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Frequently Asked Questions (FAQ)
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No, it is not possible to set user-defined values when viewing stress results on a solid. These unfortunately do not work like results on a surface. It is possible to activate the result values on each FE Mesh Node using the settings shown below under Values on Surface. To access the filter settings you must right click on the label "Values on Surfaces."You can then also set your results to Solid Point Display under the Results menu. This will help give a better visual on where those results are located graphically.
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).
The indices of the stresses from RF‑LAMINATE, such as σb,90, do not refer to the local surface axis system from RFEM, but to the orthotropy directions defined in Window "1.2 Material Properties" in RF‑LAMINATE, see Image 01.
The orthotropy directions can be displayed graphically by activating them in the Display navigator, see Image 02. The red arrow represents the "zero direction" of the stress, that is, the direction of the stress σb,0.
The colors of the arrows can be adjusted within the display properties (category General, Axis System, Surface Axis Systems x, y, z (orthotropy directions)), see Image 03.
Thus, the stress σb,0 in this direction applies to each orthotropy direction of a layer defined in RF‑LAMINATE, and σ b,90 applies to the stress transverse to the defined orthotropy directions.
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.
According to DIN EN 1993‑1‑1, Section 6.2.9, the moment resistance is reduced due to a high axial force utilization, thus the maximum design ratio for the cross-section design "biaxial bending, shear and axial force according to 6.2.10 and 6.2.9" is unusually high.
If using Equation (6.2) from Section 6.2.1 for the cross-section design instead of Equation (6.41) from Section 188.8.131.52, the design ratio can be reduced significantly.
In the RF‑/STEEL EC3 add-on module, you can activate the linear interaction of the axial force and moment loading in the Details tab, see the image.
AnswerIn 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 184.108.40.206.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.
While Member 1 is an upstand beam, Member 2 is a downstand beam. This results in a compression axial force for Member 1, and a tensile force for Member 2.
For the concrete design, a compressed cross-section is more favorable than a tensioned cross-section. For comparison purposes, here are the axial forces of the members:
Now, if you deactivate the axial forces for the design in RF‑CONCRETE Members, the result is a required reinforcement that is affine to the moment distribution:
With this setting, you are on the safe side for Member 1, but on the unsafe side for Member 2.
In most cases, slender beams receive a parabolic shear stress in the web of the cross-section, which has the maximum value in the centroid of double-symmetric cross-sections.
According to DIN 18800, Part 3, Section 403, the following applies:
Shear stresses that are variable over the width b of the buckling panel should be considered with the larger of the following two values:
- Mean value of τ
- 0.5 max τ
In this case, the mean value of the shear stress is used for the buckling design.
Since the variable shear stress τz depends on the statical moment Sy, there is a table with the details of the c/t-parts of the cross-section in FE‑BUCKLING. This also includes the average statical moments which are used to determine the corresponding shear stresses for the buckling design according to the usual formula, but with the average statical moment, see the formula and Image 01.
Accordingly, the following shear stress results in FE‑BUCKLING, see Image 02.
The respective statical moments that are used to determine the shear stresses in RF‑/STEEL for the stress analysis can be displayed in the result window by clicking the "Show Cross-Section Values and Extended Stress Diagram" button, see Image 03.
If there is no stability analysis displayed in the results in RF‑/STEEL EC3 although the stability analysis has been activated, it is very likely not necessary.
For example, if the slenderness ratio λLT is less than or equal to 0.4, the lateral-torsional buckling analysis may be omitted according to Eurocode 3 and only cross-section design should be performed.
In the graphic, this is not possible for clarity reasons. However, the RF‑LAMINATE add-on module allows you to also display the stresses in all points. This is deactivated by default because it quickly produces a huge amount of data for large structures.
If you also filter by the stress component that interests you, the results in the table becomes quickly clear, and you can easily evaluate the distribution of stresses at a point using the layers there.
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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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