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
AnswerThe RF-STEEL AISC module does not optimize cross-sections for the Serviceability Limit State design. Optimization is only calculated for the Ultimate Limit State design.Users must manually adjust the cross-section in RFEM or within the add-on module and can export the cross-section back into RFEM. In either scenario, the model must be rerun in order to calculate the correct internal forces with adjusted member size.
Section F2 out of the AISC 360-16  states that doubly symmetric I-Shapes and Channels that are bent about their major axis must be compact sections in order to be designed. An example of this can be seen below.Non-compact sections cannot be designed according to F2. Figure 2 shows a non-designable section.
Yes, the AISC module will detect if there are bending or torsional forces on a member and design accordingly per Design Guide 9. The add-on module combines the shear stresses due to bending and axial loads calculated by RFEM and shear stresses calculated using St. Venant's Torsion to make design checks per Design Guide No. 9.The Steel AISC module also has the option under "Details" to activate the RF-STEEL Warping Torsion add-on module extension where a nonlinear warping torsion analysis is performed using 7 degrees of freedom. Normal and shear stresses on the member are independently determined from the AISC Design Guide No. 9. The loading used in this extension is taken directly from RFEM for analysis.
When designing general cross-sections in the RF-STEEL AISC module, a "Non-designable" message is given for the design ratio. General cross-sections are defined in the program as user-defined sections or shapes which are not included in the specification. Though, some user-defined cross-sections can be designed under specific conditions. The warning message is displayed because shear buckling is not provided for general cross-section in the AISC 360-16  Chapter G. More info on this topic can be found in the RF-STEEL AISC manual linked below.This warning can be turned off in RF-STEEL AISC add-on module under the "Details" button > Shear Buckling > "Shear buckling warning for general cross-section."
Displaying Main Support Direction in RF-LAMINATE Add-on ModuleWhile entering data in the RF‑LAMINATE add-on module, there is an option to graphically control the orthotropic direction of each individual layer. To do this, simply place the cursor in the desired row of the corresponding position. Then, a coordinate system is displayed in the surface in the RFEM model (see Figure 01). This is to be interpreted as follows:red axis = x-axis = β-value of the corresponding layerGenerally, the outer layers specify the main support direction, which is why it is sufficient to only consider the first layer. The red axis specifies the primary load-bearing direction (see Figure 01).
Displaying Main Support Direction in RFEMHowever, the main support direction can also be interpreted directly in RFEM. For this, you can display the local axis systems of the surfaces in detail (see Figure 02). The orthotropic direction β refers to the local x‑axis of the surface. For the example shown in Figure 03, it has a consequence that the main support direction for the left surface runs from one support to another and the secondary surface direction to the right surface. If you want to change the support direction for the right surface, it is possible to either rotate the local surface axis system (see Figure 04) or create a new structure and rotate the orthotropic direction β by 90° (see Figure 05).If the main support direction is not clearly evident, it is worth taking a look at the stiffness matrix of the surface (see Figure 06). There, it is possible to find the "principal" support direction by means of the bending stiffness, for example. The element D11 refers to the local x‑axis of the surface and the element D22 refers to the local y‑axis of the surface.
AnswerTo add different supports to a structural component, this must consist of several members and the design must be carried out by using a set of members. It is then possible to assign different parameters to the individual members. The video shows the procedure.
AnswerFor a stability analysis of any cross-section, the add-on modules RF‑/STEEL EC3 Warping Torsion (extension for RF‑/STEEL EC3) and RF‑/FE‑LTB (stand-alone module) are particularly suitable.By using the calculated critical buckling value, you can determine critical loads and perform the design according to the second-order analysis.
There are many cross-sections according to American standards integrated in the cross-section library.
The following cross-section types are for example included:
W-sections, M-sections, S-sections, and HP-sections.
In addition to the determination of internal forces, you also have the possibility to perform the design of steel sections according to ANSI / AISC 360-10. However, it is only possible with the module RF-/STEEL AISC.
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. ”