I built a STAAD model for the design of a concrete basin (aka tank) and have zero columns in my design yet the program will not run all the way through because as you can see from the snip below "columns are missing." Can someone please help me to understand what columns this program is expecting to see?
I have reviewed your model (which you send to support) and found that the subtype of the walls are defined as WALL_TANK.
When you use this subtype, it is intended that you will be using the water tank structure module in RCDC. If you set it none this wall will be used as a general wall or shear wall in RCDC. So, with your model you should try to enter in water tank structure module in RCDC. But this module is only available for Euro code for the time being. So, if you choose any code from Euro code group this option will be available to sue and you can choose that.
Once you follow these steps you will be able to import the structure. Hope this helps.
I am attaching few links for videos related to this water tank complete workflow.
https://www.youtube.com/watch?v=iYo8NeC8lzw&list=RDCMUC7zF2mK5oLl64VMzh-FOwoQ&index=2
https://www.youtube.com/watch?v=abFpeQym9jo&list=RDCMUC7zF2mK5oLl64VMzh-FOwoQ&index=15
https://www.youtube.com/watch?v=auw3XLt-mvE&t=322s
https://www.youtube.com/watch?v=FdwBlTMxGtY
If you want to design the walls as per other codes, please change the subtype to none manually in command file and rerun the file and try.