Numerical evaluation of energy absorption in ship-offshore fixed platform collisions

Abstract

Both the maritime traffic and the number of built offshore platforms have been continuously increasing over recent times. Among the structures built offshore, the fixed type constitutes the majority. The consequent diversity of plausible collision scenarios involving offshore platforms and passing ships must therefore consider aspects such as different ship size, different impact energy or different impact locations. For high energy collisions, large deformations are expected on both the platform and ship structures. It is expected that part of the energy absorption in the platform is confined to localized zones where plastic deformations take place, although the elastic strain energy may also be significant. For such impact problems, the amounts of strain energy in each structure are mainly dependent on the relative stiffness of the structures. By taking different ship and platform configurations as well as different contact points between the two bodies, different relative stiffness of the two structures can be tested in order to provide a clearer understanding of the dissipation of strain energy. The possible plastic deformation mechanisms are analyzed and simplified approaches are considered for prediction in comparison with the numerical results carried out by finite element analysis. Based on the results, some evaluations are made with respect to the code of practice in offshore platform design against ship impact.