This study is fundamentally relevant to the development of a new enhanced Roller Track Gate (RTG) for the gravity type Self-unloading Bulk Carriers (SULS), called the Multi-functional Roller Track Gate (MRG). Self-unloading Bulk Carriers (SULS) are specialized types of dry bulk carrier vessels, principally because these ships discharge their cargoes without the assistance of external sources. In 1908, the first commercial vessel of these types started trading in the Great Lakes region of North America. Subsequent to the inception of SULS, the technology has developed mainly in the hull structure and onboard unloading systems. Due to the 1980s GL shipping recession, SULS migrated internationally and are now trading worldwide. Eight gravity gates for SULS were investigated in detail prior to designing the MRG. These examinations of previous gates were primarily to address the inherent issues and develop a new gate that would correct the current problems, when discharging dry bulk cargo with the existing gravity gates. The newly designed gate is accompanied with special control system that improves the discharging operations of these type vessels. This gate resulted in being heavier when compared to the existing RTG. However, this study also addresses and mitigates the associated improvements in this new type gate that increases the ship’s lightweight with the possibility of increasing payload / deadweight. High tensile steel was introduced for the hull to compensate for the added gate weight. The steel weight reduction investigation resulted in greater weight than what was required for offsetting the gate weight. The additional weight savings allowed for greater cargo lift for the vessels examined. The economic case study confirmed that by replacing the present Roller Track Gate with the Multi-functional Roller Track Gate, the shipowners’ would benefit from improve discharging performance, less port turn around time and reduced manning cost.

Over the past decades there have been many losses of the merchant vessels due to either accidents or exposure to large environmentally induced forces. The potential for the structural capability degrading effects of both corrosion and fatigue induced cracks are profoundly important and must be fully understood and reflected in vessel’s inspection and maintenance programme. Corrosion has been studied and quantified by many researchers, however its effect on structural integrity is still subject to uncertainty, particularly with regards to localized corrosion. The present study is focused on assessing the effects of corrosion and fatigue induced cracks on the strength degradation in marine structures. Various existing general corrosion models for tanker structures have been studied and compared for time variant neutral axis, section modulus at deck and section modulus at keel based on various years of service. Simplified formulae to estimate time variant vertical/horizontal section modulus degradation and stress change at upper deck and keel are developed based on the double hull tanker. A fatigue assessment study which considers the new corrosion degradation model has also been carried out for the side shell stiffened plates of a North Sea operating shuttle tanker and of a world wide operating tanker. In addition, over 265 non-linear finite element analyses of panels with various locations and sizes of pitting corrosion have been carried out. The results indicate that the length, breadth and depth of pit corrosion have weakening effects on the ultimate strength of the plates while plate slenderness has only marginal effect on strength reduction. Transverse location of pit corrosion is also an important factor determining the amount of strength reduction. When corrosion spreads transversely on both edges, it has the most deteriorating effect on strength. In this study, The multi-variable regression method and the Artificial Neural Network (ANN) method are applied to derive new formulae to predict ultimate strength of both uncorroded and locally corroded plate. It is found out that the proposed formulae can accurately predict the ultimate strength of both uncorroded and locally corroded plate under uni-axial compression. It is certain that undetected defects and developing cracks may lead to catastrophic fracture failure. Fracture control is necessary to prevent the ship’s structure safety not to fall down below a certain safety limit. It is very important to calculate how the structural strength is affected by cracks and to calculate the time in which a crack growth to the unacceptable limits. Fatigue analysis can estimate the elapsed time and locations where cracks could develop, whereas fracture mechanic approach can estimate crack growth times and response of structural strength as a function of crack size. In this study, the linear elastic fracture mechanics (LEFM) method based on stress intensity factor (K) and the elastic plastic fracture mechanics (EPFM) approach based on J-Integral and crack tip opening displacement (CTOD) have been investigated under different loads and crack sizes and material properties by using finite element analyses method. The finite element modelling and calculation for stress intensity factor (K) and J-computation are not easy tasks for most of engineers and researchers who do not have enough experiences. Accordingly some useful macro programs are developed for automatic creation of geometry, mesh details, boundary condition and applying loads, for automatic calculation of stress intensity factor (K) and computation of J-integral value. Proposed formulae based on multi-variable regression method and ANN might be useful to assess structural integrity during the initial design, on-site inspection and maintenance. In addition the developed macro programs for stress intensity factors (K) and J-computation could save time and efforts from time consuming finite element analyses.

