Analysis and design of floating production storage and offloading unit against extreme ice actions

Abstract

To explore the Arctic regions, ice conditions are taken into account. Ice-structure interactions are analyzed for ice region FPSO FPU-ICE of SEVAN Marine, especially for extreme level ice events (ELIE) and accidental level ice events (ALIE). With respects to ISO/CD 19906 standard, ice conditions including physical properties and mechanical properties are reviewed respectively. Different principles behind DNV, IACS, NORSOK and ISO ice region design codes are discussed, with emphasis on ISO/CD 19906. Local and global ice actions from Barents Sea are researched according to ISO 19906. The conical part of the FPSO is simplified as a stiffened plate with deck and stringer. Simple plastic analysis of FPU-ICE substructure is compared with the nonlinear simulation carried out by ABAQUS. Six models chosen from design preference with regards to optimization by weight have been applied in ABAQUS nonlinear finite element analysis. It is performed to investigate the plastic bending capacity and energy dissipated in plastic strain. Arctic region structure design check ELIE and ALIE are carried out respectively. The nonlinearity of structure under ice loading is presented based on the principles of nonlinear finite element analysis. Sensitivity of mesh size in NLFEA is investigated by convergence test. The target to find ultimate strength capacity of the substructures by critical strain level is integrated in ABAQUS in terms of arch length method with both small (ELIE) and large deformations (ALIE). General guidelines for ELIE design events are introduced on the basis of investigation experience