Parameters

When the Parameters tab is selected on the Non-linear Model Definition dialog, the following displays.

The options on this tab let you define a non-linear model. At the top of the dialog, the Name field displays the name of the active non-linear model and the following options: Symmetry, positive semi-axis, and negative semi-axis. When Symmetry is selected, the options: positive semi-axis, and negative semi-axis are not available. Model definition concerns the positive axis; whereas, the negative axis is determined automatically based on the positive axis definition. If the Symmetry option is cleared, then the options: positive semi-axis and negative semi-axis are available, and they are defined separately.

The following non-linear types are available:

• Linear
• Bilinear
• Rigid with linear hardening
• Parabolic
• Parabolic according to EC2
• Perfectly plastic
• Plastic with hardening
• Gap/hook
• Function.

When a diagram is defined using the Function option, the quantities that characterize a function diagram are not recalculated, therefore, they should be defined in the base units of the Robot, that is, force (N), moment (Nm), displacement (m), and rotation (rad). In other cases, parameters describing individual functions are the quantities expressed in the units displayed in the dialogs, and they will be recalculated automatically after the units are changed.

The contents at the bottom of the dialog (Definition) depend on the selected non-linear type. Parameters are displayed that are necessary to define a non-linear model. The following parameters are available for the available types of non-linear models:

	Linear	Parameters: K ≥ 0
	Bilinear	Parameters: K1 ≥ 0 D1 ≥ 0 K2 ≥ 0
	Rigid with linear hardening	Parameters: K ≥ 0 Flim > 0 stiffness parameter > 0
	Parabolic (e.g. concrete)	Parameters: K ≥ 0 Dlim > 0 Dmax - falls within the range (0, 2*Dlim) Flim > 0
	Parabolic according to EC2 (e.g. concrete)	Parameters: K ≥ 0 Dlim > 0 Dmax - falls within the range (0, 2*Dlim) Flim > 0
	Perfectly plastic (e.g. ground)	Parameters: K ≥ 0 Dlim > 0 Flim > 0 W (or a) - W falls within the range (0, 1)
	Plastic with hardening (e.g. steel)	Parameters: K0 ≥ 0 K1 ≥ 0 Dlim > 0 Flim > 0 W (or a) - W falls within the range (0, 1)
	Gap/hook	Parameters: K ≥ 0 D ≥ 0
	Function	Parameters (for a model with a rigid non-linear support - the Rigidity coefficient option switched on): D ≥ 0 stiffness parameter > 0 Allows the definition of the model composed of functions operating within the determined ranges. Functions are defined by specifying Expression. Function operation covers the range: (Origin, Origin of the next expression). The first expression assumes -∞ as the origin of the range, whereas the last one assumes +∞. (Note that if the inf expression is used, then the last interval ends at a value of the maximal displacement/rotation). If the value such as "5" is entered into the Expression field, it indicates the definition by specifying a discrete point with this coordinate (Note that if the value 5 is entered without quotation marks, it indicates adopting the constant function y=5). Successive discrete points are connected by segments.

Parameters units for available types of non-linear models:

	Type: Force - Displacement	Type: Moment -- Rotation
K	Force / Structure dimensions such as, kN / m	Moment / Angle (results) such as, kN * m / rad
D	Linear displacement such as, cm	Angle / Rotation (results) such as, rad
F	Force such as, kN	Moment such as, kN * m
W	Dimensionless quantity	dimensionless quantity