RF-/STEEL EC3 Version 5/8

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RF-/STEEL EC3 Version 5/8

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2.1.4 National Annex (NA)

National Annex (NA)

In the list in the upper right corner of Window 1.1 General Data, you can select the National Annex whose parameters you want to apply to the design and the limit values of the deformation.

Figure 2.9 Selecting the National Annex

If necessary, to check and adjust the preset parameters (see Figure 2.10), click the button. Use the button to create a user-defined annex.

Moreover, in every input window you find the [Nat. Annex] button which you also can use to open the National Annex Settings dialog box that consists of two tabs.

Base
Figure 2.10 Dialog box National Annex Settings - CEN, tab Base

In the individual sections of this tab, you can check and adjust, if necessary, the Partial Factors, the Serviceability Limits (Deflections), and the Parameters for Lateral-Torsional Buckling.

In the General Method Acc. to 6.3.4 section, you can specify if the stability analyses are always performed according to [1] clause 6.3.4. According to the German National Annex, the general method is only allowed for I-shaped cross-sections. The option Enable also for non I-sections allows you to use the method for other cross-sections, too.

In addition, you can perform a stability analysis using the European lateral-torsional buckling curve by Naumes [4]. In his dissertation [5], Naumes expanded the "General Method for Buckling and Lateral Torsional Buckling Designs of Structural Components" according to [1] clause 6.3.4 for additional transverse bending and torsion. The adapted method is also available for designing unsymmetrical cross-sections as well as tapered members and sets of members with biaxial bending (torsion is currently not considered in RF-/STEEL EC3).

According to [1] clause 6.3.4 (4), the reduction factor χop is to be calculated either

  1. as the minimum value of the values for buckling according to 6.3.1, or χLT for lateral-torsional buckling according to 6.3.2 using the slenderness ratio λop, or
  2. as a value that is interpolated between χ and χLT – see also [1] equation (6.66).

As the method by Naumes is based on the standardized European lateral-torsional buckling curve taking into account the modified imperfection factor α*, the interaction between flexural buckling and lateral-torsional buckling according to [1] equation (6.66) can be omitted.

Figure 2.11 Calculation run for method by Naumes

In the first step, the calculation is carried out separately for the main and secondary load-bearing plane. Simultaneously, the moment factor qMz is determined according to Figure 2.12.

In the second step, the design criterion ΔnR is determined.

Finally, the design is performed by summing up the design ratios of the main and secondary load-bearing plane and comparing them to the design criterion ΔnR.

Figure 2.12 Determination of moment factor qMz

The buttons in the National Annex Settings dialog box have the following functions:

Table 2.2 Buttons in National Annex Settings dialog box

Resets the program's presettings

Imports user-defined default settings

Saves modified settings as default

Deletes user-defined National Annex

Stainless Steel (EN 1993-1-4)

RF-/STEEL EC3 allows for the design of structural components made of stainless steel according to EN 1993-1-4 [3].

In the second tab of the National Annex Settings dialog box, you find the Partial Factors and the Parameters for Stability Design.

Figure 2.13 Dialog box National Annex Settings - CEN, tab Stainless Steel (EN 1993-1-4)
Literatur
[1] Eurocode 3: Design of steel structures - Part 1-1: General rules and rules for buildings; EN 1993-1-1:2010-12
[3] EN 1993-1-4 (2006): Eurocode 3: Design of steel structures - Part 1-4: General rules - Supplementary rules for stainless steels [Authority: The European Union Per Regulation 305/2011, Directive 98/34/EC, Directive 2004/18/EC]
[4] Johannes Naumes, Isabell Strohmann, Dieter Ungermann and Gerhard Sedlacek. Die neuen Stabilitätsnachweise im Stahlbau nach Eurocode 3. Stahlbau, 77, 2008.
[5] Johannes Naumes, Markus Feldmann and Gerhard Sedlacek. Biegeknicken und Biegedrillknicken von Stäben auf einheitlicher Grundlage, Band 70, Shaker Verlag 2010