When we use ocean space for human activities, we should consider sustainability and allowable human impacts.After the 1960's, we have lost 90 percent or more of the tideland of Tokyo-bay by the reclamation. "Uminokouen" is one of the artificial seashore parks developed in 1988 at the southeast of Yokohama and is well known as a relaxation place for the citizens. Over 20,000 people visit there for seashell-digging (SHIO-HIGARI) in a holiday in the spring.It is easy to understand that the human impact is quite large to an ecosystem of living bivalves in the park. Actually,the most part of living bivalves which are grew up after the last summer or autumn disappeared during the season. In this paper, we propose a computational model which predicts the human action of seashell-digging at this park using a multi-agent-algorithm. Comparing the simulation result with the actual data, the staying time of the visitors agrees well. Then, we investigate the relation among the initial spatial distributions of the bivalves, the spatial distributions of the amount of the caught short-neck clam and the trace of the visitors. Then we predict the human impact in the best weekend for the seashell-digging and examine the sustainability of the relaxation park.

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To mitigate the global warming and ocean surface acidification caused by increase of atmospheric CO₂ concentration, ocean sequestration of CO₂ has been proposed. Because the technology has risks on deep-ocean ecosystems, its implementation needs public acceptance. In such a process, environment assessment indices are useful for making decisions. Recently, the Triple I was developed to show totally inclusive index for environmental and economical matters, consisting of ecological footprint, ecological risk, human risk, cost, and financial benefit. The present paper presents the Triple I for CO₂ ocean sequestration, where the object of comparison was set to be the effects of ocean surface acidification and its consequent impacts in the deep ocean. Particularly focused on in this study was the calculation of ecological risk. In general, risk is represented by the products of probability and hazard. Here, the former was obtained by a semi-quantitative probability method based on the results of expert enquiry; the latter was converted to land area by using the species-area relationship. The resultant Triple I became negative and indicated that the technology is worth to implement. Also elucidated is that the ecological footprint and the ecological risk had the largest and the smallest portions, respectively, in the index.

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Deep ocean water (DOW) is cold,nutrient-rich and pathogen-free seawater found at depths of several hundred meters or more.Artificial upwelling of DOW may significantly enhance marine primary production. The fisheries agency of Japanese government has undertaken an in-situ experiment of a prototype ocean nutrient enhancer,named TAKUMI,which is driven by a conventional diesel engine,in Sagami Bay.They have also designed a large-scale practical machine,which is driven by an ocean thermal energy conversion (OTEC) engine.In this paper,inclusive impact assessments of TAKUMI and the practical machine,which evaluate environmental and economical sustainability by an integrated evaluation indicator using ecological footprint and gross domestic product,were performed.The assessment results show that renewable energy sources should be employed to operate the system in order to realize sustainable artificial upwelling.The ecological footprint per unit biomass of fish production by the practical machine is much lower than that of land-based commercial meet productions,such as beef,pork and chicken.

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Coastal development is supporting improvement of economic activity and convenience for city residents. On the other hand, the development has brought loss of 90% or more of natural beach line and disappearance of the tideland,which has purification function in Tokyo-bay. In the recent years, sustainability is one of the important keywords for the development. In general, the development such as constructing an offshore airport carries both economical advantage and environmental disadvantage. It is generally very difficult to consider their balances and to judge which is important. Inclusive Impact Index (Triple I) is proposed by Marine Environmental Committee in JASNAOE. The index includes environment factor, which is obtained by the method of Ecological Footprint, and economical factor,which is converted to global hectare. We can objectively discuss the social importance of the development by using this index. In this research, we obtained the Triple I (III) of construction of an offshore airport and discussed its social importance from both environment viewpoint and economical viewpoint.

