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Frequently Asked Questions (FAQ)
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In RFEM, you can model and design connections with the individual dimensions. The video on the left shows an example of modeling and calculation of a rigid bolted connection by using member and surface elements as well as contact solids.
Furthermore, you can define bolt prestressing forces and perform plastic design (RF‑MAT NL add-on module required), for example.
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).
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.
AnswerThe option to enter a taper on a beam can be activated in the Arrangement section of Window 1.4 Geometry. Here you can model the taper on the bottom or top side of the beam.The plate thicknesses as well as the height of the taper are defined by selecting the cross-section of the taper, since the cut rolled cross-sections are often used, for example. If user-defined plates are used, you can select a parametric T‑section. The length of the taper as well as the material are entered in the same section. The weld thicknesses for connecting the taper to the beam can be defined in the Welds section.If there is a tapered member already used as a beam (entered in the "Nodes and Members" section by specifying different cross-sections and lengths), it is not possible to model an additional taper.
AnswerIn addition to geometry input errors, this discrepancy is usually caused by a different calculation basis of both add-on modules.The design of an end plate joint with the RF‑/JOINTS Steel - DSTV add-on module is carried out by comparing the saved ultimate limit states with the design internal forces. The underlying resistances are taken from the current DSTV guidelines.When using the RF‑/JOINTS Steel - Rigid add-on module, the joint resistances of are calculated according to DIN EN 1993‑1‑8 by means of the component method. Thus, you can directly affect the results via the settings you have made.In this case, an elastic distribution of bolt forces is used as a basis by default. By selecting the plastic force distribution in the joint, you can activate additional load capacities. These are already included in the ultimate limit states according to the DSTV guidelines.In order to obtain the comparable results between both add-on modules, it is necessary to apply the plastic force distribution for the calculation. Furthermore, you should pay attention to the correct modeling of the joint geometry.
If the flanges are not continuous and the diagonals are fastened to the flanges, it may be necessary to enter an intermediate member.
Figure 1 shows a structural system where the flange is not continuous, but the diagonals are rigidly connected to the flange. To transfer the moments of the diagonals to the flange, the diagonal must get to the flange before the joint, otherwise the moment of the diagonal will be transferred to the opposite member (see Figure 02).
In the case the diagonals are also connected by hinges, you can waive the intermediate member. Please note that at least one member will not be hinged in order to prevent the connection node to rotate freely (see Figure 03).
If using a vertical, this must be connected on one of the two flanges or be between both flanges. In both cases, the model from Figure 1 arises, and has to be modified accordingly. Figure 04 shows the model with the vertical between the flanges and Figure 05 shows the model with the vertical on the right flange.
AnswerThis message means that a particular cross-section cannot be used for any types of the Sikla connections. Some cross-sections can be used as a supporting element in a particular connection, but not as an attached beam.
Depending on the geometric requirements of bricks, these are integrated into Class 1 to Class 4. All geometric requirements for the brick classes are listed in Table 3.1 of EN 1996‑1‑1. An example of assigning the classes according to the total percentage of the brick holes (% of the gross volume) is as follows:Class 1 (all bricks)≤ 25Class 2vertical hole ratio> 25; ≤ 55Class 3vertical hole ratio ≥ 25; ≤ 70Class 4horizontal hole ratio> 25; ≤ 70
A mortar joint is available when the bricks of a wall are not laid on one but on two mortar strips. In this case, the mortar has to be applied to the outer edges of the support surfaces of the bricks. By using a mortar joint, it is necessary to take into account the restrictions in the ultimate limit state as the unfavorable stress diagrams occur in the wall.
Whether to apply the mortar joint in a European country is governed by the respective National Annex. The German National Annex does not alllow to use the mortar joint for the masonry construction. Therefore, in Germany, bed joints must always be mortared over the entire surface.
AnswerFor rod end joints where the reference system is related to the local rod axes, the joint is placed directly on the rod end or rod end. If the joint is to act directly at the node, the reference system must be related to the global axis system.
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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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