Steel-concrete-steel sandwich structures in ship and offshore engineering

Concrete is commonly used in many civil engineering structures, often re-enforced in some way with steel, either as tensioning rods or as part of a composite structure. Composite steel-concrete structures have been used in bridge building for many years, with rules for design freely available (British Standards Institution, 2008a,b), and has been a topic of research for maritime structures, e.g. for arctic structures (Matsuishi et al. 1985) or impact resistance (Iwata & Hattori 1994). This paper explores the potential of steel-concrete-steel sandwich in floating structures and exposes the advantages, disadvantages and challenges of using this material through two design studies. The use of light weight concrete (with a density as low as 1000 kg/m(3)) is compared with more traditional higher strength concretes (density 2500 kg/m(3)) and it is found that the lighter weight concrete is desirable if the sandwich is to be competitive with steel designs on weight. The paper concludes by proposing where this technology may have potential and suggests areas for further exploration.