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Many environmental restoration technologies for enclosed coastal seas have been developed. The environmental restoration functions of these technologies are conventionally assessed by field monitoring or ecosystem modeling. On the contrary, the social functions of these technologies are usually evaluated by some economic analysis methods, such as Contingent Valuation Method (CVM) and Travel Cost Method (TCM). However, there have been very few assessment methods for both environmental and social functions from the viewpoint of sustainability. In this paper, the authors perform an inclusive environmental assessment, which is based on Inclusive Impact Index (Triple I) proposed by The Research Committee on Inclusive Marine Pressure Assessment and Classification Technology (IMPACT Research Committee) in The Japan Society of Naval Architects and Ocean Engineers, for an artificial lagoon in Kobe Airport island in Osaka Bay.The assessment method consists of the ecological footprint accounting for the environmental sustainability and the TCM for the social sustainability. The environmental assessment results show that the artificial lagoon is environmentally sustainable, when the life cycle is assumed to be more than 9 years. However, the ecological footprint of the fundamental reclamation is much larger than that of the lagoon construction and the biocapacity of the lagoon ecosystem. The social assessment results demonstrate that more than 35,000 visitors are required for the socially sustainable system, when the life cycle is assumed to be 50 years.

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The environmental impacts of the aquaculture system were inclusively assessed by using the Triple I (III: Inclusive Impact Index),which was developed by IMPACT Committee of the Japan Society of Naval Architects and Ocean Engineers. Triple I is calculated based on ecological footprint, biocapacity, ecological risk, human risk, cost, and benefit, and these values except ecological and human risks were estimated for 2ha of cultivation ponds of the shrimp,Penaeus japonicus, which annually produce 20 tones of shrimps. As a result, the change in Triple I due to the shrimp cultivation act was estimated as 159.84 [gha], which means that the shrimp cultivation act actually requires a large ecological footprint within the scope of the present discussion. The ecological footprint was quite larger than the production of biocapacity and the profit of the shrimp cultivation act. The large ecological footprint was attributed to feed production, which requires marine ecosystems sustaining the fish production, and to fuels to catch the fish. As future studies, the accuracy of the estimation of Triple I should be improved by including the effects of the distribution processes, the processing of feed and shrimps, ecological risk, and human risk.

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A new numerical method to generate anisotropic turbulence field in the large eddy simulation was proposed. Based on the assumption that the mean shear is the only external force to maintain the structural equilibrium of the small-scale turbulence,appropriate forcing component is estimated from the energy balance under the conditions of arbitrary energy dissipation rate and stratification. Removing nonlinear operation from the forcing process enables the stability and accuracy of the calculation. The energy dissipation rate, which can also be estimated by the turbulence model, had the error of at most 7 %, compared with the set value. Several calculations under the conditions of fixed stratification and different dissipation, the both of which are representative in the mixed layer of the open ocean were conducted. It was found that the Richardson number at the structural equilibrium increases with the decrease of energy dissipation rate, corresponding to the increase of the stability of stratified turbulence. The present method is applicable to the investigation of various phenomena in the small-scale stratified turbulence, such as turbulence diffusion of heat and mass in the ocean.

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Sea surface waves had been observed remotely by using a continuous wave (CW) X-band microwave Doppler radar at off Hiratsuka of Sagami-bay. A new algorithm was applied to retrieve a sea surface elevation from the radar output Doppler signals. The sea surface waves observed by the microwave Doppler radar have been compared with the sea surface waves measured by the supersonic wave height meter. There were good correlations in both wave height and wave period between the waves observed by the microwave Doppler radar and measured by the supersonic wave height meter. The correlation of wave height was better than that of wave period. The microwave irradiation width on sea surface does a role of space filter. It seems that the filtering effect is a kind of low pass filter involving aliasing, the energy of short wavelength waves move to low wave number region. The algorithm to retrieve a sea surface elevation is described by the relation of the water surface profile and the orbital velocity of water particle on water surface that generated by water surface waves. A linear superposition method has been used to retrieve sea surface elevation. No empirical parameters are used in the algorithm. The water surface profile can be obtained from the water particle velocity on water surface by using the mathematical relation of the water surface profile and the orbital motion of water particle. Water particle motion on sea surface is affected by sea surface wind, currents, and sea surface waves. Water particle motion generated by sea surface waves can be separated by the difference of the fluctuation scale of each physical process

