Full-scale Experiment on Computer Aided Navigation System for Safety

Ship motions are usually employed to analyze water transportation system. Interpolation of ship motions can be used for estimating the lost ship movement information, which is important for analyzing water traffic. Although some methods are proposed to interpolate ship trajectory, these methods are needed to improve interpolation accuracy. In addition, the course and speed of ship are not interpolated in previous studies. This article proposes a novel estimation algorithm for interpolating ship motions. First, the bilateral filtering is used to smooth the navigation trajectories, then a novel interpolation approach forecasts the vessel positions during the interpolation time period by taking into account the dynamic information of Automatic Identification System (AIS), and then forms the interpolation track of the moving vessel. In order to validate the proposed method, the AIS data of Yangtze River is collected from the AIS stations and the proposed restoration methods are verified by MATLAB under simulation. The results show that the proposed method can effectively remove the inaccurate ship motion data and interpolate the lost ship motion data.

The nuclear power plant for ship must be able to endure sufficently to the severe ship motion in rough sea. Therefore, in the design of reactor, we must predict the magnitude of acceleration_ or inertia force acting on it. In this paper, we attempted to the statistical considerations on the vertical acceleration due to the pitching and heaving, and some consideration of rolling acceleration. They are as follows.1. From the response amplitude operator of vertical acceleration that is measured at model experiment in regular wave and Neumann's spectrum of sea wave, we calculated the statistical magnitude of vertical acceleration of small fine ship, high speed cargo liner, and large oil tanker for various ship speed and wind velocity.2. From the above data, under the following condition, we obtained the values shown in Table 4 which was regarded as the reasonable values of vertical acceleration to use in the design of reactor part of various nuclear ship.a) As the ship speed, we adopted the maximum mean speed obtained from the point of view of resistance increase only.b) As the sea condition, we adopted the fully developed sea for wind velocity U=20 m/s.c) As the statistical magnitude of acceleration, we adopted the maximum acceleration a0, which is the vertical acceleration that the probability which maximum vertical acceleration in 5, 000 continuous waves exceeds a0 is 10%.3. The rolling acceleration at resonant condition are expressed by Ts·√g/B only approximately such as Fig. 17.The magnitude of rolling acceleration is smaller than that of vertical acceleration by pitching and heaving, but it must be careful because of the difference of its direction.

The prediction of the added resistance and attainable ship speed under actual weather conditions is essential to evaluate the true ship performance in operating conditions and assess environmental impact. In this study, a reliable methodology is proposed to estimate the ship speed loss of the S175 container ship in specific sea conditions of wind and waves. Firstly, the numerical simulations are performed to predict the added resistance and ship motions in regular head and oblique seas using three different methods; a 2-D and 3-D potential flow method and a Computational Fluid Dynamics (CFD) with an Unsteady Reynolds-Averaged Navier-Stokes (URANS) approach. Simulations of various wave conditions are compared with the available experimental data and these are used in a validation study. Secondly, following the validation study in regular waves, the ship speed loss is estimated using the developed methodology by calculating the resistance in calm water and the added resistance due to wind and irregular waves, taking into account relevant wave parameters and wind speed corresponding to the Beaufort scale, and results are compared with simulation results obtained by other researchers. Finally, the effect of the variation in ship speed and therefore the ship speed loss is investigated. This study shows the capabilities of the 2-D and 3-D potential methods and CFD to calculate the added resistance and ship motions in regular waves in various wave headings. It also demonstrates that the proposed methodology can estimate the impacts on the ship operating speed and the required sea margin in irregular seas.

Recently, digital transformation has become crucial for the safe operation and extended lifespan of ships and offshore structures. Structural health management is gaining importance and driving interest in digital twin technology for monitoring structural integrity. Digital twins enable proactive maintenance through the real-time monitoring and prediction of structural responses. This study developed a reduced-order model (ROM) for a container ship and validated it against a full-scale model. To address irregular wave loading challenges, we applied a snapshot-based Krylov subspace method. Unlike conventional methods that use unit force vectors in axial directions, this approach considers time-varying pressure distributions from irregular waves. Numerical simulations showed that with 20 reduced orders, the structural response had a relative root mean squared error of 0.02% compared with the full-scale model, whereas computation time decreased by over 99%. The ROM maintained performance under varying heading angles and ship speeds, with 20–30 reduced orders balancing accuracy and efficiency. Thus, Krylov subspace-based model-order reduction is a valuable tool for predicting the structural responses of ships and offshore structures under real-time irregular waves. It is expected to be widely used in digital twins for structural health assessment, including damage detection and fatigue strength evaluation.

