• 한국항해항만학회지
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• 제43권5호
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• pp.310-319
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• 2019

With the recent increase in the volume of liquid cargo transportation, there is a need for STS( Ship To Ship) globally. In the case of the STS mooring, the safety assessment should be conducted according to other criteria because mooring is different from the general mooring at the quay, but there is no separate standard in Korea. Thus in this study, STS mooring simulation and sensitivity analysis using OPTIMOOR program, the numerical analysis program, was conducted to identify the characteristics of the STS mooring. The target sea modeled the Yeosu port anchorage in Korea and the target ship was selected as the case of VLCC (Very Large Crude Oil Carrier)-VLCC. Through the numerical simulation and sensitivity analysis, the characteristics of STS mooring were identified. Also based on these results, we focused on establishing the standard for STS mooring safety assessment. Numerical simulation results show that the STS mooring safety can be changed according to a ship's cargo loading condition, pre-tension of mooring line, sea depth, encounter angle with the weather, and the weather condition. Additionally, the risk matrix is prepared to establish the safe external force range in the corresponding sea area. This result can be used to understand the mooring characteristics of STS and contribute to the revision of mooring safety assessment criteria.

• 해양환경안전학회지
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• 제25권3호
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• pp.287-297
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• 2019

The recent increase in crude oil trading has led to an increase in the workings of SPM for crude oil carriers. VLCCs generally encounter difficulty entering port due to limitations in terms of sea depth and maneuverability. The SPM is a system that allows mooring to the buoy located in the outer sea for such vessels. However, the buoy is more affected by relatively external forces because of their of shore location. Therefore, the safety assessment of SPM is particularly important as it can lead to large oil pollution disasters in the event of SPM accidents. Despite this, in the implementation of the Marine Traffic Safety Audit Scheme in Korea, there exists no guidance for SPM. In this study, a SPM mooring safety assessment is performed using OPTIMOOR, a numerical analysis program, so as to understand the mooring characteristics of SPM. As a result, it is confirmed that the tension of mooring lines and hull movement in the SPM are greatly affected by the encounter angles with external forces. In addition, it is found that the maximum tension of the mooring line is elevated as the water depth becomes shallower through sensitivity analysis. According to SPM characteristics, which has a large influence on the encounter angle, this study has proposed an amendment to setting criteria in the implementation of the Maritime Traffic Safety Audit Scheme which could improve the reliability and accuracy of mooring safety assessments.

• 대한조선학회논문집
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• 제59권3호
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• pp.157-163
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• 2022

An automatic mooring system for a ship consists of a vacuum suction pad and a mechanical part, enabling quick and safe mooring of a ship. In the development of a mooring system, the design of a vacuum suction pad is a key to secure enough mooring forces and achieve stable operation of a mooring system. In the vacuum suction pad, properly designing its rubber seal determines the performance of the suction pad. Therefore, it is necessary to appropriately design the rubber seal for maintaining a high-vacuum condition inside the pad as well as achieving its mechanical robustness for long-time use. Finite element analysis for the design of the rubber seal requires the use of an appropriate strain energy function model to accurately simulate mechanical behavior of the rubber seal material. In this study, we conducted simple uniaxial tensile testing of Chloroprene Rubber (CR) to explore the strain energy function model best-fitted to its experimentally measured engineering strain-stress curves depending on various temperature environments. This study elucidates the temperature-dependent mechanical behaviors of CR and will be foundational to design rubber seal for an automatic mooring system under various temperature conditions.

• 한국해양공학회지
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• 제32권1호
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• pp.21-27
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• 2018

The design and analysis of a quayside mooring system for safe mooring of Prelude FLNG under extreme environmental conditions were carried out. The design of the mooring system considered the yard operation conditions and maximum wind speed during a typhoon. In order to secure the mooring safety of Prelude FLNG under an extreme environment, a special steel structure was designed between the quay and Prelude FLNG to maintain the distance from the quay to a certain extent to avoid a collision with the inclined base. The mooring safety was also ensured by installing additional new parts on the quay. A mooring analysis and mooring safety review were performed with more rigorous modeling considering the nonlinearity of the mooring rope and fender. In order to secure additional safety of the mooring system under extreme environmental conditions, a safety assessment was conducted on the failures of the mooring components proposed in the marine mooring guidelines. Based on the results of the mooring analysis, it was confirmed that the Prelude FLNG can be safely moored even under the extreme conditions of typhoons, and a worst case scenario analysis verified that the mooring system design was robust enough. The proposed mooring analysis and design method will provide a basis for the safe mooring of ultra-large floating offshore structures of similar size in the future.

• 해양환경안전학회지
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• 제25권3호
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• pp.313-319
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• 2019

As vessels become larger and competition between ports intensifies, there has been an increase in the number of cases where vessels that exceed the available berths are berthed at the pier. Therefore, there has been an increase in the number of cases in which the bow or stern of a ship is projected and moored. The risk of overhanging berthing is that mooring safety can be compromised because it is not possible to connect the bow and stern mooring line to the ship properly. In addition, collision accidents may occur between moving vessels if the view of a vessel moving in the port is obstructed. Therefore, in this study, the simulation of mooring safety was performed according to the overhanging range in Piers No. 6 and 7 in Ulsan's main port to propose the overhanging limit and operational standards according to each ship. As a result of the assessment, 30,000 DWT bulkers are able to overhang up to 0.75B, and 50,000 DWT bulkers can overhang up to 0.50B. The results of this study are expected to be used as basic data for setting the allowable overhang limit, as well as clear usage criteria for safe unloading operations.

