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Frequently Asked Questions (FAQ)
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AnswerIn this case, it is recommended to use the module extension RF-/STEEL Warping Torsion :RF-/STEEL Warping Torsion is an extension of the RF-/STEEL EC3 and RF-/STEEL AISC add-on modules. It performs flexural-torsional buckling analyzes of members according to the second-order analysis with seven degrees of freedom and a form of imperfection affecting the mode shape.You can find more information in the links below this FAQ.
The setting of the load application specified in the Details refers to the principal axes of the respective cross-section. For a Z-Profile as an example, a box with nine edge nodes is set around the profile. The load application is then always related to the rotated principal axis angle and the corresponding eccentricities.
AnswerFor the design using Equivalent Member Method and General Method, there are four degrees of freedom considered in the eigenvalue solver. These are as follows:
If the RF‑/STEEL Warping Torsion add-on module is activated, there are seven degrees of freedom available:
- uY' (displacement from the plane)
- φX' (rotation about the X'-axis)
- φZ' (rotation about the Z'-axis)
- ω (warping)
- ux (displacement in x)
- uy (displacement in y)
- uz (displacement in z)
- φx (rotation about the x-axis)
- φy (rotation about the y-axis)
- φz (rotation about the z-axis)
- ω (warping)
AnswerThat is correct. For the verification of the relevant components, these must be defined as rod sets and selected for design. It is also important that in the design case of the wölbkraftanalyse no bars are selected for the dimensioning, which are either already included in the staff sets or claimed to torsion, since the module RF- / STEEL EC3 then want to measure these by means of replacement rod method and this possibly no proof due to the torsion is possible and the warning appears.
In RF‑/STEEL Warping Torsion, the imperfection is applied in both directions (+/-). Therefore, the + imperfection can be governing at one x‑location while the - imperfection prevails at the adjacent x‑location. The governing result is shown in the result tables and in the graphic. This could be the cause of the described effect.
Please check the boundary conditions, that is the definition of nodal supports and especially the application of imperfection in Window 1.13 "Parameters - Sets of Members." The imperfection is preset as L/150, which can represent a conservative solution.
In order to perform the calculation without imperfection, select the "L Manually" check box (see the figure) and keep the length at 0.00 ft.
Unfortunately, the output of support forces is not possible. However, you can perform design with RF‑/FE‑LTB: the output of support forces is included there.
That is right, both add-on modules calculate with the 7th degree of freedom, the warping.
The difference is that RF‑/FE‑LTB automatically detects only those loads that directly act on a set of members. Loads from other structural components, that indirectly act on the designed set of members, must be added manually as secondary loads. RF‑/FE‑LTB then performs a complete recalculation of the structural system.
On the other hand, RF‑/STEEL Warping Torsion analyzes the internal force distributions from the calculation of the main program and then calculates the loads back. These are then applied again and calculated. Thus, you do not need to enter loads, which saves your time.
Nodal supports and boundary conditions are preset, but not imported. As a rule, you have to adjust them.
In the case of the General Method for the set of members design in RF‑/STEEL EC3, nodal supports phi_x ' and u_y' are predefined at the set of members start and end, which represents a support with torsional restraints for all straight sets of members.
In RF-/STEEL Warping Torsion, nodal supports u_x, u_y, u_z, and phi_x are always predefined at the set of members start and end.
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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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