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Analysis of the accident of the MV Nakhodka. Part 2. Estimation of structural strength*

 

TETSUYA YAO1,YOICHI SUMI2, HIROYASU TAKEMOT03, ATSUSHI KUMANO4, HIDETOSHI SUEOKA5 and HIDEOMI OHTSUB06

1Department of Naval Architecture and Ocean Engineering, Faculty of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima 739-8527, Japan

2Department of Naval Architecture and Ocean Engineering, Yokohama National University, Yokohama, Japan

3Ship Research Institute, Ministry of Transport, Tokyo, Japan

4Research Centre, Nippon Kaiji Kyokai, Chiba, Japan

5Shipbuilding and Ocean Development Headquarters, Mitsubishi Heavy Industries Ltd., Yokohama, Japan

6Department of Naval Architecture and Ocean Engineering, University of Tokyo, Tokyo, Japan

 

Abstract: In the early morning of January 2, 1997, a Russian tanker, the MV Nakhodka, broke in two in the Sea of Japan. The fore part of the vessel drifted and was stranded on the coast of Japan, and the aft part sank. The coast of Japan was seriously polluted by spilled heavy oil. Following this disaster, the Japanese Government established a Committee for the Investigation of the Causes of the Casualty of the Nakhodka. This paper deals with the structural strength of MV Nakhodka at the time of the accident. First the structural characteristics of the Nakhodka are described, and the reduction in thickness of the structural members are estimated based on the data measured on the fore part of the vessel which drifted ashose. Then the ultimate longitudinal strength of the hull girder at the time of the accident is evaluated by applying Smith's method, and the possibility of break-up collapse due to excess loads is discussed. The mechanism of fracture at the bottom plate is also discussed based on the observed fracture surface of the cross section. Finally an FEM (finite element method) simulation of the break-up of the hull girder is performed. It is shown that buckling/plastic collapse took place at the deck plate near Fr.153, which was followed by the successive buckling collapse of the side shell plate of the hull girder. Right after the collapse of the deck structure, the bottom plate fractured just in front of the transverse bulkhead at Fr.153.

 

Key words: analysis of accident, buckling/plastic collapse, fracture, longitudinal ultimate strength, progressive collapse analysis

 

Address correspondence to: T. Yao

Received for publication on Jan. 12, 1999; accepted on Jan. 21, 1999

* This article is based on an article that appeared in Japanese in the Journal of the Society of Naval Architects of Japan, vol. 183(1998).

 

Introduction

 

In this paper, the structural strength of the MV Nakhodka is investigated, The information was obtained from the activities and discussions of the Committee for the Investigation of the Causes of the Casualty of the Nakhodka.1 We then suggest how the Nakhodka broke in two in the Sea of Japan.

First the structural characteristics of the Nakhodka are explained, including the reduction in thickness based on the data measured on the fore part of the vessel which drifted onto the coast of Japan, and measurements taken in Singapore in 1993. The longitudinal strength is examined by applying the NK rule. The ultimate longitudinal strength is then evaluated by applying a simplified method of progressive collapse analysis. The mechanism of fracture at the bottom plate is also examined based on the observation of the fracture surface on the fore part, and fracture mechanics

analysis is performed to examine the possibility of the occurrence of brittle fracture. Finally, an elastoplastic large deflection analysis is performed on a hull girder

using the finite element method (FEM) code LS-DYNA3D, and the progressive collapse behavior of the cross section is simulated, starting with the buckling/plastic collapse of the deck plate followed by fracture of the bottom plate.

The causes of the accident of the MV Nakhodka were described in Part 1 of this paper, which includes an estimation of external loads.2

 

 

 

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