This thesis primarily concerns control and identification of FPSO and Shuttle Tanker vessels, where nonlinear hydrodynamics raise the associated issue of nonlinear control. A 3-DOF model is presented for investigating Dynamic Positioning control, a problem where directional thrusters maintain ship position and heading against environmental disturbances. The coupled, multivariable dynamics are controlled using rapid tuning techniques to decouple the plant, yielding successful multivariable PI feedback designs. Identification of a coupled FPSO and Shuttle Tanker is achieved using an MLP neural network. Initially, the network is trained with simulation data for proof of concept, before employing real data from a Mitsubishi Heavy Industries scale model. Identification is successful, but performance degrades with increasing wave height. Two adaptive controllers are developed, based on polynomial LQG and LQG PC optimal control theory. The first uses a standard stochastic cost, approximated to produce a restricted structure controller that permits optimisation across several plant models at once, yielding a multiple model controller. Augmenting linearised ship models with online identification produces adaptive control giving interesting trade-offs between robustness and performance. The second adaptive controller is very similar, but based on a multi-step predictive cost function. Both controllers are applied to FPSO surge axis velocity control, where the LQGPC version produces better performance for a wave-induced reference. A multivariable nonlinear controller is examined for "sandwich" systems consisting of a linear transfer function "sandwiched" between input and output nonlinearities of a particular form. This system description is substituted into the solution of a time-varying polynomial optimal control problem, where the assumption of a frozen plant at each sampling instant requires slowly-varying plant signals in practice. The controller is successfully applied to a 2 x 2 plant with deadzone input and backlash output, with a demonstration that the performance is superior to a well-tuned linear controller.

Conventional marine fuels have always limited the endurance of high-speed ships leading to fast but inefficient cargo ships. This research considers the fuel weight barrier in high-speed ship design and the use of hydrogen as a marine fuel to overcome this barrier. Simultaneously, it is now accepted that environmental pollution from ships, particularly large containerships, contributes to climate change. Hydrogen marine utilization provides a solution for both. As common to other hydrogen research the fuel system spans production to utilization. This hydrogen marine system utilizes an established production method to obtain hydrogen from natural gas through steam methane reformation. To achieve an acceptable storage volume meeting the typical highspeed ship dimensions the hydrogen also requires liquefaction. The hydrogen is then converted onboard into shaft power via combustion in aero-derivative gas turbines. This research establishes the necessary system components spanning both onshore and ship components. The novelty of the research has resulted in new design tools. Research into large hydrogen transport applications is not new and a substantial body of research is available from passenger aviation studies performed during the 1980s and 1990s. Additionally, a more current body of research is available describing hydrogen utilization in large gas turbines for energy and oil/gas industries. This combined research provides the characteristics of the onboard hydrogen system of a high-speed foil-assisted containership. This ship is capable of transporting 600 industry standard 20’ containers on long-haul ocean routes, i.e. 5000 nautical miles, at a speed of 64 knots (118.5 km/hr). Such ship performance is not feasible with conventional marine fuels. The design is complex involving a combination of buoyancy and dynamic lift and two distinct operational modes at floating and dynamic draughts. Research involving this ship configuration is included here in conjuction with suitable design methodologies. Besides technical feasibility, economic feasibility of this containership has also been investigated based around the unit transport price required to recoup costs and achieve zero net present value. Such analysis identified that the containership has higher minimum freight rates than conventional containerships but substantially lower rates than aviation cargo. Due to its high-speed and improved endurance it can compete with aviation on transport time and price. Economic review also identified that shorter container door-to-door times are now demanded by the consumer production industry and this hydrogen marine container transport system meets this demand.