평탄빙 상태에서 쇄빙연구선 ARAON호의 선체 강도 평가

Abstract

As the oil price soars and the Russian economy revives, new orders of icebreaking cargo vessels increased and that trend becomes an important issue in the world's shipbuilding market. One of the technical problems concerned during navigation in ice-covered waters is an accurate estimation of ice load exerted on ship's hull. However, that still remains as a rather difficult task in the design of icebreaking vessels.

To correctly estimate ice load on ship's hull, it is essential to carry out full-scale ice field trials to measure hull responses under given ice conditions. And it is necessary to gather sea ice information in understanding the ice-ship interaction dynamics. The first Korean-made icebreaking research vessel ARAON had an ice field trial in the Arctic Ocean during the summer season of 2010. The data gathered from the ice field trial in Chukchi Sea and Beaufort Sea during the Arctic voyage of ARAON includes material properties of sea ice such as ice temperature, density and salinity, compressive strength of sea ice as well as ship's hull responses such as strain gauge records.

This study focuses on two issues

Firstly, the procedures of ice field trial of ARAON and the collected sea ice data are described. Ice thickness is a primary parameter among various ice properties. Sea ice thickness in the summer season in the Arctic Ocean changes greatly year to year depending on prevailing weather conditions. The ice thickness at each test sites was less than 2m but sea ice was often superimposed hence the thickness sometimes exceeds 4m.

Ice strengths are also important factors in consideration of ice load on ship's hull. Compressive strength and flexural strength of sea ice were measured. Due to warm weather conditions, it was difficult to find a large ice floe to conduct a proper ice trial and the ice was generally weak.

Secondly, hull strength for the ARAON was analysed in consideration of a level ice conditions. The nonlinear FEA approach to analyse hull structural responses to the level ice load was described in this study. Concerning possible ice-ship interaction scenarios, the stresses and deformation of side hull structures were calculated using a commercial FEA program PATRAN

Based on an FMA Ice Class Rule "Tentative Guideline for Application of Direct Calculation Methods Longitudinally Framed Structure (FMA, 2003)", the estimated ice load was applied to ARAON's narrow horizontal strip areas of the side hull structures and the responses (i.e., maximum deformation at maximum ice pressure) were calculated according to loading and unloading paths.

Certain design requirements, such as frame spacing and shell thickness are discussed.