• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.9
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• pp.569-574
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• 2020

A floating dock is the main facility for launching ships. In the early 2000s, ship-launching technology using floating docks was developed in Korea. Therefore, the opportunity to participate in new construction projects without investment in dry docks has expanded. In this paper, a basic calculation for the safe mooring of a floating dock was performed, and a mooring system was designed based on this. This study was conducted considering the typhoon situation, which is the most serious environmental requirements of Daebul Pier, a site to be installed and operated, for a floating dock. The design load was calculated by wind load, tidal load, and wave-induced load in accordance with the internationally accepted standards. After performing the initial arrangement of the mooring line of the floating dock using the existing mooring facilities of Daebul Pier, the minimum breaking load for each mooring line was calculated for the given load. Based on the calculation, the mooring arrangement was modified to minimize the breaking load, and a final specification of each mooring line was selected.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.7
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• pp.767-776
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• 2020

Due to the recent climate change caused by global warming, weather changes in a different pattern from the past have occurred, and the increase in seawater temperature has led to an increase in the size and intensity of typhoons. Accordingly, there is an increasing need for bitts that can be used to secure mooring safety of the ship when a sudden gust occurs. Based on 12 scenarios of a mooring safety evaluation program, this study analyzed the criteria for arranging bollard and bitt, and analyzed the sensitivity of mooring safety when using storm bitts. As a result of the evaluation, it was analyzed that the mooring factor value decreased compared to the general mooring line arrangement when the fore and stern breastline were added to the bitts for gusts. The results of this study can be used as basic data for proposing storm bitts arrangements for gusts in consideration of the characteristics of berth ships and ports. From the perspective of ship operators, storm bitts at the pier will be an effective method for securing the ship's mooring safety in case of a gust of wind.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.04a
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• pp.69-75
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• 2001

It is very important to secure the marine vessels during entire loading and off-loading operations. The environment influences on loading conditions. the western coastal area of Korea is characterized as a strong current due to a high tidal range. The tension of mooring lines varies as per the current and wave changing its magnitude during the day. A proper mooring arrangement and design of mooring line should be determined as per environment conditions. In this study, a 50,000 DWT container ship being moored is investigated numerically. The dynamic tension of mooring lines is estimated by MORA (Mooring Response Analysis) software. Environmental conditions of selected offshore terminal site are plugged as input data. The mooring line tensions are obtained for various wave frequencies per wave directions. The results demonstrate the change of tensions of lines and the allowable range of safe conditions in berthed mooring.

• Ocean Systems Engineering
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• v.2 no.3
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• pp.217-228
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• 2012

As the size of container ships continues to increase, not many existing harbors can host the super-container ship due to its increased draft and the corresponding dredging requires huge budget. In addition, the minimization of waiting and loading/offloading time is the most important factor in harbor competitiveness. In this regard, mobile-harbor concept has been developed in Korea to achieve much improved harbor capacity and efficiency. In developing the concept, one of the most important elements is the operability of crane between two or more floating bodies in side-by-side arrangement. The container ship is to be stationed through a hawser connection to an outside-harbor fixed-pile station with the depth allowing its large draft. The mobile harbors with smart cranes are berthed to the sides of its hull for loading/offloading containers and transportation. For successful operation, the relative motions between the two or more floating bodies with hawser/fender connections have to be within allowable range. Therefore, the reliable prediction of the relative motions of the multiple floating bodies with realistic mooring system is essential to find the best hull particulars, hawser/mooring/fender arrangement, and crane/docking-station design. Time-domain multi-hull-mooring coupled dynamic analysis program is used to assess the hydrodynamic interactions among the multiple floating bodies and the global performance of the system. Both collinear and non-collinear wind-wave-current environments are applied to the system. It is found that the non-collinear case can equally be functional in dynamics view compared to the collinear case but undesirable phenomena associated with vessel responses and hawser tensions can also happen at certain conditions, so more care needs to be taken.

• Journal of Ocean Engineering and Technology
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• v.27 no.4
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• pp.22-32
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• 2013

This paper presents the conceptual design procedure for the taut-leg mooring lines of a floating-type combined renewable energy platform. The basic configuration of the platform is determined based on an understanding of floating offshore plants. The main dimensions and mass distribution are determined based on a hydrostatic calculation. To identify the motion history of the floating platform and the tension history of the mooring lines, a hydrodynamic analysis is executed using Ansys.Aqwa. This helps in the selection of the best configuration for the mooring system such as the number of mooring lines, wire types, anchored positions, etc. In addition, the fatigue life of the mooring lines can be predicted from the tension history using the rain-flow cycle counting method.

