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Frequently Asked Questions (FAQ)
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AnswerLine releases on components are currently not possible.
If the linear release properties are concerned, it is possible to quickly arrange them as line releases of the components.
In the case of the nonlinear release properties, it is necessary to use the components. For this, the "Convert Intersection into Line" option is useful. You can find this function in the shortcut menu of the generated intersection line. Then, you can create a boundary of the surface by using a new line and assign the line release.
If the line hinge has been defined correctly, the problem may be in the incorrect support definition.Although the structural system (see Figure 01) would seem to be the same, there is a moment in the mid-span resulting from the determination of internal forces on the surface.In the present case, the cause can already be derived from the error message after the load case calculation.There are very large deformations resulting in the bottom structure, so that this already indicates an incorrect support of the surface.When checking the line supports, it becomes clear that the bottom structure is rotated about the global Y-axis due to the missing restraint. In the end, this leads to the non-meaningful distribution of internal forces in the basic internal force m-x.If you adjusted the line support, you will get the expected result.
Figure 01 shows an example. As you can see, the same contact stresses are generated at each location of the surfaces and thus the elastic foundation springs have been applied correctly everywhere.
Since line hinges are internal line releases, the same applies to the line releases.
AnswerAs of the RFEM version 5.17, there is the graphical result display (only available for line hinges and line releases) as well as the result display in tables. The latter can be found in the following tables:
- 4.45 Line Hinges - Deformations
- 4.46 Line Hinges - Forces
- 4.47 Member Hinges - Deformations
- 4.48 Member Hinges - Forces
- 4.49 Nodal Releases - Deformations
- 4.50 Nodal Releases - Forces
- 4.51 Line Releases - Deformations
- 4.52 Line Releases - Forces
AnswerThere are several possibilities to evaluate the results of line hinges:
- Graphical evaluation of the results: Under "Releases" in the Results navigator, you can display various forces and deformations of the line releases in the graphic.
- Display of the results in tables: For the tabular evaluation of the results, Table "4.45 Line Hinges - Deformations" and Table "4.46 Line Hinges - Forces" are available.
- Evaluation by means of result diagrams: You can use the shortcut menu to view the result diagram of the line hinges.
The result diagram of a line release (Figure 1) or a line hinge (Figure 2) can be displayed by right-clicking the relevant line release or line hinge. From the shortcut menu, select the "Result Diagrams" entry.
The video shows how the results of a line release/a line hinge can be displayed in the work window and in the "Result Diagrams" dialog box.
AnswerBasically, elements in RFEM are rigidly connected with each other. To solve this problem, RFEM provides two elements. The line hinges and the line releases. The difference is explained in the link below.
If you define line loads on a line that is decoupled from the overall system, that line becomes semi-rigid. The program checks this incorrect entry and gives a hint (Fig. 1). However, there are structures where this line is kept at a different point. In this case, the program continues to calculate after the user has confirmed the note. However, since the deformation for such a decoupled line becomes very large, it is not displayed in the graphic output.We generally recommend not to load lines that are decoupled via a Line release or Line hinge.The theoretical background will be explained in this Article.
AnswerAxial / Shear hinge or springThe degrees of freedom are based on the following definition of the axis system: The axis x points in the direction of the line; the axis y represents the tangent to the surface plane, the axis z the normal to the surface.The text boxes and table columns control the degrees of freedom for axial and shear forces. If a check box is selected, it means that the displacement in this direction is possible and thus the force is not transferred.It is also possible to enter the constant of a translational spring.Moment hinge or springThe degrees of freedom for the moments refer to the local axis system of the hinge (axis x in the direction of the line, axis y as tangent, and axis z as normal to the surface plane).A check mark indicates that the rotation is free and the internal force is not transferred.It is also possible to enter the constant of a rotational spring.There is already an interesting article about line hinges available on our website .
Line hinges control the connections between surfaces. It is possible to consider entire decouplings of surfaces or semi-rigid couplings by means of linear springs. Internally, line hinges are also line releases, except for integrated lines. Such a line hinge works in such a way that the stiffness in the adjacent first element row of the assigned surface is reduced according to the selected degrees of freedom. In concrete structures, it is possible to define e.g. an assembly joint by a line hinge. In timber construction, a modeling via line hinges is necessary, in particular because of the very limited rotation transmission of forces.
Line releases allow you to decouple elements connected to a line (members, surfaces, and solids) from each other. A new line is generated at the same location, which only transfers the locked degrees of freedom. A line hinge can, however, also consider nonlinear effects (see Figure 2).
First, the line release type must be created. This way, the program defines the open degrees of freedom or spring constant and, if necessary, nonlinearities. Then, you can apply the line release to members, surfaces, and solids on single lines. You can also manipulate the axis system of the release in the same dialog box.
If line hinges have already been used in an item, they can be quickly converted to a line release (see Figure 3). In this way, it is very easy to consider nonlinear effects in the structure.
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Wind Simulation & Wind Load Generation
With the stand-alone 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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