I design a tapered beam and get the message: 'Non-designable: ER051) Moment about z‑axis on asymmetric cross-section, taper or set of members'. Why?

Answer

The reason for this warning is that tapered cross-sections cannot be designed by using the methods 6.3.3 of EN 1993‑1‑1. The RF‑/STEEL EC3 module designs such cross-sections by using General Method 6.3.4 of EN 1993‑1‑1. However, this method is only allowed for loading in the support direction, that is, without the transverse bending moment. Therefore, the warning appears.

You can perform the stability analysis as cross-section design according to the second-order theory, which is possible by using the add‑on modules RF‑/FE‑LTB or RF‑/STEEL Warping Torsion.

As an alternative, you can neglect the transverse bending in the filter options of the 'Details' dialog box, the 'Stability' tab, or activate the adapted method according to Naumes in the 'National Annex' dialog box, which enables transverse bending.

Keywords

Transverse bending Equivalent member method General Method Naumes Set of members Tapered member Taper Stability analysis Moment about axis z ER051 Non-designable

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RSTAB Steel and Aluminium Structures
STEEL EC3 8.xx

Add-on Module

Design of steel members according to Eurocode 3

Price of First License
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RFEM Steel and Aluminium Structures
RF-STEEL EC3 5.xx

Add-on Module

Design of steel members according to Eurocode 3

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1,480.00 USD