rectangular to round concrete columns

[calculor]

Curious if anybody came across a situation where the architect wanted to change the shape of a column from one floor to the next. In my situation the architect wants to change from a 12x24 concrete column to a 20" dia. column. How do you detail column reinforcement?

 

[csd72]

Is it a beam between these, or a flat slab?

If it is the latter then I would probably require a drop panel to assist in transfer of stresses.

If it is abeam, make sure it matches the width of the widest column dimension.

 

[271828]

You'll just have to terminate a few of the bars coming up from the bottom column with 90 deg hooks and add others going up into the upper column as necessary.

As for transferring the axial load in the 4" +/- part of the upper column that doesn't have any column below it: it depends on how heavily it's loaded. Maybe it would be good to place a small layer of polystyrene under the part that overhangs the column below. Make sure the smaller part of the 20" dia column above is plenty strong enough to transfer the load. It depends on the magnitude of the load, presence of moment, etc., whether this makes any sense or not.