STAAD.Pro is capable of performing design operations on specified members. Once an analysis has been performed, the program can select the most economical section (i.e., the lightest section which fulfills the code requirements for the specified member).  The section selected will be of the same type section as originally designated for the member being designed.  Member selection can also be constrained by the parameters DMAX and DMIN which limit the maximum and minimum depth of the members.