A step toward the preliminary design of seagoing multi-purpose cargo vessels

The preliminary design stage is a starting and vital step in the ship design process which generally involves the adaptation of a prototype selected from an available and trustworthy vessel database. This investigation was prompted by the noticeable lack of systematic literature data on multi-purpose cargo vessels (MPCV), especially in the range of medium size fleet, with respect to gross tonnage. A procedure is presented for optimum MPCV characteristics determination in the preliminary design stage. It is grounded on a statistical analysis of the database gathered upon reliable MPCV built over the past 30 years. Using the proposed set of diagrams and formulas, the designers could determine ship principal dimensions upon required deadweight as a main prerequisite, as well as optimum energy efficiency design index, tank capacities, lightweight, etc

Estimation of ship lightweight reduction by means of application of sandwich plate system

Sendvič panel sistem predstavlja alternativu konvencionalnom orebrenom panelu i sastoji se od dva metalna lima razdvojena ispunom od elastomera. Uzimajući u obzir visok odnos čvrstoće i težine, jednostavnost konstrukcije, otpornost na udare i eksploziju, SPS je široko rasprostranjen u mnogim industrijama, a najviše u remontu brodova. Mada se često navode veoma optimističke prognoze u vezi potencijalnih ušteda u ukupnoj težini konstrukcije, činjenica je da još nijedan kompletan trup broda od SPS-a nije zaista napravljen. Ideja ovog rada je da se analiziraju mogućnosti SPS-a u ovoj nameni. Kao primer trupa broda je uzeta tipična rečna barža. Kombinujući različite koncepte gradnje i tipove brodova, ukupno 21 model konvencionalne konstrukcije broda je definisan i njihove težine su detaljno sračunate. Isto je urađeno pod pretpostavkom da je barža napravljena od SPS-a, koristeći 'Lloyd's Provisional Rules'. Svi rezultati su sistematski poređeni i analizirani.Sandwich plate system is an alternative to conventional stiffened plate composition that consists of two metal plates separated by an elastomer core. Considering high strength to weight ratio, simplicity, blast and ballistic properties of the material, SPS has been widely used in a range of industries but its most dominant application has become ship repair. Regarding new buildings some very brave estimations of possible weight savings can be found, but still no complete hull made of SPS has been actually produced. The idea of this paper is to analyze possibilities of SPS for such application. A typical river barge is used as the basic hull shape. Combining different framing concepts and cargo types 21 different model of conventional hull structure is defined and their weights calculated. Subsequently the same is done presuming that barge hull is built of SPS, and using related Lloyd's Provisional Rules. All results are systematically compared and analyzed

A STEP TOWARD THE PRELIMINARY DESIGN OF SEAGOING MULTI-PURPOSE CARGO VESSELS

The preliminary design stage is a starting and vital step in the ship design process which generally involves the adaptation of a prototype selected from an available and trustworthy vessel database. This investigation was prompted by the noticeable lack of systematic literature data on multi-purpose cargo vessels (MPCV), especially in the range of medium size fleet, with respect to gross tonnage. A procedure is presented for optimum MPCV characteristics determination in the preliminary design stage. It is grounded on a statistical analysis of the database gathered upon reliable MPCV built over the past 30 years. Using the proposed set of diagrams and formulas, the designers could determine ship principal dimensions upon required deadweight as a main prerequisite, as well as optimum energy efficiency design index, tank capacities, lightweight, etc

NUMERICAL INVESTIGATION OF INTERCEPTOR EFFECT ON SEAKEEPING BEHAVIOUR OF PLANING HULL ADVANCING IN REGULAR HEAD WAVES

In this paper an attempt has been made to assess the capability of numerical algorithm based on Reynolds Averaged Navier Stokes (RANS) for predicting the motion characteristics of the planing hull in calm water and regular waves. The focus of the present study is the impact of interceptors on the sea keeping quality of a planing vessel investigated through the application of numerical methods. The wave properties such as wavelength and wave height are taken into consideration to investigate the effect of wave steepness on vessel response. It is found that numerical data can efficiently simulate the motion attitude and the hydrodynamic characteristics of planing craft in regular head waves. The planing hull with and without interceptor fitted at the transom is simulated in numerical wave tank. The results show reduction in heave and pitch motions which gave favorable sea keeping behavior for the hull fitted with interceptor. The numerical solution is useful for the preliminary prediction of navigation safety during sailing

