In the Stiffness Analysis Configuration dialog box, you can define basic specifications for determining the stiffness of a steel joint. These settings are applied to the Submodel that is created in the background for the calculation.
The 'list' on the left shows all configurations available in the model. You can use the
you can create a new configuration based on the default values of the
General Data
standard. As an alternative, you can copy by using the button
you can create an existing configuration and then adjust the design parameters. The
deletes the configuration selected in the list.
Base
The Main tab manages important 'design parameters' for the stiffness analysis.
Stiffness Analysis Type
Specify whether to determine the 'Initial Stiffness' Sj,ini or to create a 'Stiffness Diagram' (in preparation).
Joint-Structure Interaction (in preparation)
The check box 'Generate hinges in global model' allows you to apply the results of the stiffness analysis to the RFEM model in the form of member end hinges. RFEM creates hinges with the spring stiffnesses of the connections and assigns them to the members.
Classification by stiffness
The check box 'Frame with bracing systems' indicates a bracing system that reduces the horizontal displacement by at least 80%. Finally, the selection of this option affects the coefficient Kb, which is then only 8 instead of 25.
Analysis
The list for the Analysis Type provides a selection option between a geometrically linear and a second-order analysis. (PΔ).
If the calculation does not converge with the default setting of a maximum of 100 iterations, you should increase the 'Maximum number of iterations' accordingly. Find more information in Chapter Static Analysis Settings of the RFEM manual.
For better convergence and to avoid instabilities in nonlinear structural systems, it is recommended to use several load steps. However, a large 'number of load increments' has a detrimental effect on the duration of the calculation.
Modelling
The 'member length factor' controls the length of the equivalent model of the member. The larger value of the length and width of the circumscribed rectangle is multiplied by the value specified here.
Net
The latter category provides various setting options for an FE mesh, as different meshes may be required depending on the joint type. You can specify the minimum and maximum element size in the 'General'.
Furthermore, you can adjust the number or size of finite elements for various components - members, plates, bolts, welds - to the geometry of the joint. The greater the number of elements or the smaller their size, the finer the meshing.
The default settings of the design parameters should be suitable for most cases and also provide sufficiently accurate results with regard to the calculation time.