Stiffness Analysis

In the Connections layout, select Connections menu > Rigidity Analysis to display the Stiffness analysis dialog.

Currently, stiffness calculations are available for connections with the front plate (such as beam-column and beam-beam) only for Eurocode 3 (2005).

Note: The stiffness analysis uses the DSC (Discontinuity) algorithm. Therefore, it is impossible to apply the stiffness analysis for a structure including offsets.

During calculations, a connection type is determined for defined connections and is presented in a calculation note for every connection.

Considering stiffness, connections are defined as:

• nominally pinned
• rigid
• semi-rigid.

Considering resistance, connections are defined as:

• nominally pinned
• connections of full resistance
• connections of partial resistance.

How a connection is classified depends on the global analysis type you perform.

Several types of structure analysis are possible:

• Elastic - a connection is classified due to stiffness
• Rigid-plastic - a connection is classified due to resistance
• Elasto-plastic - a connection is classified due to stiffness and resistance.

In the Stiffness analysis dialog, in the List of connections classified as rigid field, there will be a group of connections that were ascribed the semi-rigid connection type during the connection calculations.

The stiffness analysis and result update consists of several stages:

1. Assigning elastic releases to the ends of structure bars corresponding to the bars in the calculated connections; for individual structure bars, appropriate release types are defined automatically. These types will be overwritten when recalculating stiffness for the same nodes.
2. Structure recalculation considering the releases assigned.
3. Recalculations of all connections considering new values of sectional forces.

Note: To run the stiffness analysis, first perform connection calculations (you should do this every time you change connection parameters, such as geometry).