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Frequently Asked Questions (FAQ)
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AnswerA suspended, linearly supported membrane roof structure can be modeled in RFEM using the RF-FORM-FINDING module. To do this, define as follows:
- The load -bearing structure around the membrane roof
- The edging elements of the membrane consist of cable elements with corresponding form -finding settings
- The membrane between the edging elements with corresponding form -finding settings
- The support boundary conditions for transferring the loads
- A load case with the action category "Form -finding" to describe the form -finding loads in addition to the prestress.
AnswerTurning on Advanced Lighting in Program Options should solve the problem. Alternatively, try adjusting the lighting in the Navigator on the View → Rendering → Lighting tab. On some computers, all the lights may be off, try turning them on gradually until it is ideal for you.
When a graphic is scaled in the printout report, it is also automatically displayed in the printout report graphic. Generally, the display of the scale cannot be hidden.
You have probably activated the perspective view. You can also edit the graphic in the printout report retrospectively and deactivate the display of the perspective view. Then the scale is displayed as expected.
In the background, the profile of the turbulence intensity over the altitude is a pure factor function depending on the altitude. By multiplying the altitude -dependent factors by the entered turbulence intensity, the turbulence intensity profile applied at the wind tunnel entrance results.
The generic turbulence intensity profiles from the RFEM 5 or RSTAB 8 environment are each referenced to the bottom edge of the wind tunnel. Thus, the factor function at this ground location has the value 1 and thus defines the unmodified input value of the turbulence intensity at this location. At a higher position with a factor ≠ 1, the turbulence intensity input multiplied by this factor is applied accordingly.
To delete elements, there is the "DeleteObjects ()" function in the model data interface. Deleting all members looks like this:Sub test_delete_objects ()Dim iApp As RFEM5.ApplicationSet iApp = GetObject(, "RFEM5.Application")iApp.LockLicenseDim iMod As RFEM5.IModel3Set iMod = iApp.GetActiveModelOn Error GoTo e' get interface for model dataDim iModData As RFEM5.IModelData2Set iModData = iMod.GetModelData'get all membersDim mems() As RFEM5.Membermems () = iModData.GetMembers'create member listDim mem_list As StringDim i As IntegerFor i = 0 To UBound(mems, 1)mem_list = mem_list & mems (i) .no & ","Next'delete membersiModData.PrepareModificationiModData.DeleteObjects MemberObject, mem_listiModData.FinishModificatione:If Err.Number <> 0 Then MsgBox Err.description, vbCritical, Err.SourceiMod.GetApplication.UnlockLicenseSet iMod = NothingEnd Sub
Please note that the "DeleteObjects" function only works with the object number and not with the object index. These numbers are transferred as a string separated by commas.
For this reason, all members had to be fetched first. Then the member field was looped through and all member numbers were entered in the string.
The change of the vertical position or an eccentricity has an effect on the bending moment My only if there are other forces acting on the model, which are included in this moment, such as the axial force in the following example.
A slab, supported as a single-span beam, is only loaded vertically on the left in the image. The bending moments of the result members positioned above and below the slab do not differ.
On the right, the slab is additionally loaded by an axial force. Therefore, the result members obtain additional negative or positive moments. The eccentricity acts as a lever arm.
Yes, it is. You can keep the results of RWIND Simulation if the FE mesh is deleted. To do this, select the Keep wind simulation results if mesh is deleted option in the RWIND Simulation settings:
A new calculation by RWIND Simulation is not required if the material is changed, the support conditions are adjusted, or other changes are made that do not affect the CFD analysis.
After adjusting the material, the FE mesh is deleted and thus also the RWIND load case. However, you can generate this RWIND load case again in a few seconds by creating the loads again in RFEM using Calculation → RWIND Simulation - Calculate All in Background.
Then, the results are available again.
AnswerA tent roof with two cone tips can be modeled in RFEM using the RF‑FORM‑FINDING add-on module. For this, proceed as follows:
- For each conic area, generate a separate membrane surface around the larger boundary line.
- Integrate the opening of the cut cone tips into the base areas.
- Align the axis systems of the respective conical membrane surfaces to the center line.
- Define the "Projection" form-finding method for the conical membrane surfaces.
- Support the membrane edges sufficiently and start the form-finding process.
Various international standards or codes specify additional secondary values for the description of the load value specific for a location.
For example, the wind load description of the United States according to the code ASCE/SEI 7‑16 specifies various wind speeds for a location, depending on the defined risk category.
The Geo-Zone Tool always uses all location-specific parameters available from the load standard. In addition to the actual primary load value, further parameter maps are carried out in the background. These maps can be selected and displayed in the "Map" list box.
According to the national provision of ÖNORM EN 1993‑1‑5:2007, Section 4.5.3(3), it is possible to abandon the increase of σcr,c, allowed in the note, with respect to the elastic critical buckling stress σcr,sl of the longitudinal stiffener adjacent to the compression edge as this results in very conservative results with regard to the resulting reduction factor ρc for the buckling analysis according to ÖNORM EN 1993‑1‑5, Section 4.5.4(1), Equation 4.13. Image 01 shows an example of a longitudinally stiffened buckling panel, designed according to the Austrian National Annex.
In DIN EN 1993‑1‑5, the note given in Section 4.5.3(3) applies, so it results in the following difference, see Image 02.
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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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