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The present paper, at first, presents the author's understanding of the problem caused by the use of ITTC (International Towing Tank Conference) 1957 Line in conjunction with three-dimensional analysis. Then, how the ideal friction line should be within the range of model Reynolds number is discussed.As a conclusion of this paper, the answer to the question "Should ITTC 1957 Line be revised?" is as follows. It is "Yes" in a sense that ITTC 1957 Line prepared for two-dimensional analysis should be revised, if we employ three-dimensional analysis. It is "No"in another sense that the expected gain by the revision of the friction line would be almost negligible and, on the other hand, we have to expect the setback caused by changing from the well-accustomed line to new one.

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ln this paper,a visualization technique of wave making phenomena around small-scale ship models in circulating water channel is suggested.Wave patterns around the small model can be visualized by using a flat plate with longitudinal white and black stripes fixed on the bottom of the observing section in the circulating water channel lightened by a few electric lamps over the free surface.In front of a small model,however,ripples(capillary waves)are caused by the surface tension effect,which disturb the observation of clear Kelvin wave patterns around the model.In order to eliminate ripples,an effective experimental way to weaken the surface tension effect is adopted.Kelvin wave patterns in various conditions can be observed clearly by using the present experimental technique.

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On the numerical simulation using the BEM, the computational disadvantage by dealing with the particular fluid domain due to the jet flow is discussed and the adaptive schemes for robust time-donain computation are proposed.The developed computational models for the jet flow and splash are applicable to the water impact problem of a bow section with an arbitrary shape. Two numerical studies are demonstrated for the validity of the present method through some comparisons with experimental and other computational results.

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To estimate the performance and risk of an icebreaker, we are developing a numerical simulator for icebreaker performance under conditions that many ice pieces colliding and scraping against the icebreaker hull. Open Dynamics Engine (ODE) is incorporated into our simulator to allow the use of physically based modeling to illustrate these mutual interactions. We carry out pre-sawn ice test in the ice model basin of National Maritime Research Institute, and compare its result with simulation results to verify the numerical method. In the simulation,virtual fluid force acts on each ice piece to reproduce ship advance. Buoyancy with static pressure is also considered. Coefficient of restitution is set to zero and friction coefficient between ice pieces is set to 1:35. Ice motion in the simulation generally agrees with the experimental results. Appropriate relaxation parameter for virtual fluid force is investigated.

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A wave-piercing catamaran was developed in Australia, and has been increasing in size for these twenty years. The first largest wave .piercing car ferry, "Natchan Rera" was built in Australia and introduced in the Hokkaido-Aomori route in September 2007.The seakeeping performance of this ship has been investigated by model experiments and revealed the superiority compared with conventional mono-hull ship. However, the seakeeping performance in real sea where irregular and combined waves are outstanding has not been revealed yet. In the present study, measurements of motions using real ship during winter season were carried out.From measured motion data, seakeeping performance of this ship in real seas is revealed. From comparison of measured motions between real ship with a ride control system and its scale model without it, the effectiveness of the ride control system is also discussed.

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Broaching-to is a phenomenon in which a ship cannot keep her desired course despite the maximum steering effort. Once this dangerous phenomenon happens, she could capsize due to violent yaw motion. Generally a PID autopilot, however, has been used in model experiments and numerical simulations for investigating broaching-to although PID auto-pilot does not properly represent the "maximum steering effort". This paper attempts to apply an optimal rudder control for a ship in following and quartering seas with high speed. We performed the numerical optimization of rudder control for higher speed region which includes surf-riding threshold,i.e. heteroclinic bifurcation point. To the trajectory optimization nonlinear programming method was applied in conjunction of the method based on calculus of variation, e.g. Sequential Conjugate Gradient-Restoration Algorithm (SCGRA). Numerical results indicate an example that a ship cannot prevent significant course deviation even with course keeping rudder control based on the optimal control theory. Calculation results also showed that the optimal rudder control during surf-riding takes opposite maximum value. As a result, it was concluded that if the yaw motion became unstable around stable equilibrium point, she could consequently face broaching-to in spite of rudder control process before a ship is surf-ridden.

