Determining dimensioning loads for the cross-deck of ice-breaking trimarans

This thesis studies the dimensioning principles of cross-deck structures of icebreaking trimarans. The methods for calculating the dimensioning loads are derived for the conditions of the Baltic Sea for both open water and ice. These methods are examined by calculating the loads for an example ship,...

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Bibliographic Details
Main Author: Valtonen, Ville Mikko
Other Authors: Ranki, Erkki, Insinööritieteiden korkeakoulu, School of Engineering, Sovelletun mekaniikan laitos, Kujala, Pentti, Aalto-yliopisto, Aalto University
Format: Master Thesis
Language:Finnish
Published: 2012
Subjects:
Online Access:https://aaltodoc.aalto.fi/handle/123456789/100540
Description
Summary:This thesis studies the dimensioning principles of cross-deck structures of icebreaking trimarans. The methods for calculating the dimensioning loads are derived for the conditions of the Baltic Sea for both open water and ice. These methods are examined by calculating the loads for an example ship, which has a length of 7sm and a beam of 40m. The structural responses from the loads are compared with a finite element model. The load cases studied in open water included still water, wave and slamming loads. Wave loads were calculated with the static-balance method and the classification rules of GL and LR. Rule formulas of the LR trimaran rules could not be used for the icebreaking trimaran, because the size of the side hulls exceeds the applicability limits of the rules. Thus a static roll angle method from the direct calculation procedure was used instead. In the calculations made with the example ship, the largest of all loads were the wave loads. All used calculation methods for wave loads provided fairly similar loads. Slamming loads may also be significant and should be considered in dimensioning of the cross deck. The studied loads in ice included loads from icebreaking, compressive ice, beaching and manoeuvring. Icebreaking loads were slightly smaller than the wave loads, but still sufficiently large to be significant in dimensioning. Loads from beaching on ice ridges were significantly smaller than icebreaking loads and are not significant in dimensioning. The loads from both compressive ice and manoeuvring were lower than icebreaking loads, manoeuvring being larger of these two. Due to the different orientation of these forces, the larger of these two has to be considered in dimensioning. The dimensioning loads for the example ship are wave loads, slamming, icebreaking and manoeuvring in ice. The results suggest that the cross deck structure of an icebreaking trimaran similar to the example ship can be feasibly built. The dimensioning methods developed can also be used for icebreaking trimarans with ...