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7.9  Curves and data sets

Curves are used to specify inputs (for time or frequency domain simulation) and store results from simulations. They can be stored as entries {'curve', Name, data} in the model stack or in the case of inputs in the load.curve cell array. Curves can be displayed using the iiplot interface.

A curve can be used to define a time (or frequency) dependent load {F}=[B]{u}. [B] defines the spatial distribution of the load on DOFs and its unit is the same as F. [B] is defined by a DOFLoad entry in the Case. {u} defines the time (or frequency) dependency as a unitless curve. There should be as many curves as columns in the matrix of a given load def. If a single curve is defined for a multi-load entry, it will affect all the loads of this entry.

As an illustration, let us consider ways to define a time dependent load by defining a .curve field in the load data structure. This field may contain a string referring to an existing curve (name is 'input' here)

 model=fe_time('demo bar');fe_case(model,'info')

 % redefine curve
 model=fe_curve(model,'set','input','TestStep 1e-3');
 % have load reference that curve
 model=fe_case(model,'setcurve','Point load 1','input');

 TimeOpt=fe_time('timeopt newmark .25 .5 0 1e-4 100');
 model=stack_set(model,'info','TimeOpt',TimeOpt);
 def=fe_time(model); feplot(model,def); fecom ColorDataAll

or a data structure generated by fe_curve

 model=fe_time('demo bar');fe_case(model,'info')
 model=fe_case(model,'remove','fd'); % loads at both ends
 data=struct('DOF',[1.01;2.01],'def',1e6*eye(2),...
             'curve',{{'test ricker 10e-4 1',...
                       'test ricker 20e-4 1'}});
 model = fe_case(model,'DOFLoad','Point load 1',data);

 TimeOpt=fe_time('timeopt newmark .25 .5 0 1e-4 100');
 model=stack_set(model,'info','TimeOpt',TimeOpt);
 def=fe_time(model); feplot(model,def); fecom ColorDataAll

Multi-dim curve

A curve is a data structure with fields


.IDOptionnal. It can be used to generate automatically vertical lines in iiplot. See ii_plp Call from iiplot for more details.
.Xaxis data. A cell array with as many entries as dimensions of .Y. Contents of each cell can be a vector (for example vector of frequencies or time steps), a cell array describing data vectors in .Y (for example response labels) with as many rows as elements in corresponding dimension of .Y.
 (obsolete) x-axis data.
.Xlaba cell array giving the meaning of each entry in .X. Each cell can be a string (giving the dimension name) or itself a cell array with columns giving {'name','UnitString',unitcode,'fmt'}. Typical entries are obtained using the fe_curve datatypecell command. Multiple rows can be used to describe multiple columns in the .X entry.
 fmt, if provided, gives a formating instruction for example 'length=%i m'. If more intricate formatting is needed a callback can be obtained with '#st3{j2}=sprintf(''PK=%.2fkm'',r2(j2)*1e-3);'.
.Yresponse data. If a matrix rows correspond to .X values and columns are called channels.
.Ylabdescribes content of .Y data. It can be a string, a 1x3 unit type cell array, or a number that indicates which dimension (index in .X field cell array) describes the .Y unit.
.namename of the curve.
.type'fe_curve'.
.Interpoptional interpolation method. Available interpolations are linear, log and stair.
.Extrapoptional extrapolation method. Available extrapolations are flat, zero and exp.
.PlotInfoindications for automated plotting, see iiplot PlotInfo
.DimPos

For other use, following type can exist.

Response data

Response data sets correspond to groups of universal files of type UFF58 that have the same properties (type of measurement, abscissa, units, ...). They are used for identification with idcom while the newer curve format is used for simulation results. They are characterized by the following fields


.wabscissa values
.xfresponse data, one column per response, see section 5.8
.dofcharacteristics of individual responses (one row per column in the response data as detailed below)
.fungeneral data set options, contain [FunType DFormat NPoints XSpacing Xmin XStep ZValue] as detailed in ufread 58.
.idoptoptions used for identification related routines (see idopt)
.headerheader (5 text lines with a maximum of 72 characters)
.xabscissa description (see xfopt('_datatype'))
.ynnumerator description (see xfopt('_datatype'))
.yddenominator description (see xfopt('_datatype'))
.zthird axis description (see xfopt('_datatype'))
.group(optional) cell array containing DOF group names
.load(optional) loading patterns used in the data set

The .w and .xf fields contain the real data while other fields give more precisions on its nature.

The .dof field describes DOF/channel dependent options of a MIMO data set. The dof field contains one row per response/DOF with the following information (this corresponds to data in line 6 of ufread 58 except for address)

 [RespNodeID.RespDOFID ExciNodeID.ExciDOFID Address ...
 RespGroupID ExciGroupID FunID LoadCase ZaxisValue]

The idopt field is used to point to identification options used on the data set. These should point to the figure options ci.IDopt.

The Group field is used to associate a name to the group identification numbers RespGroupID ExciGroupID defined in the .dof columns 4 and 5. These names are saved by ufwrite but currently not used in other parts of the SDT.

The load field describes loading cases by giving addresses of applied loads in odd columns and the corresponding coefficients in even columns. This field is used in test cases with multiple correlated inputs.

Shapes at DOFs

Shapes at DOFs is used to store modeshapes, time responses defined at all nodes, ... and are written to universal file format 55 (response at nodes) by ufwrite. The fields used for such datasets are

.popole values, time steps, frequency values ...

For poles, see ii_pof which allows conversions between the different pole formats.

.resresidues / shapes (one row per shape). Residue format is detailed in section 5.6.
.dofcharacteristics of individual responses (follow link for description).
.funfunction characteristics (see UFF58)
.headerheader (5 text lines with a maximum of 72 characters)
.idoptidentification options. This is filled when the data structure is obtained as the result of an idcom call.
.labelstring describing the content
.lab_inoptional cell array of names for the inputs
.lab_outoptional cell array of names for the outputs
.groupoptional cell group names

FEM Result

See section 7.8.


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