# Stiffness of the connection between two entities

## Details of Stiffness of the connection between two entities

• Module code ESA1103
• Software
• SCIA Engineer
• FAQ topic

The stiffness of the connection between two entities is in the first place dependent on the chosen environment (Structure) in the Project data (Main menu > File > Project settings) dialog:

Tip: The creation of connections as such, regardless of the chosen environment, is discussed in the FAQ Connections between two entities

• In a Truss XZ and Truss XYZ environment all beams are fully hinged connected to each other and to the supports. It’s not possible to make the connections fixed.
• In all other environments the connection between two entities is regarded by default as infinitely rigid.

There is nevertheless an option to adapt the stiffness of the connection, namely via Input panel > workstation Structure > category Boundary conditions > Hinge on 1D. Such a hinge can be added to the beginning and/or end node of a beam.

For the different degrees of freedom (for displacement & rotation) can in each case be chosen between:

• Rigid (infinite stiffness)
• Free (no stiffness)
• Flexible (define a stiffness value)

Keep in mind that in case of flexible stiffness, the stiffness isn’t limited (is infinitive). Stiffness can be limited only by nonlinear behavior and you have to use nonlinear calculation.

If you activate Nonlinearity and Beam local nonlinearity in the Functionality tab of the project settings dialog (Main menu > File > Project settings), the option Nonlinear appears in the properties of Hinge on 1D. You can create the diagram of behaviour of the hinge. In this case the stiffness or the rotation of the hinge is limited and you can set the ends of the diagram:

• Free – Bending moment is limited and the rotation is unlimited
• Rigid – Bending moment is unlimited and the rotation is limited
• Flexible – the bending stiffness of the hinge continue according to diagram

The stiffness mentioned in the properties of hinge is used for the linear analysis.

### Steel connections

In case a steel connection has been created in a node, an option Update stiffness is available in the property panel. By selecting this option, the stiffness value of the connection is calculated automatically. When the linear (or nonlinear) analysis is executed again, this stiffness value is taken into account in the analysis model for the distribution of the internal forces.

After the analysis, a hinge is automatically added to the node, so you can retrieve the calculated stiffness value.