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FAQ 003544 | I would like to carry out the flexural buckling design for timber components with imperfections and internal forces according to the second-order analysis. Is it sufficient to activate this in Details of the RF‑/TIMBER Pro add-on module or is it necessary to make additional settings?
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I would like to carry out the flexural buckling design for timber components with imperfections and internal forces according to the second-order analysis. Is it sufficient to activate this in Details of the RF‑/TIMBER Pro add-on module or is it necessary to make additional settings?Answer
The setting in Figure 01 only controls the effect on the design side. After activating this function, the buckling designs in the "Effective Lengths" window are deactivated. Thus, the lateral-torsional buckling analysis is only performed.
Figure 01 - Detailed Settings in RF-/TIMBER Pro Add-on Module
In order to calculate with the design values of stiffnesses, it is necessary to reduce them by the partial safety factor according to [1]. For this, select the highlighted option in the calculation parameters (see Figure 02).
Figure 02 - Reduction of Stiffness by Partial Safety Factor
If using the automatic combinations for the standard EN 1990 + EN 1995, this setting is automatically activated in the combinations for ULS according to the second-order analysis. In the case of the combinations for SLS and the combinations generated according to the linear static analysis, this option is automatically deactivated. However, the combinations are only assigned automatically by using the method of analysis in the "Combination Expressions" tab (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" option in the calculation parameters and modify the stiffnesses manually.
Keywords
Dlubal FAQ Second-order analysis Buckling Stability analysis Timber structures Equivalent member method Frequently Asked Question FAQ about Dlubal Question and Answer about Dlubal
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Lateral-Torsional Buckling in Timber Construction | Examples 2
The previous article Lateral-Torsional Buckling in Timber Construction | Examples 1 explains the practical application for determining the critical bending moment Mcrit or the critical bending stress σcrit for a bending beam's lateral buckling by using simple examples.
New
Increased Calculation Performance by Reducing the Nodal Degrees of Freedom
The number of degrees of freedom in a node is no longer a global calculation parameter in RFEM (6 degrees of freedom for each mesh node in 3D models, 7 degrees of freedom for the warping torsion analysis). Thus, each node is generally considered with a different number of degrees of freedom, which leads to a variable number of equations in the calculation.
This modification speeds up the calculation, especially for models where a significant reduction of the system could be achieved (e.g. trusses and membrane structures).
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