Σύγχρονος σχεδιασμός της μεταλλικής κατασκευής πλοίων bulk carrier

174 σ.Στο πρώτο κεφάλαιο της διπλωματικής με τίτλο «σύγχρονος σχεδιασμός της μεταλλικής κατασκευής πλοίων bulk carrier», γίνεται προσπάθεια να εξοικειωθεί ο αναγνώστης με την έννοια της σχεδίασης της μεταλλικής του bulk carrier. Το δεύτερο κεφάλαιο αποτυπώνει τις βασικές αρχές που ακολουθούνται στο σχεδιασμό της μεταλλικής κατασκευής των χώρων φορτίου, ξεκινώντας από την περιγραφή της διαδικασίας, που είναι υποσύνολο της σπειροειδούς διαδικασίας κατά τη μελέτη του πλοίου.Το τρίτο κεφάλαιο είναι αφιερωμένο στον προσδιορισμό των φορτίων που επηρεάζουν την κατασκευή του πλοίου. Στο τέταρτο κεφάλαιο της διπλωματικής, γίνεται η παρουσίαση των υπολογισμών, σύμφωνα με τους κανονισμούς του Αμερικανικού Νηογνώμονα (ABS), για τη διαστασιολόγηση των στοιχείων που απαρτίζουν τη μεταλλική κατασκευή του bulk carrier, στην περιοχή της μέσης τομής. Το πέμπτο κεφάλαιο ασχολείται με την ανάλυση της αντοχής του πλοίου. Το έκτο κεφάλαιο επικεντρώνει στο συνολικό σχεδιασμό της μεταλλικής κατασκευής στην περιοχή των αμπαριών, όπως αυτή επηρεάζεται από τα λειτουργικά χαρακτηριστικά και τις ανάγκες που παρουσιάζονται κατά την επιχειρησιακή λειτουργία του πλοίου. Τέλος, στο έβδομο κεφάλαιο παρουσιάζονται όλα τα εναλλακτικά σχέδια της μορφής της μεταλλικής κατασκευής των bulk carrier που έχουν προταθεί τα περασμένα χρόνια, ενώ καταγράφονται και οι κυριότερες περιοχές καινοτομιών που μελετώνται και είναι υπό εξέταση η εφαρμογή τους στη λειτουργία του πλοίου.In the first chapter of this thesis an effort is being made to familiarize the reader on the concept of the bulk carrier design. The second chapter outlines the design principles followed in the structural design of the cargo spaces of a bulk carrier, starting from the structural design process, that is part of the design spiral. The third chapter mentions the determination of loads affecting the hull structure. In the fourth chapter, the calculations for the structural components in the midship section area of a bulk carrier are presented, whereas the fifth chapter of this study copes with the strength analysis of the hull structure. The sixth chapter copes with the overall design of the hold area in a bulk carrier, seen from an operational point of view. Finally, the seventh chapter outlines the main alternative designs that have been implemented last decades in bulk carrier structural design, whereas the major areas of concern for the design of the future are also listed.Σπανολιός Παντελεήμω

Asphalt Carriers from Kraljevica Shipyard, Croatia

This article is based on the materials presented by the experts from Kraljevica Shipyard at the annual meeting of the Croatian shipbuilding designers held in Kraljevica in October 2005. Asphalt tanker Asphalt Seminole and her sister-ships are rather sophisticated vessels having a complex hull structure, cargo space and cargo survey and control equipment. Therefore, firstly the technical data of the already delivered asphalt tanker Asphalt Seminole are given and then, the very interesting development of her design in presented. Special emphasis is given to the design of the cargo space, to the stability survey of the intact ship at various loading cases as well as to the damaged ship stability and floatability calculation in accordance with the pollution prevention regulations. Finally, a comparison of the present ship with various similar asphalt tankers in exploitation is made

Committee V.1: Accidental Limit States

Concern for accidental scenarios for ships and offshore structures and for their structural components leading to limit states. Types of accidental scenarios shall include collision, grounding, dropped objects, explosion, and fire. Attention shall be given to hazard identification, accidental loads and nonlinear structural consequences including strength reduction, affecting the probability of failure and related risks. Uncertainties in the use of accidental scenarios for design and analysis shall be highlighted. Consideration shall be given to the practical application of methods and to the development of ISSC guidance for quantitative assessment and management of accidental risks

