Ultimate strength of ships and offshore structures

It is now well recognized that limit state-based methods are superior to traditional allowable working stress-based approaches in the design and strength assessment of ships and offshore structures. Although four types of limit states are relevant in this respect, this chapter focuses on Ultimate Limit States (ULS). The key issue in the ULS-based design and strength assessment framework is determining how to identify the ultimate strength characteristics of structural members and system structures accurately and efficiently. Various methods of computing the ultimate strength of structural components or entire structural systems can be found in the literature, some of which are relatively simple and others more sophisticated. All such methods basically involve geometric and material nonlinearities, the former of which are associated with buckling and large deformation and the latter with plasticity. This chapter presents ultimate strength formula methods for plates, stiffened panels, and hull girders.