When designing a frame it is often convenient to group members together and treat them as a single member for the purposes of design. This is often the case when a physical member in a frame has been subdivided into a number of members in the Multiframe model.
Members can be combined into a single design member in the Frame Window. To create a design member,
Ø Select the members to be grouped
Ø Choose "Create Design Members" from Group menu.
or
Ø Press Ctrl+D
The members that form each design member are displayed in the Design Details and Design Efficiency data tables.

To delete or split design members, select members that are part of the design member(s) and choose "Ungroup Members" from the Design menu.