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• ### Why are the equivalent member designs grayed out in the Stability tab when the plastic designs are activated by means of the partial internal force process (RF- / STEEL Plasticity)?

New FAQ 003582 EN

Since the equivalent member designs of Eurocode 3 have different interactions than are the case for the designs according to the partial internal prescalcision method and a mixture of these different designs is not desired for reasons of clarity, RFEM deactivates the equivalent member designs when using the RF- / STEEL Plasticity add-on.
• ### What is the easiest way to delete the node of two crossing members?

New FAQ 003563 EN

Unfortunately, there is no automated function. In this case, you can use the drag-and-drop function to move the node to one of the corner nodes and then create the crossing members again.
• ### I would like to analyze bending buckling for timber components with imperfections and internal forces according to the second-order analysis. Is it sufficient to activate it in Details in the RF- / TIMBER Pro add-on module, or are other settings necessary?

New FAQ 003544 EN

The setting in Figure 01 only controls the influence on the design side. After activating this function, the buckling designs in the "Effective Lengths" window are deactivated. Thus, only a lateral-torsional buckling analysis is performed.

In order to calculate with the design values of the stiffnesses, they have to be reduced by the partial safety factor according to [1] . To do this, select the marked option in the calculation parameters (see Figure 02).

If the automatic combinatorics was used for the standard EN 1990 + EN 1995, this setting is automatically activated for combinations for the ULS according to the second-order analysis. For combinations for SLS, this option is automatically deactivated as well as for combinations generated according to the 1st order. However, the automatic assignment is only carried out by means of the calculation type in the "Combination Expressions" window (see Figure 03).

If you want to calculate the component stiffnesses with the 5% quantile value of the stiffness parameters divided by the partial safety factor, you have to additionally activate the "Modify Stiffness" function in the calculation parameters and modify the stiffnesses manually.

• ### How can I transfer a field with a node instead of just a single node via the COM interface in VBA?

New FAQ 003542 EN

To transfer several elements, you first have to create a field (array) in VBA:

Dim nodes (0 to 2) as RFEM5.Node

Then, you can transfer all nodes at once to the field (here three elements 0,1,2) with the method IModelData.SetNodes ().

These methods are also available for the following structural elements, for example:

IModelData.SetLines ()IModelData.SetMembers ()IModelData.SetSurfaces ()
• ### I recently purchased RSTAB with the CONCRETE module. Is it possible to perform a stability analysis of reinforced concrete columns?

New FAQ 003532 EN

Yes, the CONCRETE for RSTAB 8 module also includes the nonlinear reinforced concrete design. Thus, you can activate the "Nonlinear design (state II)" in the "Ultimate Limit State" tab.

In the detail settings for the nonlinear design, you can select the "General design method for members subjected to compression according to the second-order analysis".

It is important that you define the imperfections in RSTAB and apply load curves (CO) according to the second-order analysis for the design, no result combinations (RC)!

###### Note on RFEM 5:

In RFEM 5, the same procedure is possible in RF-CONCRETE Members. However, the add-on module RF-CONCRETE NL in RFEM is required for the non-linear reinforced concrete design.

• ### In the global calculation parameters, the option "Special treatment" of members is grayed out and can not be activated. What is the reason for this?

New FAQ 003526 EN

This option is only available even if nonlinear structural elements (for ex Tension members) are contained in the structure. You can easily check if this is the case. Open the global calculation parameters and check the "Nonlinearities" dialog box at the bottom left to see if the option "Members due to member type" or the option "Member Nonlinearities" is available. If they are grayed out, there are no members with these parameters and the "Special treatment" option is accordingly unavailable, because then there will be no failing members.
• ### In which directions do the member types 'Spring' and 'Dashpot' have a stiffness?

New FAQ 003498 EN

Members with the member type 'Spring' or 'Damper' have only axial stiffness, that is, in the direction of the local x-direction. The bending stiffness and the stiffness perpendicular to the longitudinal member axis are negligibly small and are not considered in RFEM and RSTAB.

If a spring should be applied in the structure, it acts only in one direction; in the other two directions (local y- and z-direction), this member type must receive additional support, otherwise, the system becomes unstable.

• ### How many divisions must a member have for the calculation in RFEM so that I get accurate results?

New FAQ 003485 EN

It is not possible to globally answer this question because it depends on the system. There are several divisions to be considered in RFEM.

###### 1. Member divisions for results tables
You can create member divisions for result values by using the menu 'Insert > Model Data > 'Member Divisions'. This division ensures that - e.g. in the RFEM results tables - the internal forces of members can also be displayed at intermediate points. The graphical output remains unaffected.

###### 2. Member divisions
The divisions for the graphical result diagram and the determination of the extreme value can be viewed and influenced in the FE mesh settings (see Figure 1).

For cable, foundation, and tapered members or members with plastic properties, you can specify the number of internal divisions. They lead to a real division of the member by intermediate nodes. However, if a member is arranged on the boundary line of a surface or if the definition line has an FE mesh refinement, the specification has no effect.

Select the 'Activate Internal Member Divisions for Large Deformation Analysis' option to divide also beams by intermediate nodes for the calculation according to large deformation analysis so that these members are calculated with higher accuracy. The number of member divisions is taken over into the input field above.

If using the division even for straight members, which are not integrated into surfaces, FE nodes are generated on all free members and considered for calculations according to the linear static and second-order analysis. The length of the finite elements is either determined by the global target length l FE set in the General dialog section or entered manually.

With the option 'Use Division for Members with Nodes Lying on Them', RFEM generates FE nodes on those locations of the member where end nodes of other members are lying, without having any connection existing between these members.
• ### Is there an easy way to create a spatial structure from a 2D model whereby the nodes in columns and lines will be extruded into walls?

New FAQ 003476 EN

For lines, such an option is already directly accessible in the shortcut menu. For extruding nodes into members and lines in surfaces, it is also possible in the detail settings of Copy/Rotate/Mirror. The new elements will also be created as soon as at least one copy is generated.
In case this feature is not wanted anymore, it should be deactivated in the detail settings again.
• ### Is it possible to display relative member deformation in RFEM?

New FAQ 003467 EN

This function cannot be assessed or determined at the level of the basic program. This issue is fixed at the level of add-on modules such as RF-STEEL EC3 or RF-DEFORM. The second module is generic and can be used for any rod. For more information, visit: https://www.dlubal.com/en-US/products/rfem-and-rstab-add-on-modules/others/rf-deform .

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