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Frequently Asked Questions (FAQ)
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RF-/ALUMINUM checks the symmetry of general cross-sections and compares them with the SHAPE-THIN evaluation if activating the "Determine symmetry by module and compare with SHAPE‑THIN definition" check box (Figure 01).
If both methods provide different results, the corresponding error message appears (Figure 02).
Usually, there are small inaccuracies in the SHAPE‑THIN cross-section. Thus, the cross-section Sec‑1.du9 shown in Figure 03 is not absolutely symmetrical to the Z‑axis: The Z‑coordinates of Node 1 and Node 4 as well as Node 55 and Node 60 do not match in the second decimal place.
SHAPE‑THIN classifies the cross-section as asymmetrical, but RF‑/ALUMINUM as monosymmetric to the z‑axis, so the error message shown in Figure 02 appears.
The SHAPE‑THIN cross-section should be checked for symmetry. When modeling in SHAPE‑THIN, it is useful to only display one side of the cross-section and to create the other half by mirroring. This is also shown in the video.
AnswerThe reason is that there is no stability analysis for unsymmetrical, open cross-sections according to EN 1999‑1‑1 if the compressive normal forces and bending moments are effective.You can neglect the bending moments in Details, the Stability tab, by selecting the corresponding filter. Then, the flexural buckling design is performed without moments. However, this is under your own responsibility. Another way is to check the stability according to the second-order analysis, which would be possible by using the RF‑/FE‑LTB add-on module.
AnswerIf you need to define different types of lateral intermediate supports, it is necessary to divide the specific member. After that, you can create a set of member and with that done, you can easily define different types of intermediate supports along this set of member, or you can use different nodal supports in the nodes of the set of member.
AnswerThis kind of result may occur if the limit internal forces of the cross-section cannot be determined. In most cases, the problem lies in a wrongly defined cross-section or in the selection of an unsupported cross-section. Please check if you have selected the cross-section allowed for the aluminum structure in the add-on module. These include the rolled cross-sections and parametric thin-walled cross-sections.The cross-section HK 120/40/5/5/5/5 shown in Figure 01 is not a valid cross-section as it has been selected from the area of solid cross-sections (concrete components).
In this case, it is necessary to change the cross-section to TO 120/40/5/5/5/5.In the case of the design in RF‑/ALUMINUM, please note that you have to select the material which also involves thicknesses used for the cross-sections. A material that is only allowed up to t=3 mm cannot be used for a cross-section with t=5 mm.
AnswerYou can usually set the standard and the National Annex in the top right corner of an add‑on module (see Figure 01). In most cases, it is also possible to display the factors of the National Annex and edit them, if necessary (see Figure 02).
AnswerBy default, the computation kernel of the cross-section program SHAPE‑THIN is used in the RF‑/ALUMINUM add‑on module to determine the stresses of the effective cross-section in an iterative procedure. This method is precise as all corners and edges of the cross-section are covered, but can be very time-consuming in the case of compound cross-sections.As an alternative, it is possible to determine the effective cross-section by using the simplified analytical method (see Figure 01), which is significantly faster. In the case of using this approach, the corners, roundings, and others, are neglected and then compensated by a factor. No iterative calculation is performed. Therefore, the effective cross-section values might be higher than with the SHAPE‑THIN calculation.In such a case, it is recommended to carry out the calculation using the analytical method and then to only design the governing structural component with the governing load combination by using the SHAPE‑THIN solution.
With the COM interface, you can access most operating elements as well as results of the following programs or add-on modules:
- RF-/STEEL EC3
- RF-/TIMBER Pro
- RF-/DYNAM Pro
AnswerThe limits cannot be modified in the mentioned add-on modules. However, you can create a new material with modified limits based on the desired material. Figure 1 shows the window of the material library. Select a suitable base material here and then click on "Create new material ...". In the following dialog you can assign the material a new name and change all parameters of the material.
Unfortunately not. Intermediate supports and nodal supports have to be set manually. The default configuration for effective lengths is 1,0*member length and for set of members, one nodal support with definition u_y' and phi_x' is defined on each side of the set of member.To speed up the process of defining nodal supports, you can pick more nodes in one step by using the highlighted function in the attached picture.
In the general data, the sets of members must be selected first in order to be able to design them for the corresponding limit states (see Figure 1). Then, you can enter different specifications for the serviceability limit state design in the serviceability data (see Figure 2).
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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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