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Frequently Asked Questions (FAQ)
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The shear correction factor is specified in the respective National Annex. You can only change it by creating a new user-defined National Annex (Figure 01).
The corresponding parameters can be adjusted in the user-defined annex.
The shear correction factor can be changed in the "Other Settings" tab (Figure 02).
AnswerIn the case of the "Main member only" joint type, the member can be cut at any angle. The cutting angle δ can be adjusted under the geometry properties (see the figure).
AnswerThe RF-TIMBER AWC module does not optimize cross-sections for the Serviceability Limit State or the Fire Resistance design. Optimization is only calculated for the Ultimate Limit State design.Users must manually adjust the cross-section in RFEM or within the add-on module and can export the cross-section back into RFEM. In either scenario, the model must be rerun in order to calculate the correct internal forces with the adjusted member size.
An overpressed joint between two members can be controlled in RFEM by using the member stress results. For members, this stress result is the effective stress as a color gradient across the member surface, depending on the assigned cross-section.
Figure 01 - Stresses on Members
Based on the local member axis, the member stress result gives the following stress components and reference stresses with an associated color palette:
- Elastic stress component
- Elastic equivalent stresses
By activating the display of the members connected to the joint and displaying the σx stresses, it is possible to visualize the stress state on the members and thus also between the members. If there are only negative stresses in the area between the members, the joint is overpressed.
In the case of timber, the "Orthotropic Elastic/Plastic 3D" material model has to be assigned to the "Material" solid type (Figure 01).Since the program considers the "Contact" solid type as a member, it usually requires the isotropic material model (Figure 02).
AnswerThe RF-/JOINTS add-on module is divided into several joint groups. For this, see the following FAQ.Therefore, there is no straightforward answer to the special aspects of the design as in this FAQ.In contrast to the RF‑/TIMBER Pro add-on module described in the mentioned FAQ, however, it is obvious that the RF‑/JOINTS add-on modules cannot design EC2, even if manually changing the LDC, for example in the RF‑/JOINTS Timber - Steel to Timber add-on module (see Figure 01).Furthermore, this also applies to the add‑on modules RF‑GLASS and RF‑/CONCRETE NL.The reason for this is that there are stiffnesses exported in the program in the case of some joint groups of the RF‑/JOINTS add‑on module. For nonlinear calculations, the superposition with result combinations is not allowed. In the case of the second result combination mentioned above, there is the special feature that the superposition is no longer conservative, even in the case of simple structures. The design cannot be also performed correctly by manually changing the LDC.Nevertheless, if a result combination should be superimposed with constant and alternative additive, it is necessary to split EC2 in the attached file into load combinations as follows.
- RC2*=CO1 or CO2
AnswerTo define a dowel connection, the add-on module requires the minimum member length. This is 42 cm. If a member is shorter, the text "Member is too short" appears in Window "1.2 Nodes and Members" (see Figure 01). However, the structural component is often broken by intermediate nodes, and consists of several members. In such cases, the structural component can remain as a member in RFEM and the nodes can be used with the "Create Node 'On Line'" feature (see Figure 02). Thus, the member is not divided. All members connected to these nodes are then connected to each other, even if the member is not divided. As an alternative, it is possible to use the "Divide Member" feature with the "Place new nodes on the line without dividing it" option (see Figure 03).
In this case, the most suitable combination is a member elastic foundation with nodal supports, which may fail at compression.
Figure 01 shows a model with such a support. As you can see from the results, the member elastic foundation absorbs the compressive forces and the nodal supports absorb the tension forces.
AnswerIn the current standards, fasteners or connections are always designed in one plane only. The reason for this is that the designs for shear etc. can only be analyzed in the 2D plane. The hole design, for example, is not possible for a failure from the plane.Since internal forces in v y and v z can always occur in a three-dimensional calculation, it has been proven in practice to allow a small proportion of internal forces in secondary direction and not fully utilize the connection. However, if the ratio of shear force in secondary direction is too high, a detailed analysis with an FE simulation might be necessary.
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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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