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Answer
In principle, it is also possible to perform detailed analysis in RF‑LAMINATE. In the case of a very high shear distortion, for example, it can be reasonable to use orthotropic solids for modeling. The video shows a simple modeling and result evaluation of a layer structure by using solids.
A criterion, as of when is the modeling using solids useful, is the shear correction factor. Further information and other criteria can be found in the following FAQ:

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The Poisson's ratio is set under the material by using the Edit Material dialog box. 
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Orthotropic surfaces are nonlinear and cannot be designed within the RFSTEEL Surfaces addon 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 addon module.

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The default definition of surface elements assumes an isotropic material behavior. The load attempts to get to the supports as quickly as possible. The stiffness of the elements also plays a role here.
For plates, the structural behavior or the load transfer is best represented and understood with the trajectories of the principal moments α_{b}. For wall elements, it is necessary to consider the trajectories of the principal axial forces α_{m}.
In this example, the load is not applied parallel to the free plate´s edges but almost perpendicular to the supports, because this is the shortest path of the load transfer.
At the blunt corners of the system, the load absorption area is larger than in the support centers, corresponds to a singularity point and has as a consequence of that large peak values.
In order to force the system to remove the load parallel to free plate edges, the following procedure is the fastest:
Definition of an orthotropic plate. It is recommended to use the orthotropy type 'Effective Thicknesses'. The effective plate thickness has to be specified in the support direction and a very small thickness (e.g. 1mm) in the secondary support effect.
The second graphic shows the difference between both models. 
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The directions of the warp and weft are linked to the axes of the surface. With the default setting, only an isotropic prestress can be applied. If the axes are aligned, orthotropic or radial prestress will be available as well.
The procedure is demonstrated in the video.

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The material model according to TsaiWu unifies plastic with orthotropic properties. This way, you can enter special modelings of materials with anisotropic characteristics such as plastics or timber. When the material is plasticized, stresses remain constant. A redistribution is carried out according to the stiffnesses available in the individual directions. The elastic zone corresponds to the material model Orthotropic  3D. For the plastic zone, the yielding according to TsaiWu applies:${\text{f}}_{\mathrm{crit}}\left(\mathrm\delta\right)=\frac1{\mathrm C}\left[\frac{\left({\mathrm\delta}_{\mathrm x}{\mathrm\delta}_{\mathrm x,0}\right)^2}{{\mathrm f}_{\mathrm t,\mathrm x}{\mathrm f}_{\mathrm c,\mathrm x}}+\frac{\left({\mathrm\delta}_{\mathrm y}{\mathrm\delta}_{\mathrm y,0}\right)^2}{{\mathrm f}_{\mathrm t,\mathrm y}{\mathrm f}_{\mathrm c,\mathrm y}}+\frac{\left({\mathrm\delta}_{\mathrm z}{\mathrm\delta}_{\mathrm z,0}\right)^2}{{\mathrm f}_{\mathrm t,\mathrm z}{\mathrm f}_{\mathrm c,\mathrm z}}+\frac{{\mathrm\tau}_{\mathrm{yz}}^2}{{\mathrm f}_{\mathrm v,\mathrm{yz}}^2}+\frac{{\mathrm\tau}_{\mathrm{xz}}^2}{{\mathrm f}_{\mathrm v,\mathrm{xz}}^2}+\frac{{\mathrm\tau}_{\mathrm{xy}}^2}{{\mathrm f}_{\mathrm v,\mathrm{xy}}^2}\right]$with:${\mathrm\delta}_{\mathrm x,0}=\frac{{\mathrm f}_{\mathrm t,\mathrm x}{\mathrm f}_{\mathrm c,\mathrm x}}2$${\mathrm\delta}_{\mathrm y,0}=\frac{{\mathrm f}_{\mathrm t,\mathrm y}{\mathrm f}_{\mathrm c,\mathrm y}}2$${\mathrm\delta}_{\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\delta}_{\mathrm x,0}^2}{{\mathrm f}_{\mathrm t,\mathrm x}{\mathrm f}_{\mathrm c,\mathrm x}}+\frac{{\mathrm\delta}_{\mathrm y,0}^2}{{\mathrm f}_{\mathrm t,\mathrm y}{\mathrm f}_{\mathrm c,\mathrm y}}+\frac{{\mathrm\delta}_{\mathrm z,0}^2}{{\mathrm f}_{\mathrm t,\mathrm z}{\mathrm f}_{\mathrm c,\mathrm y}}$The yielding condition can be thought of as an elliptical surface in a sixdimensional space of tension.If one of the three stress components is applied as a constant value, the surface can be projected onto a threedimensional stress space. Projection of yielding surfaces for normal stresses according to TsaiWu If the value for fy (σ) is smaller than 1, the stresses lie within the elastic range. The plastic zone is reached as soon as fy (σ) = 1; values greater than 1 are not allowed. The model behavior is idealplastic, which means no stiffening takes place. 
Answer
In the case of timber, the "Orthotropic Elastic/Plastic 3D" material model has to be assigned to the "Material" solid type (Figure 01).
Since the program considers the "Contact" solid type as a member, it usually requires the isotropic material model (Figure 02). 
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In this case, the orthotropic material model is probably assigned to both the surfaces/solids and the members. However, timber members require an isotropic material model. Therefore, it is necessary to create another timber material and assigned it to the corresponding members or crosssections.

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In the case of userdefined matrices, the stiffness matrices of orthotropic surfaces are saved in the MatrixConstants.cfg file in the C:\ProgramData\Dlubal\Global\General Data folder. The folder requires the standard installation! 
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If 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 TsaiWu 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.
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First Steps
We provide hints and tips to help you get started with the main programs RFEM and RSTAB.
Wind Simulation & Wind Load Generation
With the standalone 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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