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7.9  Curves and data sets

• Multi-dim curve
• FEM Result
• Inputs
• Response data
• Shapes at DOFs

Curves are used to specify Inputs (for time or frequency domain simulation) and store results from simulations. The basic formats are the Multi-dim curve and FEM result def. For experimental modal analysis, Response data and Shapes at DOFs are also used.

All these formats can be displayed using the iiplot interface.

Multi-dim curve

A curve is a data structure with fields

The following gives a basis generation example.

 t=linspace(0,10,100)';lab={'ux';'uy'};
 C1=struct('X',{{t,lab}},'Xlab',{{'Time','DOF'}}, ...
  'Y',[sin(t) cos(t)],'name','Test');
 iicom('curveinit',C1.name,C1);iicom('ch1:2');

FEM Result

See section 7.8 or sdtweb('def').

Inputs

Inputs for time or frequency simulations are stored as entries {'curve', Name, data} in the model stack or in the case of inputs in the load.curve cell array.

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')

 % Define input curve structure (single input step) 
 % For examples see: sdtweb fe_curve#Test 
 model=fe_curve(model,'set','input','TestStep t1=1e-3');

 % define load.curve{1} to use that input
 model=fe_case(model,'setcurve','Point load 1','input');

 % Run a simulation
 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

It is also possible to directly define the .curve field associated with a load

 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 dt=1e-3 A=1',...
                       'test ricker dt=2e-3 A=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

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

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]

• Standard DOF definitions of the form NodeID.DOFID are introduced in section 7.5. When considering sensors in general directions (see section 4.6) the SensId should match RespNodeID.RespDOFID.
• Addresses are integer numbers used to identify columns of xf matrices. They typically correspond to a measurement number.
• Sensor / actuator groups are correspond to the group names given in the group field (this is really only supported by ufread).
• Other columns are given in the universal format specification but unused in SDT.

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