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Frequently Asked Questions (FAQ)
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AnswerIn RFEM 5 and RSTAB 8, there is the option to assign various stiffnesses to the individual objects, such as nodal supports, by load case. This feature can be found in the calculation parameters of the load cases and load combinations (see Figure 01).
In RFEM 5, the individual objects can also be deactivated by load case (see Figure 02).
The tab allows you to ignore certain objects of the model in the calculation. In this way, the effect of temporary members (construction supports) or supports can be analyzed, for example.
AnswerIn the Edit dialog box of the respective surface, in the "Modify Stiffness" tab, you can select which type of stiffness modification is to be performed. For example, you can use "Multiplier Factors" as shown in Figure 01.Multiplier factors can be specified for various stiffness components (for example, membrane stiffness).Whether these factors or the defined stiffness modification will be applied in the individual load cases or load combinations is controlled via the calculation parameters. Now, this means that the modification is taken into account as soon as the check box shown in Figure 02 has been selected. When unselecting the check box, the modification will not be considered for the surfaces.Thus, it is possible to control the stiffness modification by load case or by load combination.
AnswerIf you have edited the cross-section values of a cross-section or the stiffnesses of a bar with the function "Modify stiffnesses", these are not used in the additional module STAHL EC3. The modified stiffnesses are only used in the internal force calculation. Therefore, it is better to work with double bars when using the STAHL EC3 design.
AnswerThe easiest way to manipulate rigidity is to use a new material that manually reduces the modulus of elasticity and shear, and assigns it only to the appropriate walls. Alternatively, you can use such line joints with springs on the connection to the ceiling.Otherwise it is still possible to use a scaling factor for E and G. But also for this one would have to create a new material. However, it is a bit prone to error as this stiffness reduction must be assigned to the desired LF's and LK's. It is not automatically applied to all LF's and LK's, but only to those assigned - unless the button "Settings ... for all LK's use "is pressed.
I have modified cross-section properties or reduced stiffnesses of a members in RFEM/RSTAB. After a new calculation, the deformation of the structural system has adjusted itself to the new cross-section properties. However, this change is not taken into account when performing design in add-on modules.
In principle, the modified cross-section properties are not transferred into add-on modules, such as RF‑/STEEL or RF‑/STEEL EC3. They are only used for the calculation of internal forces.
In the add-on modules, stresses are calculated using the real cross-section dimensions, which cannot be modified. This would be difficult to implement as many designs require the element width or height and due to the modification, it is not known which parameter has been reduced exactly. This is important for the c/t-designs in RF‑/STEEL EC3, for example.
AnswerFor items created before version X.06., the stiffness coefficients are applied by default only for load combinations, not for load cases. In the 'Calculation Parameters' section, it is necessary to use the corresponding option of the 'Activate Stiffness Factors' to ensure that the stiffness modification is also applied to the load cases. The stiffness modification is automatically active for new positions from version X.06.
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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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