The **force_element_edge** record with the same
*index* is imposed with the sum of the sine functions;
the first sine function has frequency *freq_0* and amplitude *amp_0*,
the second sine function has frequency *freq_1* and amplitude *amp_1*,
etc.. The sine functions start at time 0.
More general behavior in time can be imposed by using **force_element_edge_time**
records. For a specific *index* only one of **force_element_edge_sine** and
**force_element_edge_time** can be specified.

The sine loads will be only imposed after *start_time*.

More general time behaviour can be specified with **force_element_edge_time**.

tochnog 2001-09-02