Leaderboard

mhdhamood, Since you have increased the column thickness in one direction only, my proposed solution may or may not work in the present case. You will have to verify it, by treating the 'enlarged column neck' as the part of mat footing. In order to deal with punching shear, you normally need to increase shear perimeter 'bo'. This may be done either by increasing thickness of footing (more common and simpler), or by increasing the column size. I was talking about the first option (increasing mat thickness locally), whereas you are tackling the problem using second option (increasing column size). If you are interested in using locally increased footing thickness (instead of increased column size concept), you may do it easily in SAFE along with proportioning of required reinforcement. Regards.

Dear The reason is when we suddenly increase the size of column for example from 600 to 300, the forces accumulated at these locations. Actually at each joint the lateral forces normally distributed to adjacent members and also to the below columns. If you suddenly reduce the column size there are much chances of improper stress/forces distribution. So a gradual change is required. Secondly in your case you are suddenly increasing the size at Slab on Grade level. This situation is much more complex. Your structure in soil (structure from slab on grade to foundation level) act as one unit. It means there will be much inplane shear force at slab on grade level. Your complete structure will vibrate starting from slab on grade not from foundation as you provided much thicker columns below slab on grade and made this portion rigid. If you increase the size and do not model slab on grade, I think it will not be good. You can model slab on grade and check the inplane forces distribution at slab on grade level. In this case you can be sure that increasing the column size is affecting or not. This is my concept, anybody can disagree........