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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)

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)

A curve is a data structure with fields