Some recent developments on ultimate limit state design technology for ships and offshore structures

Abstract

It is now well recognized that the ultimate limit state (ULS) approach is more useful for design and safety assessment than the traditional allowable stress approach, because it is difficult to determine the real safety margin of any economically designed structure using linear elastic methods alone. This paper presents some recent advances in the areas related to the ULS design of ships and ship-shaped offshore structures. The ultimate strength formulae of structural components (e.g., support members, plates, stiffened panels, corrugated panels) and global system structures (e.g., ship hulls) are presented. During the last decade, fast advances have been achieved in the areas of the ULS design, and it is convinced that the developments are mature enough to enter in the day-by-day design approach. In the present study, some recent developments related to the ULS design technology, mostly obtained by the authors, are summarized. However, there still remain problem areas to be solved for the ULS assessment of structures in terms of accommodating the effects of structural damages and dynamic/impact loading. Future trends are then addressed in terms of further research and developments.

Keywords:

• Ultimate limit state (ULS)
• steel-plated structures
• steel plating
• stiffened panels
• corrugated panels
• ship hulls
• fabrication related initial imperfections
• corrosion
• fatigue cracking
• local damage
• dynamic/impact loading