Accidental Loads

Abstract

The article deals with the analysis and design of ships against accidental actions with focus placed on the consequences of collision and grounding. Compared to offshore structures, the design against accidental actions is more indirect; the relatively few rules that exist for quantitative design against ship collisions and residual strength requirements are reviewed. Principles for design against collisions based on relative strength are discussed. Methods for analysis of the local behavior in the contact area and global hull motions during grounding and collision are described; for collisions, the decoupled approach of internal and external mechanics is explained. Assessment of local damage and energy dissipation during accidental actions by means of simplified plastic mechanism analysis is discussed. More recently, damage analysis with the nonlinear finite element method has become popular. The method has enormous potential, but a few challenges still exist, which are discussed. The assessment of hull girder strength, notably regarding bending moment capacity in damaged condition, and is addressed. Finally, some proposed improvements in ship design with respect to collision robustness are briefly discussed.