Why is it that the concrete column interaction diagram is not plotted in the output although track 2 was specified?
If you open the file in the STAAD editor (go to the Edit menu, and choose Edit Input Command File), and go to the end of the file, you will observe the following :
CLB 0.25 MEMB 1 TO 481DESIGN ELEMENT 1 TO 456 458 TO 481DESIGN COLUMN 457TRACK 2 MEMB 457END CONCRETE DESIGNFINISH
The TRACK command has to be specified before the DESIGN commands. In others words, the order of these commands must be the following :
CLB 0.25 MEMB 1 TO 481TRACK 2 MEMB 457DESIGN ELEMENT 1 TO 456 458 TO 481DESIGN COLUMN 457END CONCRETE DESIGNFINISH
If you make this change, you will get the interaction diagram.