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Answer
No, the "Isotropic Nonlinear Elastic 1D" material model is not suitable for a bending beam because the nonlinear stress distribution over the height of the crosssection cannot be modeled here. The reason for this is that there are no stress points/FE mesh points over the height of the crosssection. Thus, it is not possible to simulate the crosssection cracking.
On the other hand, the "Isotropic Nonlinear Elastic 1D" material model would be suitable for a cracking of the entire crosssection subjected to a pure axial force loading, but not for bending and compression.
For the simulation of a crosssection subjected to bending in the cracked state, it is recommended to perform a nonlinear analysis with RF‑CONCRETE Members and the RF‑CONCRETE NL module extension. Creep and shrinkage can be considered by using the module extension in RF‑CONCRETE Members.
After the calculation, the nonlinear stiffness of the crosssection can be imported back into RFEM (see Image 01) and the internal forces can be determined again, taking into account the cracked concrete crosssection.
Image 01  Export of Nonlinear Stiffness
You can find more details about this procedure under the following links:
https://www.dlubal.com/en/supportandlearning/support/faq/002881
https://www.dlubal.com/en/supportandlearning/support/knowledgebase/000992

Answer
Warning No. 1136 ("During the calculation of material nonlinearity, the material with a decreasing branch of the diagram can be calculated with one load increment only.") refers to the entries in the global calculation parameters.
In our example file, the number of load increments has been set globally to 10 for load cases and load combinations:
Image 02  Calculation Parameters  Settings
For this material, one load increment can only be expected. If you adjust the number of load steps for load cases and load combinations globally to 1, you can define your material:

Answer
Materials are required to define surfaces, crosssections, and solids. The material properties affect the stiffnesses of these objects.
There are 13 material models available if you have a license for the RF‑MAT NL addon module.
In the case of the abundance of material models, it is necessary to make sure that you assign the corresponding material model to the members and their surfaces/solids.
In the example shown here, surfaces have been generated from a member for a detailed analysis. There is still an unused crosssection defined (marked in blue) and the material is entered for the member crosssection as well as for the surfaces. When editing an existing material to Isotropic Nonlinear Elastic 2D/3D , the 2D/3D material model is also defined for the created member crosssection, which leads to the error message.
When working with members and surfaces / solids, it is recommended to create more than one material.

Answer
For the first point, the modulus of elasticity of the material is assumed in the material model, so that there is quasi an initial state for the solver to ensure the numerical stability.
If there is no material selected, the first point is not calculated as expected when creating the material model using the Diagram definition type, and cannot be adjusted reasonably.
Figure 02  Creating Material Model  Wrong Process
To avoid this, you have to select the material in advance. Then, you can create the material model as usual, and also adjust the points. The first point can now be adjusted with regard to the stress.

Answer
The difference between the two material models is as follows:
 In the Isotropic Nonlinear Elastic 1D material model, no plastic deformations are considered. This means that the material returns to its initial state after the load relief.
 In the case of the Isotropic Plastic 1D material model, however, the plastic deformation is taken into account.
For both material models, you can define the nonlinear properties in an additional dialog box. When entering data by means of a diagram, it is possible for both models to define a distribution after the last step.
For the 'Isotropic Nonlinear Elastic 1D' material model, an antimetric input of the stressstrain diagram is possible (different for the positive and negative range), while for the 'Isotropic Plastic 1D' model, only symmetric input is allowed.

Answer
When using a diagram in the program, the first strain is always given (initial strain). It depends on the resulting modulus of elasticity and cannot be controlled directly. For this, you can use a trick in the program and adjust the first strain to a desired value anyway. To do this, you have to calculate the initial modulus of elasticity and enter it in the material parameter. In your case, it would be possible to use the following procedure.

Answer
The "RF‑MAT NL" addon module allows you to use the nonlinear material model "Isotropic Damage 2D/3D" in RFEM to define the stressstrain diagram for the steel fiber concrete. The internal forces and deformation can be determined in the subsequent nonlinear FE calculation.The two links of the FAQ contain two interesting technical articles about the steel fiber concrete. 
Answer
The RF/DYNAM Pro  Equivalent Loads addon module only contains a linear analysis of structures. If you now apply a nonlinear model for the calculation, RF‑/DYNAM Pro  Equivalent Loads will modify it internally and treat it as a linear model. The nonlinearity in your model is the masonry, which cannot absorb any tensile forces.
The problem is as follows: RF/DYNAM Pro  Equivalent Loads calculates the equivalent loads linearly and exports the load cases from them. However, the load cases are subsequently calculated nonlinearly on the basis of the material model, which is not entirely correct. Furthermore, the results are superimposed according to the SRSS or CQC method, which results in tensile and compressive forces being present in the model.
In this case, you could change the masonry to isotropic linear and work with linear properties of the material model, for example. Additionally, it is possible to insert line hinges at this location, which could be used to avoid the moment restraint, for example.

