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
AnswerIf you want to define failure criterion s for orthotropic material you have to define a orthotropic plastic material in the Material Model (picture 1).The yield criterion will be done according the Tsai-Wu criterion (picture 2).By this Link you can find a full set of verification examples to this material model.The material model itself is explained in several Knowledge base articles.
AnswerThe add-on module RF-MAT NL is already integrated in RFEM 5. It is assumed that the following material models can be used:Isotropic Plastic 1DIsotropic Plastic 2D/3DIsotropic Nonlinear Elastic 1DIsotropic Nonlinear Elastic 2D/3DOrthotropic plastic 2DOrthotropic 3D plasticIsotropic Masonry 2DIsotropic damage 2D / 3D
AnswerThe RF- / EL-PL add-on module is designed only for the elastic-plastic design of steel cross-sections. As a result, you can only calculate materials from the "Steel" category in the add-on module.
AnswerIn RSTAB, it is also possible to determine plastic internal forces. To do this, you have to select a plastic hinge as nonlinearity by using the member properties (see Figure 1). However, this does not include an interaction of the plastic internal forces. Another possibility is to set releases with nonlinear properties directly. However, you have to use this method to estimate beforehand where these joints form.RFEM provides the option to select a corresponding material model (see Figure 2).
AnswerWhen calculating nonlinear material models, especially for plastic material models, the calculation is always performed in relation to the original constant internal forces.Therefore, you should set the smoothing of the FE elements to "Constant."Furthermore, the stresses are related to the principal stresses $ \ sigma_1 $ or $ \ sigma_2 $.Even if all these factors have been taken into account, there may still be deviations from the defined limit stress. These usually result from the defined hardening modulus.This fact is explained in detail for the technical articles listed below.
In an older model in RFEM 4 or RSTAB 7, I designed a DuenQ cross-section or general cross-section in STEEL EC3. At that time, a cross-section class 1 or 2 was determined. Now I have opened the model in RFEM 5 and now the cross-section is only classified Class 3 or 4. What is the reason for this? Was the design more economical at the time?
AnswerThe design of general cross-sections or DuenQ cross-sections is always performed elastically in STEEL EC3, which means according to Class 3 or 4. Since the conditions of interaction are restricted to some cross-sections, no plastic design is possible for any cross-section shapes. In RFEM 4 or RSTAB 7, however, it was possible to classify a cross-section as class 1 or 2, even though the subsequent design was carried out elastically.To eliminate this ambiguity and to create consistency, the classification has also been changed to cross-section classes 3 and 4.
AnswerThe plastic stresses are output exclusively in the representation type isosurfaces . The display type can be selected via the icon in the toolbar (see Figure 1) or in the Project Navigator - Show under Results -> Display type can be set.
No, when using a nonlinear material model, it is not absolutely necessary to determine according to Theorie II. Or III. To calculate order. The material nonlinearity is also considered in the calculation according to the linear static analysis.
The calculation according to Theorie II. Or III. Order means that the equilibrium is set on the deformed system. Thus, it is a geometric nonlinearity.
Difference between II. And III. Order is that at III. Also large rotations may occur.
Thus, if there is no stability problem or the stability problem is analyzed in another way, the calculation according to the linear deformation analysis is sufficient.
For example, this check box enables the use of the Simplex method, also for I-sections, which would otherwise be designed automatically with the partial internal -angidivision process including the redistribution.
If the check box is clear, the simplex method or the partial internal local area method (depending on the selection) is only used if a general cross-section (for example of SHAPE-THIN) is available.
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.
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.”