To ensure the safety of maritime operations in polar waters, the IMO enforced the International Code for Ships Operating in Polar Waters (Polar Code) in 2017. To address ice navigation related risks, the Polar Code refers to a set of guidelines known as the Polar Operational Limit Assessment Risk Indexing System (POLARIS). Following POLARIS, operational limits for ice navigation are defined based on the Risk Index Outcome (RIO) value, which takes into account the prevailing ice conditions and the ice class of a ship.

Recent studies indicate that the POLARIS guidelines are well-founded. However, no direct relationship between RIO values and the probability of an ice-induced hull structural damage has been established. To enable a more accurate analysis of ice navigation risks, this article addresses this issue by (i) relating measured ice-induced loads to RIO values corresponding to the ice conditions in which the loads were measured, (ii) calculating the load limits for plastic deformation and rupture of the ice belt of hull structures representing different ice classes, and (iii) defining the probability of structural damage for different load limits. The study utilizes long-term full-scale ice load measurements carried out onboard Polar Supply and Research Vessel (PSRV) S.A. Agulhas II in the Antarctic Ocean. The load limits were calculated for ice class standards, PC3, PC4, PC5, PC6, and PC7 in accordance with the Unified Requirements of the International Association of Classification Societies (IACS).

On a general level, the results are consistent with earlier findings indicating that the POLARIS guidelines are well-founded. If a ship operates mainly at ‘normal operation’ level, the probability for fracture at hull are at probability levels of 10^-3 and 10^-4 for ice classes PC3 to PC5. The probability levels for PC6 and PC7 are higher that is possibly a result from conservative load probability distributions. When the portion of operations at ‘special consideration’ level becomes significant, the probability of fracture at the hull increases significantly. However, large ice thicknesses and the largest load magnitudes may be associated with positive RIO values. Some inconsistencies are recognized, and the uncertainty and limitations of the analysis are discussed.

为了确保极地水域海上作业的安全，IMO于2017年强制执行了《极地水域船舶营运国际规则》（《极地规则》）。为了解决冰区航行相关风险，《极地规则》引用了一套称为《极地水域航行规则》的指南。操作限额评估风险指数系统（POLARIS）。遵循 POLARIS，冰区航行的操作限制是根据风险指数结果 (RIO) 值定义的，该值考虑了当前的冰况和船舶的冰级。

最近的研究表明 POLARIS 指南是有根据的。然而，RIO 值与冰引起的船体结构损坏概率之间尚未建立直接关系。为了更准确地分析冰面航行风险，本文通过以下方式解决了这个问题：(i) 将测量的冰引起的载荷与与测量载荷的冰况相对应的 RIO 值相关联，(ii) 计算塑料的载荷限制代表不同冰级的船体结构冰带的变形和破裂，以及（iii）定义不同载荷限制下结构损坏的概率。该研究利用了在南极海洋极地补给和研究船 (PSRV) SA Agulhas II 上进行的长期全尺寸冰载荷测量。根据国际船级社协会（IACS）的统一要求，计算了冰级标准PC3、PC4、PC5、PC6和PC7的载荷极限。

总体而言，结果与早期发现一致，表明 POLARIS 指南是有根据的。如果船舶主要在“正常运行”水平下运行，则对于冰级PC3至PC5，船体破裂的概率为10 ^-3和10 ^{-4的概率水平。}PC6 和 PC7 的概率水平较高，这可能是保守负载概率分布的结果。当“特殊考虑”级别的操作部分变得很大时，船体破裂的可能性显着增加。然而，大冰厚度和最大载荷大小可能与正 RIO 值相关。认识到一些不一致之处，并讨论了分析的不确定性和局限性。