Using time domain nonlinear ship motion simulations to assess safety of people and cargo onboard a container vessel

Classical frequency domain linear seakeeping approaches are suitable for design purposes in relatively mild sea states, when performances (operability) and/or comfort are the primary objectives (Lloyd 1989, NORDFORSK 1987). However, when the interest is on the actual safety of people and cargo onboard, more severe environmental conditions are expected to be taken into account. In such case the linear (or linearised) approaches can become no longer suitable and they need to be substituted by simulation tools which are able to handle the dynamics of the ship from a nonlinear perspective. This is particularly true when the interest is on the case of a vessel freely running and manoeuvring in waves.