Evaluating an Inland Waterway Cargo Vessel's Energy Efficiency Indices

Although the International Maritime Organization (IMO) introduced the energy efficiency requirements for ships more than a decade ago, to date, inland navigation has not been affected by corresponding regulations at all. Therefore, inland waterway vessels are left with no mandatory requirements that could push their technology into more energy efficient design. Fortunately, there are certain pioneering attempts to define energy efficiency criteria for inland vessels. This paper tries to gather and provide a review of such methods. Moreover, a typical Danube cargo inland vessel's data are used to evaluate their current energy efficiency levels with respect to provisional criteria. Consequently, two methods are found and used here. They are both based on IMO's energy efficiency concept but modified for the inland waterway vessels. The methods delivered a significant difference in applicability and were difficult to compare. Moreover, shallow and deep-water effects are explored in the same regard but provided unsound conclusions. The final results displayed discrepancies in energy efficiency levels for the same vessels and so the methodology should be improved and harmonised, if it is to be introduced as mandatory for inland waterway vessels. The analysis provided a glimpse into the current condition of the traditional design of the Danube inland fleet, with respect to the emerging energy efficiency policies

Hot spot along corner curvature of rectangular plate opening

Koncentracija napona u uglu kvadratnog otvora u ploči je poznata činjenica. Najčešće se uzima da je najveća koncentracija napona u samom temenu ugla (na ugaonoj koordinati od 45 stepeni u slučaju kvadratnog otvora). Rigoroznije analize, ipak, prikazuju da ovo baš nije najtačnije. Iako maksimalni napon nikada "ne napušta" ugao, u nekim proračunima koncentracije napona, ozbiljnije analize ovog fenomena dobijaju na značaju. U ovom radu prikazani su i poređeni rezultati analitičke, numeričke i eksperimentalne analize tačne pozicije koncentracije napona u uglu otvora, u slučaju ploče pri istezanju.Development of stress concentration in the corner zone of rectangular plate opening is a well-known fact. It is usually literally taken that the largest stress concentration factor (SCF) occurs exactly in the corner (at angle coordinate of 45 degrees in case of square opening). More rigorous analyses, however, reveal that this is not perfectly true. Although maximum stress never really "leaves the corner", for some hot-spot analyses, more scrupulous investigation of this phenomenon has significance. In this paper, results of some analytical, numerical and experimental investigations of this topic, for plate in tension, are presented and compared

Power reduction considerations for bulk carriers with respect to novel energy efficiency regulations

After introducing an energy efficiency design index (EEDI) in 2011, International Maritime Organization (IMO) pursued their short- and long-term goals to reduce greenhouse gas (GHG) emissions from ships by presenting, among others, an energy efficiency existing ship index (EEXI). Contrary to EEDI which is used for new ships solely, EEXI is addressing an energy efficiency of already built ships and is set to become formally applicable starting from 2023. Existing designs cannot be essentially and rapidly changed to comply the criterion. The only main particular from the preliminary design phase that can be meaningly optimized ???post festum??? is a required engine power, and thus, the speed. Therefore, the paper explores the effect of EEXI policy on a fleet of 153 bulk carriers built between 2000 and 2020 in order to address their near future and prompt design changes, specifically considering the power reduction. For that purpose, an attained and a required EEXI are calculated for each ship. The results showed that only 15% of the ships built in 2000-2012 satisfied 2013-2014 IMO criterion. This impacted the design of ships built in 2013-2022, as they complied the same criterion by 88% of share. However, no ship from the whole database satisfied the present day EEDI requirement and only one ship fulfilled the contemporary EEXI requirement meaning that the current designs are not able to match the emerging criteria to a large extent. In order to meet an energy efficiency criterion, a main engine power reduction and speed are predicted assuming that the engine power and shaft limiter are installed. The investigation showed that MCR reduction of the total fleet taken into account had to be reduced by 50% and speed by 15% on average in order for ships to meet current requirements. Moreover, a graphic method is developed for the estimation of EEXI by using only deadweight (DWT) and could be used on existing bulk carriers with an aim to satisfy novel regulation with reliably evaluate an energy efficiency of existing ships

Hot spot along corner curvature of rectangular plate opening

Koncentracija napona u uglu kvadratnog otvora u ploči je poznata činjenica. Najčešće se uzima da je najveća koncentracija napona u samom temenu ugla (na ugaonoj koordinati od 45 stepeni u slučaju kvadratnog otvora). Rigoroznije analize, ipak, prikazuju da ovo baš nije najtačnije. Iako maksimalni napon nikada "ne napušta" ugao, u nekim proračunima koncentracije napona, ozbiljnije analize ovog fenomena dobijaju na značaju. U ovom radu prikazani su i poređeni rezultati analitičke, numeričke i eksperimentalne analize tačne pozicije koncentracije napona u uglu otvora, u slučaju ploče pri istezanju.Development of stress concentration in the corner zone of rectangular plate opening is a well-known fact. It is usually literally taken that the largest stress concentration factor (SCF) occurs exactly in the corner (at angle coordinate of 45 degrees in case of square opening). More rigorous analyses, however, reveal that this is not perfectly true. Although maximum stress never really "leaves the corner", for some hot-spot analyses, more scrupulous investigation of this phenomenon has significance. In this paper, results of some analytical, numerical and experimental investigations of this topic, for plate in tension, are presented and compared

