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Frequently Asked Questions (FAQ)
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Yes, the load can be entered in RFEM as a surface load. In the Edit Surface Load dialog box, you can find the Generate Load due to Shrinkage... button. This allows you to obtain the internal forces due to shrinkage.
In order to consider the shrinkage in the RF‑CONCRETE Surfaces design, it is not necessary to enter a load. The RF-CONCRETE Surfaces add-on module automatically apply the loads due to the shrinkage.
AnswerThe problem is caused by different result smoothing. In this case, you have set the interpolation by the individual surfaces, so the values are interpolated regardless of the adjacent surface.
In RFEM, built-up sections called Castellated Beams are available in the cross-section library. They allow you to place openings in the web of sections such as W-shapes for example. The layout of the openings is parametric where the diameter and spacing can be adjusted. These cross-sections can further be designed in the RF-STEEL AISC add-on module.
You can then set separate cross-sections for the start and end of the member allowing you to create a tapered section.
Curved members cannot be designed for stability within the RF-STEEL AISC module. These stability checks include flexural buckling (strong axis and weak axis) and flexural torsional buckling according to Chapter E. Lateral torsional buckling is also not checked according to Chapter F for these types of members.
A possible workaround to carry out stability design for a curved member is to convert the line element to a polyline and design as a straight member instead. Alternatively, a series of straight line segments can be modeled and convert to a set-of-members which can also be designed in the RF-STEEL AISC module including stability checks.
The "temperature difference" load type always refers to the cross -section height in RSTAB and RFEM. For a rib, however, the plate component is not taken into account for the determination of the cross -section height, which is necessary for the determination of the load size. For a rib, it is therefore necessary to define the loading for the member and for the surface separately.
- Cross -section rib → rectangle 200/200
- Surface thickness → 200 mm
- Temperature difference between the top and bottom of the component = 200 K.
Result for the deformation when modeling the component as a T -beam (cross -section)
The load for the model by means of surfaces and rib is theoretically composed as follows:
The temperature load of the surface is also determined according to this scheme.
In the attached model file, there are two further modeling variants in which the temperature distribution for the plate component was considered more realistically. The deformations in these two model variants are slightly larger for this example than in the other models.
No, it is not possible to set user-defined values when viewing stress results on a solid. These unfortunately do not work like results on a surface. It is possible to activate the result values on each FE Mesh Node using the settings shown below under Values on Surface. To access the filter settings you must right click on the label "Values on Surfaces."You can then also set your results to Solid Point Display under the Results menu. This will help give a better visual on where those results are located graphically.
AnswerA line hinge is nothing more than a line release where an object is released. In the case of a line release, a surface is released, and in the case of a line hinge, this is defined on the line of a surface. Therefore, 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. In the case of line hinges, this means that the forces act on the surface without a line hinge.Now, it is necessary to clarify the sign conventions, that is, 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 Image 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 (= a surface without a 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 (= a surface without a 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 (= a surface without a line hinge). Since the resulting value is displayed 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 (= a surface without a line hinge). Since the resulting value is displayed 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 image, 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' is the tangent to the surface plane, and results from the "right-hand rule."
AnswerThe effect results from the shrinkage application in the nonlinear deformation analysis in RF‑CONCRETE Surfaces. The shrinkage is considered as a change in length or a shortening in the form of an additional load.Since the reinforcement prevents the shrinkage, an asymmetrical reinforcement of 2.57 cm²/m on the top and 5.24 cm²/m on the bottom, for example, can reduce the cross-section on the top side because of the smaller steel core. This results in an additional curvature (longer bottom side), which occurs in addition to the actual deformation.If the difference between the steel cross-sections on the top and bottom becomes even larger (for example, 2.57 cm²/m on the top and 10.47 cm²/m on the bottom), this additional curvature becomes larger as well.You can create additional design cases in the file and, for example, analyze symmetrical reinforcement, or deactivate the shrinkage as a test.More information about applying shrinkage in a nonlinear deformation analysis can be found in the technical article 001574 on our homepage.
AnswerContact stresses are not covered by the average regions.The average regions only deal with the surface internal forces that are also visible in the dialog box when entering the average region, as well as the stresses that are derived from these surface internal forces.
As a basis for the analysis of temporary structures, both RFEM and RSTAB can be used. For both programs, there are the standards available according to which the steel, aluminium, and lightweight structures can be calculated and designed. If you want to design membrane and cable structures, RFEM is required.
Main Programs RFEM or RSTAB
The main programs RFEM or RSTAB are used to define structures, materials, and actions.
In order to also analyze membrane and cable structures, RFEM is required. When it comes to pure beam structures, it is sufficient to purchase RSTAB. In any case, RFEM is more versatile it can be equipped and extended with the corresponding add-on modules for all materials and structural models.
- RF-/ALUMINUM according to Eurocode 9 (EN 1991-1-1:2007)
- RF-/ALUMINUM ADM according to ADM 2020 (US code)
- RWIND Simulation
Complex analysis of any structures in the digital wind tunnel with the transfer of load cases to RFEM or RSTAB for further processing
Dynamic AnalysisIf it is necessary to perform seismic analysis or vibration designs of a building, the RF‑/DYNAM Pro add-on modules provide special tools for determining natural frequencies and mode shapes, for an analysis of forced vibrations, a generation of equivalent loads, or for a nonlinear time history analysis.
- Building Information Modeling (BIM)
An extensive collection of interfaces allows for data exchange with other programs.
If you have any question about the Dlubal Software programs, please do not hesitate to contact our sales department.
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Wind Simulation & Wind Load Generation
With the stand -alone program RWIND Simulation, you can simulate wind flows 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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