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)
Search FAQ
Further Information
Customer Support 24/7
-
Answer
Yes, that is possible.
First, RF-STABILITY (or RSBUCK in RSTAB 8) can be used to determine the effective lengths for a particular structure and loading.They can then be imported into RF- / TIMBER Pro in the "Effective Lengths" dialog box. -
Answer
Since the equivalent member designs of Eurocode 3 have different interactions than are the case for the designs according to the partial internal forces method and a mixture of these different designs is not desired for reasons of clarity, RFEM deactivates the equivalent member designs when using the RF-/STEEL Plasticity add-on. -
Answer
The term "shear panel" indicates that the translational spring, which is created along the beam length by means of the shear panel type including the corresponding parameters, is smoothed, see Figure 1.
This is also the case for the shear panel type "Bracing", so that the mode shape always appears to be arbitrary at this location, see Figure 2.
In order to obtain accurate results, it is recommended to manually define a lateral support by means of a nodal support according to the general method (Figure 3) or to define the effective lengths according to the equivalent member method, including intermediate restraints, if necessary. Finally, a eigenvector with visible lateral restraint in the mid-span is created (Figure 4).
Figure 03 - Lateral support according to the general method
Figure 04 - Mode shape with lateral support in the mid-span by general method
-
Answer
The critical load factor specifies the factor by which you can increase a load until the system fails. If it is smaller than one, a calculation according to the second-order analysis is usually unstable because the system is already stressed by the critical load. This factor is also taken into account in standardization. For example, Eurocode 3 specifies that a calculation according to the second-order analysis is no longer necessary from a critical load factor of 10.The critical load factor can be determined by the RSBUCK module or RF-STABILITY. -
Answer
Both RFEM and RSTAB are suitable as a solution. Numerous European and international standards as well as various add-on modules are available for both programs, which will facilitate the daily work in steel structures .Basic programs RFEM or RSTAB
Structures, materials, and actions are defined in the basic programs RFEM or RSTAB. In addition to creating spatial frame structures, for example, halls, RFEM also provides plates, plate and shell structures, making it a more versatile option. This pays off if it is also to be designed in other disciplines, such as solid construction.Available standards
- EN 1993-1-1 (Eurocode 3),
- AISC according to ANSI / AISC 360 (US standard),
- SIA according to SIA 263: 2013 (Swiss standard),
- IS according to IS 800: 2007 (Indian Standard),
- BS according to BS 5950-1: 2000 (British Standard) or BS EN 1993-1-1 (British Annex),
- GB according to GB 50017-2003 (Chinese standard),
- CSA according to CSA S16-09 and CSA S16-14 (Canadian standard),
- AS according to AS 4100-1998 + Annex 1 - 1999 (Australian Standard),
- NTC-DF according to NTC-RCDF (2004) (Mexican standard),
- SP according to SP 16.13330.2011 (Russian standard),
- SANS according to SANS 10162-1: 2011 (South African standard),
- NBR according to ABNT NBR 8800: 2008 (Brazilian standard),
- HK according to the standard for steel structures 2011 (Buildings Department - Hong Kong)
- RF- / STEEL - General Stress Checks
Add-on Modules for Structural Steelwork
Add-on modules supplement the functionality of the basic programs. With RF- / STEEL EC3, for example, you perform the design according to Eurocode 3 for the structure. The add-on module RF-STEEL Warping Torsion supplements this design according to Eurocode 3 with lateral-torsional buckling designs with up to 7 degrees of freedom, if it is not a standard case of EC3.
Other more specialized applications such as the plastic design, the stability analysis according to the eigenvalue method or the generation of geometric equivalent imperfections and pre-deformed equivalent models are available. Single modules such as PLATE-BUCKLING support you in the design of rigid or stiffened plates. With the SHAPE-THIN add-on module, you can create any thin-walled cross-sections. The cross-section properties are determined and stress analyzes or plastic designs can be performed.
