Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, June 2003. / Thesis advisor(s): Fotis Papoulias. Includes bibliographical references (p. 69). Also available online.

Tubular joints are of great importance in offshore jacket structures. This thesis examines the ultimate state behaviour of tubular joints in offshore structures. In particular, the validity of a nonlinear finite element method was investigated and it was subsequently used to determine the ultimate load behaviour of a range of tubular joints. A geometrically nonlinear, eight node isoparan-letric shell finite element program is developed which allows six degrees of freedom per node. The material laws in the model include elastic and elastoplastic multilaver solution with integration across the thickness. Strain hardening elfects can be included. The nonlinear solution strategies are based on the Newton-Raphson Method. The load is applied in increments where for each step, equilibrium iterations are carried out to establish equilibrium, subject to a given error criterion. To cross the limit point and to select load increments, iterative solution strategies such as the arc length and autoniatic load increments method are adopted. To analyse tubular joints, a simple inesh generator has been developed. Struc- Cural symmetry is exploited to reduce the number of elements. The hibular joijil. is divided into a few regions and by means of a blending function. each region is discret, ised into a joints have been analysed using this finite element method. The numerical results have been compared with experimental tests undertak- en by the Wimpey Offshore Laboratory using large scale specimens. Finally, the applicabiliy of the nonlinear finite element developed here is briefly discussed all potential areas of research in the ultimate behaviour of tubular joints are proposed.

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British land use planning's ability to accommodate rapid or unexpected large scale change is investigated in terms of the land requirements and political implications of maritime industrial development, and the redevelopment opportunities and problems of obsolete docklands. It is established that land use generally responds to changes in maritime commerce and marine technology. Stereotype models of port decline and growth are critically applied to selected Severnside ports. The thesis subsequently concentrates on behavioural and political aspects of two contrasting implications of maritime change: the development needs of bulk processing coastal industry and the redevelopment potential of inner city docklands. Recent proposals to build an oil refinery at Cliffe, in North Kent, indicate that maritime industrial sites have become a scarce planning resource. Comprehensive reappraisal of the 1972 Deep Water Sites Study suggests demand for such sites will continue, though at an uncertain level. A coast-wise survey of relevant planning policies has several possible interpretations, but generally indicates modest provision because of political and environmental constraints. This awkward balance between supply and demand emphasises planning processes and the nature of legitimisation, with scope for strategic planning initiatives to overcome procedural limitations. Five dockland redevelopment case studies show that, despite ambitious plans, implementation has been difficult and little achieved. An incremental approach is proposed to encourage local investment and immediate beneficial use of idle land. The final chapter combines several theoretical concepts. EIA provides a focus for discussion of planning processes involving maritime industrial development. Dockland redevelopment raises more practical questions, though also concerning the effectiveness of planning machinery. In conclusion, successful political and administrative adaptation to new circumstances favours an uncritically optimistic assessment of existing procedures, while functionally unjustified inertia justifies concern, and procedural as well as policy changes.

Green water problem and its loading effects on high speed containerships was investigated with the purpose of developing a modelling framework that can practically guide naval architects to a better understanding of this problem and improvements in design. The research began by reviewing extensive publications relevant to the understanding of green water, limitations in the ways the problem had been addressed and establishing a methodology that could effectively unlock the physics and efficiently solve the problem. As a first step, a summarised background to how green water started, developed and finally took place was presented. An experimental programme was then implemented in order to observe the occurrence and to explore the physics behind these events. From the outcome of the experiments, it was obvious that green water modelling could be developed and solved by Computational Fluid Dynamics (CFD) technique through Volume of Fluid (VoF) method. To provide a starting point for this research, theoretical background of CFD was briefly introduced. Furthermore, in order to validate this approach, two benchmark tests were implemented and compared with published experimental data. It showed that in both cases, the simulation could accurately reproduce the results obtained from experiments. Following this analysis, research continued to expand the CFD simulation to modelling of green water. Due to the complex and random nature of green water, development of the simulation framework was semi-empirical and based partly on experimental data. A pure theoretical approach could have been adopted. However, taking into consideration current limitations in ship motion prediction theories and sensitivity of green water to elemental factors, it was justified that semi-empirical approach was appropriate. The simulation was conducted and the output results were compared with experimental results for a variety of test conditions that involved ship velocity, wave height and period. Good agreement between simulation and experiment was obtained. For all loading cases, experimental results were reproduced fairly well. This suggested that the modelling framework was adequate for all practical purposes. Investigation was also conducted on a series of rectangular breakwaters that were fitted on the forecastle deck. Changes in water behaviour and loading following changes in the breakwater were well reflected. This implied that instead of a rectangular breakwater, the simulation model could also be applied to other types of breakwaters. The results suggested that the simulation methodology has many practical applications. Within naval architecture, it can be used to perform parametric studies in order to select an optimal design of breakwater for a ship. In other sectors such as coastal engineering, the methodology can be adopted to investigate the interaction between water surge and a seawall or offshore breakwater. In conclusion, it was found that the developed modelling framework shows potential for simple modelling of green water in which the behaviour of the water and its loading effects could be well reflected. It was further concluded that, provided appropriate principles are applied, the methodology has potential for other engineering applications. While it is acknowledged that current model may be limited by its semi-empirical basis and issues associated with computational requirements, it is noted that considerable possibilities for future research and development remains to be explored.

