Hull girder ultimate strength of bulk carrier (HGUS-BC) evaluation: Structural performances subjected to true inclination conditions of stiffened panel members

Abstract

To enhance the safety of ship structure design, this study evaluated time-dependent hull girder ultimate strength considering thick corrosion and the inclination conditions of stiffened panels. The hull girder ultimate strength was calculated using incremental–iterative methods based on IACS-CSR in a bulk carrier hull model. The corrosion effect was measured as the thickness reduction in structural members, and inclination conditions were considered such as non-uniform uniaxial thrust, which influences the yield strength of structural members. The corrosion effect was investigated from 5 to 20 years of service time, wherein the corrosion rate was obtained based on a reference and was then divided into standard and severe corrosion rate conditions. The effect of non-uniform uniaxial thrust was considered the yield stress reduction on all the stiffener elements in an inclined position. The safety level of the design within each timeframe of the measured corrosion effect was then considered based on the ultimate limit state. This study found that the corrosion rate greatly affects HGUS, with severe corrosion having a greater affect than standard corrosion. In 20 years of service time with uniform loads in hogging conditions, the highest HGUS reduction caused by standard corrosion is 5.87%, while severe corrosion causes a reduction of 24.48%. Moreover, non-uniform uniaxial thrust was found to have a negative effect on HGUS, lowering the HGUS value on benchmark hull models both in hogging and sagging conditions.

Keywords

• Hull girder ultimate strength
• Bulk carrier
• IACS-BC
• Ultimate limit state
• Corrosion