The Steel Joints add-on provides you with the option to connect circular hollow sections using welds.
It is possible to connect the circular sections to each other or to planar structural components. The fillets of standard and thin-walled sections can also be connected with a weld.
Go to Explanatory VideoIn the Steel Joints add-on, you can classify the joint stiffness.
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".
Go to Explanatory VideoIn 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 initial stiffness Sj,ini is a crucial parameter for evaluating whether a connection can be characterized as rigid, semi-rigid, or pinned.
In the "Steel Joints" add-on, you can calculate the initial stiffness Sj,ini according to Eurocode (EN 1993‑1‑8, Section 5.2.2) and AISC (AISC 360-16, Cl. E3.4) with regard to the internal forces N, My, and/or Mz.
The optional automatic transfer of initial stiffnesses allows for a directly transfer as member hinge stiffnesses in RFEM. The entire structure is then recalculated and the resulting internal forces are automatically adopted as loads in the analysis and design of the connection models.
This automated iteration process eliminates the need for manual export and import of data, reducing the amount of work and minimizing potential sources of error.
Explanatory Video: Calculation of Initial Stiffness Sj,iniThe 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.
Go to Explanatory VideoIn the Steel Joints add-on, you can design connections according to the American standard ANSI/AISC 360‑16. The following design procedures are integrated:
- Load and Resistance Factor Design (LRFD)
- Allowable Stress Design (ASD)
- Consideration of 7 local deformation directions (ux, uy, uz, φx, φy, φz, ω) or 8 internal forces (N, Vu, Vv, Mt,pri, Mt,sec, Mu, Mv, Mω) when calculating member elements
- Usable in combination with a structural analysis according to linear static, second-order, and large deformation analysis (imperfections can also be taken into account)
- In combination with the Stability Analysis add-on, allows you to determine critical load factors and mode shapes of stability problems such as torsional buckling and lateral-torsional buckling
- Consideration of end plates and transverse stiffeners as warping springs when calculating I-sections with automatic determination and graphical display of the warping spring stiffness
- Graphical display of the cross-section warping of members in the deformation
- Full integration with RFEM and RSTAB
You can perform the calculation of the warping torsion on the entire system. Thus, you consider the additional 7th degree of freedom in the member calculation. The stiffnesses of the connected structural elements are automatically taken into account. It means, you don't need to define equivalent spring stiffnesses or support conditions for a detached system.
You can then use the internal forces from the calculation with warping torsion in the add-ons for the design. Consider the warping bimoment and the secondary torsional moment, depending on the material and the selected standard. A typical application is the stability analysis according to the second-order theory with imperfections in steel structures.
Did you know that The application is not limited to thin-walled steel cross-sections. Thus, it is possible for you, for example, to perform the calculation of the ideal overturning moment of beams with solid timber cross-sections.
- You can activate or deactivate the use of torsional warping in the Add-ons tab of the model's Base Data.
- After activating the add-on, the user interface in RFEM is extended by some new entries in the navigator, tables, and dialog boxes.
Due to the integrated RF-/STEEL Warping Torsion module extension, it is possible to perform the design according to Design Guide 9 in RF-/STEEL AISC.
The calculation is performed with 7 degrees of freedom according to the warping torsion theory and enables a realistic stability design, including consideration of torsion.
The determination of the critical buckling moment is carried out in RF-/STEEL AISC by using the eigenvalue solver which allows an exact determination of the critical buckling load.
The eigenvalue solver shows a display window of the eigenvalue graphics, which enables checking of the boundary conditions.
In STEEL AISC, it is possible to consider lateral intermediate supports at any location. For example, it is possible to stabilize only the upper flange.
Furthermore, user-defined lateral intermediate supports can be assigned; for example, single rotational springs and translational springs at any location at the cross-section.
At first, the governing joint designs are arranged in groups and displayed with the basic geometry of the joint in the first result window. In the other result windows, you can see all fundamental design details.
Dimensions, material properties, and welds important for the connection construction are displayed immediately and can be printed directly. Similarly, export to DXF-file is enabled. The connections can be visualized in the RF-/JOINTS Timber - Timber to Timber module as well as in RFEM/RSTAB.
All graphics can be included in the RFEM/RSTAB printout report or printed directly. Due to the scaled output, an optimal visual check is possible as early as in the design phase.
The following design results are displayed:
- Check of minimum spacing
- Load-carrying capacity of each screw
First, select the joint type and the design standard.
The connected members are imported from the RFEM/RSTAB model. The add-on module automatically checks if all geometry conditions are fulfilled.
In addition, the loads are imported automatically from RFEM/RSTAB. In the Geometry window, you can specify the screw parameters (diameter, length, angle, and so on).
