This window appears only if at least one set of members is set for design in the 1.1 General Data window and the Equivalent Member Method for sets of members is selected in the Details dialog box (see Figure 3.2). Then, Windows 1.7 and 1.8 are not displayed. In this case, lateral intermediate supports can be defined in Window 1.4 by using division points.
The concept of this window is similar to the previous Window 1.5 Effective Lengths - Members. Here, you can enter the effective lengths for buckling about both principal axes of the set of members, as described in Chapter 2.5. They define the boundary conditions of the set of members that is handled in its entirety as an equivalent member.
In our Knowledge Base, you can find an example of entering effective lengths for sets of members:
https://www.dlubal.com/en-US/support-and-learning/support/knowledge-base/001557