In the Steel Joints add-on, you can classify the joint stiffnesses.
In addition to the initial stiffness, the table also shows the limit values for hinged and rigid connections for the selected internal forces N, My, and/or Mz. The resulting classification is then displayed in tables as "hinged", "semi-rigid", or "rigid".
In the "Steel Joints" add-on, you can consider preloaded bolts in all components during the calculation. You can easily activate the preloading using the check box in the bolt parameters, and it has an impact on the stress-strain analysis as well as the stiffness analysis.
Preloaded bolts are special bolts used in steel structures to generate a high clamping force between the connected structural components. This clamping force causes friction between the structural components, which allows for the transfer of forces.
Functionality Preloaded bolts are tightened with a certain torque, causing them to stretch and generate a tensile force. This tensile force is transferred to the connected components and leads to a high clamping force. The clamping force prevents the connection from loosening and ensures safe force transmission.
Advantages
High load-bearing capacity: Preloaded bolts can transfer large forces.
Low deformation: They minimize the deformation of the connection.
Fatigue strength: They are resistant to fatigue.
Easy assembly: They are relatively easy to assemble and disassemble.
Analysis and Design The calculation of preloaded bolts is performed in RFEM using the FE analysis model generated by the "Steel Joints" add-on. It takes into account the clamping force, friction between structural components, shear strength of bolts, and load-bearing capacity of the structural components. The design is carried out according to DIN EN 1993‑1‑8 (Eurocode 3) or the US standard ANSI/AISC 360‑16. You can save the created analysis model, including the results, and use it as an independent RFEM model.
The design of cold-formed steel members according to the AISI S100-16 / CSA S136-16 is available in RFEM 6. Design can be accessed by selecting “AISC 360” or “CSA S16” as the standard in the Steel Design Add-on. “AISI S100” or “CSA S136” is then automatically selected for the cold-formed design.
RFEM applies the Direct Strength Method (DSM) to calculate the elastic buckling load of the member. The Direct Strength Method offers two types of solutions, numerical (Finite Strip Method) and analytical (Specification). The FSM signature curve and buckling shapes can be viewed under Sections.
In the Steel Joint add-on, you can design the connections of members with composite cross-sections. Furthermore, you can perform joint design checks for almost all thin-walled cross-sections in the RFEM library.
In the Steel Joints add-on, you can design connections according to the American standard ANSI/AISC 360‑16. The following design procedures are integrated:
In the case of rectangular cross-sections, you can usually achieve a direct connection by using welds. However, you can also connect them to other cross-sections in the same way. Furthermore, other components such as end plates help you to connect the rectangular cross-sections to other structural components.
Design of a frame connection with taper and stiffened members. A stress analysis and a buckling stability analysis were carried out for the connection. To display the buckling results, the connection was converted into a separate model.
For joint components, you can check whether the stability failure is relevant. This requires the Structure Stability add-on.
In this case, you calculate the critical load factor for all analyzed load combinations and the selected number of mode shapes for the connection model. Compare the smallest critical load factor with the limit value 15 from the standard EN 1993‑1‑1, Clause 5. Furthermore, you can perform user-defined adjustment of the limit value. As a result of the stability analysis, the program displays the corresponding mode shapes graphically.
For the stability analysis, RFEM uses the adapted surface model to specifically recognize the local buckling shapes. You can also save and use the model of the stability analysis, including the results, as a separate model file.
Automatic generation of FE analysis models: The add-on automatically creates a finite element model (FE) of the steel connection in the background.
Consideration of all internal forces: The calculation and design checks include all internal forces (N, Vy, Vz, My, Mz, MT) and are not limited to planar loading.
Automatic load transfer: All load combinations are automatically transferred to the FE analysis model of the connection. The loads are transferred directly from RFEM, so manual data input is not necessary.
Efficient modeling: The add-on saves you time when modeling complex connection situations. You can also save the created FE analysis model and use it further for your own detailed analyses.
Extensible library: An extensive and extensible library with predefined steel connection templates is available.
Wide applicability: The add-on is suitable for connections of any type and shape, compatible with almost all rolled, welded, built-up, and thin-walled cross-sections.
No manual editing of the FE model required by the user, the essential calculation settings can be changed via the configuration settings
Automatic adaptation of the connection geometry, even if the members are subsequently edited, due to the relative relation of the components to each other
Parallel to the input, a plausibility check is carried out by the program to quickly detect missing input or collisions, for example
Graphical display of the connection geometry that is updated in parallel with the input
The program supports you: It determines the bolt forces on the basis of the FE analysis model and evaluates them automatically. The add-on performs the standard-compliant design of bolt resistance for failure cases, such as tension, shear, hole bearing, and punching, and clearly displays all required coefficients.
Do you want to perform weld design? The welds are modeled as elastic-plastic surface elements, and their stresses are read out from the FE analysis model. The plasticity criteria is set in the way that they represent failure according to AISC J2-4, J2-5 (strength of welds), and J2-2 (strength of base metal). The design can be performed with the partial safety factors of the selected National Annex of EN 1993‑1‑8.
