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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AnswerThe programs RFEM or RSTAB are very well suited to perform these designs . Add-on modules for steel or solid construction support your individual solutions.
Special add-on modules from the RF-/MAST series extend and simplify the possibilities.
Main Programs RFEM or RSTABThe basic programs are used to define structures and materials as well as actions.With RSTAB, you can edit and calculate truss-like or frame-like structures. RFEM also allows for plate, slab, shell, and solid elements.
Add-on modulesRF-/TOWER Structure
helps in the efficient generation of three- or four-sided tower structures
includes a comprehensive library with add-on parts and allows for a quick and easy integration into your model.
supports you professionally in the generation of wind, ice and traffic loads.
RF-/TOWER effective lengths
determines the effective lengths of members especially for masts
does the design according to EN 1993-1-1, EN 1993-3-1 and EN 50341 incl.
RF-/JOINTS Steel Tower
designs hinged bolt connections of lattice towers according to EN 1993-1-8
Wind analysis in a digital wind tunnelUse RWIND Simulation for advanced flow behavior analyzes. The results can be used directly as loads or load cases in RFEM or RSTAB.
Dynamic AnalysisIf earthquake calculations or vibration analyzes are necessary, the RF-/DYNAM Pro add-on modules provide suitable tools for determining natural frequencies and shapes, for analyzing forced vibrations, for generating equivalent loads, or for nonlinear time history analysis.In case of having any further questions about the Dlubal software, contact the sales department, please.
AnswerBoth RFEM and RSTAB are ideally suited for use in mechanical engineering and are used by numerous users in daily practice. Due to the modular structure, you only need the add-on modules required for your applications.
Main Programs RFEM or RSTABThe basic programs define the structures and materials as well as the actions.RSTAB supports you best when it comes to truss or frame-type structures
In addition, RFEM provides the best support if you want to additionally calculate structures with surface or solid elements.
Dynamic AnalyzesIf seismic calculations or vibration analyzes are necessary, the RF-/DYNAM Pro add-on modules provide suitable tools for the determination of natural frequencies and shapes, the analysis of forced vibrations, the generation of equivalent loads, or for the nonlinear time history analysis.If you have any further questions on the Dlubal programs, please do not hesitate to contact the sales department.
Calculation of stresses and comparison with the limit stresses
Modeling of Pipe Tilts (only in RFEM)
- RF-PIPING Design
Design of Pipelines (only in RFEM)
AnswerIn RF-/JOINTS Steel - Rigid, the design is implemented according to EN 1993-1-8 Chapter 6.2.7 Equation 6.24. If the design axial force exceeds 5% of the plastic resistance Npl, Rd, Equation 6.24 is used.
AnswerDuring the development of the FRAME-JOINT Pro add on module, the lower end plate extension was fixed because it results in an improved load transfer of the compressive force into the column.
It is not possible to deactivate the extension and its minimum dimension is defined as follows:
uu = max
- End plate thickness
- √2 * bottom flange weld
- for end plate depths < 200 mm → min 10 mm
- for end plate depths > 200 <400 mm → min 20 mm
- for end plate depths > 400 → min 30 mm
AnswerFrom the formula of EC 3-1-8, it is obvious that the ultimate tension forces of the beam's end plate are introduced into the column flange and thus directly into the column web.
Therefore, the upper end plate is not fully stressed by these forces.
For purely structural reasons, the column end plate is available for the stiffening and the panel boundary and serves for the transmission of the proportional force flowing into the stiffener in case of a required diagonal stiffener.
AnswerTo enter a taper on a beam, it is necessary to select the Layout dialog section. A taper can be modeled either on the bottom side or on the top side of the beam.The plate thicknesses, as well as the height of the taper, are defined by selecting a tapered cross-section, since, for example, repeatedly cut rolled cross-sections are used. If any plates are used, a parametric T-section can be selected. The length of the taper, as well as the material, are entered in the same dialog section. The weld thicknesses for connecting the taper to the beam can be defined in the Welds dialog section.If a tapered member is already used as a beam (entered in the 'Nodes and Members via Different Cross-Sections and Lengths' section), it is not possible to model an additional taper.
AnswerThe easiest way is to change to the design notes after having made the calculation or when the note appears in the design notes (see Figure 2). In this case, it is demonstrated there that the width of the end plate is not correct. When changing to the input window 1.4.2, it is possible to quickly recognize in the graphic that the value is not within the allowable range.This can be corrected very quickly by adjusting the horizontal bolt spacings (see Figure 3).
AnswerThe RF-/JOINTS add-on module is divided into several joint groups. For this, see the following FAQ.Therefore, there is no straightforward answer to the special aspects of the design as in this FAQ.In contrast to the RF‑/TIMBER Pro add-on module described in the mentioned FAQ, however, it is obvious that the RF‑/JOINTS add-on modules cannot design EC2, even if manually changing the LDC, for example in the RF‑/JOINTS Timber - Steel to Timber add-on module (see Figure 01).Furthermore, this also applies to the add‑on modules RF‑GLASS and RF‑/CONCRETE NL.The reason for this is that there are stiffnesses exported in the program in the case of some joint groups of the RF‑/JOINTS add‑on module. For nonlinear calculations, the superposition with result combinations is not allowed. In the case of the second result combination mentioned above, there is the special feature that the superposition is no longer conservative, even in the case of simple structures. The design cannot be also performed correctly by manually changing the LDC.Nevertheless, if a result combination should be superimposed with constant and alternative additive, it is necessary to split EC2 in the attached file into load combinations as follows.
- RC2*=CO1 or CO2
AnswerIn addition to geometry input errors, the cause is usually the different calculation principles of both modules.The design of an end plate joint with the RF-/JOINTS Steel - DSTV add-on module is carried out by comparing the saved ultimate load capacities with the design internal forces. The underlying load capacities are taken from the current DSTV guidelines.When using the RF-/JOINTS Steel - Rigid add-on module, the capacities of the connections are calculated according to DIN EN 1993-1-8 by means of the component method. Thus the results can be directly influenced by the used settings.By default, an elastic distribution of bolt forces is used as a basis. By selecting a plastic force distribution in the connection, you can activate additional load capacities. They are already included in the limit load capacities according to the DSTV-guideline.Therefore, to obtain comparable results between both add-on modules, a plastic distribution of forces must be applied for the calculation. In addition, it is important to ensure a correct modeling of the connection geometry.
AnswerSpecifically, for the "Column web, Compression Force, Bottom" design, a specified web stiffener is only applied to the design if it is actually required, or if the design without web stiffener cannot be performed. In the latter case, the comment "Web Stiffener Needed" appears in the last column of the results table.It is also important to note whether a continuous rib or a partial rib is applied.In the case of the partial rib, the compressive force is divided into web and rib and thus designed.If a continuous rib is used, the column web is first fully loaded and the excess load is applied to the rib. In the case of T-joints and cross joints, this approach prevents the rib from being overloaded.
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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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