• 해양환경안전학회지
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• 제22권1호
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• pp.67-73
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• 2016

항만물동량이 증가하고 선박의 대형화가 급격하게 이루어짐에 따라 부두의 설계 접안능력보다 큰 선박이 부두를 이용하는 사례가 빈번하게 발생하고 있다. 본 연구에서는 우리나라 주요 위험물 취급항만인 울산항을 대상으로 접안능력을 초과하여 위험물 부두를 이용한 선박 실태를 조사하였고 기존 부두 접안능력의 최대 3배가 넘는 선박이 이용하는 것으로 분석하였다. 그에 따라, 50,000 DWT급 부두를 모델링하여 50,000 DWT급, 70,000 DWT급, 100,000 DWT급 선박을 대상으로 계류 프로그램을 통해 선박 규모의 변화에 따른 계류 안전성 평가를 수행하였다. 평가는 OCIMF에서 제시하고 있는 표준환경기준에 따라 수행되었으며 50,000 DWT급 선박은 대체로 허용기준을 만족하는 것으로 평가되었으나, 70,000 DWT급 선박의 경우 풍속 60 kts, 파고 1.5 m 이상의 기상조건에서 100,000 DWT급 선박은 풍속 60 kts 조건 등에서 허용한계를 초과하는 것으로 분석되었다. 도출된 결과를 바탕으로 평가 대상부두에 대한 안전 계류 가이드라인 사례를 제시하였고 향후 다양한 사례에 대한 평가를 수행하여 해당항만에 일반적으로 적용 가능한 가이드라인을 수립하도록 제언하였다.

• 대한조선학회논문집
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• 제54권5호
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• pp.430-438
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• 2017

This study presents the reliability-based flaw assessment for the crack in the mooring chain of a floating type offshore structure. BSI(British Standard Institution) flaw assessment procedure BS7910 was combined with first- and second-order reliability method (FORM, SORM) so that the acceptance of a given flaw can be assessed considering the uncertainties of parameters that play important role in the flaw assessment. Considering the probabilistic nature of the crack size and long-term distribution of the stresses acting on the crack in mooring chain, the failure probability was calculated using FORM and SORM. To check the validity of the FORM and SORM, Monte Carlo simulation was also carried out to derive the true limit state function and compared with the results of FORM and SORM.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2019년도 춘계학술대회
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• pp.135-137
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• 2019

최근 액체화물운반선 운송량이 증가함에 따라 국내외에서 해상환적(Ship-to-ship)에 대한 필요성이 대두되고 있다. STS 계류의 경우, 일반적인 부두에서의 계류와 그 특성이 다르기 때문에 다른 기준으로 안전성 검토가 이루어져야 하지만, 국내에서는 별도의 기준이 부재한 상황이다. 따라서 본 연구에서는 STS계류의 특성을 파악하기 위해 상용 수치해석프로그램인 OPTIMOOR 프로그램 이용한 STS 계류 시뮬레이션 및 민감도 분석을 시행하였다. 대상해역은 여수항의 D2 정박지를 모델링하였으며, 대상 선박의 모델링은 VLCC-VLCC의 Case로 선정하였다. 이 수치해석과 민감도 분석을 통하여 STS 계류의 특성을 파악하고자 하였으며 이를 바탕으로 STS 계류안전성 평가에 대한 기준을 확립하고자 하였다. 수치해석 시뮬레이션 결과, STS 계류는 선박 재화상태, 기상상태(파주기 및 파고영향) 및 만남각, 그리고 계류삭의 초기장력 등에 따라 변화함을 확인하였다. 또한 Risk Matrix를 작성하여 해당 해역에서의 안전외력범위를 설정하였다. 이 결과를 통해 STS의 계류 특성을 파악할 수 있으며, 계류안전성 평가 기준을 개정에 기여할 수 있을 것으로 기대한다.

• 대한조선학회논문집
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• 제47권6호
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• pp.813-820
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• 2010

The spread mooring system for FPSO is developed to explore deep sea area, in which swell is dominant. It is known that the tension response of mooring lines in this sea area shows bimodal spectrum. Assuming normal distribution of tension profile and Rayleigh distribution of tension amplitude, the power spectral density function (PSD) of the mooring tension under the bimodal stationary random process is applied for the calculation of spectrum fatigue. Three popular methods, which are simple summation method, combined spectrum method and Jioa-Moan method, are used to combine fatigue damages from bimodal spectrum characteristics. Each damage value is compared with damage using Rainflow Cycle Counting (RCC) method which is believed to be close to exact solution. Vanmarcke' parameter and RMS(Root Mean Square) ratio are employed to assess relative damage variations between from RCC method and from three combination methods. Finally the most reliable fatigue damage combining method for spread mooring system is suggested.

• 한국해양공학회지
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• 제23권1호
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• pp.89-95
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• 2009

The purpose of the present study was to evaluate the safety under extreme environmental conditions and the dynamic safety under service environment conditions, of oceanographic buoy mooring systems consisting of a variety of materials, including chain, wire rope, nylon rope, and polypropylene rope. For the static safety assessment of a mooring system, after the calculation of external forces and the division of a mooring system into finite elements, the numerical integral was conducted to yield the elemental static tension until satisfying the geometrical convergence condition. To evaluate the dynamic safety, various processes were considered, including data collection about the anticipated areas for mooring, a determination of the parameters for the interpretation, the interpretation of the dynamic characteristics based on an analytic equation that takes into account the heave motion effect of a buoy hull and a mooring system, and a fatigue analysis of the linear cumulative damage. Based on the analysis results, a supplementary proposal for a wire rope that has a fracture in an actual mooring area was established.