In Window 1.4, you can define lateral supports for members. RF-/STEEL EC3 always assumes these intermediate supports to be perpendicular to the cross-section's minor axis z (see Figure 2.20). Thus, it is possible to influence the members' effective lengths (only for Lateral and torsional restraint type) which are important for the stability analyses concerning flexural buckling and lateral-torsional buckling.
In the upper part of the window, you can assign up to nine lateral supports to each member. The Settings section shows the entry displayed in a column view for the member selected above.
To define the intermediate restraints for a member, select the check box for Lateral Restraints in column A.
With the 
button you can select the member graphically to activate its row in the table.
When the check box has been selected, the fields where you can enter the parameters are available.
In column B, you can select the Restraint Type from the drop-down list. A lateral and torsional restraint is preset. It is also possible to place intermediate restraints at the lower or upper flange. The User-Defined option allows you to specify the restraint parameters individually (support in direction of member axis y, restrained about longitudinal member axis x, eccentricity of support) in the Settings section.
In column D, you can define the Number of intermediate restraints. Depending on the setting, you can access one or more of the following Intermediate Lateral Restraints columns for defining the x-locations.
When the check box for Relatively (0 ... 1) is selected, you must define the support points by relative input: The locations of the intermediate supports result from the member length and the relative distances to the member start. It is also possible to define the distances manually in the table, if the Relatively (0 ... 1) check box is cleared.
Set of members
If sets of members are designed according to the equivalent member method (see Chapter 3.1.2), supports of the lateral and torsional restraint type within the set of members must be defined here. Such restrained regions must not be described by effective lengths in Window 1.6!
You can find an example of using intermediate lateral restraints in our Knowledge Base:
https://www.dlubal.com/en-US/support-and-learning/support/knowledge-base/001557