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ObjectiveTo address the problem of the increased height of the center of gravity caused by the installation of testing equipment and relevant supporting construction in refitting, it is necessary to apply adequate technical measures to control the stability of the testing ship.MethodsAccording to the real ship environment, a combination of ballasting countermeasures is selected to satisfy the stability requirements, which involves using the existing ballast tanks, adding a new ballast water tank and changing a fresh water tank for ballasting, while fixed ballast is omitted. Considering that the testing ship is equipped with desalination devices, the fresh water tank capability can be reduced. As this refitting project is not permanent, a fresh water tank is selected to be filled with fresh water which is forbidden from consumption, realizing the ballasting function in a soft way. As an additional countermeasure, timely fresh water self-replenishment by the desalination devices is also suggested to prevent the stability from being reduced by over-consumption. ResultsWith the above measures applied, in normal displacement, the height of the center of gravity is reduced by 0.31 m, the metacentric height (GM) is increased by 0.25 m and the maximum wind resistance ability is increased by 9.64 m/s; in full load displacement, the height of the center of gravity is reduced by 0.27 m, the GM is increased by 0.24 m and the maximum wind resistance ability is increased by 8.89 m/s.ConclusionsThe proposed ballast method is proven effective in controlling the stability of the ship, while the flexible application of various technical approaches has certain reference significance for naval architecture projects.

Intact stability represents one of the most important topics when addressing ship safety, and it is ruled by the IMO Intact Stability code, evaluating ship stability in a calm water scenario. However, the interest in ship stability in waves has increased in recent years and this has led to the formulation of the second generation intact stability criteria (SGISc), finalized at IMO in 2020. In this research, an approach to quantitatively and comprehensively evaluate the ship stability performance in waves has been pursued. A methodology is developed with reference to the SGISc. The intact stability in waves index (ISWI) has been proposed, with the aim to become a complementary tool for designers and shipbuilders in the assessment of stability performance in waves. The ISWI represents a comprehensive stability index, able to capture the stability in waves performance of a vessel. The stability index has been verified on a set of megayacht units and its sensitivity to the wave characteristics has been tested, changing the environmental conditions. The outcomes point to a good agreement between the ISWI and the influence of environmental condition changes on the stability performance.

In this paper, the methodology of seaworthiness and stability analysis of a pontoon for holiday house has described. A 3D model of the pontoon was modelled in the NAPA software to perform hydrostatic analysis. It is necessary to emphasize the fact that hydrostatic analysis has been made for several drafts and trims of pontoons. The hydrostatic analysis yielded data such as displacement, moulded volume, longitudinal centre of buoyancy, the transverse metacentric height, change of displacement, moment to change trim, and more. This part of the analysis also includes the loading scale from which we can see the deadweight at a given draft. Further, it is necessary to make weight study to get moulded displacement for pontoon for a holiday house. The pontoon also includes capacity tanks, so it is necessary to know the accurate dimensions of the tanks and their position for further analysis. It is necessary to know the exact geometry of the tanks because of the free surface effect. When calculating the stability of the pontoon, it is necessary to determine the minimum metacentric height and the maximum distance from the keel to the centre of gravity. Intact stability conditions must be met for GM limit curves and also for KG curves. Intact stability criteria of the pontoon were tested for four loading conditions: lightship, pontoon with 10% consumables without passengers, pontoon with 100% consumables with passengers, pontoon with 50% consumables with passengers. It is important to emphasize that all tasks meet the stability criteria. [ABSTRACT FROM AUTHOR]

Tugboat operations present a high degree of risk and to prevent accidents, the crew must know and manage very well all the necessary maneuvers. Stability is a critical aspect for the safety of tugboats and towing operations, so recently new international regulations have been developed. The tugboats perform several functions, the main one being pulling, but by being equipped with certain equipment and installations, the tugboats are intended for rescue, firefighting, depollution, ice breaking and occasional transport. For this study, two categories of tugboats were considered to determine the geometric characteristics, hydrostatic, of stability and longitudinal strength. The Modelmaker module is used to create the ship's body (Geometry File), the superstructure and all appendages, after which the compartmentation is created and the types of compartments and tanks are positioned in the ship's body. To determine the safety of the two tugboats from the point of view of stability, the heeling moment (the heeling arm) that occurs during towing with the righting arm was checked. At the end, the safety status of the two categories of tugboats was analyzed and new projects were proposed for the future, regarding the use of stability criteria for tugboats. [ABSTRACT FROM AUTHOR]

