#### Further Information

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• ### How can I generate a restraint or spring for the support in RX-TIMBER BSH?

FAQ 003129 EN-US

In addition to the predefined supports "fixed" and "free", you can define a restraint in the RX-TIMBER BSH using the "Column" function. Spring stiffnesses are calculated analytically and displayed in the bottom right corner of the window (see Figure 1), whereby the relationships referring to height, cross-section and the definition going from "Hinged" to "Restrained" is used. These are considered for the later calculation. If you want to connect the beam rigidly to the column, you can make use of this function.

• ### How can you specify in PLATE-BUCKLING, whether it shall comprise a rigid or non-rigid stiffener (end post) when calculating the reduction factor at shear buckling?

FAQ 002923 EN-US

In the Details, the PLATE-BUCKLING provides a choice between a rigid and non-rigid stiffener (end post) to specify the shear buckling reduction factor (see Figure 1).

• ### Is it possible to model a semi-rigid composite beam with a line release using members in RFEM?

FAQ 002560 EN-US

Yes, it is possible. For this, you should ensure that one beam is only modelled first, whose lines are released with a line release. You will then add another member to the automatically generated copies of the lines.

For split beams, make sure that both members connected on the nodes are released in the table of line releases. Under Downloads below, you can find an example of a composite plate made of timber and concrete from [1] as a calculated model and the workflow as a video.

• ### How can I enter the torsional rigidity (cross-section deformation) in the rotational restraint? I cannot find them anywhere in the program.

FAQ 002531 EN-US

Cross-section deformations can be activated or deactivated in the parameters of members and sets of members (see Figure 01). The cross-section deformation is calculated according to EN 1993‑1‑1 as follows:

$\frac{\displaystyle1}{\displaystyle{\mathrm C}_{\vartheta,\mathrm k}}=\;\frac{\displaystyle1}{\displaystyle{\mathrm C}_{\mathrm{ϑR},\mathrm k}}\;+\;\frac{\displaystyle1}{\displaystyle{\mathrm C}_{\mathrm{ϑC},\mathrm k}}\;+\;\frac{\displaystyle1}{\displaystyle{\mathrm C}_{\mathrm{ϑD},\mathrm k}}$

After the calculation, the value is displayed in result tables (see Figure 02).

The information about calculating the value can be found in the relevant literature or in the manual for the RF-LTB add-on module.

• ### In the design of a classic rigid end plate joint, the moments about the major axis (y‑axis) are only considered. If the moments are entered about the minor axis, the resulting tensile forces are not taken into account in the design. Am I correct?

FAQ 002513 EN-US

Designs in our module RF-/JOINTS Steel - Rigid are based on the assumptions and regulations of the standard EN 1993‑1‑8. Here, bending from the main beam plane is not considered.

In RFEM, it is possible to model any rigid joint. All internal forces can then be taken into account.

• ### How can I display the internal forces of a coupling member or rigid member?

FAQ 002416 EN-US

The display of internal forces for couplings (coupling members, rigid members) is deactivated by default. However, you can quickly enable the display of internal forces and deformations for these member types in the Display navigator (see the figure).

• ### I would like to create a cross‑section consisting of several elements in SHAPE‑THIN. However, I do not succeed to connect the elements in such a way that they act as a single entity.

FAQ 002389 EN-US

Elements are connected together if you have a common node. Thus, Elements 1 and 2 shown in Figure 01 are connected by Node 2.

If there is no common node available, you can create a shear-rigid connection by using a null element. In the case of the null element, the normal thickness t is equal to zero. However, the shear thickness t* must be greater than zero. Determination of the shear thickness t* is required for the null elements that are not affected by "normal" elements (t > 0) along their entire length. It is recommended to specify the thickness of the thinnest element adjacent to the null element.

A null element can be defined manually or created by using the "Connect node and element" function. Please make sure that the connection is always created by using nodes of the elements and not help points (see Figure 02).

• ### How can I consider eccentric load introduction?

FAQ 002361 EN-US

Since program version 5.19, you can directly consider the eccentric load introduction in RFEM by using the member loads (see Figure 1). The eccentric load introduction can be used for the load type "Force".

Alternatively (for example in RSTAB), a coupling by means of a rigid member can be defined to take account of external concentrated loads that act eccentrically on the member. The rigid member is to be connected perpendicularly to the corresponding member. The length of the rigid member corresponds to the amount of the eccentricity (see Figure 2).

Alternatively, you can enter the torsional moment due to the eccentric load introduction as external loading (also for eccentric member loads). Thus, the eccentric action would be taken into account and the definition of a rigid member would not be necessary (see Figure 3).

• ### I have only defined one element. If I swap the long and short side (that is, the thickness becomes the length), the St. Venant torsion constant is, in my opinion, calculated incorrectly.

FAQ 000418 EN-US

SHAPE-THIN is (as the program name suggests) a program for designing thin-walled cross-sections. Cross-section properties are determined according to the theory of thin-walled sections. Strictly speaking, this theory only applies if the width-to-length ratio is below approximately 1/10.

SHAPE-THIN determines the torsional constant according to the expression shown in Figure 01. The element thickness t* is included with the third power, explaining the differences for swapped thicknesses.

These It,St.Ven. results obtained with a very great element thickness are therefore useless and also should be evaluated accordingly after the transfer to RFEM/RSTAB.

Thus, you should confirm the query appearing before SHAPE-THIN shows a incorrectly modeled element (see Figure 02).

• ### I would like to use couplings in a model. What is the difference between the coupling, dummy rigid and rigid members?

New FAQ 000401 EN-US

A Coupling member is a virtual member with definable rigid or hinged properties. There are four options available to couple the start and end node. The axial and shear forces or torsion and bending moments are directly transferred from node to node. Couplings allow you to model special situations for the force and moment transmission.

If specifying Dummy Rigid as a description of the cross-section, you can use a member with a high degree of stiffness, taking into account releases or other member properties. In RFEM 5 and RSTAB 8, Dummy Rigid was replaced by the Rigid member. However, for compatibility reasons, it is still possible to use Dummy Rigid.

The stiffnesses in these members are calculated in relation to the member length L:

• EAx = GIx = 1013 ⋅ L
• EIy = EIz = 1013 ⋅ L3
• GAy = GAz = 1015 ⋅ L (RFEM) or GAy = GAz = 0 (RSTAB)

where

EAx is the strain stiffness

GIx is the torsional stiffness

EI is the flexural stiffness

GA is the shear stiffness