Consider connection stiffness for global analysis

Did you know that you could use Consteel to consider connection stiffness for global analysis?

One of Consteel’s unique strengths is its ability to integrate joint modeling and calculation directly into the global analysis.

The Joint module performs all analyses in line with the standard procedures of Eurocode 3 Part 1-8, covering almost the entire scope of the code. This ensures results that are both reliable and fully compliant, across a wide range of connection types such as: Moment connections, Shear connections, Hollow section connections.

Modern structural design increasingly considers the mechanical interaction between the global model and its joints — whether rigid, semi-rigid, or pinned.

This integrated approach leads to results that are both more realistic and more economical, but it also requires more sophisticated modeling. Consteel makes this process straightforward:

• Joints can be created manually or automatically based on the model geometry.
• The create joint by model function examines member positions and cross-sections, then offers suitable joint types.
• Once defined, the joint can be placed into the global model, and its connection stiffness can be included in the global analysis.
• After placement, the joint is always rechecked against the latest analysis results.

In order to consider the connection stiffness of the placed joint, open the analysis parameters, tick the Include connection stiffness checkbox, and rerun the analysis.

Let’s explore how the behavior of a simple frame changes under different connection assumptions:

In the first case, where no actual connection stiffness was considered and the members were assumed to have continuous rigid ends, the results showed a bending moment (My) of 129.23 kNm at the column upper end and 115.25 kNm at the beam midspan. The corresponding deflection in the beam’s midspan (z-direction) was -17.4 mm.

In the second case, the connections were modeled with their actual semi-rigid stiffness of 29.8% and partial strength. Here, the bending moment at the column upper end decreased to 90.45 kNm, while the beam midspan moment increased to 154.03 kNm. The beam midspan deflection reached –26.5 mm, representing an increase of 52% compared to the rigid assumption.

In the third case, with a higher semi-rigid stiffness of 53.6% and partial strength, the results balanced between the two extremes: the column end moment was 104.37 kNm, the beam midspan moment was 140.11 kNm, and the midspan deflection was –23.2 mm. This corresponds to an increase of 33% in deflection compared to the rigid assumption.

These examples clearly demonstrate how connection stiffness significantly influences global structural behavior. Assuming rigid connections may underestimate beam deflections and distort moment distribution, while considering realistic semi-rigid stiffness, provides a more accurate representation of structural performance.

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