Further Information

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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.
• In RF- / STEEL EC3, I receive the error message saying that a node with supports does not exist in the set of members. What is the reason?

New FAQ 003524 EN

One support was defined at a node that is not part of the set of members in the window ‘1.7 Nodal Supports’ of RF-/STEEL EC3. In this case, it is necessary to define support at a node existing in the set of members or delete this nodal support in the window '1.7 Nodal Supports' of RF-/STEEL EC3.

In Figure 1, for example, a set of member supports was defined for the set of members 1 on nodes 2 and 7. When the calculation starts, the message 'Node No. 7 with support does not exist in the set of members No.1. Please correct this in Table 1.7.' appears (Figure 2, Figure 3).

In window ‘1.7 Nodal Supports’ of the RF-/STEEL EC3, it is possible to get displayed only the selected set of members by clicking the 'Show Only Current Object' button and the node numbering can be displayed by clicking the 'Local Coordinate System' button (Figure 4). It is obvious that the node 7 is not contained in the set of members. Instead of at node 7, the support must be defined on a node contained in the member set (for example, node 6).

• I would like to define lateral supports along the component´s axis that sometimes act on the top chord, sometimes on the bottom chord. However, only one item can be selected for each member. How can I create the input?

New FAQ 003494 EN

To provide a component with different supports, it must consist of several members and be designed by a set of members. Different parameters can then be assigned to the individual members. The procedure can be found in the video.
• What is the meaning of the warning message ER061) Minimum amplifier of design loads <1?

New FAQ 003491 EN

This message indicates that the critical load of the structure or the cross-section has been exceeded.

The causes for this are very diverse. Often, insufficient lateral supports have been defined in the STEEL EC3 add-on module.

It is also possible that the used cross-sections or the structure itself cannot be calculated according to the general method in EC3. This FAQ provides information about such a case.
• The design ratio of the cross-section check is different for the RF-/STEEL and RF-/STEEL EC3 add-on module. What is the reason?

New FAQ 003489 EN

Cross-sections assigned to class 1 or 2 are designed plastically by RF-/STEEL EC3 by default. In order to be able to compare the results with RF-/STEEL, please activate the elastic design of class 1 and 2 cross-sections (Figure 2) in the Details of RF-/STEEL EC3.

Please also check whether the partial safety factors γ for the resistances of the cross-sections are defined identically in both add-on modules (Figure 3 and 4).

• When designing a set of members by means of the equivalent member method in RF-/STEEL EC3, the calculation fails. The system is unstable delivering the message 'Non-designable — ER055) Zero value of the critical moment on the segment'.What could be the cause?

New FAQ 003440 EN

Please check if all sets of members selected for the design are sets of members. The equivalent member method is only applicable for straight sets of members with a uniform cross-section involving, for example, no taper. In this case, use the preset General Method.
• According to which formula is the elastic critical buckling load for the torsional buckling Ncr,T calculated in RF-/STEEL EC3?

New FAQ 003376 EN

The elastic critical buckling load for torsional buckling Ncr,T is calculated as follows:

${\mathrm N}_{\mathrm{cr},\mathrm T}\;=\frac1{{\mathrm i}_{\mathrm M}^2}\;\cdot\;\left(\frac{\mathrm\pi^2\;\cdot\;\mathrm E\;\cdot\;{\mathrm I}_{\mathrm w}}{{\mathrm L}_{\mathrm T}^2}\;+\;\mathrm G\;\cdot\;{\mathrm I}_{\mathrm t}\right)$

${\mathrm i}_{\mathrm M}\;=\;\sqrt{{\mathrm i}_{\mathrm u}^2\;+\;{\mathrm i}_{\mathrm v}^2\;+\;{\mathrm u}_{\mathrm M}^2\;+\;{\mathrm v}_{\mathrm M}^2}$

with

 E Modulus of elasticity G Shear modulus Iw Warping resistance It Torsion moment of inertia iu, iv Pricipial radius of gyration um, vm Shear center coordinates in the principal axis system LT Torsional buckling critical length

• I cannot see any members if I have selected the RF-/STEEL EC3 add-on module as a "Load Case", why?

New FAQ 003369 EN

This is because no results have been selected. If at least one check box is activated which leads to results, the members are also displayed.

• I need to define different types of lateral intermediate restrains for a single element in RF-/STEEL EC3. Is this possible?

New FAQ 003361 EN

If you need to define different types of lateral intermediate supports, you need 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.

• I am trying to compare a design for flexural buckling according to the equivalent member method and internal forces according to the linear static analysis with a stress calculation according to the second-order analysis including imperfections and obtain very large differences. What could be the reason?

New FAQ 003335 EN

While the influence of imperfection increases significantly with increasing axial force and the design increases exponentially, it only increases linearly in the equivalent-member design to the increase of the axial force. Therefore, very strongly and very weakly loaded systems usually deviate more strongly in the ratios of the linear static analysis by means of equivalent member methods compared to second-order analysis by means of stress design.

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