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)
Customer Support 24/7
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.
Regarding the analytical calculation of SLS, you should note that the calculation is based on a provided or applied reinforcement for SLS.
The provided reinforcement can result, for example, from the ultimate limit state design, the defined basic reinforcement, or the automatically determined required reinforcement for SLS. The reinforcement applied to the SLS design can be displayed graphically.
If there are too small or no reinforcement results from ULS or the basic reinforcement in some areas and no required reinforcement is determined for SLS at the same time, the serviceability limit state design is performed without or with too small reinforcement. In this context, very high results may occur during the deformation, for example. Also, there may be poor convergence.
It is necessary to ensure that there is a reinforcement in each area of the structural system. For this, you can apply a basic reinforcement or a minimum reinforcement, for example.
AnswerYes, the results can be partially exported. The export function is available for the result tables in the add-on module (as of Window 2.1).Using the example of the steel stress in SLS, it would be possible to only perform the steel stress analysis and then export the table in Window 3.3, for example.When displaying the table in Window 3.3, you can choose between FE mesh points and grid points. The grid can be adjusted as a property of the surface.
AnswerThe fire resistance design is based on the temperature course from Annex A EN 1992‑1‑2.The initial values for temperature courses cannot be adjusted in the add-on modules (RF‑/CONCRETE Members and RF‑/CONCRETE Columns). The temperature curves according to Annex A EN 1992‑1‑2 are based on the following assumptions:
- The specific heat of concrete corresponds to the specifications according to EN 1992‑1‑2, 3.2.2.
- The moisture is 1.5%. For moistures greater than 1.5%, the specified temperatures are on the safe side.
- The thermal conductivity of concrete is the lower limit value mentioned in EN 1992‑1‑2, 3.3.3.
- The emissivity value of the concrete surface is 0.7.
- The convective heat-transmission coefficient is 25 W/m²K.
RF-/ALUMINUM checks the symmetry of general cross-sections and compares them with the SHAPE-THIN evaluation if activating the "Determine symmetry by module and compare with SHAPE‑THIN definition" check box (Figure 01).
If both methods provide different results, the corresponding error message appears (Figure 02).
Usually, there are small inaccuracies in the SHAPE‑THIN cross-section. Thus, the cross-section Sec‑1.du9 shown in Figure 03 is not absolutely symmetrical to the Z‑axis: The Z‑coordinates of Node 1 and Node 4 as well as Node 55 and Node 60 do not match in the second decimal place.
SHAPE‑THIN classifies the cross-section as asymmetrical, but RF‑/ALUMINUM as monosymmetric to the z‑axis, so the error message shown in Figure 02 appears.
The SHAPE‑THIN cross-section should be checked for symmetry. When modeling in SHAPE‑THIN, it is useful to only display one side of the cross-section and to create the other half by mirroring. This is also shown in the video.
RF-/STEEL Cold-Formed Sections is a module extension of RF‑/STEEL EC3. The only thing you need to do is to activate the design for cold-formed cross-sections in the detailed settings of RF‑/STEEL EC3 (Figure 01).
Common cold-formed cross-sections can be modeled in SHAPE‑THIN. In General Data, select the "c/t parts and effective cross-section properties" check box (Figure 01).
Then, select the "EN 1993‑1‑3 (Cold formed cross-section)" option in the "c/t-Parts and Effective Cross-Section" tab of the Calculation Parameters dialog box (Figure 02).
You can optionally check the geometric conditions for the applicability of the standard specified in EN 1993‑1‑3 , 5.2. To do this, select the corresponding check boxes. If the geometric conditions are not met, an error message appears before the calculation.
First, enter the elements of the cross-section. The notional flat widths are usually generated automatically from the geometry conditions, but can also be created as user-defined in Table "1.7 Notional Flat Widths | EN 1993‑1‑3" (Figure 03) or in the corresponding dialog box.
Then, you can define stiffeners in Table "1.8 Stiffeners" or in the corresponding dialog box (Figure 04).
Furthermore, you should specify the buckling panel in Table "1.9 Buckling panels" (Figure 05) or in the dialog box. To do this, select the elements of the buckling panel. The stiffeners located in the stiffened panel are identified automatically.
For the design of a cold-formed cross-section in RF‑/STEEL Cold‑Formed Sections, it is sufficient to define the stiffeners and panels of the cross-section. It is not necessary to additionally calculate the effective cross-section in SHAPE‑THIN. Thus, you can start the calculation and click "OK" to confirm the warning message (Figure 06).
After saving the calculated cross-section, it can be imported into RFEM or RSTAB.
AnswerThe PLATE‑BUCKLING add-on module allows you to only calculate rectangular buckling panels.The panel is entered in Window 1.1 of the add-on module. Another option is to create the panel from an existing RFEM or RSTAB file by selecting the respective c/t-part.
An overpressed joint between two members can be controlled in RFEM by using the member stress results. For members, this stress result is the effective stress as a color gradient across the member surface, depending on the assigned cross-section.
Figure 01 - Stresses on Members
Based on the local member axis, the member stress result gives the following stress components and reference stresses with an associated color palette:
- Elastic stress component
- Elastic equivalent stresses
By activating the display of the members connected to the joint and displaying the σx stresses, it is possible to visualize the stress state on the members and thus also between the members. If there are only negative stresses in the area between the members, the joint is overpressed.
AnswerThe zero coefficient of structural soil strength can be used for better convergence of deeper excavations or small loading. Damaged soil has no structural soil strength. Therefore, it is better to model the 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.
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.
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.
“Thank you for the valuable information.
I would like to pay a compliment to your support team. I am always impressed how quickly and professionally the questions are answered. I have used a lot of software with a support contract in the field of structural analysis, but your support is by far the best. ”