Excited About Steel Joints Add-on

Understanding steel connection rigidity is crucial in structural design. Often, connections are treated as strictly pinned or rigid, but this can lead to uneconomical or even dangerous design checks. Explore how Dlubal Software's RFEM and Steel Joints add-on help verify connection stiffness and moment resistance, ensuring safer and more economical design checks.

This article explains how the calculation in the initial stiffness analysis in Steel Joints works.

The advantage of the RFEM 6 Steel Joints add-on is that you can analyze steel connections using an FE model for which the modeling runs fully automatically in the background. The input of the steel joint components that control the modeling can be done by defining the components manually, or by using the available templates in the library. The latter method is included in a previous Knowledge Base article titled “Defining Steel Joint Components Using the Library". The definition of parameters for the design of steel joints is the topic of the Knowledge Base article “Designing Steel Joints in RFEM 6".

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".

Go to Explanatory Video

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.

• "Steel Joints" Add-on
• Explanatory Video: Preloaded Bolts for Steel Joints

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.

In the Member Editor component, you can also select the entire member as the modifying object instead of the individual member plates. This way, you can apply both operations "Notch" and "Chamfer" to several member plates.