Ongoing developments in improving ship safety indicate the gradual transition from a compliance-based culture to a sustainable safety-oriented culture. Sophisticated methods, tools and techniques are demanded to address the dynamic behaviour of a ship in a physical environment. This is particularly true for investigating the flooding phenomenon of a damaged ship, a principal hazard endangering modern ships. In this respect, first-principles tools represent a rational and cost-effective approach to address it at both design and operational stages. Acknowledging the criticality of ship survivability and the various maturity levels of state-of-the-art tools, analyses of the underlying uncertainties in relation to relevant predictions become an inevitable component to be addressed. The research presented in this thesis proposes a formalised Bayesian approach for quantifying uncertainties associated with the assessment of ship survivability. It elaborates a formalised procedu re for synthesizing first-principles tools with existing knowledge from various sources. The outcome is a mathematical model for predicting time-domain survivability and quantifying the associated uncertainties. In view of emerging ship life-cycle safety management issues and the recent initiative of "Safe Return to Port", emergency management is recognised as the last remedy to address an evolving flooding crisis. For this reason, an emergency decision support framework is proposed to demonstrate the applicability of the presented Bayesian approach. A case study is enclosed to elucidate the devised shipboard decision support framework for flooding-related emergency control. Various aspects of the presented methodology demonstrate considerable potential for further research, development and application. In an environment where more emphasis is placed on performance and probabilistic-based solutions, it is believed that this research has contributed positiv ely and substantially towards ship safety, with particular reference to uncertainty analysis and ensuing applications.

Although substantial effort has been devoted in the design process of ships to reduce the operational risk level by preventing and mitigating accidental events, the societal expectation on the safety at sea is growing faster than ever. The framework of the safe return to port for passenger ship safety reflects this trend in pursuance of zero tolerance to loss of human life in the event of an accident. Along these lines the emphasis of the survivability of a damaged ship is placed on the damage stability and the hull girder collapse under the explicit assumption that the initial damage extent is fixed. However, in practice it is often observed that progressive degradation of the damaged structure threatens the survival of a ship by causing significant reduction of its strength, as it was witnessed in the loss of MV Prestige. Hence, the information of progressive structural failure in timeline and its effect on the hull girder residual strength is of paramount importance in the course of evaluating survivability of a damaged ship and mitigating the ensuing consequences. This provides an obvious objective for this study, which is the elaboration on a method for progressive structural failure analysis under time varying wave loads and the development of a parametric tool for fast and reliable assessment of the structural survivability of a damaged ship with respect to the damage propagation. The developed tool provides the probability of unstable damage propagation over time, from which the window of safe intervention in emergency operations can be extracted and support the decision-making process in the course of the rescue and salvage operation. Moreover, this work also sets the foundation of a new dimension in the early ship design phase, namely the structural survivability with respect to the progressive structural failure. In this way, it contributes to the holistic safety assessment approach advocated by the design for safety philosophy and the riskbased ship design methodology. The developed tool is fully parametric so as to support decision-making both in the emergency operations, where fast and reliable information is required, and in the early design stage, where various damage cases need to be assessed in order to administer appropriate structural design solutions.

Ship weather routing was first developed for determining the minimum time of a voyage. However, after 90's, driven by the increasing oil price and the environmental considerations, most shipping companies have began to show more and more interest in minimising fuel consumption in a route, in the meantime, maintaining a certain time schedule which is specified in the chartering contract of a merchant vessel. This topic is the focus of this thesis. A novel three dimensional dynamic programming method (3DDP) has been developed in this research to determine the optimised ship course and its corresponding engine power for minimum fuel consumption. During the optimisation process, Kwon's method as a new empirical formula is used to calculate ship speed in different weather conditions and an IMO guideline is applied to ensure ship safety during a voyage. In addition to the 3DDP method developed, three multi-objective evolutionary algorithms (MOEAs) are also proposed to treat we ather routing as a multi-objective and constrained optimisation problem. Based on ship hydrodynamic knowledge and optimisation algorithms an Intelligent Tool for Energy Efficient and low environment impact Shipping (ITEES) has been developed. ITEES is established by using the object-oriented software development theory, consisting of several independent functional modules. The OPeNDAP as an advanced communication technique is employed by ITEES for downloading deterministic weather forecast at no cost. Case studies are given in Chapter 8 of this thesis to evaluate the performance of the 3DDP method in a comparison with other different optimisation algorithms under different weather conditions. A 54,000 DWT container ship is used as the case ship. The case studies have demonstrated that, in medium sea condition, different route optimisation methods offer the similar results that the shortest route with a constant engine power brings the lowest fuel consumption. However, the results of different route optimisation methods vary significantly in rough sea states. Optimised results are not only just for fuel saving but also, most importantly, for ensuring ship safety during a voyage. Among the optimisation algorithms evaluated by the research, the 3DDP used in ITEES is able to give a better performance for fuel saving than other methods. In addition, it has the characteristics of using straight forward theory and less parameter settings compared with MOEAs that make the ITEES programme easy and convenient for operators to use.

