I would like to carry our the flexural buckling analysis for timber components with imperfections and internal forces according to the second-order analysis. Is it sufficient to activate it in Details in the RF-/TIMBER Pro add-on module or are other settings necessary?

Answer

The setting in Figure 01 only controls the influence on the design side. After having activated this function, the buckling designs in the "Effective Lengths" window are deactivated. Thus, only a lateral-torsional buckling analysis is performed.

Figure 01 - Detailed Settings in RF-/TIMBER Pro Add-on Module

In order to calculate with the design values of the stiffnesses, they have to be reduced by the partial safety factor according to [1]. To do this, select the highlighted option in the calculation parameters (see Figure 02).

Figure 02 - Reduction of Stiffness Due to Partial Safety Factor

In case of having used the automatic combinatorics for the standard EN 1990 + EN 1995, this setting is - according to the second-order analysis - automatically activated for the ULS in respective combinations. This option is automatically deactivated for combinations with SLS as well as for combinations that are generated according to the linear static analysis. However, the automatic assignment is only carried out by means of the analysis type in the 'Combination Expressions' window (see Figure 03).

Figure 03 - Calculation Method of Combinations

If you want to calculate the component stiffnesses with the 5% quantile value of the stiffness parameters divided by the partial safety factor, you have to additionally activate the 'Modify Stiffnesses' function in the calculation parameters and modify the stiffnesses manually.

Figure 04 - Modifying Stiffnesses for Load Combinations

Keywords

Second-order analysis Buckling Stability analysis Timber structures Equivalent member method

Reference

[1]   Eurocode 5: Design of timber structures - Part 1-1: General - Common rules and rules for buildings; EN 1995-1-1:2010-12

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