Modelling and simulation of ice impact loads relevant to non ice strengthened hull forms

Maritime activity in polar waters has been steadily on the rise in recent years, resulting in increasing interest into the ability of low- and non-ice strengthened ships (NISS) to conduct limited operations in ice infested regions. Modelling and simulation of ship-ice impact loads has traditionally focused on scenarios relevant to the design and classification of ships purpose built for navigation in ice, with assumptions that may not be suitable for the evaluation of ice loads on NISS. As such, there has been recent research activity aiming to rectify this, adapting and modifying traditional models as part of the development of safe speed studies seeking that evaluate NISS in ice. The present thesis focuses on the application of the Popov-Daley method, the current ice crushing load model used the International Association of Classification Societies (IACS) Unified Requirements for Polar Class Ships (Polar URs), to scenarios relevant to NISS. First, an analytically derived time-history model of a Popov-Daley style ship-ice impact is developed as a first step towards the modelling of moving loads, which may be a concern for ice impacts involving NISS that result in a plastic hull structure response. Next, the frictionless assumption on the ice crushing force from the original Popov-Daley method is tested for impact scenarios with finite floe sizes more relevant to NISS. After this, a structural response model of the Ex-HMCS IROQUOIS, taken as a representative naval hull form, was developed using the Popov-Daley method to model the ice indentation energies. This model allows for the calculation of the reduced impact force when considering structural response, calculation of the expected structural indentation depth, and determination of the expected structural consequence level, ranging from local denting of the hull plate to the buckling of main transverse stiffeners. Lastly, the Ex-HMCS IROQUOIS was simulated using the computer program GEM in forward transit through a variety of parametrized ice regimes meant to represent possible environments where NISS may wish to consider limited operations in exceptional scenarios, such as for search and rescue (SaR). The previously developed time-history and structural response models were used to process the GEM data, and an operational capability assessment of the Ex-HMCS IROQUOIS was completed that evaluates performance of the ship structure in all simulated conditions.