SACS is not very good at dealing with this type of situation (as far as my experience). SACS is good at dealing with beam elements (where it uses "Timoshenko Beam Theory" to solve its beams).
SACS does offer this information about plates:
"Plate offsets can be used to model transition points...
Any joint that is called out as a "dummy" joint must be only part of the dummy structure only (as in a joint in the center of a primary column is not a dummy joint).
The user manual states:
"Loading incurred by the dummy structure is distributed to the boundary joints assuming that the dummy...
There is an indication (shown in the members Unity Check) of if a member is exceeding the Euler Buckling parameters. This is explained in the output file as:
(2) IF THE AXIAL COMPRESSIVE LOAD ON A MEMBER EXCEEDS THE EULER BUCKLING LOAD, THEN THE AXIAL UNITY CHECK VALUE FOR THE MEMBER IS...