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Marine renewable energy sources are crucial alternatives for a sustainable development. The idea of generating electrical power from water waves has been realized for many years. In fact, waves are now considered as an ideal renewable energy source since a Wave Energy Converter (WEC) has no fuel cost and provides cleanly a high power density that is available most of the time. The third generation of WECs is intended to be installed offshore. This allows the device to harvest the great energy content of waves found in deep water and minimise the environmental impacts of the device. On the other hand, moving WECs to offshore locations will increase the initial and maintenance costs. So many types of device may be suggested for wave power extraction that the task of selecting a particular one is made complicated. Therefore modelling of different WECs allows the comparison between them and the selection of the optimum choice. Recent studies showed that the SparBuoy Oscillat ing Water Column (OWC) has the advantage of being simple, axi-symmetrical, and equally efficient at capturing energy from all directions, but its efficiency (capture factor) is affected significantly by the incident wave periods variation due to the dynamic coupling of the water column and the floating structure. The proper modelling of the device allows the optimization of the geometries and the Power Take-Off (PTO) mechanism in order to maximise the power absorbed. The main objective of this research is to develop experimentally validated numerical wave power prediction tool for offshore SparBuoy OWC WEC. The numerical tool should be able to predict the spar motions and the water column oscillations inside the structure, in addition to the estimation of the pneumatic power absorber and the evaluation of the device performance. Three uncoupled linear second order differential equations have been used to predict the spar surge, heave and pitch motions, where wave forces have been calculated. Three uncoupled linear second order differential equations have been used to predict the spar surge, heave and pitch motions, where wave forces ha ve been calculatedanalytically in frequency domain in inertia and diffraction regimes. Mooring system has been involved in surge motion only using static and quasi-static modelling approaches. Finite element multi-static model have been developed using OrcaFlex to validate the analytical results. Single Degree of Freedom (DOF) mechanical oscillation model has been presented to simulate the water column oscillations inside captive cylindrical OWC where PTO damping and stiffness due to air compressibility inside the pneumatic chamber have been taken into account linearly. Later on, nonlinearity due to large waves has been investigated. Linearized frequency domain model based on classical perturbation theory and nonlinear model where wave forces are calculated in time domain have been proposed. Furthermore, nonlinearity due to damping forces has been considered. First, iterative procedure has been used to optimise the linear and quadratic damping coefficients in frequency domain. Then, another model has been provided where equivalent viscous damping coefficients are calculated in time domain by taking into consideration the instant oscillation amplitude. Finally the nonlinear effects due to air compressibility inside the OWC chamber has been considered in a time domain model which include the water column oscillations amplitudes. Two different dynamic models have been implemented to describe floating OWC and will be referred to in the text as simplified 2DOF model and Szumko model. Both models considered two translational modes of motions in heave direction. Simplified 2DOF model has been solved analytically in frequency domain due to its simplicity, while numerical solutions in time domain have been provided for both models using Matlab. Different approaches have been adopted to modify both models in order to obtain a satisfactory agreement between the predicted and measured results. A floating platform consists of four similar SparBuoy OWC WECs rigidly attached together by trusses where spars are located at the corners have been tested experimentally. Numerical model has been developed to predict the platform motions. Finally the experimentalresults have been compared to those obtained from the modelling of single SparBuoy OWC.

