Question:
I cannot define effective lengths for the design of a set of members in STEEL EC3. Am I doing something wrong?
Answer:
In addition to the stability analysis in Section 6.3.1 to Section 6.3.3 of EN 1993‑1‑1 (Equivalent Member Method), RF‑/STEEL EC3 provides the General Method according to Section 6.3.4 of EN 1993‑1‑1.
This can be extended with the following options:
~ The European lateral-torsional buckling curve, regulated in the German National Annex to EN 1993, for example.
~ The adaptation for biaxial bending according to a dissertation by Dr. Naumes.
~ The interpolation between lateral buckling and lateral-torsional buckling.
When designing sets of members according to the General Method, a window is available in Window "1.7 Nodal Supports - Sets of Members" where the nodal supports are displayed graphically on the set of members. This way, the General Method represents a useful supplement to other design methods; it has proven itself particularly when designing tapers. It is not necessary to enter effective lengths in this method.
In the "Details" of the add-on module, you can select the method to be used for sets of members in the "Stability" tab (see Image 01).
The equivalent member method may only be used for straight sets of members with a uniform cross-section (that is, not for tapered joints). For members with a variable cross-section, use the preset General Method.
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