New Inactive Members

Tekla Structural Designer
Tekla Structural Designer
release notes
update release notes

New Inactive Members

This new feature enables the definition of members which are required for load decomposition but that you do not wish to be considered otherwise by the analysis, nor to be designed, and is a companion feature to the new Line and Area Ancillaries feature described above. However it potentially has a considerably wider use and appeal for many types of structure, for example in defining staircases as shown in the second image below. For more information see the new Help topic Inactive members.

  • As shown in the picture above, the option to set members inactive - by unchecking the member properties “Active” checkbox - is now extended to the Beam, Purlin (Track) and Rail (Stud) characteristics (formerly limited to Brace and Analysis elements). Furthermore, all loads applied to inactive members are now decomposed to the rest of the structure.

    • Load decomposition - during the pre-analysis load decomposition stage, the inactive members receive decomposed loads as normal (which could be from two-way as well as one-way spanning slabs etc). The resulting end reactions are then calculated and applied during this stage to supporting primary members. Only these resulting loads are then carried forward into the subsequent global analyses.

    • Review View > Show/Alter State - a new “Active” Attribute is also added to the Review View > Show/Alter State options, enabling rapid graphical review and editing of the Active status of members (see picture below)

  • Staircases - A clear general use-case is for staircases and members (that the engineer does not wish to be designed or add additional stiffness to the structure) supporting the landings and top/bottom of staircase Area Ancillaries, as illustrated above right. As shown, the inactive members transfer the area load of the staircase to the supporting primary members/ supports, but will not add any additional stiffness to the analysis model.

    • There can be many other use-case scenarios for industrial structures and line/ area ancillaries e.g. the engineer may be required to allow for equipment and associated access arrangements that will be supplied by others during fit out of a plant.

    • Note another use-case for staircases, could be an area ancillary stair spanning onto a slab edge. This is currently beyond scope, however an inactive member can be added along the slab edge to provide the required load path (requires slab to be meshed in 3D). Note that, while this ensures the load is applied, it will introduce some approximation as the ancillary line load (see “Stage 1” above) becomes two point loads at the ends of the inactive member.

  • Other potential use-cases are:

    • Cladding Members - secondary/ tertiary members such as Purlins (Studs) and Rails (Joists) supporting cladding are typically modeled primarily to decompose wind wall and roof loads and to provide design restraints to main structural members. They are commonly cold rolled/ formed and so are not designed within the program.

      • However, they may develop internal forces - such as axial loads - and/ or cause additional forces in the main structural members that are neither expected nor desired by the engineer. Furthermore, their results can clutter the Results View Analysis result diagrams, obscuring those of the main structural members in which the engineer is principally interested.

      • Both these problems can now be avoided by setting such members to be inactive, as illustrated below - load applied to the inactive members is applied as required to the main structure (during the pre-analysis load decomposition stage), but a) they are not included in the analysis model and so do not develop any internal forces and b) hence there are no analysis results for them to clutter the Results View diagrams or output.

    • Grouped Design - Inactive members could be used to speed up the Design process where group design is enabled, by limiting the number of active members in a group.

      • So for example for regular floor arrangements, where all the beams in the group have very similar forces, only one beam could be set as active and designed rather than every beam in the group (which could run into 10’s or more) thus improving performance. For this scenario note that:
        • Only secondary beams can be inactive - primary beams must be active to provide support to secondary members in the analysis model.

        • The user is responsible for choosing critical beam(s) (an initial design run could establish this then all other beams inactivated for subsequent design runs).

    • Wind Wall & Roof Panel Supports - where previously the engineer may have used inactive Analysis elements to assist with the support of Wind Wall and or Roof Panels - for example for overhangs or at the base of vertically spanning walls - inactive beams can be used.

      • All loads decomposed to such members will now be applied to the structure/ supports where previously they would not (errors in the Load Summary check would highlight this issue to the engineer).

Was this helpful?