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This paper reports model experiments of a wave-piercing tumblehome hull in following and quartering waves for examining the applicability of a system-based simulation model proposed by the authors to stability of an unconventional ship. In captive model experiments, the wave-induced surge force and roll restoring moment were measured and confirmed that conventional hydrodynamic prediction methods are applicable. In free-running model experiments, broaching and stable surf-riding were frequently realised. Here the maximum roll angle due to the severe yaw motion is about 70 degrees. The existing simulation model is compared with these experiments. The comparison shows that the current simulation well estimates boundary between the oscillatory motion and non-oscillatory ones such as surf-riding and broaching but it underestimates the yaw motion and overestimates the roll motion.

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Recently, serious accidents due to parametric rolling of container carriers and pure car carriers have been reported. For the prevention of parametric rolling, an Anti-Rolling Tank (ART) is regarded as one of the most effective devices. To estimate the performance of ART, however, an estimation of damping coefficient of ART is required for numerical simulation of parametric rolling. In the previous report, the MPS method (Moving-Particle-Semi-implicit method) were applied to the estimation of damping coefficient of ART, and it was confirmed that the MPS method can estimate not only damping coefficient but also natural period of ART in reasonable computation time. Furthermore, numerical simulation method with damping coefficient of ART obtained by the MPS method can well reproduce experimentally observed parametric rolling of a post-Panamax containership. In this report, the developed estimation method of ART performance is applied to a more practical and complicated ART having an appendage aimed for increasing eddy-making component of damping of ART.Free decay tests and free running model experiments are conducted for several sets of the height and position of the appendage to confirm its effect on parametric rolling prevention. Finally, the improvement of ART form is proposed to enhance the ART performance as a parametric rolling prevention device without increasing of tank water volume.

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Recent systematic model experiments demonstrate that broaching and bow-diving are major causes of ship capsizing in following and quartering seas. Once these dangerous phenomena happen, even a ship complying with the current Intact Stability Criteria of the IMO could capsize. To get over this situation, we proposed the wing-type appendage fitted into the bow above the water line as a new capsizing prevention device. When a ship heels significantly, one of two wings is submerged into water geometrically. Then a ship obtains an additional restoring moment induced by lift force acting on a submerged wing. In a previous paper, we conducted free running model experiment and confirmed that the proposed wings can prevent capsizing due to broaching and bow-diving in extremely severe astern seas while a ship without the wings capsizes in the same condition. In this research, several wings are tested by a captive model experiment to examine the effects of the wing parameters on lift and drag forces, and interaction between the wing and ship hull. Then a mathematical model is developed for broaching prediction of a ship with the wings for quantitative assessment or designing tool in place of free running model experiments. Finally the developed mathematical model is applied to other high-speed slender vessel, and the effectiveness of designed wings and the reliability of numerical simulation are investigated by comparing with newly conducted free running model experiment.

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The roll damping plays a very important part of amplitude of roll motion in resonance and trigger of parametric rolling of a ship. Since the viscous damping components are usually dominant in the roll damping, the theoretical calculation is difficult for predicting it. A method of predicting roll damping of a conventional cargo ship proposed by Ikeda, et al. is widely used and it has been also applied to high speed slender vessels, small hard-chine vessels, barge vessels etc.. In this paper, the characteristics of roll damping of two types of multi-hull vessel, high speed catamaran and trimaran, whose vessel is different from above mentioned is investigated experimentally. A forced roll motion test is carried out with and without forward speed, and their characteristics are investigated. Moreover, a simplified prediction method of roll damping of multi-hull vessel is proposed..

