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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Orthotropic surfaces are non-linear and cannot be designed within the RF-STEEL Surfaces add-on module. It is possible to get a full stress analysis in RFEM for the orthotropic surfaces defined with the orthotropy type "constant thickness" and compared to limiting stresses manually. For all other orthotropy type, the program is not aware of the geometric properties for the surface at every FE mesh point which is needed to calculate stresses. An extensive and detailed FE model would need to be created. See FAQ 2468 for an example of this. Surface types need to be set to "standard" to be designed within the add-on module.
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
- Continuous Within Surfaces
- Continuous Total
- Continuously by Groups / 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 Project Navigator Display → Results → Surfaces → Distribution of Internal Forces/Stresses (Figure 02). In RF‑STEEL Surfaces, this can be displayed or changed in Details → "Options" tab (Figure 03).
AnswerIn order to consider smooth ranges in the design in RF‑STEEL Surfaces, they must always be activated in the detail settings of the add-on module. See Figure 01 with the detail settings in RF‑STEEL Surfaces.
AnswerIn the RF‑/STEEL add-on module, the equivalent stress analysis is carried out according to von Mises. The elastic stress analysis (EL-EL) is to be performed. In RF‑/STEEL EC3, a classification is done before the design. If a cross-section is classified as Class 1 or Class 2, the design is carried out against the plastic limit internal forces. The EL-PL design is to be 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.
AnswerIn this case, take a look at the stress points in the cross-section details. If they are not accessible (grayed out), no stress points have been defined in SHAPE‑MASSIVE and the design is not possible. In SHAPE‑MASSIVE, it is necessary to activate the "Stresses by Stress Points" option in General Data. After recalculating and saving, the cross-section can be designed in the RF‑/STEEL add‑on module.
Cross-sections assigned to Class 1 or Class 2 are designed plastically in RF‑/STEEL EC3 by default. In order to be able to compare the results with RF‑/STEEL, please activate the elastic design the cross-sections of Class 1 and Class 2 (Figure 02) in Details of RF‑/STEEL EC3.
Please also check whether the same partial safety factor γ for the resistances of the cross-sections is defined in both add-on modules (Figure 03 and Figure 04).
AnswerThe membrane, bending or other stresses can be displayed in RF‑STEEL Surfaces by using the Details button.
AnswerThe RF‑STEEL Surfaces add-on module performs an elastic stress analysis for surfaces. The fire resistance design is not implemented, but can be carried out by manually adjusting the stiffness in RFEM and adjusting the yield strength in the add-on module.
AnswerWhile the influence of imperfection increases significantly with increasing axial force and the ratio increases exponentially in the case of the second-order analysis,, the influence of imperfection only increases linearly in relation to the axial force in the case of the equivalent member design. Therefore, there is usually a greater difference between the design ratios according to the linear static analysis by using the equivalent member method and the second-order analysis by using the stress analysis for the structural systems with very high or very low design ratio.
AnswerIn RF‑/STEEL, the stresses are calculated on stress points of a cross-section. The stress points defined for the cross-section can be displayed in the details of the cross-section. For the cross-section shown in Figure 01, the stress points are defined along the cross-section. Thus, the stress points (here, Stress Points 1 and Stress Point 9) are also available in the roundings.In SHAPE‑THIN, you can only calculate the stresses on elements. It is not possible to calculate the stresses on the point elements that are used to model irregularities in the cross-section geometry, such as roundings and so on. The stress points of the SHAPE‑THIN cross-section are displayed in Figure 02. In the case of the cross-sections with point elements, minor deviations in stresses may thus occur due to the different stress points.Furthermore, SHAPE‑THIN provides the option to calculate the stresses for the most unfavorable element edges or for element center lines only. In RF‑STEEL, the stresses are calculated exclusively on the stress points.
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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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