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Answer
The setting of the load application in the Details refers to the principal axes of the respective crosssection. For a Zprofile as an example, a box with the 9 edge nodes is put around the profile. The load application is then always related to the rotated principal axis angle and the corresponding eccentricities.

Answer
Areas with dual stiffnesses should be avoided during the modeling. If a downstand beam and a wall are modeled at the same location, these elements divide the load transfer. A disadvantage of separating the members on the wall section is that singularities occur at this location. Moreover, the area of the load introduction from rib into the wall is at the ceiling height.
Thus, there is no optimal solution in this combined modeling of members and surfaces.For small models, it is possible to alternatively model the downstand beams and carry out the design by means of the result beams. 
Answer
By activating the addon module RFFORMFINDING, a highquality formfinding process is defined according to the URS method before the actual structural analysis for each element with formfinding properties. After the calculation, this process results in an optimal equilibrium shape that almost exactly reflects the specified shapefinding parameters (prestress, sag, etc.).
Since this URS method requires an iterative calculation to display results, the program provides an interactive graphic mode based purely on the force density method for pure modeling. This mode displays the resulting element shape on the basis of the stored formfinding properties stored when the elements are entered.To avoid possible initial complications due to incompletely defined models, it is possible to switch the mode on and off at any time in the shortcut menu by using the "Show Shape" option.The graphics mode considers all forcerelated formfinding inputs on member and surface elements in the determination. A stable boundary condition in the respective direction is assumed for all relevant nodes with a connected element or support definition. In addition, integrated openings in surfaces are considered for the optimized display of tent points.This interactive formfinding is generally only intended for the graphical display of elements with applied loading and works independently of the URS formfinding, which is always done before the pure structural analysis. However, the mesh's mesh is based on the currently displayed shape and can thus be influenced by the activation of the interactive formfinding. 
Answer
The tolerance epsilon can be found in the FE mesh settings in the "General" window section. It controls the behavior of the FE mesh generator when nodes are very close to lines. Figure 3 shows the difference. If the tolerance is greater than the distance of the node to the line, this small local difference in the mesh generation is neglected. In the case shown, the mesh of the line is deflected towards the node. In this case, the line is no longer ideally straight. If the tolerance is smaller than the distance, a separate FE node is generated for the node.The error message appears if the distance between two adjacent nodes is smaller than epsilon and they are connected by a line (see Figure 3). In most cases, this is due to an inaccuracy in the modeling. Since the error message contains no information about node numbers, you can use the model check "Identical Nodes". The program searches for nodes whose distance meets the tolerance delta. Now set the Tolerance value to the value of epsilon. Then, the nodes are listed in the upper part of the dialog box.As described below, the descriptions differ depending on the case. If there is an inaccuracy in the modeling, it can be adjusted. In other cases, it is, of course, possible to further reduce the tolerance of epsilon. 
Answer
When components are calculated with the Finite Element Method (FEM), you can choose between surfaces and solids in RFEM. The big advantage of surfaces is the calculation time, because the FE elements are only defined in the surface plane. The third dimension, that is the thickness, is considered as a physical property in the calculation. Thus, a surface can be considered as a mathematical simplification. In addition, surfaces can be meshed more easily than solids (Jacobi Matrix).Plate elements are divided into two types of elements. Whereas in the classical thin plate theory (Kirchhoff) shear deformations due to shear forces are neglected, special extended approaches have to be assumed for the thick plate theory (ReissnerMindlin). For thin plates, the pure bending reaction is dominant. Therefore, the simplified bending theory is also sufficient. As the thickness increases, the proportion of the transversal shear influence on the load bearing capacity increases. Starting at a certain thickness, the error due to neglecting this component is so large that it is absolutely necessary to have the higher theory of the thick plate. Considering a slab as being "thin" or "thick" does not depend on the ratio "dimension to thickness" of the single finite element, but on the conditions in the structural system. Influencing factors include, in addition to the plate thickness, especially the span lengths (length, width, radius), the type of support and the load type as well as their distribution. Due to the multitude of influences, it is not possible to specify a mandatory value.Figure 01 shows a guideline describing the validity of the corresponding elements. The size "d" is the thickness of the structural component and "L" the length of the structural component or the distance between the supports. The ratio d/L gives an indication of when an element is valid for an analysis. If d/L is large, the shear deformation is a critical parameter and the user should prefer to use solids. If d/L is small, the shear deformation has no decisive influence and surface elements are the most effective choice.Figure 02 performed calculations with the different elements. A top view is shown so that the deformations can be interpreted on the image plane. For a small d/L ratio of 0.2, the deformations very well match for all three variants. If d/L = 0.4, differences between the thin and thick plate calculations are already noticeable. In the extreme case d/L = 0.7, a difference of the thick plate to the solid is additionally observed. The loads have been selected in such a way that the same deformation is achieved for all solid elements to produce a meaningful printout. 
Answer
The definition of surface supports (foundation) in RFEM is a property of the surface.
Figure 01  Dialog Box "Edit Surface" with Definition of SupportThis means that you have to divide the entire floor slab  depending on the areas with different subgrade moduli  into several surface components. 
Answer
This message is related to an incompletely defined solid.
Presumably, the solid definition has been destroyed while entering other elements. In this case, open the solid text definition and check the input of the boundary surfaces for completeness. It has to be ensured that the set boundary surfaces result in a "watertight" solid.If the error occurs despite defining all surfaces, check the model for double lines. The following FAQ helps here. 
Answer
The stiffness type "Membrane Without Tension" describes the plate and block stiffness of surfaces.
The plate stiffness including the shear stiffness perpendicular to the surface plane is linearly elastic and the plate stiffness in the surface plane is defined nonlinearly elastic with the material model according to "DruckerPrager" depending on the defined thickness and the assigned material.In order to ensure that the surface behaves "Without Tension" in the pane direction, the nonlinear material model reacts with yielding tensile stress f_{y,t} going to almost zero in tensionloaded elements in combination with a relatively small hardening modulus E_{p} . For compression forces, however, the elements remain linearly elastic due to a relatively high yielded compressive stress f_{y,c} and react with an unrestricted compression transmission.Since the "Membrane Without Tension" stiffness type fundamentally modifies the wallrelated degrees of freedom of surfaces, it is only applied to surfaces of the relevant model types 3D, 2D  XZ (u_{X}/u_{Z}/φ_{Y}) and 2D  XY (u_{X}/u_{Y}/φ_{Z} ).To better describe the partial nonlinearity of this surface stiffness type, the release RFEM 5.06.1103 from 4.02.2016 renames the type from "Without Tension" to "Membrane Without Tension".The Knowledge Base article "Modeling Approaches for Shear Bearing Connections by FEM" shows a possible application. 
Answer
The most suitable combination is a member elastic foundation with nodal supports, which may fail each.
Figure 01  Bolted Support on a Bracket to a Member
Figure 1 shows a model with such a support. As it is obvious from the results, the member elastic foundation absorbs the compressive forces and the nodal supports absorb the tension forces.

Answer
To open an RXTIMBER file in RFEM or RSTAB, select the option “All Files (*.*)” as “File Type” (see Figure 01). The geometric data, loads as well as load combinations will be imported. Settings relevant for the design, for example, shear force reduction, fire protection definitions, serviceability limit state parameters, etc., are not applied and must be redefined in RF/TIMBER Pro.
If the model does not appear in the work window, display the view with the option “Show Whole Model” (see Figure 02).
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