Ultimate strength characteristics of aluminium plates for high-speed vessels

Marine-grade aluminium alloy is an established structural material for medium-to high-speed commercial craft and has also been used as the primary hull material for several naval vessels. The analysis of large high-speed craft operating in deep ocean environments requires rigorous methodologies to evaluate the ultimate strength of the hull girders. Representative plate load-shortening curves form part of simplified hull girder ultimate strength methodologies; for the case of a high-speed aluminium vessel, the curves need to account for the effects of parameters including alloy type, geometric imperfection, softening in the heat-affected zone, residual stresses, lateral pressure and biaxial load. This paper examines the strength of a series of unstiffened aluminium plates with material and geometric parameters typical of the midship scantlings of a high-speed vessel, using a non-linear finite element approach. The parametric studies show that these factors can have a significant influence on the strength behaviour of the plates both prior to and after the collapse point has been attained.