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Frequently Asked Questions (FAQ)
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If this error message is displayed, the cross -section is obviously not sufficient because there is no remaining cross -section after the specified fire resistance period. You can check this very easily by reducing the fire resistance time in the detail settings until the design is just possible.
In the result of the fire protection design, you can see very well in the graphic how much residual cross -section is still available after the set fire duration. -
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In RF‑/STEEL EC3, the uniaxial bending stress is always related to the local y-axis of a member and the local y-axis of a member is always assumed as the major axis in the case of symmetric cross-sections, therefore it is only possible in such a case to change the cross-section description from "100/5" to "5/100", see the image. Thus, the stability analysis is performed accordingly.
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As already described in FAQ 4386, the imperfections in the graphic are always aligned with a support.
If no member is connected to a support, the display may differ. For example, if you work with member lists, you can Edit Imperfection and Reverse Member Orientation in the corresponding dialog box, and check whether the graphical display is visually the same.
Image 01 - Edit Imperfection - Reverse Member Orientation
Since the graphical imperfection is virtually an equivalent load, the display is only of visual relevance in this case.
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The optimization of cross-sections in RF‑/TIMBER Pro is based exclusively on the ultimate limit state (ULS), not the serviceability limit state (SLS), see the image from the RF‑TIMBER Pro manual.
More information about the cross-section optimization can be found in the RF-TIMBER Pro manual on pages 76-78 (also available with the F1 key in the add-on module).
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In the "Geometry" or "Supports and Releases" dialog box, you can specify in the "Supports" tab whether the support compression should be checked for a support.
In the case of an asymmetrical system, separate entries are possible for the support on the ridge, for example. In this way, it is possible to determine different support widths of both rafters.
If there is a rafter birdsmouth cut, the cross-section reduction is usually known (Column D).
The supports can be related "globally" to the directions of the axes XYZ or "locally" to the directions of the member axes xyz. The corresponding selection is possible in the list.
The support orientation has effects on the design of the support compression, among other things: In the case of a global arrangement, the compressive stresses in the birdsmouth cut are considered at an angle to the grain direction according to the roof inclination, in the case of a local arrangement under 90° to the grain direction.
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Yes, if activating the stability analysis in the "Stability" tab as well as the "Elastic design (also for Class 1 and Class 2 cross-sections)" option in the "Ultimate Limit State" tab (see the image), the stability analyses are also performed with the elastic cross-section properties.
Image 01 - Elastic Design (Also for Class 1 and Class 2 Cross-Sections)
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A drilling can be performed with a surface model. For this, it is first necessary to split the member (the finer is the division, the more accurate is the result) and then generate surfaces from it.
The resulting cross-section outlines can then be easily rotated. Please note that the cross-section shortening is not taken into account. The RF‑IMP add-on module provides more accurate results as it can pre-deform the FE mesh.
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The RF-/STEEL Warping Torsion module extension is available in RFEM and RSTAB
For this, the RF‑/STEEL EC3 or RF‑/STEEL AISC add-on module as well as the corresponding license for the Warping Torsion module extension are required.
If these requirements are met, the module extension can be activated as shown in the following figure:
Image 01 - Activating Warping Torsion
For more information about RF‑/STEEL Warping Torsion, see the product description.
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In terms of the consideration of creep and shrinkage, the program concept is as follows: Creep and shrinkage are only considered in RF‑CONCRETE Members if there is a curvature and if the cross-section is cracked. The explanation of this can be found in the manual, see Chapter 2.4.5.2.The concept for determining the longitudinal stiffness is designed for curved components. In the case of pure axial loading, the program is not able to determine the exact deformation in connection with the creep and shrinkage according to the current concept. -
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The deformation uz,local under the "Serviceability Limit State Design" category only refers to the simplified analytical method. However, in the case of a nonlinear calculation, you can display the deformations in the "Nonlinear Analysis" category for the serviceability limit state by using the "Nodal Displacement ug" entry.
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First steps
We provide information and tips to help you get started with the basic program RFEM and RSTAB.
Wind Simulation & Wind Load Generation
With the stand -alone program RWIND Simulation, you can simulate wind flows around simple or complex structures 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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