Designing the support structures for floating wind turbines (FWTs) involves a step-by-step process, typically in three phases, i.e., starting from concept selection and determining the overall dimensions for a given configuration, and finally, determining the detailed specifications. The global design of the hull is used to select the floater concept and determine the global dimensions for the subsequent detailed design. This global design process is a crucial part of the entire design cycle because it has a significant impact on the detailed design, which can be computationally expensive. However, because FWTs are still in the infancy stage of development, there is a lack of effective methods and procedures for determining the global dimensions of floaters. Additionally, the global response characteristics of different hull layouts are not yet well understood. To address these limitations, this paper deals with a global design of semi-submersible floaters to support large-scale wind turbines (using a 10-MW turbine as an example). The paper proposes and describes a methodology and procedures for the global design in detail, specifying criteria and values for a case study. Furthermore, a sensitivity study is conducted to determine the global dimensions of the floaters. Then, intact stability is studied to evaluate their safety in operation under wind loads. Subsequently, global aspects of structural design are analyzed based on wave-induced response amplitude operators (RAOs) of cross-sectional forces and moments, taking into account representative environmental conditions for an offshore site. These analyses provide a foundation for the subsequent detailed design. The results indicate that the spacing of the column centerline and the outer column radius are the most critical design variables for the global response of the semi-submersible hull. Moreover, increasing the outer column radius or freeboard can effectively enhance intact stability. In addition, the study highlights the importance of critical wave periods that cause splitting or prying force on the hull columns in the structural design. Finally, the main findings and conclusions are summarized. This study presents a simplified yet innovative methodology for the global design of mainstream semi-submersible hulls for FWTs. It addresses the lack of effective methods for determining global dimensions and provides valuable insights into the structural design considerations. [ABSTRACT FROM AUTHOR]

Kapal penumpang feri Ro-Ro merupakan moda transportasi yang cukup efisien dan efektif. Karena bisa mengangkut manusia, kendaraan, dan muatan secara bersamaan. Akan tetapi kapal jenis ini masih banyak memiliki kekurangan berupa kondisi kapal feri Ro-Ro yang saat ini beroperasi di indonesia, di mana kebanyakan geladak kendaraan tidak kedap air karena banyaknya bukaan yang ada di sekeliling kapal sehingga apabila dihitung stabilitasnya baik intact maupun damage akan berpengaruh dalam memenuhi kriteria sesuai ketentuan IMO. Metode yang digunakan untuk penelitian ini adalah menggunakan software komputasi numerik yaitu maxsurf. Kriteria yang digunakan dalam analisa stabilitas intact dan damage menggunakan IS CODE 2008 MSC.267(85) Code on intacts stability Part B For Passengers dan SOLAS 2009 Chapter II-1 Resolution MSC.281 (85) (based on the probabilistic concept). Hasil analisa intact stability untuk kapal Ro-Ro 1000 GT (61.30 m), dan 5000 GT (109.40 m) telah memenuhi kriteria pada 3 kondisi dengan max GZ melebihi dari 250. Analisa damage stability yang menggunakan konsep problabilistik dengan perhitungan indek subdivisi R (required subdivision index), dan A (attained subdivison index), di mana nilai indeks A harus lebih besar atau sama dengan nilai indeks R (A≥R). Nilai indeks R dipengaruhi oleh jumlah penumpang kapal dan panjang ls, sedangkan nilai indeks A dipengaruhi oleh faktor pi dan si. Hasil perhitungan pada kedua kapal yaitu, kapal Ro-Ro 1000 GT dengan indek R = 0,69405 dan indek A= 0,7207, dan kapal Ro-Ro 5000 GT dengan indek R = 0,71449 dan indek A = 0,8679. Hasil Problabilistic Damage Stability untuk kedua kapal telah memenuhi kriteria (A ≥ R).

