침몰된 항타선 분석을 통한 한국선급 규칙 적용에 관한 연구

A Study on the Adoption of Korean Register of Shipping Rules through the Analysis of Pile Driving Boat Capsizing

Abstract

2012년 12월, 한국 울산항 앞바다에서 항타선이 침몰되었다. 본 사고 선박의 침몰원인은 인적요소, 기상악화 등의 복합적인 문제라 여겨진다. 사고 이후 선박안전기술공단에서는 리더부(크레인)는 충분한 안전율이 확보된 강도로 설계되었다고 결론을 내렸으나 국립과학수사 연구원의 현장조사 감정서에서는 선박 침몰은 리더부의 파손으로 인한 것이라고 결론 내렸다. 이에 본 저자들은 선박안전기술공단이 선박 검사에 사용하는 선박안전법과 강도 계산 및 구조해석 방법 등을 검토하였다. 나아가 한국선급의 규칙을 기반으로 두어 선박 침몰원인을 분석하기 위한 유체동역학적해석 및 구조해석에 관한 수치시뮬레이션을 수행하였으며 국립과학수사연구원의 현장조사 결과와 유사한 결론을 얻을 수 있었다. 결론적으로, 본 사고 선박과 같이 선급 규칙의 적용을 받지 않고도 자유롭게 국내에서 운항 될 수 있는 항타선의 경우 유사한 사고가 발생할 수 있으며 이를 방지하기 위하여 한국선급 규칙의 적용을 받는 검사가 수행되어야 할 것임을 제안한다.

In December 2012, a pile driving boat sunk off the coast of Ulsan port in Korea. The cause of capsizing of these boats was considered a complex problem. Although Korean Ship Safety Technology Authority concluded that leaders (cranes) of the vessel were designed with sufficient safety factors, National Forensic Service concluded that the capsizing was caused by the failure of leaders. This study reviewed the related laws, strength calculations, and structural analysis methods used by the Korea Ship Safety Technology Authority. In addition, numerical simulations were carried out on hydrodynamic analysis and structural analysis to analyze the cause of vessel capsizing based on the rules of the Korean Register of Shipping. The results were similar to those found by National Forensic Service. In conclusion, the study suggested that inspection especially for a pile driving boat subjected to the Korean Register of Shipping rules should be carried out to prevent the similar accident.

Fig. 1 Features of the vessel (a)before and (b)after the accident

Fig. 2 Procedure of numerical analysis for the accident vessel

Fig. 3 In the past three years(2012-2014), the marine condition of Iduk-seo (a)wind velocity pdf data and (b)significant wave height pdf data

Fig. 4 The incident angle of the waves and wind according to the location of the vessel (a)at the initial time and (b)at the accident time

Fig. 5 Hydrodynamic analysis for the hull of the accident vessel through HydroSTAR ver. 7.3

Fig. 6 RAO of roll motion of the DCM vessel in full-load condition

Fig. 7 RAO of acceleration of the DCM vessel for longitudinal direction in full load condition at 83 m height

Fig. 8 Boundary and loading conditions for the local-structural analysis

Fig. 9 Structural analysis results with von-Mises stresses

Table 1 Main particulars of the accident vessel for hydrodynamic analysis

Table 2 Comparison of G₀M of the accident vessel between KST and HydroSTAR

Table 3 Acceleration and pressure of longitudinal direction applied on the leader induced by waves in an accident case under full load condition

Table 4 Total weight of the leader parts of the pile driving boat

Table 5 Discretization of wind pressure with heights