The Risk-Based Ship Design (RBD) methodology, advocating the systematic integration of risk assessment in the conventional design process so that ship safety is treated as an objective rather than a constraint, has swept through a wide spectrum of the maritime industry over the past fifteen years. Through this methodology, safety is situated at a central position alongside conventional design objectives, so that wellbalanced design effort could be spent and consequently comprehensive design optimisation can be performed. Despite the recognition and increasing popularity, important factors that could potentially undermine its implementation arise both from qualitative and quantitative aspects. This necessitates the development of an objective, reliable and efficient methodology for risk-based ship design implementation. The research presented in this thesis proposes a formalised methodological framework to fulfil this global objective. It comprises three interrelated stages to be performed during risk assessment, namely the development of next generation marine accident/incident database, risk modelling in Bayesian networks by deploying data mining techniques, and the integration with the framework for risk-based design decision making. Working procedures, techniques, methods and algorithms have been developed and applied to representative examples and case studies to demonstrate the applicability and the potential offered by this framework. Each stage of the framework is a field with vast potential for further research, development and application. The ensuing findings firm the faith that an optimal approach towards risk-based design is achievable and extensive applications need to be conducted before experience and confidence can be gained. It is believed that this research has contributed positively towards the evolvement of risk-based ship design.

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An ocean going vessel, sailing in severe seas, experiences motions and loads that are largely affected by nonlinear phenomena. These effects deviate the responses from the linear prediction, modifying their magnitudes, symmetry and frequency characteristics. The change of the actual wetted geometry due to motions and large ambient waves elevation and the occurrence of impulsive phenomena, such as bottom impact, are some of the main sources of nonlinearities. Current state-of-art in seakeeping, applied to ship design, is based on the assumption of small amplitude motions and linearity between the excitation and the response. These techniques have been proved, during the years, to be reliable for small and moderate sea states, but they are not effective in large amplitude waves. The understanding and prediction of the behaviour of the vessel in rough seas is of crucial importance for its design, and therefore there is a need for better methods and practices. Application of nonlinear seakeeping methods in a every-day design situations is limited. The complexity and the computational cost of some methodologies, together with the absence of standardised procedures, are the main causes for the reduced use of such a methodologies. The work presented in this thesis aims to develop a practical nonlinear seakeeping approach that can be used in a design content to model wave induced motions and loads in large amplitude waves. The wave-body interaction problem is solved using a time domain nonlinear two dimensional approach, that considers the actual wetted hull portion and the relative velocity between the structure and the waves. The vessel is modelled as a flexible body to allow structural dynamics. The proposed formulation takes into account impulsive phenomena due to water impact, on both the bottom and the flare of the hull, using a combination of analytical and empirical techniques. The proposed methodology is applied to the S-175 and the Wils II 13,000 TEU container ships. The validation of the proposed method, conducted in both small and large amplitude regular waves, shows the capability of the technique to correctly predict the behaviour of the vessel also when linear methodologies fail. The analysis demonstrates the importance and the reliability of hydroelastic methods for the prediction of wave induced loads, especially when whipping is relevant. A procedure, which applies the proposed methodology for the evaluation of maximum expected values of wave induced motions and loads is presented. Long term analyses are conducted, using both linear and nonlinear method, to study the e ect of nonlinearities. The comparison between linear and nonlinear approaches shows an increase of maximum load responses when nonlinear hydroelasticity is applied. This study highlights also the dependency of the results on the selection of the return period and operational velocity profile of the vessel.

Smart Materials have been investigated for decades and widely used in the automotive and aeronautics industries to measure and control noise and vibration. This study covered ship structure vibration and Smart Materials were employed for the purpose of ship vibration attenuation. One specific Smart Material, piezoelectric material, was the focus of the study. Although previous research has been conducted on vibration mitigation employing piezoelectric shunt systems, this study identified the need for specific applications regarding ship vibration mitigation. Passive piezoelectric shunt damping systems for ships were described and investigated in this study. Computational methods were used to investigate structural vibration of a cantilever beam, a Liquid Natural Gas (LNG) carrier and a bulb keel. The Finite Element Method (FEM) was used to calculate the vibration and vibration treatment with the passive piezoelectric shunt damping system. The numerical results of the passive piezoelectric shunt system bonded to the cantilever beam were compared to experimental results obtained from a previous study. The FEM delivered results, which showed a high degree of similarity in comparison to the experimental results. Both experimental and numerical studies validate the theory that piezoelectric material, connected to an electrical circuit, can be successfully used to achieve vibration reduction. Significant vibration attenuation was found in the numerical simulation of the LNG vessel. The simulation of the bulb keel also provided promising outcome regarding substantial vibration reduction by means of piezoelectric shunt system.