Investigation of ship vulnerability to SGISC based failure modes in different sea areas

Abstract

This thesis investigates the vulnerability of ships to dynamic stability failure, as defined by the Second Generation Intact Stability Criteria (SGISC). The study addresses a key limitation of SGISC, which uses a standard wave scatter table based on North Atlantic data. This study aims to investigate the effect of different sea areas on the applicability of SGISC by using modern hindcast wave data. The studied sea zones are selected based on high-traffic global shipping routes for cargo and ro-ro passenger (ropax) vessels and are aligned with zones defined in the Global Wave Statistics (GWS) database. Level 2 vulnerability assessments are performed for three of the five stability failure modes within the SGISC: pure loss of stability, parametric rolling, and excessive acceleration. Four sample ships representing a large and small container ship, a bulk carrier, and a ropax vessel are studied under multiple loading conditions and wave environments using NAPA software. The vulnerability analysis of all failure modes and sample ships revealed that the standard wave scatter table consistently gave higher vulnerability index values than the other zones studied. Based on the results, it is concluded that the standard wave scatter table (Rev.1) is suitable to use as a wave environment input for approving ships for unrestricted operations. Among all sea areas, the Pacific Ocean zones experienced the highest vulnerability to cargo ships, whereas Ropax vessels showed the highest vulnerability in the European sea areas. When comparing all sample ships, the fine-hull ropax vessel is most vulnerable to parametric rolling and pure loss of stability, whereas the bulk carrier is most susceptible to excessive acceleration due to its fuller hull form.