• Journal of Wind Energy
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• v.14 no.2
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• pp.26-33
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• 2023

In this study, the global response characteristics of floater and mooring for floating offshore wind turbine with a detachable mooring system are performed. Global motion and structural response result extracted from the coupled motion analysis of 10MW DTU floating offshore wind turbine with detachable mooring system modeled by high-order boundary element model and finite element mesh, were used to study the characteristics of tension on mooring lines subjected to three different types of ocean loads. Breaking limit of mooring line characterized by wind, current and wave load has a major effect on the distribution of mooring tension found in time domain analysis. Based on the numerical results of coupled motion analysis, governing equation for calculating the motion response of a floater under ocean loads, and excitation force and surge motion and tension respectively are presented using excursion curve. It is found that the response of floater is reliable and accurate for calculating the tension distributions along the mooring lines under complex loadings. This means that the minimun breaking limit of mooring system satisfied a design criteria at ultimate ocean environmental loading condtions.

• Journal of the Society of Naval Architects of Korea
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• v.60 no.5
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• pp.320-331
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• 2023

In this study, a model test was conducted using the soft-mooring technique to evaluate the added resistance of the ship in waves. The study also examined the specific factors that should be considered during the soft-mooring test. The main purpose of soft-mooring is to prevent drifting caused by waves by providing horizontal restoring forces. However, it can also create undesired restoring forces in the vertical direction. Therefore, we examined the restoring force of the ship's 6-DOF motion based on the arrangement of the soft-mooring and the height of the mooring connection point. We also checked the corresponding resonance period and drift distance. The soft-mooring test was conducted twice, once with self-propulsion and once without self-propulsion, allowing us to review the advantages and disadvantages of each test technique. The main parameters measured in these model tests were 6DOF motion and added resistance on the ship. We compared these measurements obtained from two different techniques (with and without self-propulsion). Additionally, we also compared the measurements based on the types of measuring sensors used (2D load cells on FP, AP, and 1D load cells on each mooring line) as well as the height of the mooring connection point.

• Journal of Ship and Ocean Technology
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• v.9 no.1
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• pp.11-26
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• 2005

In this study, the program to investigate the multiple body interaction effects between a floating platform and a shuttle tanker considering the coupled effect of hull (FPSO) with mooring lines and risers was developed. The coupled analysis program, which is called WINPOST-MULT using the hydrodynamic analysis results by WAMIT, was made. For the verification of WINPOST-MULT by means of numerical experiments, two multiple-body models of an FPSO-FPSO and an FPSO-shuttle tanker system are adopted. With the FPSO-FPSO model and a two-mass-spring system to idealize two identical bodies for the 100-year storm wave condition in GOM, the numerical simulations were performed to investigate the interaction effects between two identical bodies. For the more reality, the coupled analysis for the FPSO-shuttle tanker model in the tandem arrangement was carried out in the consideration of the environmental condition of the West Africa Sea as a rather mild condition. Through the case studies with interaction effect and without interaction effect by the iteration method and the combined method, it is verified that the program is a very useful tool for the analysis of the interaction problem of multiple-body system and the coupled problem of the hull/mooring/riser.

• Journal of the Society of Naval Architects of Korea
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• v.52 no.4
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• pp.283-289
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• 2015

RGT(Riser Guide Tube) is a part of mooring on the bottom of a turret system to be connected with a production riser, and DBSC(Diverless Bend Stiffener Connector) is a latching component between them. In this paper, appropriate lug arrangement is decided mathematically for the case that a DBSC is lifted and installed on a RGT under the water while FPSO is under construction. Considering asymmetric arrangement & position of RGT and initial lug position, additional lug positions are determined by using an optimization method. The modified installation scheme with new lug points is investigated with a lifting simulation system, SIMSON. The simulation result shows that the installation of DBSC on RGT under the given conditions is quite feasible; therefore the mathematical method is proven to be appropriate.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.5
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• pp.215-226
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• 2018

In this paper, to estimate the dynamic behavior of a submerged floating tunnel(SFT) by underwater explosion(UE), the SFT is modeled and analyzed by the explicit structural analysis package LS-DYNA. The section of SFT near to explosion point is modeled to shell and solid elements using elasto-plasticity material model for concrete tubular section and steel lining. And the other parts of the SFT are modeled to elastic beam elements. Also, mooring lines are modeled as tension-only cable elements. Total mass of SFT is including an added mass by hydrodynamic effect. The buoyancy on the SFT is considered in its initial condition using a dynamic relaxation method. The accuracy and the feasibility of the analysis model aree verified by the results of series of free field analysis for UE. And buoyancy ratio(B/W) of SFT, the distance between SFT and an explosion point and the arrangement of mooring line aree considered as main parameters of the explosion analysis. As results of the explosion analysis, the dynamic responses such as the dent deformation by the shock pressure are responded less as more distance between SFT and an explosion point. However, the mooring angle of the diagonal mooring system can not affect the responses such as the horizontal displacement of SFT by the shock pressure.