An alternative methodology for the simplified operational guidance in the framework of second generation intact stability criteria

Within the framework of the second-generation intact stability criteria (SGISc), a procedure to provide simplified operational guidance (OG) has been proposed. In particular, the phenomenon of parametric rolling has been investigated. The proposed methodology is meant to be an intermediate level between the suggested simplified OG and the deterministic OG, as defined in the MSC.1/Circ.1627. The proposed guidance relies on a simplified numerical tool able to assess ship roll motion due to non-linear irregular wave effects in the time domain. Outcomes are elaborated in the post-process phase, taking the maximum roll angle as leading criterion. Once defined the structure of this tool, an application has been carried out to a representative model of post-panamax container vessel. As benchmark study, the results have been compared to those obtained by the application of MSC.1/Circ.1228 and MSC.1/Circ.1627 (simplified OG) by means of polar diagram representation. Outcomes have been discussed and a general agreement can be found between the simplified OG and the proposed one. Although, it appears that the latter can detect dangerous roll motion for a more comprehensive set of sailing condition.