The plates in the connection are designed plastically by comparing the existing plastic strain to the allowable plastic strain. The default setting is 5% according to EN 1993‑1‑5, Annex C, but can be adjusted by user-defined specifications, as well as 5% for AISC 360.
You can display all essential results on the FE model. In this case, you can filter the results separately according to the respective components.
Furthemore, RFEM delivers you all design checks in a tabular form, including the display of the formulas used. If you wish, you can transfer the result tables to the RFEM printout report.
The result windows list all results of the calculation in detail. In addition, 3D graphics are created, where individual components as well as dimension lines and, for example, This allows you, for example, to display or hide the weld data. The summary shows if the individual designs have been fulfilled: The design ratio is additionally visualized with a green data bar, which turns red when the design is not fulfilled. Furthermore, the node number and the governing LC/CO/RC are displayed.
When selecting a design, the module shows the detailed intermediate results including the actions and the additional internal forces from the connection geometry. There is the option to display the results by load case and by node. The connections are represented in a realistic 3D rendering possible to scale. In addition to the main views, it is possible to show the graphics from any perspective.
You can add the graphics with dimensions and labels to the RFEM/RSTAB printout or export them as DXF. The printout report includes all input and result data prepared for test engineers. It is possible to export all tables to MS Excel or in a CSV file. A special transfer menu defines all specifications required for the export.
After opening the add-on module, it is necessary to select the joint group (Pinned Joints), then the joint category and joint type (web cleat, fin plate, short end plate, end plate with cleat). Then, you can select the nodes for design in the RFEM/RSTAB model. RF-/JOINTS Steel - Pinned automatically recognizes the joint members and determines from its location whether they are columns or beams.
It is possible to exclude particular members from the calculation, if required. Structurally similar connections can be designed for several nodes at the same time. Loads require selection of the governing load cases, load combinations, or result combinations. Alternatively, you can enter the cross‑section and load data manually. In the last input window, the connection is configured step by step.
First, the governing design checks of the connection for the respective load case, and load combination, or result combination are displayed. In addition, it is possible to display results separately for sets of members, surfaces, cross-section, members, nodes, and nodal supports.
You can use a filter to further reduce the displayed results and thus present them in a clearer way.
After the design, all results are displayed in clearly arranged result tables; for example, by load case or by node. The governing internal forces are compared with the limit values listed in the DSTV guideline.
You can visualize the joints graphically in the add-on module or in RFEM/RSTAB. In addition to the input and result data, including design details displayed in tables, you can add all graphics into the printout report. This way, comprehensible and clearly arranged documentation is guaranteed.
The extensive DSTV guideline is included in the database of the RF-/JOINTS Steel - DSTV add-on module. Each joint is characterized by a unique alphanumeric code.
The possible DSTV connections can be filtered out by the corresponding specifications for the DSTV connection type (IH, IW, IS, IG, and IK) and the used cross-section. This way, it is possible to determine the load-carrying capacity of the selected joint.
After opening the add-on module, it is necessary to select the joint type (moment resistant or pinned I-beam connection). You can select the individual nodes graphically in the RFEM/RSTAB model.
The RF-/JOINTS Steel - DSTV add-on module recognizes the cross-section including the corresponding material automatically, and checks if a joint design according to the DSTV guideline is possible. Furthermore, you can model and design structurally similar connections on several locations in the beam structure.
Design of moment resistant and simple joints of I-shaped rolled cross-sections according to Eurocode 3:
Moment-resisting end plate connections (type IH/IM)
Moment resistant purlin splices (PM type)
Simple joints with angle cleat and long angles (IW and IG types)
Simple joints with header end plates mounted either on web only or on web and flange (IS type)
Check of coped connections (IK) in combination with pinned end plates (IS) and angle connections (IW)
Automatic design of required joint with bolt sizes (all types)
Check of required thickness of load-bearing members for shear connections
Results of all required structural details such as appliances, hole arrangements, necessary extensions, a number of bolts, end plate dimensions, and welds
Results including stiffnesses Sj,ini of bending-resistant connections
Documentation of available loading and comparison with resistances
Results of design ratio for each individual joint
Automatic determination of governing internal forces for several load cases and connection nodes
The RF-/FRAME-JOINT Pro add-on module designs connections of structures calculated in RFEM/RSTAB. If there is no RFEM/RSTAB structure available, you can define the geometry and loading manually; for example, when checking external calculations, for example.
Designed nodes are usually imported from RFEM/RSTAB. The module recognizes all connected members automatically and assigns a connection type to them. Depending on the connection type, you can define further details of ribs, backing plates, web plates, bolts, welds, and hole spacing. As loads, you can select any load case, load combination or result combination in RFEM/RSTAB.
In the case of the "preliminary design" calculation mode, RF-/FRAME-JOINT Pro performs the first calculation step to suggest applicable layouts. After you select the relevant layout, the module displays all designs in detailed result tables and various graphics.