Optimal control of the heave motion of marine cable subsea-unit systems

One of the key problems associated with subsea operations involving tethered subsea units is the motions of support vessels on the ocean surface which can be transmitted to the subsea unit through the cable and increase the tension. In this paper, a theoretical approach for heave compensation is developed. After proper modelling of each element of the system, which includes the cable/subsea-unit, the onboard winch, control theory is applied to design an optimal control law. Numerical simulations are carried out, and it is found that the proposed active control scheme appears to be a promising solution to the problem of heave compensation

Design Procedure and Mathematical Models in the Concept Design of Tankers and Bulk Carriers

Paper presents design procedures and mathematical models applicable in initial design of merchant ships with high block coeffi cient. Special attention has been paid to two dominant ship`s groups: tankers and bulk carriers. Presented design procedure is common for both groups and it can be applied using various application techniques: from the simplest handy methods to the most sophisticated optimization methods and techniques. Presented mathematical model includes optimization of main ship characteristics as well as optimization of commertial effects of newbuildings. Mathematical models are based on designer´s long-time work experience. Large number of data has been derived from more than 150 executed designs and more than 40 ships built in Shipyard Brodosplit. Recommendations for execution of design are shown in number of pictures and diagrams. Presented design procedure and mathematical models have been applied in the multiattribute decision support optimization programme developed in Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb

Ultimate strength

Concern for the ductile behaviour of ships and offshore structures and their structural components under ultimate conditions. Attention shall be given to the influence of fabrication imperfections and in-service damage and degradation on reserve strength

Ultimate and Residual Strength Assessment of Ship Structures

The prevention of ship structural failures and reduction of accident consequences contribute to increased safety at sea and reduced environmental impact. A need for reliable and efficient ship designs facilitates knowledge accumulation and the development of tools for the assessment of hull structural responses to acting loads. Important in this regard, ship design criteria are the ultimate and residual strengths of a hull that determine whether a ship may be safely operated in intact and accidentally damaged conditions. Thus, an accurate and reliable procedure for estimating a ship’s strength accounting for all actual foreseeable scenarios and reasonably practicable conditions is necessary.The main objective of this thesis is to develop a new precise and time-efficient methodology for the assessment of the ultimate and residual strength under vertical and biaxial loading conditions. A coastal oil tanker and a RoPax vessel were chosen for the parametric study of the ship’s structural arrangement, load type and corrosion effect on the crashworthiness and ultimate strength. Collision simulations under varying conditions were carried out by means of the finite element method. The assessment of the ultimate and residual strength was performed with the Smith method together with finite element analyses.The thesis work contributed to a better understanding of the modelling and analysis setup for the realistic ultimate and residual strength estimates. A new approach for modelling corrosion in ship structures, which includes models for plate thickness reduction and corroded materials, was developed. Different collision damage modelling techniques were compared, and the importance of making full collision simulations, including plastic deformations and residual strains, was shown. The differences and limitations of the finite element and Smith methods were discussed, and improvements to the Smith method along with a new calibration procedure were introduced. The study resulted in a new unified methodology, combining the precision of the finite element method and the efficiency of the Smith method, for the assessment of the ultimate and residual strength of ships

Influence of Oil Tanker Subdivision on Probabilistic Oil Outflow Following Side Damage

