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Oil and gas exploration and production activities in deep and ultra deep waters in hostile environments necessitates the need to develop innovative riser systems capable of ensuring transfer of fluids from the seabed to a floating vessel and vice versa, with little or no issues with respect to influences of environmental loads and vessel motions.The design of the riser system must focus on different types of loading and load effects than for traditional water-depth. A variety of different riser concepts are proposed, both with respect to geometric shape and selection of materials.In the last few years, steel catenary risers have been a preferred riser solution for deep-water field developments due to its simple engineering concept, cost effective, flexibility in using different host platform and flexibility in geographical and environmental conditions. In this report, a case study considering a steel catenary riser operating in 1000 m water depth was conducted. The riser was subjected to extreme environmental conditions and static and dynamic response analyses were performed by the computer program RIFLEX.Last, parametric study is carried out to investigate the effects of parameter variation based on some parameters like current profiles, mesh density, wall thickness and so on. These parameters have significant effect on the structural response, especially in the touch down region.

Subject of the present study was the investigation of the wake behind stepped circular cylinders. Experiments were performed using particle image velocimetry (PIV). Cylinder models with diameter ratios D/d=1, D/d=6/5 and D/d=2 were investigated at Reynolds numbers Re_{D}=2243.6, Re_{D}=12820.5 and Re_{D}=51282.1 with respect to the large diameter. Of main interest were the influences of step size and Reynolds number on the formation of vortex shedding cells. Mean flow characteristics and instantaneous captures of the flow field were analyzed in order to gain insight into vortex development in the wake. Spectral analysis was applied to obtain information on the number of forming vortex shedding cells.It was found that an increase in Re_D leads to a decrease in eddy formation length $L_f$. At the largest investigated Reynolds number, turbulence gained strong influence on the flow characteristics. An increase in stepsize leads to the development of a large and a small diameter wake with distinct eddy formation lengths L_{f,L} and L_{f,S}.Due to a mismatch in vortex shedding frequencies in the two wakes, vortices that come out of phase connect to subsequent vortices on the same side of the step. This occurs more frequently for a higher diameter ratio.Several vortex shedding cells were found in the wake of the step cylinders, their number increasing with the step size and differing for different Reynolds numbers.The wake behind step cylinders was discovered to be strongly three-dimensional. I order to complete the information about flow characteristics, measurements were performed in several parallel vertical and horizontal planes along the cylinder.PIV proved to be a good method for the investigation of flow features in the wake of step cylinders for the chosen model dimensions and Reynolds numbers.

Due to the substantial increase in oil and gas activities in Polar areas the demand for ice strengthen vessel has increased greatly. This increase in demand has highlighted the importance of designing ice strengthened ship structures that are more producible and maintain adequate safety and integrity. In order to encounter these new challenges, the international association of classification societies (IACS) has developed unified regulations for the designing of ice strengthened ship. In addition to these requirements, most of the classification societies have their regulation for design of polar ships. Stiffened plates are the basic structural building blocks of ships. So, the study mainly explores the plastic response of stiffened plate subject to lateral ice loads. The Non Linear Finite Element Method (NLFEM) is extensively used to study the plastic behavior of stiffened plates. The Abaqus non linear finite element program is used in this study.The aims of the study are to investigate the validity of the limit state equation employed in the IACS new Unified Requirements for Polar Ships [6], investigate the membrane effect at large deformation, determine the ALS design load, and assess limit loads when fracture in plating likely to take place. The study also focuses on the warping effect of unsymmetrical sections and the effect of end brackets on the lateral load carrying capacity of the stiffener. The effect of mid-span tripping bracket on the load deflection behavior of L and T stiffeners is also studied. In particular, the study focuses on the behavior of inclined T and L stiffener. As ships move forward by crushing ice, sides of ships’ bow come across with ice initially. To design ice strengthen vessel, it’s very important to understand the behavior of ships’ side structure subjected to ice loads. So, this study extensively focuses on the non-linear finite element analysis of ships’ side structure subjected to ice loads. Normally, ship design rules are based on the behavior of single frame subjected to loads. It’s reasonable to consider frames singly under the uniform loading but in case of ice loading which is non uniform, the behavior of the structure obtained from single frame based design does not accurately represent the true behavior of the structure. The load-deflection characteristic of frames in isolation, frames as part of a ½+1+½ frames and frames as part of a grillage subjected to unsymmetrical loading is studied. As, stiffeners in the side structure of ships’ bow are not normally perpendicular with shell plate, the lateral capacity of frames as part of a ½+1+½ frames and as part of a grillage is obtained for inclined stiffener.The analyses in this study cover the full range of stiffener behavior from elastic, through yield, through the formation of initial mechanisms, through large deformations. The parameters considered for the analyses are: •frame profile: Angle, Tee•frame span•load length: patch (transverse), uniform (longitudinal)•web thickness•end brackets: with, without•Angle of inclination of stiffener web with the plate flange•Tripping bracket at mid span

