In addition to our technical support (e.g. via chat), you’ll find resources on our website that may help you with your design using Dlubal Software.
Frequently Asked Questions (FAQ)
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In the case of cross-section design, RF‑CONCRETE Members or CONCRETE uses in the calculation the stress-strain diagram for reinforcing steel according to DIN EN 1992‑1‑1, 3.2.7(2)a, that is, the increasing upper part up to ftk and the strain limitation of εud = 0.025.
In RF‑CONCRETE Members or CONCRETE, there is no option to switch to the design with the horizontal part according to 3.2.7(2)b.
However, you can possibly use a user-defined material with ftk = fyk.
After the calculation, you can switch to the result window "2.4 Required Reinforcement by x‑Location" in the RF‑CONCRETE Members (RFEM) or CONCRETE (RSTAB) add-on module.
Here, you can select a certain result row for a particular design and x-location (upper table in Window 2.4). Then, you can evaluate the intermediate results in the lower table in Window 2.4. This covers the "Neutral Axis Depth x", for example. The location of the neutral axis for the selected design location is displayed in the graphic on the right of Window 2.4 .
Furthermore, you can display the distribution of the neutral axis depth along the member length graphically in the model or in "Result Diagrams on Member."
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
- Not continuous
- Continuous within surfaces
- Continuous total
- Continuously by groups or 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 the Project Navigator Show → Results → Surfaces → Distribution of Internal Forces/Stresses (Figure 02). In RF-STEEL Surfaces, this can be displayed or changed in the Details → 'Options' tab (Figure 03).
AnswerThe zero coefficient of structural soil strength can be used for better convergence of deeper excavations or small loading. Damaged soil have no structural soil strength. Therefore, it better picture damaged subsoil in the upper layers with this function. The possible entry for the depth of the soil failure is from 0.0 m to 1.0 m.
Since there are only the directions x- and y- in the plane for surfaces, it is first necessary to define which should be the hoop stress and which the axial stress. In the following example, sigma_x should be the axial stress and sigma_y the hoop stress.
The example consists of an inclined circular container (Figure 01). After the modeling, the program tries to align the local axis systems on the global axis system (Figure 02). However, the x‑axis should run along the container for all surfaces in this case. This orientation can be achieved as follows.
First, the z‑axis of all surfaces must point inwards or outwards. In the example, the outside direction has been selected. If this is not the case for the surface, you can right-click the surface and use the "Reverse Local Axis System" feature to move the z‑axis to the other surface side. Then, select all surfaces and open the Axes tab in the Edit Surface dialog box. Figure 03 shows the dialog box. In this case, one of the boundary lines oriented axially has been selected. Figure 04 shows the aligned local axis systems now. All x-axes are axial and all y-axes run in the circumferential (hoop) direction.
Figure 05 shows the results of the membrane stresses axial (sigma‑x,m) and along the circumference (sigma‑y,m).
AnswerBoth RFEM and RSTAB are ideally suited for the application in mechanical engineering and are used by numerous users in daily practice. Due to the modular system, you can only use the add-on modules required for your purposes.
Main Programs RFEM or RSTABThe main programs are used to define structures, materials, and loads.RSTAB provides optimal tools for beam, truss or frame structures.
In addition, RFEM provides you with additional options to calculate the structures with surface or solid elements.
Dynamic AnalysesIn case a seismic analysis or vibration designs are required, 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.If you have any question about the Dlubal Software programs, please do not hesitate to contact the sales department.
Calculation of stresses and comparison with limit stresses
Modeling of pipelines (in RFEM only)
- RF-PIPING Design
Design of Pipelines (only in RFEM)
This is possible over a detour in RFEM.The soil pressure, from which the bending moment is determined for the design using integration, can be applied as an 'external load' in an RFEM initial model.Compressive Stress Distribution in RF-/FOUNDATION ProThis compressive stress can be applied to an equivalent system in RFEM as a 'Free Surface Load'.In this case, the equivalent system is a rigid surface. The size of the surface depends on the position of the design section set in RF-/FOUNDATION Pro. In this case, it is necessary to set 'In Column Center'.With this equivalent system, it is possible to recalculate the 'Moment from Compression Stress Distribution' determined in RF-/FOUNDATION Pro.You can download the example described above using the link below and open it in RFEM 5.
The directions of the warp and weft are linked to the axes of the surface. With the default setting, only an isotropic prestress can be applied. If the axes are aligned, orthotropic or radial prestress will be available as well.
The procedure is demonstrated in the video.
AnswerMostly, it is in this case so that the 'Action Category - Prestress' in the 'Project Navigator - Display' is hidden. All loads contained in a load case with the action category ‘Prestress’ are no longer displayed in this case. When activating the function, the loads should be displayed as usual.
AnswerIn the RF-/STEEL add-on module, an equivalent stress design is performed according to von Mises. An elastic stress design (EL-EL) is to be made. In RF-/STEEL EC3, a classification is carried out before the design. If the cross-section is classified as class 1 or class 2, the design is performed against plastic limit internal forces. An EL-PL design is 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.
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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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