Answer
The material model according to TsaiWu unifies the plastic with the orthotropic properties. In this way, it is possible to specifically model the materials with anisotropic properties, such as plastics or timber. If the material is plastified, the stresses remain constant. The redistribution is carried out according to the stiffnesses available in the individual directions. The elastic region corresponds to the "Orthotropic  3D" material model. For the plastic area, the yielding according to TsaiWu applies:
${\text{f}}_{\mathrm{crit}}\left(\mathrm\sigma\right)=\frac1{\mathrm C}\left[\frac{\left({\mathrm\sigma}_{\mathrm x}{\mathrm\sigma}_{\mathrm x,0}\right)^2}{{\mathrm f}_{\mathrm t,\mathrm x}{\mathrm f}_{\mathrm c,\mathrm x}}+\frac{\left({\mathrm\sigma}_{\mathrm y}{\mathrm\sigma}_{\mathrm y,0}\right)^2}{{\mathrm f}_{\mathrm t,\mathrm y}{\mathrm f}_{\mathrm c,\mathrm y}}+\frac{\left({\mathrm\sigma}_{\mathrm z}{\mathrm\sigma}_{\mathrm z,0}\right)^2}{{\mathrm f}_{\mathrm t,\mathrm z}{\mathrm f}_{\mathrm c,\mathrm z}}+\frac{{\mathrm\tau}_{\mathrm{yz}}^2}{{\mathrm f}_{\mathrm v,\mathrm{yz}}^2}+\frac{{\mathrm\tau}_{\mathrm{xz}}^2}{{\mathrm f}_{\mathrm v,\mathrm{xz}}^2}+\frac{{\mathrm\tau}_{\mathrm{xy}}^2}{{\mathrm f}_{\mathrm v,\mathrm{xy}}^2}\right]$
where:
${\mathrm\sigma}_{\mathrm x,0}=\frac{{\mathrm f}_{\mathrm t,\mathrm x}{\mathrm f}_{\mathrm c,\mathrm x}}2$
${\mathrm\sigma}_{\mathrm y,0}=\frac{{\mathrm f}_{\mathrm t,\mathrm y}{\mathrm f}_{\mathrm c,\mathrm y}}2$
${\mathrm\sigma}_{\mathrm z,0}=\frac{{\mathrm f}_{\mathrm t,\mathrm z}{\mathrm f}_{\mathrm c,\mathrm z}}2$
$\mathrm C=1+\left[\frac1{{\mathrm f}_{\mathrm t,\mathrm x}}+\frac1{{\mathrm f}_{\mathrm c,\mathrm x}}\right]^2\frac{{\mathrm E}_{\mathrm x}{\mathrm E}_{\mathrm p,\mathrm x}}{{\mathrm E}_{\mathrm x}{\mathrm E}_{\mathrm p,\mathrm x}}\mathrm\alpha+\frac{{\mathrm\sigma}_{\mathrm x,0}^2}{{\mathrm f}_{\mathrm t,\mathrm x}{\mathrm f}_{\mathrm c,\mathrm x}}+\frac{{\mathrm\sigma}_{\mathrm y,0}^2}{{\mathrm f}_{\mathrm t,\mathrm y}{\mathrm f}_{\mathrm c,\mathrm y}}+\frac{{\mathrm\sigma}_{\mathrm z,0}^2}{{\mathrm f}_{\mathrm t,\mathrm z}{\mathrm f}_{\mathrm c,\mathrm y}}$
The stress criterion can be imagined as an elliptical surface within a sixdimensional space of stresses. If one of the three stress components is applied as a constant value, the surface can be projected onto a threedimensional stress space.
If the value for f_{y}(σ) is smaller than 1, the stresses rest within the elastic area. The plastic area is reached as soon as f_{y}(σ) = 1. Values higher than 1 are not allowed. The model behavior is idealplastic, which means there is no stiffening.

Answer
As soon as the material with a nonlinear material model assigned has been created, the license for RF‑MAT NL is used. The license is not released until you close the file or change the material model. Therefore, the license is used for the entire duration, even if no calculation is carried out.
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