ABSTRACT
The IACS (International Association of Classification Societies) Polar Code (PC rules) provides design rules for ships operating in ice floe infested waters. Such a design has a Polar Class (PC) designation ranging from PC7 to PC1 in order of more severe ice loads. The PC rules prescribe the shell plating and local framing with semi-empirical equations, and the load-carrying stringers and web frames by direct calculation with linear or Non-Linear (NL) Finite Element Analysis (FEA). For ships occasionally operating in partial ice-covered waters, following the PC rules, the added weight for ice protection may render it inefficient in other operational conditions. A direct approach for all the scantlings, balancing the actual loads and integrity requirements for limited use in ice floe infested waters may be beneficial for such ships. In this paper PC rules and full NL FEA methodologies have been applied to the intermediate bow region of a reference PC6 frigate. A structural mass reduction of up to 11% has been obtained with respect to a PC rules design. Multiple ice impacts at the same location have been considered for the reduced design to assess the maximum hull deformation to be expected for the design when operating in ice floe infested waters. The calculation method, numerical results and structural modifications are presented and discussed.
