Current ice class rules may design a structure that can undergo some plastic deformations during their design life. The amount of allowable plastic deformations is however not clearly defined in these ice class rules so as the critical deformation limit that requires repair. It is possible to increase the scantlings until no plastic deformations occur during the ship’s lifetime. This will cause a high investment cost at the construction phase but no repair cost during the design life. Another possibility is to allow some local plasticity requiring repair work at specified nominal frequencies during the ships’ lifetime, which causes smaller investments, but higher maintenance costs. The optimum between these two extremes is searched in this paper and the procedure on how to identify such concept will be described.

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