The Design menu > {Steel, Concrete, Composite Beam, Composite Column, Steel Joist} Design > Make Auto Select Section Null command is used to remove auto select section lists from selected frame elements. Typically auto select lists should be removed from all frame elements near the end of the iterative design process so that the final design iteration is completed with actual frame sections assigned, not auto select sections.
Setting the auto select section to null does not change the current design section for the frame element.
Make Auto Select Section Null as follows:
Select the Analyze menu > Run Analysis command to analyze the model.
Select the Design menu > {Steel, Concrete, Composite Beam, Composite Column, Steel Joist} Design > Start Design/Check command to initiate design. Use the other commands to advance design to near completion.
Select the elements whose auto select sections are to be made null. If no elements have been selected, this command will not be available. Often selecting all elements is the easiest approach.
Click the Design menu > {Steel, Concrete, Composite Beam, Composite Column, Steel Joist} Design > Make Auto Select Section Null command to remove the auto select section list.