Strength modelling of orthotropic ship structure panels by equivalent unstiffened plates

Проблеми понашања оребрених плоча (панела), као основних јединица бродских конструкција представљају једну од најзначајнијих истраживачких тема из области чврстоће бродских консктрукција. У овом раду оребрене плоче моделиране су неоребреним плочама, са циљем да се одзиви и једне и д руге у ш то в ећој м ери п одударају. У т у с врху р азвијена ј е процедура (метода еквиваленције) којом се за сваку оребрену плочу могу прорачунати параметри еластичности неоребрене плоче, тако да маскимални угиби и напони, у обе плоче, буду једнаки. Ово подразумева и дефинисање еквивалентног коначног елемента плоче који у својој матрици крутости, хомогенизује особине плоче и укрућења. Развијени математички алгоритам узима у обзир употребу теорије ортоторпних плоча и методе коначних елемената. С о бзиром д а ј е т руп б рoда састављен од великог броја оребрених плоча, сврха моделирања чврстоће еквивалентним плочама свакако је формирање нумеричког модела бродске конструкције са редукованим бројем елемената и степени слободе. Овај модел, за разлику од конвецнионалног, не поседује укрућења, само еквивалентне неоребрене плоче. Поређењем конкретног нумеричког модела трупа брода састављеног од конвенционалних коначних елемената и оног од нових, еквивалетних елемената, добијена је јаснија слика о примени, предностима и манама развијене методе. Циљ рада је да се употребом методе еквиваленције, поједностави структурно моделирање великих нумеричких модела бродске конкстуркције, без значајнијих губитака у квалитету анализе, односно одређеним померањима и напонима у констуркцији. Такође је урађена и серија мерења на конкретним моделима оребрених плоча да би се утврдила генерална разлика у одзивима реалне консктрукције у односу на одзив добијен применом методе коначних елемената, имајући у виду да се ова нумеричка метода користи у оквиру методе еквиваленције.One of the most important research topic in the field of ship strength analysis is the problem of structural behavior of stiffened plates (panels), as the basic units of ship structures. In this paper, stiffened plates are modeled as unstiffened ones, with the purpose to achieve the compliance in their structural response, as much as possible. Therefore, the procedure (equivalence method) is developed in order to obtain elasticity parameters of unsiffened plates so that maximum displacements and stresses would be the same in both plates. Furthermore, an equivalent finite element is defined. This element has stiffness matrix that homogenize the mechanical prorerties of both plate and stiffener. Developed mathematical algorithm takes into account application of orthotropic plate theory and finite element method. Considering that ship hull consists of large number of stiffened plates, the goal of equivalent plate strength modeling is to form a numerical model of ship structure with a reduced number of elements and degrees of freedom. This model, apart from convencional one, does not have stiffeners, just equivalent unstiffened plates. Comparing the specific numerical model of ship structure that consists of conventional finite elements and one that consists of new, equivalent elements, one can get more clear view on application, advanteges and disadvantages of developed method. The goal of this thesis is to simplify structural modelling of large numerical models of ship strucutures, without any significant loss in quality of the analysis, namely resulting displacements and stresses. Furthermore, a series of measurements is performed on specific models of stiffened plates in order to achieve general comparison of the structural response of real structure as opposed to numerically modeled one, especially having in mind that finite element method is incportporeted in equivalence method

On ultimate strength of an inland waterway barge

Due to the sudden nature of hull girder collapse caused by extreme loadings, the ultimate strength of ships, i.e., ultimate capacity, has to be evaluated. Ultimate strength analysis procedures have already been provided within the rules of the classification societies for sea-going ships. However, rules for inland vessels are not fully addressing the issue. In addition, literature data on the ultimate strength of inland vessels are almost negligible, which is alarming, considering the frequency of grounding and overloading events in inland navigation. Moreover, inland vessels' structural elements are prone to buckling due to their slender plates. In order to evaluate ultimate strength, an inland waterway (IW) barge is chosen for progressive collapse analysis (PCA) employment. PCA has demonstrated that the buckling collapse of structural elements vastly governs a vessel's ultimate capacity. Results show the extent of the safety zone between the actual loss of the ultimate capacity and the linear-elastic behavior of the structure