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A ship navigating at sea is always suffered from wind and waves. The assessment of the ship speed and thrust under external forces as the wind and waves is important from economical viewpoints. Although the estimation methods for ship performance at sea were already presented, the confirmation of the methods has not been enough using experiments due to the difficulty of the experimental setup with wind and waves. In this time, free running model test on a large container ship under heavy wind and waves was carried out at the 400m towing tank in National Maritime Research Institute, Japan. Averaged navigating conditions and time fluctuations of the ship speed, drift, rudder angle, ship motions and thrust etc. were clearly understood from the experiments. Moreover, the assessment of the ship performance is conducted using a computational calculation method. The steady-state equations are formulated based on the MMG model for ship manoeuvring simulation to obtain the steady ship conditions. As a result, some important thrust related characteristics and efficiency of the calculated method in steady running condition in heavy wind and waves for the ship are clearly revealed from the experiments.

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Estimating added resistance in waves linked to ship speed drop and an increase of horse power is getting more importance with fuel price hiking these days. Calculated results of the added resistance based on the slender body assumption show good agreements with experimental data for slender ships. However, for practical ships there are many cases that calculated results do not agree with experimental data. Especially it is well known that in the short wave range the bluntness factor has a great influence. Then, to make the effect of a ship hull form on the added resistance clear, some investigation on the amplitude function (Kochin function) is described. And calculated results by the method using proposed amplitude function are compared with experimental data for the practical large blunt ship. As a result we have found out that the Buttock Line is also important in the short wave range as well as the bluntness factor.

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In order to estimate decrease of ship speed in actual seas, it is important to calculate added resistance in waveswith accuracy. Especially added resistance in short waves is one of the predominant factors inducing the decrease of speed for a large ship in relation to wave spectrum. Various calculation methods have been proposed for the added resistance in short waves. However those methods are proposed for blunt and low-speed ships, for example, tanker,bulk carrier, etc. Those methods give poor agreement with experimental data for fine and high-speed ships. To improve the estimation method, firstly numerical investigation on the effect of draft and frequency was carried out.Thereafter experiments of wall-sided models with motion fixed were conducted. From these results a new formula is proposed, which gives good agreement with the experimental results.

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In order to estimate ship speed in actual seas it is important to calculate added resistance in waves with accuracy. Added resistance in waves usually appends the effect of wave reflection to added resistance due to ship motion. The effect is understood as the correction of the diffraction force in short waves. The conventional formula for the added resistance due to wave reflection was derived for large blunt ships. For fine ships such as a container ship, the estimation of the added resistance in short waves has poor agreement with the experimental result.We propose a practical correction method for added resistance in waves. From the point of accuracy the correction involves a tank test in the estimation of added resistance due to wave reflection. The test is conducted with different ship speed in short waves of a single kind of wave length. The correction method and the comparison with the experiments are presented here. Thereafter the influence on decrease of ship speed in actual seas is evaluated for a large container ship.

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Experimental studies on the hydroelastic response of mega-container ships have been conducted using a modified Wigley model with the elastic backbone having the rigidity equal to that of a 12,000 TEU container ship in regular waves in order to investigate the influence of whipping and springing on the hull structural strength of mega-container ships. In the tank tests, ship motions,hydrodynamic pressures and accelerations were measured. The springing of 1st harmonic resonance due to coincidence of the encountered wave period and the natural period of 2-noded hull vibration occurred in shorter wavelength. During the tank tests, the springing of superharmonic (n-th harmonic) resonance due to nonlinear higher hydrodynamic forces also occurred, although the model is simple mathematical hull forms without bulbous bow. In addition to the tank tests, a validity of 3D Rankine source method to analyze the springing was investigated and discussed by comparing the numerical results with the experimental ones. It was confirmed that the 3D Rankine source method can estimate the springing of the 1st harmonic resonance with good accuracy.

