This paper highlights the latest ABS research in the analysis and design of ice strengthened tanker structures, which supports the development work by the Finnish Maritime Administration (FMA). In search for a rational basis for design, FMA has introduced the equivalency concept and accepted application of nonlinear FEM as an alternative to applying prescriptive requirements. The recent development of ice strengthening guidelines for large commercial ships is characterized by active studies supporting this FMA initiative. ABS has developed formalized procedures for designing alternative ice-strengthened side structures, applying a nonlinear FEM approach. These procedures specify the extreme ice load definition, structural modeling, nonlinear material modeling, and acceptance criteria. This paper focuses on the analysis of the side stringer. The Finnish Swedish Ice Class Rules (FSICR) criteria for the side stringer has been under debate particularly after the new criteria for the side shell and the side longitudinal have been formalized by FMA (2005) Guidelines supported by ABS (2005) Guidance Notes. The paper describes a series of linear and nonlinear FEM analyses conducted to investigate the behavior of side stringers. The stringer thickness and ice loads were varied and the impact on the buckling and ultimate strength of the side stringer was studied. A design procedure is proposed using nonlinear a FEM and ultimate strength formulation with assumed extreme ice loads, a selected corrosion addition and acceptance criteria. The paper discusses the interaction of structural components in the given structural designs, and potential improvements of the proposed methods.

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