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This thesis investigates the structural response of modem ship structures under the effect of premeditated blast loads from acts of terrorism and extremism. The escalation of maritime terrorism and piracy has given the impetus to this study to take an introspective look into the details of ship structural performance under a series of design threats. Knowledge gained in studying the vulnerability of merchant ship structures is important in identifying the area to focus further work. As soon as the vulnerability of a typical ship structure is identified, a more detailed study on the most contributive structural members is carried out. Then, a rational increase of the highlighted members raises the reliability index of the subject panel, and proposes a target reliability index for blast-loaded stiffened panels. The benefit from meeting the suggested reliability-based vulnerability requirements is assessed in terms of a series of identified metrics of benefit for the considered design threats

The initial stability of a ship is currently evaluated by empirical formula based largely on a static approach. Evidently stability is affected by speed that causes variation of pressure distribution on the wetted surface of a ship's hull, and generated waves on the surface of water by the vessel's motion. Forces and moments resulting from bottom pressures, as the speed of the ship changes, are significantly different for the ship at rest and in a seaway. The principal aim of the research is to investigate the effect of variations of forward speed on stability of a ship in calm water. The thesis presents theoretical and experimental approaches of the research. The novelty of the research results leads to the conclusion that although increasing speed may improve the stability of a ship in some cases, it also depends on heeling angle or on any asymmetry of the wetted area of a hull. Taking into account asymmetry effects, unbalanced pressure distribution acting on the wetted surface of the hull, in some cases, hence, decrease of stability is also possible. On a moving, partially immersed body, hydrodynamic and hydrostatic forces predominate. These forces arise owing to interaction between the body's motion and its weight with respect to the surrounding water. In order to calculate these forces, the panel method of Computational Fluid Dynamics (CFD) has been applied to identify the velocity and pressure distribution on the wetted surface of a ship's hull. The mathematical model adopted is based on the source distribution on the ship's hull, known as the Kelvin source. The model for a body travelling with steady forward speed, where its motion does not disturb the free surface, is known as double body theory. For consideration of waves generated by the motion of the ship on the free surface, a three dimensional linearised potential flow solution has been utilised. Comprehensive tests conducted in the UCL towing tank have established a better understanding of the significance of variation of ship's stability associated with forward speed in calm water. It is shown that an accurate judgement regarding the ship's stability cannot be made if only the effect of forward speed, as a single parameter, is considered. The heeling angle is another important parameter that must also be taken into account. The effects of a combination of both variables have been investigated, and are reported herein. The research is presented showing that the applied CFD method may be developed as an alternative method to assess stability of a ship in seaway, but there is a long way for the CFD approach to replace towing tank testing. At present, CFD may be used for consideration as a precursor to improve ship's stability during the design stage, for modification, and before operation. It is hoped that in future the findings of the experimental approach of this form of research could be used as additional guidance to be incorporated within the stability documentation for individual ships at the design stage, and ship trials.

Depuis les années 1980, des épaves de grands navires construits à clin de la fin du Moyen-Age ont été découvertes sur les littoraux des mers septentrionales et occidentales. Elles ont régulièrement suscité individuellement un intérêt de la communauté scientifique en regard de leur architecture, puisque la fin du Moyen-Age correspond historiquement à l’apparition puis à la diffusion et à l’adaptation de la construction navale à franc-bord d’origine méditerranéenne en Europe du Nord et de l’Ouest. Pourtant, la comparaison des différentes épaves entre elles pour étudier les développements de la construction navale à clin de cette période est très récente et généralement rattachée à l’analyse des épaves nouvellement trouvées.Cette thèse étudie l’ensemble des navires de plus de 20 m de long susceptibles, par leur architecture, d’avoir évolué en haute mer sur les routes du commerce lointain. En regard du contexte technique et historique, cette étude est limitée géographiquement aux mers nordiques et chronologiquement au Moyen-Age tardif et au début de la période moderne.Le navire résulte à la fois des technique de construction navale et de la demande de ses commanditaires. Durant la période d’étude envisagée dans la thèse, les marchands, qui sont également les affréteurs, constituent les principaux armateurs avec les gens de mer, marins et capitaines, qui régulièrement sont propriétaires en totalité ou en partie des grands bâtiments.De ce fait, le contexte historique, affectant les activités de commerce et de transport, contribue à expliquer les développements de la construction navale. De plus, l’analyse technique des épaves permet de comprendre comment les charpentiers de marine ont pu répondre à la demande de ces propriétaires. Pour cela, la reconstitution des épaves, comme celle de l’Aber Wrac’h 1(France), est essentielle, car les données relatives à la construction, la conception et la forme des navires fournissent des éléments de comparaison scientifique fiables en regard des typologies chronologiques et régionales et permettent de replacer le navire dans son contexte historique et socio-économique. / Since the 1980s, several wrecks of large clinker ships adting from the late Middle Ages were found on the coasts of Northern and Atlantic seas. The scientific community was regularly interested in the architecture of each site as the late Middle Ages historically corresponds to the appearance, dissemination and adaptation of the carvel shipbuilding from the Mediterranean in Northern and Western Europe. Yet the comparison of the different wrecks themselves to study the development of the clinker shipbuilding of this period is recent and usually linked to the analysis of newly found wrecks.This thesis explores all vessels over a length of 20 meters, which were able, according to their architecture, to sail on open seas for long-distance trade. Due to the technical and historical context, this study is limited geographically to the nordic seas and chronologically to the Late Middle Ages and early modern period.The ship results from the shipbuilding technology and the demand of its owners. During the late Middle Ages, the merchant class, which was the principal user, was also the main shipowner with the seafarers, sailors and captains, who regularly owned all or part of large vessels.Therefore, the historical context, affecting trade and transport activities, helps to explain the developments in shipbuilding. Therefore, technical analysis of wrecks allows understanding how the shipwrights and carpenters could meet the demand of those owners. Hence, there construction of the wreck, such as Aber Wrac’h 1 (France), is essential because the data about the building, design and shape of the vessels provide reliable scientific information for comparison in terms of chronological and regional typologies and help to place the ship in its historical, environmental and socio-economic context.