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An Analytical Model for Ice Impact Load Prediction
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems.ORCID iD: 0000-0002-1743-0686
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems.
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems.ORCID iD: 0000-0002-9110-9401
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.ORCID iD: 0000-0002-1187-4796
2019 (English)Conference paper, Published paper (Refereed)
Abstract [en]

For ships running on ice-covered waters, the ice impact load on ship structure shall be carefully considered. This paper proposes an analytical model which takes two most important ice failure modes, localized crushing and bending breaking, into consideration. The energy method is introduced to estimate the crushing force and the indentation displacement for different scenarios. Ice bending breaking scenario is simplified as a semi-infinite plate under a distributed load resting on an elastic foundation. The two ice failure modes are assumed to share the same contact area. This model is useful to predict the ice impact load and creates a bridge between design parameters (ice properties and ship geometry) and structure loads. 

Place, publisher, year, edition, pages
2019.
Keywords [en]
Analytical model; ice-hull interaction; crushing failure; bending failure; ice load predication; ice properties; ship geometry.
National Category
Civil Engineering Oceanography, Hydrology and Water Resources
Identifiers
URN: urn:nbn:se:kth:diva-260384ISBN: 978-1-880653-85-2 (print)OAI: oai:DiVA.org:kth-260384DiVA, id: diva2:1355464
Conference
The 29th International Ocean and Polar Engineering Conference, 16-21 June, Honolulu, Hawaii, USA
Note

QCR 20191030

Available from: 2019-09-29 Created: 2019-09-29 Last updated: 2020-01-13Bibliographically approved
In thesis
1. Ice load prediction for design of ice-going ships for inland waterways
Open this publication in new window or tab >>Ice load prediction for design of ice-going ships for inland waterways
2019 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

With increasing interest in utilizing the inland waterways (IWW) in European countries, the design of IWW vessels gains attention both from a transport efficiency and an emission control point of view. However, unlike in western and central European countries, in Nordic countries, e.g. Sweden, IWW ships must deal with ice on the fairway during every winter. Usually, IWW ships are designed without ice concerns and are structurally weaker compared to ships designed according to ice class notification from the classification societies. Developing such ships requires particular concerns since there is no strict requirements regarding ice class notifications for IWW ships. A primary challenge is to estimate both the global and local ice loads acting on the ship hull structure. To consolidate the design problems for IWW ice-going ships, Lake Mälaren is selected. Ice conditions, i.e. ice type and concentration, and ice data, e.g. ice thickness and ice flexural strength, are extracted and analysed for the ice load estimation. The ice mechanical properties have great influence on the ice load. Ice characteristics are studied based on empirical formulae and properties are calibrated by reference data.

The deterministic approach is widely used to predict the ice loads. It is suitable when all variables, i.e. ship geometry and ice properties, are known and refers to rule-based design hereby. For first year light ice conditions in Lake Mälaren, the Finnish Swedish Ice Class Rule (FSICR) is widely used. The thesis uses guidelines from the Finnish Swedish Ice Class Rules as a reference and compare the results with other methods.

The probabilistic approach, on contrary, is useful when certain variables are unknow, which are interpreted as random variables, for instance ice breaking pattern. Here the probabilistic method and ice-hull interaction mechanism are studied. The probabilistic method simplifies the ice pressure in relation to the contact area between the ice and the ship hull. It predicts maximum ice pressure acting on the ship hull based on field ice test data and ice exposure conditions. Such semi-empirical method can be used regardless of ship type and size. For this, a numerical model is introduced based on ice-hull collision mechanisms and the essential ice breaking characteristics. The physical mechanism is studied for idealizing ship-ice impact model. The idealization model includes the ice failure process, ice conditions and ship geometry. The ice failure is assumed to be initiated by crushing ice and followed by breaking due to bending failure. Ice properties are set as constant values without any variations. The stochasticity in interact process is represented by randomness in collision location and number of pieces of ice floe formed after breaking. An energy method is used to calculate the ice crushing force, indentation displacement and contact area. The ice bending scenario is simplified as an infinite plate resting on an elastic foundation under a concentrated load. Ice impact load and critical load can be obtained for global and local structural assessment respectively. The structural responses and structural strength of a representative panel at linear and nonlinear contexts are investigated as well. Ship structure is commonly designed with material yield strength as limit. However, the study shows a lighter structure can be achieved if plastic deformation is allowed without causing failure. Therefore, the design can be optimized with regards to ice loading capacity and weight control.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2019. p. 73
Series
TRITA-SCI-FOU ; 2019:58
Keywords
inland waterway ship, ice load, ice conditions, ice properties, FSICR, probabilistic method, ice-hull interaction, numerical model, structural response, finite element analysis
National Category
Vehicle Engineering
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-266251 (URN)978-91-7873-405-4 (ISBN)
Presentation
2020-02-07, Sal U1, Brinellvägen 28A, Stockholm, 11:00 (English)
Opponent
Supervisors
Available from: 2020-01-13 Created: 2020-01-03 Last updated: 2020-01-13Bibliographically approved

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Cheemakurthy, HarshaGarme, KarlBurman, Magnus

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