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Frequently Asked Questions (FAQ)
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AnswerA line hinge is nothing more than a line release where an object is released. While a surface is released for the line release, it is defined on the line of a surface for the line hinges. In this case, the released surface is the surface on which the line hinge was defined.The forces always act on the original surface, that is, on the non -released surface. For line hinges, this means that the forces act on the surface without a line hinge.Now it is necessary to clarify the sign conventions, i.e. in which direction the force acts on the surface. For this, it is necessary to know the local x-axis of the lines as well as the local z-axis of the surface. The internal line hinge coordinate system is to be understood as follows:
For the example shown in Figure 01, this means the following:Example 1The x-axis of the line runs to the right .The z-axis of the surface is oriented downwards⇒ The y 'axis of the line hinge is oriented away from the original surface (= surface without line hinge). Since the value is displayed with a negative sign, the force acts in the direction of the original surface.Example 2The x-axis of the line runs to the left .The z-axis of the surface is oriented downwards⇒ The y 'axis of the line hinge is oriented towards the original surface (= surface without line hinge). Since the value is displayed with a positive sign, the force acts in the direction of the original surface.Example 3The x-axis of the line runs to the right .The z-axis of the surface is oriented downwards⇒ The y 'axis of the line hinge is oriented towards the original surface (= surface without line hinge). Since the value is output with a positive sign, the force acts in the direction of the original surface because Actio = Reactio.Example 1The x-axis of the line runs to the left .The z-axis of the surface is oriented downwards⇒ The y 'axis of the line hinge is oriented away from the original surface (= surface without line hinge). Since the value is output with a negative sign, the force acts in the direction of the original surface because Actio = Reactio.In contrast to the line releases, the axis system cannot be displayed for the line hinges. For the example shown in the figure, it is recommended not to arrange the line hinge on the surface on which the result is to be related and to orient the x-axis of the line in such a way that its y-axis is oriented in the direction of the desired surface. For this, the coordinate system of the line applies.
- The axis x 'points in the direction of the local x-axis of the line.
- The axis z 'is the normal to the surface on which the line hinge was defined.
- The axis y 'represents the tangent to the surface plane and results from the "right-hand rule".
AnswerFor this, a line of the desired shape must first be created in the surface at the point where the section is to be created. The section can then be arranged on this line (see Figure 01). If no element with a stiffness is connected to this line and no load is applied, the mesh generator must first be informed that this line should still be meshed (see Figure 02). After the calculation, the results can be read off.If two result diagrams are displayed, it is because the result is displayed from both sides of the line. In this case, you can set the smoothing of the internal forces to "Continuous total". Then they are smoothed over the lines and only a result diagram remains.
The optimization of cross-sections in RF-/TIMBER Pro is based exclusively on the ultimate limit state (ULS), not on the serviceability limit state (SLS), see the figure from the RF-TIMBER Pro manual.
More information about the optimization of cross -sections can be found in the RF -TIMBER Pro manual on pages 69 - 71 in the German version and on pages 76 - 78 in the English version (also available with the F1 key in the add -on module).
In the "Geometry" or "Supports and hinges" dialog box, you can specify in the "Supports" tab whether the support compression should be checked for a support.
In the case of an asymmetrical system, separate entries are possible for the support on the ridge, for example. In this way, the different support widths of the two rafters can be determined.
If there is a rafter mouth, the cross -section reduction is usually known (column D).
The supports can be related "globally" to the directions of the axes XYZ or "locally" to the directions of the member axes xyz. The corresponding selection is possible in the list.
The support orientation has effects on the design of the support compression, among other things: In the case of a global arrangement, the compressive stresses in the bird's mouth are considered at an angle to the grain direction according to the roof inclination, in the case of a local arrangement under 90 ° to the grain direction.
A drilling can be performed with a surface model. For this, it is first necessary to split the member (the finer is the division, the more accurate is the result) and then generate surfaces from it.
The resulting cross-section outlines can then be easily rotated. Please note that the cross-section shortening is not taken into account. The RF‑IMP add-on module provides more accurate results as it can pre-deform the FE mesh.
In the calculation parameters of the load combinations, the calculation type according to the second-order analysis is preset by default. For example, the calculation is performed according to EN 1995‑1‑1, 2.2.2(1)P, using the design values of the stiffness property of the structural component, that is, the stiffnesses divided by the partial safety factor. For this reason, this stiffness modification is activated by default (see Image 01). For the load combinations in the serviceability limit state, there should be no reduction of the stiffness, of course.
Manual Creation of Load Combinations
If you create the load combinations manually, the load combination cannot "know" which limit state is involved. In this case, it is necessary to make the setting manually (see Image 02). This setting must also be deactivated manually when switching to the geometrically linear analysis.
Automatic Generation of Load Combinations
If the load combinations are generated automatically by the program (see Image 03), the stiffness reduction is automatically deactivated for the SLS combinations specific to timber structures. For the ULS combinations, the reduction depending on the method of analysis is considered (second-order analysis and higher) or not (geometrically linear analysis). However, this requires the definition of the calculation type in the combination expressions (see Image 04). Changing the calculation type in the calculation parameters of the CO has no impact on the stiffness.
AnswerThis program is not an add-on module. The RX-TIMBER programs work independently. You can search for them, for example, via the Windows search or via the Windows START button → Dlubal → RX-TIMBER. Then, Project Manager starts. You can open one of the previous projects or create a new one by using the selected program.By default, the program is installed in C:\Program Files\Dlubal\RX‑TIMBER 2.24\ and can be started using the PRM64.exe file.
AnswerThese increments result from the creep components in a quasi-permanent combination. You can find the overview of which combinations are to be analyzed in the serviceability limit state according to DIN EN 1995‑1‑1 here or in the links of the FAQ.The creep components are then simply added to the characteristic deformation, for example with 0.8 × dead load. This results in the factor 1.8 (see also Section 2.2.3 in EN 1995‑1‑1).In this specific case, the following coefficients must be applied for the quasi-permanent design situation:Gk ⋅ (1 + 0.8) + Qk ⋅ (1 + 0.6 ⋅ 0.8) = Gk ⋅ 1.8 + Qk ⋅ 1.48
The effective length can be adjusted in Window 1.5 of the add-on module, depending on the type of bending moment in the "Define Lcr" line.
In the graphic, this is not possible for clarity reasons. However, the RF‑LAMINATE add-on module allows you to also display the stresses in all points. This is deactivated by default because it quickly produces a huge amount of data for large structures.
If you also filter by the stress component that interests you, the results in the table becomes quickly clear, and you can easily evaluate the distribution of stresses at a point using the layers there.
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Wind Simulation & Wind Load Generation
With the stand-alone program RWIND Simulation, you can simulate wind flow around simple or complex structures 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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