When the Functions tab is selected in the Non-linear Model Definition dialog, the following dialog displays.
The top of the dialog has the diagram of a user-defined non-linear model.
This tab has options that let you determine a type of hinge model. A hinge model type determines the units applied. If you select the force-displacement type, then there will be the following units, for example, of force (kN) and of displacement (mm). If you select the moment-rotation type: moment units (such as, kN*m) and angle/rotation (specified) (e.g. rad).
The options on this tab let you define a new non-linear model. To do this, you enter a model name in the Model name field and click Add. The user-defined non-linear models are visible on the list of models. You can select only one model from the list. When you select a model, it becomes active and you can modify it.
Clicking Delete button deletes the active non-linear model from the model list.
Clicking Delete all deletes all non-linear models from the list.