Fatigue is an important character for the flexible pipes as they are always exposed to dynamic loading. For nonbonded flexible pipes, fatigue and stress analysis can be performed based on different assumptions of slip behaviour. Different slip assumptions used in estimating the slip stress always play a determinative role in the prediction of fatigue damage. Thus, this thesis will focus on the study of the slip behaviour between tensile armour layers of nonbonded flexible pipes. The results can be used to support the basic assumptions for further fatigue analysis. The main object of this thesis is to summarize the existing analytical methods for stress and slip analysis of nonbonded flexible pipe armouring layers and to verify that the improved finite element models can give adequate description of the flexible pipe slip behaviour.In previous version of BFLEX, the transverse slip effect for nonbonded flexible pipes has been neglected. In this thesis, transverse slip regime has been activated in the updated BFLEX by developing a new type of beam element hshear353 and a new type of contact element hcont453. Finite element models use these two elements have been made and several case studies have been carried out.For axisymmetric loading, two analytical solutions, one obtained from the equations by Witz&Tan[13], one from Sævik[2] have been compared with the result from numerical simulation. It has been found that Sævik’s solution matches better with the BFLEX solution comparing to Witz&Tan’s solution. For flexible pipes exposed to bending, influences on slip behaviour from several pipe parameters, namely friction coefficient, axial strain and global pipe curvature, have been investigated. The numerical results are also compared with analytical solutions obtained from Sævik[2]. It has been found that the numerical solutions can give excellent agreement with analytical solutions. It is further concluded that the outer tensile armour layer do not influence much on the inner layer slip behaviour.In addition, the cyclic bending effects on nonbonded flexible pipes have been investigated. It has been found that the tendon behaves differently from case to case. The inner and outer layers behave differently. Only a few cases have been studied for this problem due to time limitation. The overall conclusion is that the developed BFLEX model is capable of describing the stresses and local displacements of flexible pipe for simple cases. The developed numerical model can further be used in the study of fatigue in flexible risers. However, more studies on influence from multi-tensile layers and cyclic bending are needed in the future.

Increasing activities on high north regions bring about a demand of safety ship navigation. Under severe weather condition considerable amounts of ice may accumulate on marine structures. Ice bridge simulator is of importance in terms of training for qualified maritime personal. The new ice module to fit for additional problem for the ship icing is introduced with low reality into bridge simulator. Regarding this our aim is to develop ice model that calculate ice load on the ship structure and stability change include parameters of air temperature, relative wind speed, wave height etc. As a result of literature survey theoretical and empirical method with its algorithm is studied. The ice thickness on cylinder and plate as a representative element of the structures are calculated as a function of liquid water content, relative wind speed and freezing fraction for simplified ship superstructures to include the effect of trapped water on deck. Since we have to deal with several thousand of element to be calculated every seconds including iteration process, computer should be used, hence new ice model is proposed by using computer language C++. In case study 300 tonnage size coast guard vessel is selected as a model ship. Under assumptions that those external parameters are stable in the duration of simulation, proposed model is validated. As a result proposed model could simulate total ice load and following stability change, with error of rolling period after 20 hours simulation being 0.14 sec compared to full scale measurement.

