1D function definition
 @FUNCTION_1D_DEFINITION {
 @FUNCTION_1D_NAME {Fun1DName} {
 @FUNCTION_1D_TYPE {Fun1DType}
 @CHEBYSHEV_POLYNOMIAL_NAME {ChbFunName}
 @HARMONIC_FUNCTION_NAME {HarFunName}
 @TABULATED_FUNCTION_NAME {TblFunName}
 @USER_FUNCTION_NAME {UsrFunName}
 @START_TIME {t_{s}}
 @END_TIME {t_{e}}
 @COMMENTS {CommentText}
 }
 }
Introduction
The 1D function utility defines an arbitrary function of a single variable, F = F(x), where x is the independent variable and F the value of the function. A plot of the function will be generated if plotting control parameters are defined. The functions can be represented in four mutually exclusive manners.
 If keyword @CHEBYSHEV_POLYNOMIAL_NAME appears, the function is represented as a Chebyshev function, ChbFunName. This approach is the simplest is the function has a simple polynomial expression.
 If keyword @HARMONIC_FUNCTION_NAME appears, the function is represented as a harmonic function, HarFunName. This approach is the simplest is the function has a simple harmonic expression.
 If keyword @TABULATED_FUNCTION_NAME appears, the function is represented as a tabulated function, TblFunName. This approach is the simplest is the function is defined by experimental measurements. If desired, these experimental measurements can be approximated through Chebyshev approximation.
 If keyword @USER_FUNCTION_NAME appears, the function is represented as a user function, UsrFunName. This approach is the simplest is the function has a given analytical expression that can be programmed easily.
NOTES
 Various types of functions can be defined to be used by various objects of the model. The list of allowable function types is given below.

Optionally, a start time, t_{s}, and an end time, t_{e}, can be defined for the 1D function. Default values: t_{si} =  DBL_MAX and t_{ei} = DBL_MAX. These start and end times are used in the following manner
F(t) = F(t_{s}), if t < t_{s},
F(t) = F(t), if t_{s} < t < t_{e},
F(t) = F(t_{e}), if t_{e} < t.  It is possible to attach comments to the definition of the object; these comments have no effect on its definition.
List of function types
The recognized types of Fun1DType are listed in the first column of table 1. The second column describes the context in which the 1D function is used. If the 1D function is defined by means of a singleentry table, column 3 and 4 list the required XentryType and DataType for the table.
Fun1DType  Description  XentryType  DataType 
FORCE_ALONG_i1 FORCE_ALONG_i2 FORCE_ALONG_i3 
Applied force distribution along i_{1}, i_{2}, i_{3} 
η 
Force/span 
HYDRAULIC_ORIFICE  Flowpressure relationship for hydraulic orifices  Pressure  Flow 
MOMENT_ABOUT_i1 MOMENT_ABOUT_i2 MOMENT_ABOUT_i3 
Applied moment distribution about i_{1}, i_{2}, i_{3} 
η 
Moment/span 
RECTILINEAR_DAMPER  Forcevelocity relationship for rectilinear dashpots or elastomeric dampers 
Force  Stroke rate 
RECTILINEAR_SPRING  Forcestretch relationship for rectilinear springs or elastomeric dampers 
Force  Stroke 
TIME_FUNCTION  Function of time for dead loads, prescribed displacements, edge loads, rigid rotations 
Time  Time function 
TORSIONAL_DAMPER  Momentangular velocity relationship for torsional dashpots  Moment  Angular velocity 
TORSIONAL_SPRING  Momentrotation relationship for torsional springs  Moment  Rotation 