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Frequently Asked Questions (FAQ)
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According to DIN EN 1993‑1‑1, 22.214.171.124 (2), the reduction factor χLT can be modified by the f factor for χLT,mod. You can activate or deactivate this option under National Annex Settings.
AnswerIn principle, RF‑/CONCRETE Columns designs the statically required reinforcement for a buckling analysis and generates a reinforcement proposal on this basis.As an alternative to this procedure, it is also possible to specify a certain minimum reinforcement ratio before starting the calculation. You can enter this data iin Window "1.4 Reinforcement" in the tab for the selected National Annex of EN 1992‑1‑1 (for example, DIN EN 1992‑1‑1).A new reinforcement concept is defined on the basis of the entries specified here and used to perform the designs.
In principle, RF‑/CONCRETE Columns designs the statically required reinforcement for a buckling analysis and generates a reinforcement concept on this basis.
This reinforcement concept can be used to perform the fire resistance design, for example.
As an alternative to this procedure, you can also specify a certain minimum reinforcement content before starting the calculation. You can enter the data for this in Window "1.4 Reinforcement," in the tab for the respective National Annex for EN 1992‑1‑1 (for example, DIN EN 1992‑1‑1).
A new reinforcement concept is defined on the basis of the entries specified here, and used to perform the designs.
The RF‑CONCRETE Columns add-on module allows you to define a "creep-producing permanent load." You can find the corresponding tab in Window "1.1 General Data."
The reason for the entry is that RF‑CONCRETE Columns can apply this "creep-producing permanent load" for the automatic determination of the effective creep ratio according to EN 1992‑1‑1, 5.8.4.
In contrast, there is no explicit input option for this creep-producing permanent load in RF‑CONCRETE Members. In RF‑CONCRETE Members, the stability analysis of reinforced concrete columns by means of nonlinear design does not automatically reduce the effective creep ratio. You can find the background to the effective creep ratio applied in RF‑CONCRETE Members in Chapter 2.4.6 of the RF-CONCRETE Members manual.
The same applies to the CONCRETE Columns or CONCRETE add-on modules for RSTAB.
AnswerIf the PLATE‑BUCKLING add-on module is not opened as a stand-alone version, but via RFEM or RSTAB, it is possible to import the panels (c/t parts of a member cross-section) and the respective load cases of the RFEM or RSTAB model to PLATE‑BUCKLING (see the figure).If there are no valid cross-sections of PLATE‑BUCKLING found in the model file of RFEM/RSTAB, the option for importing the buckling panels remains inactive.
AnswerThe PLATE‑BUCKLING add-on module allows you to only calculate rectangular buckling panels.The panel is entered in Window 1.1 of the add-on module. Another option is to create the panel from an existing RFEM or RSTAB file by selecting the respective c/t-part.
Since concrete has a nonlinear material behavior that can only be simulated with the CONCRETE NL module, it is not possible to analyze it by using the RF‑STABILITY add-on module.
The use of another material model such as isotropic linear elastic or isotropic plastic would not represent the crack formation correctly, and the results are therefore not usable.
The stability analysis on columns can be performed with RF‑CONCRETE Columns or RF‑CONCRETE NL. You can find a small example under Downloads.
This example includes the design of a column by the RF‑CONCRETE Columns add-on module. Make sure that the calculation of the internal forces in RFEM is performed according to the geometrically linear analysis and that no imperfections are required because the method used in the add-on module takes them into account.
The example also includes the design with RF‑CONCRETE NL. Here, it is also necessary to calculate according to the second-order analysis and it requires the imperfections in the form of inclinations. For better comparability, the layout of the longitudinal reinforcement was aligned with the result from RF‑CONCRETE Columns, as shown in Figure 01 and Figure 02. Since the reinforcement is optimized by the module after a new calculation, the desired reinforcement was saved as a template (see the red arrow).
AnswerThese lines represent the local torsional rotation (see Figure 01). By default, the torsional rotations φx with the standardized values greater than 0.2 are only displayed. This ensures clear arrangement of the graphic. The graphical display is controlled directly in the add-on module (see Figure 02).
AnswerThe internal forces and deformations are determined according to the second-order analysis for torsional buckling, taking into account 7 degrees of freedom. For a linear calculation of deformations, a vertical/horizontal load only results in one vertical/horizontal deformation. Since the internal forces refer to the deformed structure and there is a nonlinear analysis, this is not valid for the second-order torsional buckling analysis.
In RFEM and RSTAB, you can check the deformations in the shear center by using the RF‑/FE‑LTB add-on module (see Figure 02). The deformations that additionally result from the displacements or rotations can only be checked with a surface model in RFEM.
Yes, it is possible.First, RF‑STABILITY (or RSBUCK in RSTAB 8) can be used to determine the effective lengths for a structural system and certain loading.They can then be imported in the "Effective Lengths" dialog box in RF‑/TIMBER Pro.
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Wind Simulation & Wind Load Generation
With the stand-alone program RWIND Simulation, wind flows around simple or complex structures can be simulated by means of a digital wind tunnel.
The generated wind loads acting on these objects can be imported to RFEM or RSTAB.
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