Internal combustion engines have been very successful as power producers in the marineapplicaiton due to their simplicity of construction, high efficiency and long track of proven technology. However, as the environmental foot print of industry is gaining more and more attention, the emission from the engine must be reduced. The main emission fromthe diesel engines are namely nitrogen oxide(NOx) and particulate matter(PM). Sulfuroxide(SOx) and carbon dioxide emission(CO2). In the marine industry, the transientemission has not been brought to the table of discussion when it comes down to theregulations. However, the assessment and improvement in the transient emission willgain more attention.In order to predict the emission from the diesel engine in the generic manner, the dynamic engine model should be developed. This model must be able to capture the in-cylinder process during the combustion in cylcle-to-cycle resolution. Transient load would put more challenges to the prediction as the in-cylinder states are far from the steady-state conditions. In the thesis, the dynamic simulation model of the diesel engine is developed in order to predict the emission. Firstly, the emission from the diesel engine, with special focus on NOx formation, is reviewed in general. Then overall process of the development of the mathmatical model of the diesel engine is described. Bond graph model was used as the framework of modeling approach. Finally the simulation result is compared with the test result from the laboratory and recommendations for further development are presented.The main contributions of the thesis are:• A overall process of building the engine model of was reviewed and implemented. It covers most of the building blocks from the thermodynamic calculation to the calculation of states of the components of the diesel engine.• The model developed in the project has significant improvement in terms of computational efficiency. Implementing Grill’s method for the calculation of the equilibrium composition of the combustion gas was the key to this success.• The bond graph model based on the multi-component gases in the combustion gases was constructed and it founded a ground for adaptation of the emission reduction strategy such as exhaust gas recirculation.• The overall model was built with component libraries which can be reused in the future project. Full description of the components libraries is given so that potential users may have the easy access.• A mathmatical model for NOx is coupled with the dynamic engine model together with the two-zone model approach. The calculation of the two-zone model in the absence of the pressure profile was achieved with an effective method so that calculation time has not increased significantly from the single zone model.

Platform-ship collisions are fortunately rare events, but as the development of the offshore and oil industry and the gradually frequently used offloading operation, accidents become more and more frequent. The consequences of collisions are always severe, which includes loss of life, property and environmental damage. Thus It is important to predict the outcome of collision scenarios and assess the damage that may happen to the platform as well as the shuttle tanker.Collisions are always analyzed by means of the principle of the principle of energy conservation. Initial kinetic energy is dissipated by the two contact bodies as strain energy and in viscous force generation. There is also energy remained as the kinetic energy after the impact for both the striking and struck bodies, both for translational and rotational degrees of freedom. The external mechanics of the collision is easily evaluated, but the strain energy absorption can be rather difficult to evaluate in a correct way.In this thesis, A Samsung shuttle tanker and the Sevan SSP300 platform are analyzed as the striking and struck bodies, respectively. Structural configurations are described for both structures. Different impact scenarios are then discussed in the report, some of which are chosen to analyze in the thesis work. Non Linear Finite Element Analysis (NLFEA) model of the SSP300 platform is created. The shuttle tanker model is an exist one. One-sixth of the platform is modeled in detail with the correct stiffeners and other details, while for the other part, only the outer shell and the main bulkheads are modeled. For the tanker, adjustments are made in order to increase the calculation efficiency. Only the bow is remained in details. For the hull, only the outer shell is remained. For both structural models, adjustments are made to obtain the correct mass, added mass and inertial. Both models have a user defined material with the fracture criterion included. Integrated analysis is mainly performed. Then the integrated analysis is split into internal mechanics and external mechanics. Among these, integrated analysis and internal mechanics analysis are performed with finite element method, using the explicit NLFEA solver LS-DYNA. For the collision scenarios, only bow impact with different headings is considered. Two different impact velocities are chosen in both head on collision and collision with the glancing angle of 30 degrees. Energy absorption and force-displacement relationship can be obtained. Damage on the platform is also evaluated. Internal mechanics are then analyzed by changing the boundary condition and making the impact velocity constant. The purpose is to evaluate the damage with internal mechanics and then compare it with the results from integrated analysis. Liu’s method, which is based on Stronge theory, is mainly used in external mechanics as a simplified method. Herein a Matlab program is established to calculate the energy dissipation and the velocity after the impact. Two other simplified methods are utilized to calculate the dissipated energy and then compare them with the results from NLFEA analysis. One is from the DNV-RP-C204 and the other one is from T.de Jonge&L.laukeland’s report. The latter one is an optimized method compared to the one from DNV rules, which includes the effect of roll motion. Results from the simplified methods and NLFEA method show good correlation. All the simplified methods overestimate the absorbed energy, which is conservative. Among these, Liu’s method gives the best correlation with the NLFEA method. Two additional jobs are conducted in the end. Only the energy dissipation is analyzed in this section. One is changing the loading conditions of the two bodies. The energy dissipation becomes smaller after changing. The other one is changing the friction coefficient. The energy dissipated by the tanker is smaller, while by the platform is larger. But from the overall view, the energy does not show big difference with friction coefficient 0.15 and 0.4.

