STAAD Foundation Punching Shear - Fail. Mat Slab Design

Question

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

Kris Sathia · Accepted Answer

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.

Kris Sathia · Answer

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.

Kris Sathia · Answer

Here is a sample calculation for the area of steel for flexure for a mat per the Eurocode. PDF

STAAD Foundation Punching Shear - Fail. Mat Slab Design

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