Raft Foundation Punching Shear Check Scope & Limitation

1. Punching shear check can be performed for columns and discrete walls supported on raft foundation.
   
2. Punching shear check cannot performed for merged core walls supported on raft foundation, as the shear perimeter is irregular. 
3. Punching shear check cannot be performed for piled raft foundation, as shear perimeter is complex & influenced by irregular piles location. 

Please ensure that FE Raft Foundation Analysis must be completed before performing punching shear check, i.e. the checking cannot be performed in the absence of soil stress data. 

Refer to this article : Raft Foundation and Piled Raft Foundation Analysis & Design Example

Punching Shear Check Procedure

1. In Storey 0, select/ multiple select the columns.
   
2. Click  Column Punching Check  under the Column tab
   
3. The punching check for raft foundation dialog is similar to the punching check for wall and columns, the only difference is there are an extra column "Soil Pressure" and an input field for the value of "Tributary Area of Column Ave Soil Pressure" in punching check for raft foundation dialog. 
   
   Adjust the settings here if necessary. For other parameters and settings in this dialog, please refer to Column Punching Check.
4. Please enter the value of Tributary Area offset in the input field and the soil pressure will be automatic detected. 
   

"Tributary area offset" allows you to adjust soil pressure by adjusting offset distance from the edge of the column. If you want the column to cover more it's tributary area, you can increase the value in this input field and soil pressure will adjust accordingly.

5. Click Calculate and result will be generated in report format.
   
   

The raft can similarly be designed by accessing the FE Foundation Analytical Model and by looking at the As(d) contours for bending.  Refer to : FE Storey and Foundation Model