Lightweight design of offshore platform marine structures - optimisation of weight to strength utilisation of corrugated shell plating

The structural weight of a shell-plated structure can be reduced in numerous ways. The current investigation presents an example of innovative lightweight design of the pontoon of an offshore platform by utilisation of corrugated structure. Corrugated shell plating is compared with a conventional stiffened panel with respect to strength, weight and cost. For this purpose, an optimisation methodology is developed for shell-plated marine structures. The procedure enables the analysis/comparison of various (structural) solutions with regard to strength characteristics, weight and cost. Here, strength characteristics include ultimate tensile strength, buckling stability and fatigue life analyses. Linear elastic finite-element analyses are carried out to generate input to the structural characteristics studies, which involve several design criteria according to classification rules. The results show that in competition with the traditional stiffened panel, corrugated shell-plated structure can be used as the more lightweight design solution. It can be manufactured and installed at a lower cost. Finally, the structural strength characteristics analyses show that, when designed properly, ABS and DNV classification rules are fulfilled without compromising with the safety margins.