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Frequently Asked Questions (FAQ)
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AnswerFirst, select the type of stiffness modification to be carried out in the Edit dialog box of the respective surface in the "Modify Stiffness" tab. For example, as shown in Figure 01, by using the "multiplication factors".Multiplication factors can be specified for the different stiffness components (for example, membrane stiffness).Whether the factors or the set stiffness modification are applied in the individual load cases or load combinations is controlled by 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 set. When you remove the check box, the modifications will not be considered for the surfaces.Thus, it is possible to control the stiffness modification by load case or 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 positions prior to version X.06. By default, the stiffness coefficients are only applied to load combinations, not load cases. To apply the stiffness modification in load cases as well, use the corresponding option under "Activating stiffness coefficients" in the calculation parameters.From version X.06. the stiffness modification is automatically active for new positions.
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