A wave ramp is introduced to reduce the transient motion of the structure in severe waves at the beginning of a time domain analysis. When it is optionally applied, the wave ramp factor is determined from

(13–60)

where is the time before which the wave ramp is effective.

If you do not specify , a default value is selected automatically. For a regular wave case, this default is the wave period; for irregular waves, it will be the highest period of all of the wave components in the spectrum.

The amplitude of the regular wave, or of each wave component in a spectrum of irregular waves, is then modified as

(13–61)

Subsequently, wave-related forces will also be multiplied with this ramp factor.