The purpose of this study was to describe the investigation of the Mica shipwreck. The objectives of the investigation, as identified by nautical archaeologists from the United States Minerals Management Service and the Nautical Archaeology Program at Texas A&M University, include determining the extent and limits of the wreck site, acquisition of diagnostic artifacts to identify the temporal period of the shipwreck and its mission at the time of loss, to identify the type of ship and its country of origin, and quantify the relationship between the vessel's construction and function. The manuscript contains a thorough analysis of the equipment and approach used by archaeologists during the excavation. The manuscript also briefly explores the use of metallic ship sheathing during the eighteenth and nineteenth centuries, focusing specifically on the pure copper sheathing found on the Mica wreck. Sheathing from numerous contemporary vessels will be analyzed and compared to the Mica shipwreck sheathing.

Offshore shipbuilding industry is known for its highly customized products, which are in most cases tailor-made for specific missions. Being a traditionally conservative industry, it follows conventional design practices. Because of the urge to quickly respond to changing market situations and the need for a structured method to reuse design knowledge across different projects, modern design methodologies like modularization are of considerable interest in this industry. To implement modular thinking, it has to overcome many challenges such as non-functional engineering description of design, scaling, clustering, logistical issues, structural complexities etc. Different modular methodologies can be adopted to establish a modular product platform. Modular Function Deployment (MFDTM) is a popular theory of modularization with five distinct steps to identify the objects that should be modularized and optimize them for the whole manufacturing system. Application of MFDTM method reveals that among various spaces inside the accommodation of an OSV, crew single, crew double and officer’s cabins are the most appropriate ones to be modularized.Based on the output of MFDTM method and the vessel database from System Based Ship Design (SBSD) approach for OSVs, a decision support framework has been developed to assist the naval architect of the vessel to design the accommodation block. Standardized templates are used for arrangement of the modules. The spaces in the accommodation are categorized into three module classes. The DSF can calculate the optimum size, type and location of the modules according to design requirements and system constraints. The vessel database is used here to determine the required area for the spaces that are not standardized. The DSF is demonstrated by an illustrative example and later by a simplified real case study. A mock up of a user interface has also been developed to give an idea of user interaction with a computer tool based on the DSF. For the real case study, a small program has been developed containing some 1200+ lines of code, which can process simplified accommodation design cases.To build an effective DSS for designing the accommodation block of OSVs, standardization of spaces by modularization must be done with enough room for flexibility of design by designer intervention. This DSF exhibits the underlying logics and structure of such DSS, which can be very useful to the designers upon further development.