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Frequently Asked Questions (FAQ)
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The "Extended Display" button allows you to selectively evaluate the results for each stress point. It opens the "Cross-Section Properties and Stress Distribution" dialog box (Figure 01).
In the "Location" section, the current member number and location x on the member are preset. You can also select other members or x-locations in the list.
The "Stress Points" section lists all stress points of the cross-section. The "Coordinates" columns show the centroidal distances y and z, and the "Static moments" columns show the surface moments of the first degree Sy and Sz . The "Thickness t" column shows the thickness of the cross-section part that is required for the determination of the shear stresses. For closed cross-sections, the cell area A * is specified that is required for the determination of the stress due to torsional moment.
The "Stresses" section shows all stresses at the current stress point (selected in the section above). In this dialog box, too, it is possible to select a stress type by mouse click to display its diagrams in the graphic.
Even if the description of the add-on modules is very similar, the calculations performed are different.
This add-on module performs a general stress analysis by calculating the existing stresses and comparing them with the limit stresses. The designs are performed elastically. The designs do not depend on a standard.
This add-on module, on the other hand, performs all typical designs of ultimate limit state, stability, deformation, and fire resistance for steel members according to Eurocode 3 (numerous National Annexes are available). There is a range of module extensions available within this add-on module. These include: warping torsion analysis, plasticity analysis, designs for cold-formed sections.
Comparison of Both Add-on Modules
The results of RF‑/STEEL can be compared with the results of the cross-section design of RF‑/STEEL EC3.
Why the results can differ is explained in FAQ 003489.
Orthotropic surfaces are non-linear and cannot be designed within the RF-STEEL Surfaces add-on module. It is possible to get a full stress analysis in RFEM for the orthotropic surfaces defined with the orthotropy type "constant thickness" and compared to limiting stresses manually. For all other orthotropy type, the program is not aware of the geometric properties for the surface at every FE mesh point which is needed to calculate stresses. An extensive and detailed FE model would need to be created. See FAQ 2468 for an example of this. Surface types need to be set to "standard" to be designed within the add-on module.
It is possible to display or calculate the stresses in RFEM as well as in the add-on module by means of the following smoothing options:
- Constant on Elements
- Continuous Within Surfaces
- Continuous Total
- Continuously by Groups / Continuous by Groups
To compare the results, the same display type and calculation type must be selected in RFEM and RF‑STEEL Surfaces.
In RFEM, it is possible to do this in Project Navigator Display → Results → Surfaces → Distribution of Internal Forces/Stresses (Figure 02). In RF‑STEEL Surfaces, this can be displayed or changed in Details → "Options" tab (Figure 03).
AnswerIn order to consider smooth ranges in the design in RF‑STEEL Surfaces, they must always be activated in the detail settings of the add-on module. See Figure 01 with the detail settings in RF‑STEEL Surfaces.
AnswerIn the RF‑/STEEL add-on module, the equivalent stress analysis is carried out according to von Mises. The elastic stress analysis (EL-EL) is to be performed. In RF‑/STEEL EC3, a classification is done before the design. If a cross-section is classified as Class 1 or Class 2, the design is carried out against the plastic limit internal forces. The EL-PL design is to be performed. If you do not want to use the plastic load reserves, you can switch the design to EL‑EL in the details of the RF‑/STEEL EC3 add-on module. The results are then comparable with RF‑/STEEL.
AnswerIn this case, take a look at the stress points in the cross-section details. If they are not accessible (grayed out), no stress points have been defined in SHAPE‑MASSIVE and the design is not possible. In SHAPE‑MASSIVE, it is necessary to activate the "Stresses by Stress Points" option in General Data. After recalculating and saving, the cross-section can be designed in the RF‑/STEEL add‑on module.
Cross-sections assigned to Class 1 or Class 2 are designed plastically in RF‑/STEEL EC3 by default. In order to be able to compare the results with RF‑/STEEL, please activate the elastic design the cross-sections of Class 1 and Class 2 (Figure 02) in Details of RF‑/STEEL EC3.
Please also check whether the same partial safety factor γ for the resistances of the cross-sections is defined in both add-on modules (Figure 03 and Figure 04).
AnswerThe membrane, bending or other stresses can be displayed in RF‑STEEL Surfaces by using the Details button.
AnswerThe RF‑STEEL Surfaces add-on module performs an elastic stress analysis for surfaces. The fire resistance design is not implemented, but can be carried out by manually adjusting the stiffness in RFEM and adjusting the yield strength in the add-on module.
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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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