We live in an era of growing environmental concern. In the future no activity will be considered acceptable unless it is reasonably safe for the environment. Since the late 60's, when growing demand for oil transportation by sea introduced the concept of VLCCs, oil tanker accidents received wide coverage by the media. In 1967 the stranding of the Torrey Canyon highlighted the immense threat of massive pollution that could result from accidental discharge of oil in the event of stranding, collision, etc. The Amoco Cadiz in 1978 and the Exxon Valdez in 1989 are some of the accidents which have since greatly added to the public's concern about that threat. Measures and tentative solutions to the technical aspect of accidental oil pollution from tankers have been put forward from time to time. The U.S. Oil Pollution Act 1990 (O.P.A.'90) and amendment 13F to Annex I of MARPOL 73/78 are the latest attempts to curb accidental oil spillage, by introducing new requirements for the construction of oil tankers. The requirements prescribe double hull construction as the reference in terms of pollution prevention, with MARPOL leaving the door open to novel design solutions that provide "equivalent protection" against oil pollution. The controversy that preceded and followed, particularly in the case of the unilateral enforcement of O.P.A.'90, prompted new research on the subject of oil tanker design assessment. A probabilistic method of assessment, already applied to passenger and cargo ship damage stability, was proposed for the comparison of oil outflow behaviour in collision and grounding accidents. Unfortunately, most of the literature concentrates on the debate over the equivalence of double-hull and mid-deck designs without worrying about improving one concept or the other. The probabilistic assessment is used as a "black-box" tool, fed with an input and yielding an output, without any explicit links between design parameters and oil outflow results. Furthermore, the choice of simplifying assumptions in the application of the probabilistic assessment, obliterates even more these links and limits the usefulness of the results. The present work starts with a short review and critique of the way the probabilistic method was used in oil outflow studies, highlighting in the process their important features and their weaknesses. An enhanced method is proposed, which has the merit of taking into account the random nature of the damage characteristics in the vertical dimension of the ship. Only side damage cases are addressed but the proposed method allows for bottom damage cases to be treated in exactly the same manner, thus providing a unified framework for the complete assessment of a tanker design. With the help of the enhanced probabilistic method, a series of systematic variations of the subdivision arrangement in three tanker design concepts is assessed. An attempt is made to chart the relationship between the choice of design parameter values and the environmental performance of the resulting tanker design. The results of the analysis are validated, when possible, with results from other oil outflow studies, while an explanation is proposed for results showing discrepancies. The analysis results are also used to draw basic guidelines for improving the subdivision arrangement of typical single-skin, double-hull and mid-deck tanker designs. The work shows in conclusion that in each of these concepts the subdivision arrangement can be optimised for a given level of environmental performance and that the probabilistic method of assessment is the way forward in the evolution from purely prescriptive construction regulations to goal-orientated design

Probabilistic Concept of Ship Subdivision Applied to Tankers Oil Outflow Assessment

The oil tanker designs have suffered significant changes during the last few years. These forced modifications were a result of the introduction of recent international (IMO, 1995) and domestic (OPA '90) regulatory actions. Intensification in the research work was also noted during this last decade, giving special attention to the prediction of tanker environmental performance in collisions and groundings. Agreeing that the probabilistic concept is the only rational tool that enables a true comparison of different tanker designs, the mathematical basis for the probabilistic concept is described with references to the most important authors and their contribution to the development of probabilistic based regulations. A review on the development of international regulations for control of oil pollution from tankers is presented, with statistics of the most important accidents, in terms of oil spills. A mathematical model was developed, integrating the latest IMO regulations, using a direct probabilistic methodology. This methodology incorporates distributions of damage location and damage penetration as derived by several Classification Societies and compiled by IMO. The method was enhanced with the characteristic of not assuming total width extent of damage in case of groundings, enabling this way the assessment of the influence of longitudinal subdivision in the cargo space and in the double-bottom. Expected oil outflow calculations were performed for 107 different tankers, including Pre-MARPOL, MARPOL, Double-Hull and Mid-Deck designs. Initial oil losses following impact and oil retention in the double-hull space were taken into consideration, as well as tidal drop and dynamic effects. The work carried out include: parametric studies, varying double sides width, double-bottom heights, number and location of longitudinal bulkheads, number and location of transversal bulkheads and location of horizontal bulkheads; double-hulls comparison; different design types comparison and environmental performance ranking. A discussion of the resulting probabilistic oil outflows is presented with comparisons of the environmental characteristics of the sample tankers. These sample tankers include both variations of internal subdivision within the same ship type and also among different design types. From the analysis it was found that, in general, the mid-deck tanker designs have lower oil outflow rates, when compared with the other designs, including double-hulls. It was also concluded that the subdivision of the cargo block region has a determinant influence on the calculated expected oil outflows. A short description of new design concepts is made, presenting the different characteristics of each and the advantages claimed by each author