I am modeling a foundation on rock and wish to extract the resulting bearing pressures (Sigma yy) at the base of the footing. Should I plot draw the line cross-section directly under the plate element or at half footing thickness away from it (i.e. at 1m)?

Question

The foundation is modeled as a plate element having the following properties: 
 EA = 59450820.01 kN/m EI = 19816940 kNm2/m w = 26 kN/m/m (considering a unit weight of 24 kN/m3 for the underlying rock and a footing thickness of 2m) 
 Please note that the weight (w) of plate has been is calculated as 
 (unit weight of concrete * thickness of footing) - (unit weight of rock * 0.5 * thickness of footing) 
 where, 
 unit weight of concrete = 25kN/m3 
 thickness of footing = 2m 
 unit weight of rock = 24 kN/m3 
 The following snapshot gives a better understanding of the problem:

Dennis Waterman · Answer

Dear Boulos, 
 If you draw it directly underneath you will get the stresses directly underneath and if you draw it at half footing thickness you will get the stress at half footing thickness below the footing. This is of course completely up to you, you should choose what you think is representing best what you need or what your local building code requires. With kind regards, 
 Dennis Waterman