In late years, the size of RoRo cargo ships has continuously increased, leading to the so-called Large Car Truck Carriers (LCTC). The design of these vessels introduced new challenges that shall be considered during the ship design since the conceptual stage, which has a very strong impact on the technical and economic performances of the vessel during all its life-cycle. In this work, the concept design of an LCTC is presented based on Multi-Attribute Decision Making (MADM). A large set of design alternatives have been generated and compared in order to find out the most promising feasible designs. The proposed approach is based on a Mathematical Design Model (MDM) capable to assess all the main technical and economic characteristics for each design. Among the others, here focus has been done on the ship stability to assure the compliance with statutory rules within the MDM. A new stability metamodel has been developed capable to define the cross curves of stability at the concept design stage. The proposed MADM methodology has been applied to North Europe-Mediterranean transport scenario highlighting the impact of main particulars describing hull geometry on the technical and economic performances of an LCTC ship.

A wave-balancing approach, where a ship is hydrostatically balanced on a wave with either the crest or the trough atmidship, is often used to assess the inherent strength and stability of the vessel in waves. This work examines the differences between the wave types (sinusoidal and trochoidal) as well as the values of wave length, wave height, and position of the crest along the ship, with the goal of looking for the worst-case conditions for both intact stability and longitudinal strength. A notional destroyer is used as a case study to look at the trends in strength and stability in the upright condition and at angles of heel in waves. The notional destroyer is intentionally similar to but not the same as any existing design. The study shows that looking at a wider set of wave conditions and ship states can identifymore extreme wave loading and stability degradation, suggesting that this more detailed analysis would be beneficial as a standard practice. [ABSTRACT FROM AUTHOR]

During floods disaster in the heavy populated residential area, the lack of existing life saving appliances system such as rubber boat and wooden boat were not able to evacuate the disaster victims spontaneously in mass. The condition might be explained since the rubber boat and wooden boat have limited occupant capacity. Based on the conditions, the main objectives of the research are focused on the evaluation of the application of modular floating pontoon as multipurpose floating equipment to support floods disaster evacuation process. The investigation of the modular floating pontoon performance such as hydrostatics characteristics, the equilibrium condition and the intact stability was studied using strip theory and Krylov’s method. Furthermore, the strength analysis of the modular floating pontoon structure was calculated using finite element method. The results show that the modular floating pontoon is reliable to support the evacuation process.

Due to the accelerating demand for transporting raw materials around the world over the last century, bulk carriers are being constantly developed in order to maximise their capacity and efficiency whilst maintaining safety and durability of the vessels. With regards to safety, the International Maritime Organisation (IMO) and the International Association of Classification Societies (IACS) recurrently issue regulations and technical standards for the design and construction of ships, in order to safeguard the crew and other people on board. In light of these regulations, three issues concerning the properties of a bulk carrier are investigated. Firstly, the floodability of a bulk carrier is researched, to determine the largest possible volumes of compartments which can be flooded without causing the bulk carrier to capsize. Results were determined both manually and by means of marine design software, Maxsurf Enterprise; results generated by the two methods are compared. Additionally, a series of loadcases, each consisting of a different cargo and ballast configuration, are sought to reveal their effect on both the still water bending moment and the intact stability of the vessel. The results are analysed in relation to the IMO's criteria. [ABSTRACT FROM AUTHOR]

