Use of Corrugated Shell Plating in Semi-submersible Offshore Platforms - Study on exploring strength, weight and manufacturing implications of replacing the stiffened shell plating with corrugated panels

Abstract: The deck load capacity of new offshore platforms is increasing as these marine structurescontinue to increase in size. As a consequence, the structural weight has become a concern.The current investigation contributes to a solution of a more weight-effective structural designof shell-plated marine structures.The structural weight of a shell-plated structure can be reduced in various ways. In the currentinvestigation, an alternative design is presented by means of a corrugated structure. By theintroduction of corrugated panels, a structure may be constructed lighter and cheapercompared to traditional structures with stiffened panels. The welding work duringmanufacturing can also be reduced substantially. Even though the idea of using corrugatedshell plating has been practiced in various applications for a long time, such as in corrugatedbulkhead and deck plating, it is yet unexplored in shell structures. Thus, the aim with thisstudy is to compare corrugated shell plating with conventional stiffened panels with respect tostrength, weight and cost.A methodology is presented where various solutions are analyzed and compared with regardto strength characteristics, weight and cost. Here, strength characteristics include ultimatetensile strength, buckling stability and fatigue life calculations. Detailed numerical analysesare presented using a realistic and reasonable area of a panel structure of an offshore platform.The structure analyses are carried out using linear finite element analyses. A number of designcriteria have been evaluated and verified by comparing predictions obtained in an extensiveparametric study of basic structural strength following classification rules.Two alternative designs with corrugated shell plating are proposed with respect to corrugationsymmetry. The first one had unequal flanges and the same thickness as that of the referencestiffened model. The second had equal flange lengths. The weight reduction values achievedusing these designs were 38 percent and 59 percent in shell plating, respectively, comparedwith a reference model for traditional stiffened shell plating. The study concluded with areduction in production costs by 35 percent and 49 percent, respectively. The investigationclearly demonstrates that corrugated panels are often favourable for lightweight design andmanufacturing robustness of marine structures.