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.

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 three tabs.

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 [6]. In his dissertation [7], 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 χ_op is to be calculated either

1. as the minimum value of the values for buckling according to 6.3.1, or χ_LT for lateral-torsional buckling according to 6.3.2 using the slenderness ratio λ_op, or
2. as a value that is interpolated between χ and χ_LT – 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.

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

In the second step, the design criterion Δn_R 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 Δn_R.

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

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

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

In this tab, you can define the partial factors for designing cold-formed sections according to EN 1993-1-3 [3]. A license of the RF-/STEEL Cold-Formed Sections module extension is required for the design.

The Partial Factors Acc. to 2(3) section manages the factors γ_M, which are to be applied for the ultimate limit state design according to [3] 2(3). The recommended values or the values defined in the National Annex are preset.

If necessary, you can adjust the factor γ_M,ser in the Partial factor for verifications at serviceability limit states Acc. to 2(5) section.

According to [3] Table 3.1a, Note 1, a Reduction Factor of f_yb and f_u should be considered for steel plates with a thickness of less than 3 mm. This factor for reducing the basic yield strength and tensile strength is preset with the recommended value of 0.9.