The intact stability and damage stability of a model of an anemometer tower with buoyancy tank foundation are computed by the finite element software MOSES in this paper. The natural period of the anemometer tower is discussed through frequency domain analysis. The influence of a single factor, such as towing point position, wave height, wave direction and wave period, on towing stability is discussed through time domain analysis. At the same time, the towing stability under the condition of various combinations of many factors is analyzed based on the measured data of the target area. Computer simulation results show that the intact stability is preferable and the damage stability is sufficient under the condition of plenty of subdivisions. Within the scope of the buoyancy tank foundation, the higher the towing point position is, the better the stability is. Wave height has a great impact on the motion amplitude of buoyancy tank foundation, but the effect on the acceleration is not obvious; wave period has a great impact on the acceleration, while the effect on the motion amplitude is not obvious; following-waves towing is more conducive to safety than atry. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the relationship between stability, safety and operability for small fishing vessels is investigated. To this aim, a relevant set of small fishing vessels is selected. These have similar main dimensions and capsized in stability related accidents between 2004 and 2007. The stability and operability characteristics of such vessels are confronted with those of the vessels that had been decommissioned in order to build them, operated by the same crews, in the same areas and using the same fishing gear types. Such vessels are considered as reference safe vessels since their operational life came to an end without any hazards. With regard to stability, fulfilment of the intact stability criteria in force when the vessels were designed and built is verified. Operability criteria are selected and their fulfilment is analyzed for a range of sea states, headings and velocities using linear seakeeping analysis. In light of this analysis, operability is discussed as a valid indicator of ship safety. This step is considered relevant prior to analyzing these sets of vessels through second generation stability criteria under development by the International Maritime Organization, a subject of immediate future research. [Copyright &y& Elsevier]

The quality of the ballast water exchange scheme affects many aspects of a ship, including intact stability, structural strength, building and operational expenses, etc. This paper focuses on developing an optimization methodology for large-scale sequential ballast water exchange. The method of transversely symmetrical ballast water tanks being exchanged simultaneously is adopted, and the potentials of multiple tanks being exchanged at a time are explored. The mathematical model for the symmetrical ballast water exchange problem is built by minimizing the occurred maximum trims, maximum hull girder bending moments, and shearing forces as objectives, and the related safety assessment criteria as constraints. A multiobjective genetic algorithm with some operators specially designed for the problem is presented to obtain a set of approximate Pareto-optimal solutions for engineers to choose from. Finally, a real case study on the symmetrical ballast water exchange of a 176,000 DWT bulk carrier is conducted to illustrate the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

Abstract: Ship’s subdivision arrangement is a multi-objective combinatorial optimization problem with multiple nonlinear constraints. This study focuses on finding a methodology for ship’s subdivision arrangement that can guarantee ship’s offshore sequential ballast water exchanging (SBWE) performances in the preliminary design stage. A mathematical model is built using minimizing trims and hull girder longitudinal bending moments and shearing forces occurred in the SBWE as the objectives, and the multiple safety criteria of the SBWE as the constraints. The longitudinal lengths of the ballast water tanks (BWTs) are taken as design variables that will alter within a reasonable length range. An elitist nondominated sorting genetic algorithm (NSGA-II) is utilized to perform the optimization, in which the nondominated sorting mechanism is employed to handle the multiple objectives, and the constraint-domination principle is utilized to handle the multiple constraints. A special crossover operator called the dispersion apportioned allelic (DAA) crossover is introduced to perform the reproduction of the special problem. A real case study of the subdivision arrangement based on the SBWE of a 50,000DWT double hull product tanker is conducted to demonstrate the feasibility and effectiveness of the proposed approach. [Copyright &y& Elsevier]

For developing design and operational criteria to be used at the International Maritime Organization (IMO), critical conditions for broaching are explored in the light of bifurcation analysis. Since surf-riding, which is a prerequisite to broaching, can be regarded as a heteroclinic bifurcation, one of global bifurcations, of a surge–sway–yaw–roll model in quartering waves, the relevant bifurcation condition was mathematically formulated and then a numerical procedure for obtaining its solution was presented with successful example. This identified bifurcation condition was compared with direct numerical simulation in time domain. As a result, it was confirmed that the heteroclinic bifurcation provides a boundary between motions periodically overtaken by waves and non-periodic motions such as surf-riding, broaching and so on. Then a local bifurcation analysis was applied to the surf-riding equilibria. This results could explain a boundary between stable surf-riding and oscillatory surf-riding as a Hopf bifurcation. Furthermore, comparison with free-running model experiments shows some discrepancies and an improvement with an aid of nonlinearity in wave-induced surge force is presented. [ABSTRACT FROM AUTHOR]

