions are wrong. We are releasing a new version by the end of this week which will have the correction for this error. I will provide you with a calculation in the next 1-2 days explaining how SFA calculates the punching shear stress in this upcoming version per the Eurocode.
Joselin,
Here is a PDF file that contains the punching shear calculations for column 1 for load case 305.
PDF
Version 9.6.0.62 of the program was released last week and has the correction to the error that was noticed in the earlier versions. Here is a screenshot of the results from this version.
Answer Verified By: Joselin Madueno
Dear Kris,
Can you tell me if the punching shear is wrong in previous versions (9.3 or 9.5 versions) of STAAD Foundation in other codes such as ACI, or this error is limited to the Eurocode check?
Thanks in advanced.
Hello Joselin,
The ACI code requires that if the column transfers any bending moment to the foundation, then the punching stresses in the foundation must be calculated taking into consideration the unbalanced moment (UBM) effect (ACI-318-11 clause No. 11.11.7.2 / ACI-318-14 clause No. 8.4.4). In other words, the total stress will consist of the contribution from the axial compressive force in the column, and the UBM effect.
The UBM effect was implemented in SFA for mat foundations and pilecaps only in version 9.5. In versions before that, the punching stress was calculated solely from the compressive force in the column + weight of pedestal.
You can find this mentioned in the What's New in CONNECT Edition V9.5 section of the SFA documentation.
So, depending on the relative magnitude of the moments and the vertical force, the UBM effect may be a small value, or might have a significant contribution.
So, to answer your question, in version 9.3, the punching stress under columns on the mat will not have the UBM effect. But in version 9.5 and later, that effect is included.
well explained, may i have a continuation of the attached pdf, on how the software calculates the required amount of steel in MAT foundation
Need some time. Will get back to you.
Thank you,iam waiting.