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We have developed a new numerical scheme that combines a Eulerian scheme with Lagrangian particles to compute fluid-structure interaction caused by impact pressure. The proposed numerical model was applied to several problems such as interaction between a solid structure with dam breaking, and hydroelastic due to impact pressure acting on a vertical wall. The Lagrangian particles are useful and available to capture an interface between different phases. The model can estimate impact pressure acting on a vertical wall, its deformation, vibration, stress and strain. We made clear three dimensional impact pressure field of solid structure in space and time and advantageous effect of artificial stress term.

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Disaster mitigation management is considered a very important aspect in marine catastrophes,such as a tsunami,especially because drifting ships containing passengers and hazardous substances can cause a huge disaster in a port.It has already been analyzed that at the arrival of a tsunami,it is very hazardous for a large passenger vessel to evacuate passengers first.In this study,the assessment of evacuation at Osaka Bay in Japan is based on Automatic Identification System (AIS) data used as input for a Discrete Event Simulation (DES),which assesses ship evacuation time and using the Geographic Information System (GIS) to determine the locus of ships.The location of ship evacuation is decided in the anchorage area since the time needed for a ship to evacuate outside Osaka Bay is more than the predicted time of a tsunami arrival.In this paper,a preliminary proposed safe area for evacuation is evaluated and the possibility of large passenger vessel evacuation is shown.

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The previous research provided reciprocal forms to calculate mean wave drift forces of a freely floating body.The reciprocal form in the near field consists of the gradient of velocity potential and its normal derivative on the body surface. In this paper the scheme to calculate the gradient of velocity potential and its normal derivative based on the constant panel method is shown. Then numerical examples and comparison of wave drift forces by Maruo's and Newman's far field method, Pinkster's near field method and present reciprocal form are shown.

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There exist nonlinear wave loads such as wave drift force, wave drift damping and wave drift added mass, when the floating body is slowly oscillating in waves. In the present study, wave drift added mass acting on an arbitrarily shaped body is evaluated based on the potential theory. A moving coordinate frame following the low frequency motion of the body is adopted to express this interaction model. Two small parameters which express wave slope(ε) and the frequency of slow oscillations(σ) are used for the perturbation expansion. The boundary value problem of each order is solved by the hybrid method. The fluid domain is divided into two regions. The potentials are expressed by the eigen function expansion in the outer region while the inner region is solved by the boundary element method (BEM) with the Rankine source as the Green's function. Element functions with higher order are utilized to improve the accuracy. Wave drift added mass is contributed from five components of potentials. The following potentials are solved in this work. First is the wave potential (Ο(ε)). Second is the disturbance potential for slowly oscillation of the body (Ο(σ)). The last one is the linear potential referring to the incident wave but affected by disturbance of the body (Ο(ε σ)). In the case of the Ο(ε σ) problem, it is important to treat the inhomogeneous free surface boundary condition. In the present paper, the Emmerhoff solution and a new approach about integral over the free surface are expanded for it. The wave drift added mass is calculated. Result is compared with the semi-analytical one. Good agreement is observed.

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In order to design a floating OWC-type wave energy converter such as Backward Bent Duct Buoy (BBDB) optimally, it is necessary to develop the numerical method in time domain considering motions of BBDB, air flow in air chamber and rotation of air turbine and mooring system in waves.In this paper, first, equations of motion of a floating OWC-type wave energy converter in waves considering memory effect by body velocity and air pressure in air chamber are shown. Second, calculation results in frequency domain by 3D boundary element method for a diffraction problem and radiation problems by forced motion with unit body velocity and unit air pressure in air chamber for BBDB are shown. Experiments on exciting forces and radiation forces for heave and pitch mode are also carried out and calculation results are compared with experimental results.

