Vulnerability of Ship with a Large Breadth to Draught Ratio Against Excessive Acceleration Criteria

Abstract

A ship having a large breadth and small draught may have a large metacentric height. Therefore, the ship could be vulnerable to the excessive acceleration criteria. In order to investigate the vulnerability, an Indonesian ro-ro ferry with breadth to draught ratio of 5.31 was used to apply the criteria. The lateral acceleration and the long-term probability index with limited scatter wave data of International Maritim Organization were calculated for passenger or crew accommodation in full loading condition. The calculation was conducted for variation of metacentric height using the JONSWAP spectrum to modelled irregular wave. The results show that the maximum vertical distance from the roll axis to comply with the criteria level 1 was 8.7% of ship breadth. The metacentric height comply with the criteria level 1 for the passenger or crew accommodation was 1.4 metres corresponding to 8.7% of ship breadth. The maximum wave height comply with the criteria level 2 was 5 metres. These results show that the excessive acceleration criteria can be used to assess stability of a ship with large ratio between breadth and draught. The vertical distance from the roll axis has more significant effect on the lateral acceleration than the metacentric height.