- Design of hinged connections
- Biaxial inclination of the connected member (for example, a jack rafter joint)
- Connection of any number of members on one node for the type "Main member only"
- Screw diameter 6 mm – 12 mm
- Automatic check of the minimum distance between screws
- Optional free definition of screw distances
- Transfer of eccentricity from RFEM/RSTAB
- Crosswise or parallel screw alignment
- Definition of up to 16 screws in a row
- Graphical visualization of joints in the add-on module and in RFEM/RSTAB
- Performing all required designs
- Applicable for members defined as sets of members
- Separate solver that considers 7 deformation directions (ux, uy, uz, φx, φy, φz, ω) or 8 internal forces (N, Vu, Vv, Mt,pri, Mt,sec, Mu, Mv, Mω)
- Nonlinear design according to second-order analysis
- Input of imperfections
- Calculation of critical load factors and buckling mode shapes as well as the visualization of them (incl. warping)
- Integration into member design in the RF-/STEEL AISC and RF‑/STEEL EC3 add‑on modules
- Available for all thin‑walled steel cross‑sections
Since RF-/STEEL Warping Torsion is fully integrated in RF-/STEEL AISC and RF‑/STEEL EC3, the data are entered in the same way as for the usual design in these modules. It is only necessary to select the option "Perform warping analysis" in the Details dialog box, tab Warping Torsion (see the figure on the right). You can also define the maximum number of iterations in this dialog box.
The warping torsion analysis is performed for sets of members in RF-/STEEL AISC and RF‑/STEEL EC3. You can define boundary conditions such as nodal supports or member end releases for them.
It is also possible to specify imperfections for the nonlinear calculation.
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.
The results of warping torsion analysis are displayed in RF-/STEEL AISC and RF-/STEEL EC3 in the usual way. Among other results, the corresponding result windows include the critical warping and torsional values, internal forces, and design summary.
The graphical display of mode shapes (incl. warping) enables a realistic assessment of buckling behavior.
First, it is necessary to select the joint type, design standard, and steel plate and dowel material. For design according to EN 1995-1-1, you can select the SFS intec dowel system WS‑T. In this case, the corresponding material is preset in accordance with the technical approval of the manufacturer.
The connected members are imported from the RFEM/RSTAB model. The add-on module automatically checks if all geometry conditions are fulfilled. Alternatively, you can define the connection manually.
- The loading is also imported from RFEM/RSTAB or, in the case of manual joint definition, loads are entered. The Geometry window includes steel plate dimensions and fastener layouts.
After selecting the loads required for the design and, if necessary, the desired standard for the design, you can define the limit loads in Window 1.2 Limit Parameters. In addition to the manufacturers listed in the limit library, it is possible to add user-defined entries.
After selecting all limit elements for the design, you can optionally define the load duration class (LDC). However, this module window is available only for timber fastener design according to EN 1995-1-1 or DIN 1052.
After the calculation, the RF‑/JOINTS Timber - Steel to Timber add‑on module lists joint stiffnesses of all individual members, among other things. The following design results are displayed:
- Check of minimum spacing
- Load-carrying capacity of single fastener
- Steel plates (bearing resistance and stress according to EC 3 and AISC)
- Stress analysis with reduced timber cross‑section
- Block shear failure
- Total load carrying-capacity (including stiffness determination, transversal tension design according to EC 5, and others)
- Fire resistance design according to EN 1995‑1‑2
At first, the governing joint designs are arranged in groups and displayed with the basic geometry of the joint in the first result window. In the other result windows, you can see all fundamental design details.
Dimensions, material properties, and welds important for the connection construction are displayed immediately and can be printed directly. Similarly, export to DXF-file is enabled. It is possible to visualize the connections in RF‑/JOINTS Timber - Steel to Timber or in the RFEM/RSTAB model.
All graphics can be included in the RFEM/RSTAB printout report or printed directly. Due to the scaled output, an optimal visual check is possible as early as in the design phase.
- Design of hinged, bending resistant, and semi-rigid connections
- Definition of up to 5 steel plates slotted in timber beams
- Up to 8 members connected to one node
- Thickness of steel plate 5 mm – 40 mm
- All sizes of fasteners
- Automatic check of the minimum distance between fasteners
- Optional free definition of fastener distances
- Definition of asymmetrical fastener arrangements (for example, any polygonal chains)
- Graphical visualization of joints in the add-on module and in RFEM/RSTAB
- All required steel and timber designs, including reduction of cross‑section values
- Design of transversal tension reinforcement (for EN 1995‑1‑1 only)
- Export of the member eccentricities to RFEM/RSTAB to be considered in the determination of internal forces
- Dowel length optionally shorter than cross-section width (for wooden plugs)
- DXF Export of Connection Geometry
- Fire resistance design according to EN 1995‑1‑2
- Design of member ends, members, nodal supports, nodes, and surfaces
- Consideration of specified design areas
- Check of cross-section dimensions
- Design according to EN 1995-1-1 (European Timber Standard) with the respective National Annexes + DIN 1052 + DSTV DIN EN 1993-1-8 + ANSI / AWC - NDS 2015 (US Standard)
- Design of various materials, such as steel, concrete, and others
- No necessary linking to specific standards
- Extensible library including timber fasteners (SIHGA, Sherpa, WÜRTH, Simpson StrongTie, KNAPP, PITZL) and steel fasteners (standardized connections in steel building design according to EC 3, M-connect, PFEIFER, TG-Technik)
- Ultimate load capacities of timber beams by the companies STEICO and Metsä Wood available in the library
- Connection to MS Excel
- Optimization of connecting elements (the most utilized element is calculated)