Use the RF-JOINTS add-on modules to design hingeable or rigid connections.
The CRANWAY one-way application is available for the design of crane runways.
Dynamic AnalysisIf earthquake calculations or vibration analyzes are necessary for the building, the RF- / DYNAM Pro add-on modules provide suitable tools for determining natural frequencies and shapes, analysis of forced vibrations, generation of equivalent loads, or for the nonlinear time history analysis.
If you have any questions about the Dlubal software, contact the sales department. -
Answer
One support was defined at a node that is not part of the set of members in the window ‘1.7 Nodal Supports’ of RF-/STEEL EC3. In this case, it is necessary to define support at a node existing in the set of members or delete this nodal support in the window '1.7 Nodal Supports' of RF-/STEEL EC3.
In Figure 1, for example, a set of member supports was defined for the set of members 1 on nodes 2 and 7. When the calculation starts, the message 'Node No. 7 with support does not exist in the set of members No.1. Please correct this in Table 1.7.' appears (Figure 2, Figure 3).
In window ‘1.7 Nodal Supports’ of the RF-/STEEL EC3, it is possible to get displayed only the selected set of members by clicking the 'Show Only Current Object' button and the node numbering can be displayed by clicking the 'Local Coordinate System' button (Figure 4). It is obvious that the node 7 is not contained in the set of members. Instead of at node 7, the support must be defined on a node contained in the member set (for example, node 6).
-
Answer
This message indicates that the critical load of the structure or the cross-section has been exceeded.The causes for this are very diverse. Often, insufficient lateral supports have been defined in the STEEL EC3 add-on module.It is also possible that the used cross-sections or the structure itself cannot be calculated according to the general method in EC3. This FAQ provides information about such a case. -
Answer
Please check if all sets of members selected for the design are sets of members. The equivalent member method is only applicable for straight sets of members with a uniform cross-section involving, for example, no taper. In this case, use the preset General Method. -
Answer
The reason is that there is no stability analysis for unsymmetrical, open cross-sections according to EN 1999-1-1 when the compressive normal forces and the bending moments are effective.You can neglect the bending moments in Details in the Stability tab by selecting a filter. Then, the flexural buckling design is performed without moments. However, this is under your own responsibility. An alternative is to use a stability check according to the second-order analysis, which would be possible by means of the RF-/FE-LTB add-on module. -
Answer
The elastic critical buckling load for torsional buckling Ncr,T is calculated as follows:
${\mathrm N}_{\mathrm{cr},\mathrm T}\;=\frac1{{\mathrm i}_{\mathrm M}^2}\;\cdot\;\left(\frac{\mathrm\pi^2\;\cdot\;\mathrm E\;\cdot\;{\mathrm I}_{\mathrm w}}{{\mathrm L}_{\mathrm T}^2}\;+\;\mathrm G\;\cdot\;{\mathrm I}_{\mathrm t}\right)$
${\mathrm i}_{\mathrm M}\;=\;\sqrt{{\mathrm i}_{\mathrm u}^2\;+\;{\mathrm i}_{\mathrm v}^2\;+\;{\mathrm u}_{\mathrm M}^2\;+\;{\mathrm v}_{\mathrm M}^2}$
with
E Modulus of elasticity G Shear modulus Iw Warping resistance It Torsion moment of inertia iu, iv Pricipial radius of gyration um, vm Shear center coordinates in the principal axis system LT Torsional buckling critical length
Contact us
Did you find your question?
If not, contact us via our free e-mail, chat, or forum support, or send us your question via the online form.
First Steps
We provide hints and tips to help you get started with the main programs RFEM and RSTAB.
★
★
★
★
★
Your support is by far the best
“Thank you very much for the useful information.
I would like to pay a compliment to your support team. I am always impressed how quickly and professionally the questions are answered. In the industry of structural analysis, I use several software including service contract, but your support is by far the best.”
Dipl. Bauingenieur FH/SIA Markus Lauber
28 November 2016