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A quasi 3 dimensional VIV response analysis method which combined 2 dimensional hydrodynamic force simulation by discrete vortex method with 3 dimensional finite element method has been proposed. Use of discrete vortex method and its limitation have been shown. Usefulness and characteristics of the quasi-3D VIV response analysis method have been investigated. The most important thing of 3D VIV response analysis with a strip theory is hydrodynamic correlation length of a riser axis direction. If correlation between strips of the hydrodynamic force shows a result completely different from real phenomena, it is difficulty that a strip theory applies to 3D VIV response analysis. Generally, the phase of hydrodynamic force acting on each strip obtained by the method is random, because hydrodynamic force is simulated at each strip independently. Actually, the hydrodynamic coefficient of lift force on a fixed circular cylinder is different from the average of the hydrodynamic coefficients of lift force on each strip.However, the phase of hydrodynamic force on each strip align at the resonant frequency that the natural frequency of a circular cylinder becomes equal to the frequency of vortex separation. In a VIV response matter, a simulation of hydrodynamic force on a circular cylinder by a strip theory is valid under the resonance condition of a natural frequency and vortex separation. The quasi-3D VIV response analysis method enables 3D VIV analysis with a less computation load. It is clear that the quasi-3D VIV response analysis method is useful at only a resonance condition, but it is enough in engineering, because the biggest VIV response takes place at a resonance condition.

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A time domain analysis method of Vortex Induced Vibration (VIV) was developed for risers and towing pipes with curvature. Risers are increasingly installed in deepwater and catenary shape is used utilizing increasing relative flexibility. For example, riser designs such as Steel Catebary Riser (SCR), Compliant Vertical Access Riser (CVAR), Lazy Wave Steel Catenary Riser, etc. are investigated and put to practical use. Other application areas of deepwater pipe structures are CO2 dilution into ocean concerning global warming. Long towed pipe is used in the moving ship concept. Long pipe structure is also used in deepwater mining. VIV is expected for the inclined pipes.Quantitative analysis of VIV behavior is becoming increasingly important to estimate the fatigue damage of the structures. A time domain VIV simulation method was developed. The analysis method is basically a nonlinear FEM (Finite Element Method) of underwater line structure. The VIV hydrodynamic force is calculated at each time step consulting database of VIV hydrodynamic force. VIV hydrodynamic force on a real scale pipe section subjected to harmonic oscillation was measure at high Reynolds number and arranged into a database. A numerical filter which evaluates amplitude, frequency and phase of local response of a riser from the time history of pipe vibration was developed. Using this filter, response parameters of local vibration is evaluated, and consulting the database and amplitude and phase of VIV force is estimated. The evaluated instantaneous VIV force is applied to the riser. From the procedure the time domain response of pipe is calculated. The validity of the method was verified by comparison with small scale and large scale experimental results carried out in the towing tank. The accuracy of the method is discussed.

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Large container ship has required designers to take account of constraints such as hull girder strength due to torsional, vertical and horizontal bending moment, fatigue strength of hatch corner and hatch opening deflection. On the other hand, rapid enlargement of container ships raises large hatch opening deflection, and accurate estimation of deflection is now more important. Interferences between fittings such as hatch covers, lashing bridges and other container securing instruments need to be addressed when new size of ship is explored.The deflection has three components of torsional deflection, cross deck fore-aft deflection due to container inertia force, and hatch longitudinal deflection due to hull girder bending moment. However, there was no clear method how to combine the deflection from these three components.Therefore, the authors conducted full scale measurement of stresses and deflections of ship B between 2002 and 2004 as well as Ship A between 1998 and 2001, which revealed more accurate correlation among three components.This paper shows result of full scale measurement of Ship B in service and examples of design application are introduced.

