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Frequently Asked Questions (FAQ)
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According to the national provision of ÖNORM EN 1993‑1‑5:2007, Section 4.5.3(3), it is possible to abandon the increase of σcr,c, allowed in the note, with respect to the elastic critical buckling stress σcr,sl of the longitudinal stiffener adjacent to the compression edge as this results in very conservative results with regard to the resulting reduction factor ρc for the buckling analysis according to ÖNORM EN 1993‑1‑5, Section 4.5.4(1), Equation 4.13. Image 01 shows an example of a longitudinally stiffened buckling panel, designed according to the Austrian National Annex.
In DIN EN 1993‑1‑5, the note given in Section 4.5.3(3) applies, so it results in the following difference, see Image 02.
AnswerFor this, it is first necessary to create a line of the desired shape in the surface at the location where the section is to be created. The section can then be arranged on this line (see Image 01). If no element with a stiffness is connected to this line and no load is applied, you have to first inform the mesh generator that this line should still be meshed (see Image 02). After the calculation, the results can be seen.If there are two result diagrams displayed, it is because the result is displayed from both sides of the line. In this case, you can set the smoothing of the internal forces to "Continuous Total." Then, these are smoothed over the lines and only one result diagram remains.
Yes, the RF‑PUNCH Pro add-on module allows for defining the desired longitudinal reinforcement in the "1.5 Punching Nodes" window, see the image.
If you want to consider the minimum moments when calculating the reinforcement for columns, you can also activate this in the add-on module as described in FAQ 004371.
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.
In RF-/CONCRETE Members, the depth of the concrete compression zone can be viewed in the intermediate results of Window "4.1 Serviceability Limit State", see Image 01.
The output takes place within the printout report when activated accordingly.
In RF-CONCRETE Surfaces, the depth of the concrete compression zone is only determined if the cross-section is cracked. It can be viewed in Window "3.1 Serviceability Limit State" in the design details of a point, see Image 02.
You can use the Excel button to export the design details.
If I do not specify any basic reinforcement in RF‑CONCRETE Surfaces, I obtain the value X as an additionally required reinforcement. If I enter this value X as the provided basic reinforcement, I correctly do not get any additional required reinforcement.
However, if I enter a lower value than the determined required total reinforcement as the basic reinforcement, the additionally required reinforcement is increased in such a way that the originally required reinforcement content is exceeded. Why?
Please check the concrete covers of the basic reinforcement and the additional reinforcement. In this case, a higher concrete cover is probably defined for the additional reinforcement than for the basic reinforcement.
If the existing basic reinforcement is so small that the additional reinforcement is required, but a lower effective depth is available due to the higher concrete cover, the program must adjust the reinforcement content accordingly, that is, increase it.
Therefore, the concrete covers in the "Reinforcement Layout" tab in Window 1.4 "Reinforcement" have to be considered, see the image.
No, the load generation, such as "Surface Load on Members via Plane" only works for straight or articulated straight members.
If necessary, curved members can be converted into polygonal members as follows:
- Divide the curved member by the desired number of intermediate nodes
(right-click the member → Divide Member).
- Select all curved members.
- In the table, change the line type from "Arc" to "Polyline."
- If necessary, use the "Show Selected Objects Only" function, see Image 01.
- Change the top line type in the table.
- Select all rows → right-click → "Set", see Image 02.
- Generate the loads.
- Divide the curved member by the desired number of intermediate nodes
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.
As a basis for the analysis of temporary structures, both RFEM and RSTAB can be used. For both programs, there are the standards available according to which the steel, aluminium, and lightweight structures can be calculated and designed. If you want to design membrane and cable structures, RFEM is required.
Main Programs RFEM or RSTAB
The main programs RFEM or RSTAB are used to define structures, materials, and actions.
In order to also analyze membrane and cable structures, RFEM is required. When it comes to pure beam structures, it is sufficient to purchase RSTAB. In any case, RFEM is more versatile it can be equipped and extended with the corresponding add-on modules for all materials and structural models.
- RF-/ALUMINUM according to Eurocode 9 (EN 1991-1-1:2007)
- RF-/ALUMINUM ADM according to ADM 2020 (US code)
- RWIND Simulation
Complex analysis of any structures in the digital wind tunnel with the transfer of load cases to RFEM or RSTAB for further processing
Dynamic AnalysisIf it is necessary to perform seismic analysis or vibration designs of a building, the RF‑/DYNAM Pro add-on modules provide special tools for determining natural frequencies and mode shapes, for an analysis of forced vibrations, a generation of equivalent loads, or for a nonlinear time history analysis.
- Building Information Modeling (BIM)
An extensive collection of interfaces allows for data exchange with other programs.
If you have any question about the Dlubal Software programs, please do not hesitate to contact our sales department.
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Wind Simulation & Wind Load Generation
With the stand-alone program RWIND Simulation, you can simulate wind flow 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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