Limit mechanisms for ice loads: FEM-DEM and simplified load models

This work summarizes our recent findings on mechanisms and limits for the ice loads on wide inclined Arctic marine structures, like drilling platforms or harbour structures. The fresults presented are based on hundreds of two-dimensional combined finite-discrete element method (FEM-DEM) simulations on ice-structure interaction pro- cess. In such processes, a floating sea ice cover, driven by winds and currents, fails against a structure and fragments into a myriad of ice blocks which interact with each other and the structure. The ice load is the end result of this interaction process. Using the simu- lation data, we have studied the loading process, analysed the statistic of ice loads, and recently introduced a buckling model [1] and extended it to a simple probabilistic limit load model and algorithm [2], which predict the peak ice load values with good accuracy. These models capture and quantify the effect of two factors that limit the values of peak ice loads in FEM-DEM simulations: The buckling of force chains and local ice crush- ing in ice-to-ice contacts. The work here describes the models and demonstrates their applicability in the analysis of ice-structure interaction

Ship resistance when operating in floating ice floes: a combined CFD&DEM approach

Whilst climate change is transforming the Arctic into a navigable ocean where small ice floes are floating on the sea surface, the effect of such ice conditions on ship performance has yet to be understood. The present work combines a set of numerical methods to simulate the ship-wave-ice interaction in such ice conditions. Particularly, Computational Fluid Dynamics is applied to provide fluid solutions for the floes and it is incorporated with the Discrete Element Method to govern ice motions and account for ship-ice/ice-ice collisions, by which, the proposed approach innovatively includes wave effects in the interaction. In addition, this work introduces two algorithms that can implement computational models with natural ice-floe fields, which takes randomness into consideration thus achieving high-fidelity modelling of the problem. Following validation against experiments, the model is shown accurate in predicting the ice-floe resistance of a ship, and then a series of simulations are performed to investigate how the resistance is influenced by ship speed, ice concentration, ice thickness and floe diameter. This paper presents a useful approach that can provide power estimates for Arctic shipping and has the potential to facilitate other polar engineering purposes.Comment: 26 pages 18 figures, submitted journal pape

A comprehensive approach to scenario-based risk management for Arctic waters

While society benefits from Arctic shipping, it is necessary to recognize that ship operations in Arctic waters pose significant risks to people, the environment, and property. To support the management of those risks, this article presents a comprehensive approach addressing both short-term operational risks, as well as risks related to long-term extreme ice loads. For the management of short-term operational risks, an extended version of the Polar Operational Limit Assessment Risk Indexing System (POLARIS) considering the magnitude of the consequences of potential adverse events is proposed. For the management of risks related to long-term extreme ice loads, guidelines are provided for using existing analytical, numerical, and semi-empirical methods. In addition, to support the design of ice class ship structures, the article proposes a novel approach that can be used in the conceptual design phase for the determination of preliminary scantlings for primary hull structural members.Peer reviewe

A review of discrete element simulation of ice–structure interaction

Sea ice loads on marine structures are caused by the failure process of ice against the structure. The failure process is affected by both the structure and the ice, thus is called ice–structure interaction. Many ice failure processes, including ice failure against inclined or vertical offshore structures, are composed of large numbers of discrete failure events which lead to the formation of piles of ice blocks. Such failure processes have been successfully studied by using the discrete element method (DEM). In addition, ice appears in nature often as discrete floes; either as single floes, ice floe fields or as parts of ridges. DEM has also been successfully applied to study the formation and deformation of these ice features, and the interactions of ships and structures with them. This paper gives a review of the use of DEM in studying ice–structure interaction, with emphasis on the lessons learned about the behaviour of sea ice as a discontinuous medium.Peer reviewe