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Decision of principal particulars is the first stage of ship design. This stage is an important stage where essential information of the ship is decided and the influence on the cost and the performance is extremely large. However, various kinds of analyses which contain the error margin are used because detailed information on the ship is not available. Therefore, re-design and the deterioration of the performance occur although the margins on weight and so on are considered. The purpose of this study is to propose the design support system for considering the errors by using the robust optimization. The robust optimization is an optimization technique in which the influence of the error of the design variable is considered.However, the error margin of an analysis method is larger than the error margin of the design variable in the design of principal particulars. In order to solve this problem, new robust optimization technique to consider the error of an analysis is proposed. The characteristics of the proposed method are following points: 1) Input information and output information of analysis are defined as not a fixed value but an indeterminate value, that is,expected value and standard deviation. The error margin of preceding analytical technique is treated as an error margin of input information on the next analysis. 2) Expected value of the output is approximated to the output value without errors. 3) Standard deviation of output information is calculated by using the theory of spread of the error. 4) The accumulation of the error margin is calculated by repeating the above-mentioned process.Some examples using the proposed method are shown in the paper and these are compared with the solutions of present technique. As a result, the possibility of the improvement of the design is shown.

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A structure optimization for the initial design stage using FEM of ship is under consideration in this paper. General bulk carrier is selected for the object of the optimization. Shapes of a bottom structure of ship are taken as design variable. Individual mesh-subdivision technique and multi-point constraint method are introduced for making this optimization possible. However,creating FEM data sets for them requires a lot of human power. In order to remove this drawback, PrimeShip-HULL is used since it has a function recognizing structure members of ship. A FEM data set which can be applied individual mesh-subdivision technique and multi-point constraint method is made from structure members of PrimeShip-HULL automatically. Five design variables for shape optimization of ship structure are considered here and a numerical example is shown. Genetic algorithm is used for this optimization in this study.

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This paper studies the method for estimating the welding residual stress effect on brittle fracture of structural steel based on the Weibull stress criterion. Using wide plate (WP) specimens with and without welding residual stress, the brittle fracture tests have been conducted at -75°C. The material used is a high strength steel of 780MPa class. Welding residual stress significantly decreases the fracture force and the critical CTOD of the wide plate with welding residual stress at the onset of brittle fracture initiation. And it has been shown that the critical CTOD of the WP specimens can be predicted from fracture test results of the 3-point bend specimens without residual stress based on the Weibull stress criterion. The present paper proposes the assessment method of constraint loss effects on CTOD of wide plate with residual stress based on the equivalent CTOD ratio, βr under residual stress field. The equivalent CTOD ratio, βr is defined as the ratio, δ/δ^r_WP,whereδandδ^r_WPare CTODs of the standard fracture toughness specimen and wide plate with welding residual stress, respectively, at the same level of the Weibull stress.Fracture assessment results using βr are shown within the framework of failure assessment diagram (FAD). An excessive conservatism observed in the conventional procedure is reasonably reduced by applying the equivalent CTOD ratio, βr.

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The extension of the fatigue life of welded joints has been in demand to improve the safety and reduce the life cycle cost of ships.To meet such demand, it is effective to apply post-weld treatments which prevent crack initiation from weld toes or new steels which retard crack propagation in base metals. In this paper, the improvement on the fatigue life of welded joints by the synergy effect of ultrasonic impact treatment (UIT) and steel with high resistance to fatigue crack growth (F/M steel) is investigated. F/M steel has a microstructure with elongated and banded martensite phase distributed in a ferrite matrix, thickness of 49 mm, and EH36-class strength and toughness. Fatigue life to failure (Nf) is evaluated by dividing such into fatigue life to crack initiation (Nc) and crack propagation (Np) by means of the 5% strain drop method. As a result, the fatigue life of an out-of-surface gusset welded joint using UIT and F/M steel increases 8.7 times in Nc, 4.3 times in Np and 5.0 times in Nf, respectively, compared to an as-welded joint using conventional steel. The extension of Nc is a result of decreased stress concentration and tensile residual stress near the weld toe due to UIT. The extension of Np can be attributed to the increase of the resistance to fatigue crack growth for enhancing the roughness-induced crack closure of F/M steel with the decrease of the tensile residual stress due to UIT. Evidently, the synergy effect of UIT and F/M steel can significantly improve the fatigue life of welded joints.

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