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.