The main thrust of this research is the development of a capital investment decision support with reference to the shipping industry. This decision support system as developed is illustrated on the route to a developing part of the world (Liverpool/West Africa trade route) using a ship type particularly suited to the operating requirements of such a route; the multipurpose of Combi (for combination) carriers (chapter two). This ship design type was adopted to operationalise the general capital investment appraisal procedures as developed in this research and embodied in a comprehensive decision support model. The particular capital investment decision criteria as conceived in this study is the maximisation of the net present value of the investment but the objective function is also subject to risk analysis as measured by the coefficient of variability for outcomes. Plausible decision variables were incorporated for the accomplishment of the research objective by a process of parameterisation and the decision criteria adopted necessitated the estimation of a comprehensive system of cost and revenue functions. Ship capital and operating cost function were separately estimated (Chapter Six). It was necessary as a first step in the estimation of ship operating cost functions to aggregate component operating costs into broad categories, namely; Fuel and Lubricants, Wages and Personnel Insurance payments and contributions, Stores and Provision, Repairs and Administration and ship insurance including 'club calls'. Operating 2 cost functions were then estimated for each of the above operating cost aggregates. Ship time in port has operating cost implications particularly with regard to 'hotel load' fuel consumptions and service levels. A ship turnround time forecasting function was duly estimated to cover this category of operating expenses. (chapter five). The ship turn round function as estimated enabled the investigation of a hypothesis topical amongst researchers in shipping that the size of a ship affects its turnround time in port on the study route. The marginal effect on component operating cost functions of variations in managerially controllable variables was also investigated. The revenue model constructed is based on forecasting shipping freight tonnage demand for the provided operating capacity. As a result a freight demand forecasting model was estimated. This estimation was based on least squares and a market/market share demand function estimation procedure was used. The assumptions made for the freight demand model estimation was that national freight demand trend could be approximated by a time series model of the Box-Jenkins type while the route annual demand would be casually dependent on the national trend and relative effort level on the study route. An assumed proxy measure for annual effort level on the route was the corresponding total tonnage offered. Demand share models were also estimated along the lines of the main freight rate commodity categories i.e. foodstuffs, basic materials and manufactured goods (chapter seven). The different facets of the research as developed were subsequently integrated into a computer package which matched not 3 only the particular characteristics of the chosen problem but also general shipping problems (chapter eight). The variable selection procedure adopted for model development was a stratified Monte Carlo sampling technique. It was also desired that as part of the ex-post rationalisation of decision should be the projection of 'optimal' economic life of the investment. To this end a purpose ship residual value forecasting model was estimated and applied adopting a gross present value economic life determination criterion. The model selected a net present value maximising ship size from the parametrised decision variables of 8,000 dead weight tonnage (d.w.t.) and also included ship sizes 9,000 and 14,000 d.w.t. amongst the efficient set. These ship sizes were considered efficient to the extent that they offered plausible trade-offs between expected return and variability relative to the optimum. The model predicted an optimum ship economic life of ten years. Also the predictions of the model were found not to be sensitive to marginal variations in most of the assumptions made in model development.

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