The intact and damage stability of warships is the important performance of their security. The present intact stability is evaluated only under a few typical load conditions in the design stage, which hardly covers the various complex status of executing tasks and a naval battle. Therefore, based on the principle of careening with identical volume and small inclining angle, and depending on the corrected liquid level height, a method of real-time calculation is presented under load conditions, i. e. making use of the corrected height value measured by sounding pipes or sensors of liquid holds, and the liquid weight is acquired by real-time interpolation of holds capacity curve. Combined with the capability of efficient database and the requirements of exact calculation, the program of the real-time calculation and the floatation adjusting is developed. In the end, the example of the floatation adjusting is proved to be practicable and reliable. [ABSTRACT FROM AUTHOR]

This paper presented the conceptual design of a high speed trimaran based on the research work conducted for the design and the hydrodynamic performance of the high-speed trimaran. The results show that the trimaran vessel needs low powering requirements at high speed and can offer large deck areas and good performance in the roll motion. The stability can satisfy the regulation of IMO. The study suggests that the design can be divided into two parts, the first is to determine the principle characteristics of main hull and the second, the determination for the side hull location. The conclusion of the work is useful for the research and design of trimaran. [ABSTRACT FROM AUTHOR]

Six degrees of freedom motion response tests of a Ro-Ro model have been carried out in regular waves for intact and damaged conditions. The stationary model was tested in different wave heights and wave frequencies for the head, beam and stern quartering seas in order to explore the effect of damage and varying wave heights on the motion responses of the model. Analysis of the results indicates that damage has an adverse effect on the motion responses of the model depending upon the directionality of the waves and frequency range applied. [Copyright &y& Elsevier]

In late years, the size of RoRo cargo ships has continuously increased, leading to the so-called Large Car Truck Carriers (LCTC). The design of these vessels introduced new challenges that shall be considered during the ship design since the conceptual stage, which has a very strong impact on the technical and economic performances of the vessel during all its life-cycle. In this work, the concept design of an LCTC is presented based on Multi-Attribute Decision Making (MADM). A large set of design alternatives have been generated and compared in order to find out the most promising feasible designs. The proposed approach is based on a Mathematical Design Model (MDM) capable to assess all the main technical and economic characteristics for each design. Among the others, here focus has been done on the ship stability to assure the compliance with statutory rules within the MDM. A new stability metamodel has been developed capable to define the cross curves of stability at the concept design stage. The proposed MADM methodology has been applied to North Europe-Mediterranean transport scenario highlighting the impact of main particulars describing hull geometry on the technical and economic performances of an LCTC ship. [ABSTRACT FROM AUTHOR]

Intact stability of a monohull, catamaran, trimaran, outrigger ship, duplus, tricore, trisec is compared on the basis of dimension statistic data. [ABSTRACT FROM AUTHOR]

To face the design of a new ship concept, the evaluation of multiple feasible solutions concerning several aspects of naval architecture and marine engineering is necessary. Compressed natural gas technologies are in continuous development; therefore, there are no available databases for existing ships to use as a basis for the design process of a new unit. In this sense, the adoption of a modern multi-attribute decision-based method can help the designer for the study of a completely new ship prototype. A database of compressed natural gas ships was generated starting from a baseline hull, varying six hull-form parameters by means of the design of experiment technique. Between the attributes involved in the concept design process, stability is for sure one of the most relevant topics, both for intact and damaged cases. This work describes two approaches to identify the compliance of a ship with the intact stability regulations based on the ship main geometrical quantities. Moreover, a metamodel based on the maximum floodable length concept (damage stability) allows determining the main internal subdivision of the ship. The metamodel outcomes were compared with results from direct calculations on a ship external to the database, highlighting the adequate accuracy given by the developed methods. [ABSTRACT FROM AUTHOR]