For the component design of 1D objects, you can use both members and member sets. While the use of members is usually sufficient for cross-section checks, member sets are often required for stability analyses. The importance of member sets for steel design is explained here.
Using Member Sets
The use of a member set is particularly necessary for stability analyses so that the critical load for the lateral-torsional buckling analysis is correctly determined or the entire component length is taken into account as the effective length: For members, only the respective member length is considered. For this reason, it is generally only possible to perform cross-member design checks of the structural component with member sets. The nodes between the members of a member set can be considered as intermediate nodes in the Effective Lengths or Boundary Conditions dialog box.
As an alternative, you can model straight, uniform structural components as continuous members with nodes on members. The stability analysis is then also possible without member sets. However, some stability design methods can also design branched 2D structures as “one structural component”, for example the general method according to EN 1993-1-1 (see the chapter Boundary Conditions). In this case, the use of member sets is mandatory.
Design of Member or Member Set
The members that are part of a member set can be designed either as a member or using a member set. In order to avoid conflicting entries and results, the associated members are automatically deactivated for the steel design in the case of the design as a member set. If you define the members for the design, the higher-level member set is deactivated accordingly. You can check this rule in the Objects to Design input table by listing the objects in the “Not Valid / Deactivated” column.
After the design, a message is displayed in the Not Valid / Deactivated result table (see the chapter Overview) for all members that have been designed with a member set and thus deactivated. Similarly, member sets are marked there with a note if they have not been designed.
Assigning Design Properties
You can assign the same design specifications to a member set as to a member. Based on the restriction that it is never possible to design a member set and a member at the same time, a query appears after activating the design properties of a member in the member set asking whether to design the other members as well.
If you assign design properties to a member set, all included members receive the “Via parent member set” design property. This prevents contradictory entries.
If there is no member set yet, you create a new member set using the
button in the Design Properties section. Click the
button to edit the selected member set.