During the 1970's, the Maritime Administration, as part of its Exploratory Research Program, supported the development of shipboard instrumentation systems for the sensing of ship motions and structural responses and the prediction of response changes to be expected when a ship's course or speed is altered. Two systems were installed, one on the SS LASH Italia operating in the Atlantic/Mediterranean service and the other on the USNS Furman operating in trans-Pacific service. These systems were operated for several years during which time significant data were obtained on midship bending, bow accelerations, bow side frame stresses and rolling. Filtering allowed identification of slamming and green water events. SNAME Panel HS-2 (Impact Loads and Responses), long in need of full-scale data on heavy-weather transient loadings of the hull, wished to determine whether these data, collected for other purposes, could be useful for predicting the frequency and magnitude of loads on the bow flare structure due to slamming and green water events. This paper presents the results of the investigation that was carried out and suggests some implications regarding the establishment of criteria for bow structure design in regard to loadings of this type.

Model experiments were carried out for a container ship in long crested irregular waves to investigate the non-linear effect on ship responses such as ship motions, wave induced pressure and wave load varying with wave height. The wave condition was changed from moderate to rough sea state in head waves. Numerical computations, by means of the strip method, the slender ship theory and the non-linear time domain strip method, were also carried out. The calculation results were compared with the experimental data to confirm the accuracy and to check on the range of the applicability.As a result, non-linear effect on vertical bending moment and wave induced pressure were remarkably observed in large waves : with increase of wave height, the bending moment acting on fore part is accelerated due to the influence of slamming and the induced pressure at the position near water surface is repressed due to the influence of exposure to the air. A time domain strip method can predict well the significant/maximum value of non-linear vertical bending moment in large waves. Toki's correction method is useful for improving the calculation accuracy of the induced pressure in regular and irregular waves.

Bhutan is located in utmost active seismic zone in the belt of the Himalayan region. However, there is a prevailing architectural requirement of cornice projections away from the perimeter columns at each floor proportional to the floor level to increase floor area and retain Bhutanese architectural style. This irregular projection with thick solid brick walls resting at the edge of cantilever projection affects the structural response during a strong earthquake. To date, there is not adequate investigation on the effects of such cornice projection on seismic performance of buildings. In this study, Nonlinear Response History Analysis (NLRHA) using vertical ground acceleration of relevant earthquakes was performed to assess performance of a three-dimensional three-story typical school building, which represents stock of structures in Bhutan. This study compares response parameters of the bare frame, in-filled frame, and six models with different projection lengths to comprehend the collective effects. Relevant global and local response parameters such as lateral story displacements, inter-story drifts, internal force demands, vertical deflections and its amplifications were assessed. The results indicate that bending moment and vertical deflection of the cantilevered beams are significantly affected due to the presence of cornice projection under vertical acceleration. The bending moment is amplified by a factor of 1.65, whereas the vertical deflection is amplified by a factor of 1.80, compared to the effect of gravity load alone. Based on typical design and acceptance criteria of ACI codes, the cornice projection length should not exceed 1.4m.

Large container vessels are known to vibrate heavily in head sea storms due to its flexible hull girder, pronounced bow flare and high vessel speeds. Strong vibrations are mainly excited by bow impacts causing transient vibrations referred to as whipping. This whipping response increases both fatigue and extreme loading. Further resonance vibration by springing response is also well known to contribute to increased fatigue loading. On these large container vessels it may however not be only the vertical vibration mode that is excited but also horizontal and torsional vibrations (coupled). The current paper describes the measurement system installed on a vessel operating between East Asia and Europe. Sensors for global loading, local loading and transverse hatch opening distortions are supplemented by navigational and environmental data. The system is an extended hull monitoring system analyzing data onboard and providing decision support onboard as well as providing statistical and time series of data to shore for further assessment. The measurements confirm that the fatigue loading of critical details are dominated by the vibrations, and that the fatigue loading level in deck in a storm is higher than ever measured before, also leading to high extreme loads above IACS rule values. The full scale measurements do to some degree confirm previous model tests of the same vessel, but the real vessel has been operated at reduced speeds. So far the fatigue loading on this route is at a comfortable level, partly due to reduced speeds, but also the encountered sea states may be less severe than the route specific scatter diagram. The loading may however increase if the vessel speed is increased, and the loading may become uncomfortable high if the vessel is put on a more harsh trade like North Pacific (or North Atlantic). Also torsional and horizontal vibrations are observed, but the transverse hatch opening distortions are moderate. Stern slamming is not measured to any significant degree, but bow flare slamming is measured in the storms. Side shell fatigue loading is at a comfortable level due to the CSA-2 notation involving direct hydrodynamic load calculations in the design introducing a sufficient safety margin against fatigue cracks. Vibration is however contributing significantly also in the side shell. Only a few storms have been encountered so far. The fatigue damage is concentrated amidships and the affect of warping in front of the superstructure does not increase the fatigue loading to a level of concern.

The stable control of a ship's speed is one of the most important factors when trying to improve the automation level and enhance the navigation safety of a ship. Since the ship's speed control is time-varying and nonlinear, and its dynamic characteristics are affected by environmental factors, it is difficult to obtain satisfactory control effects using traditional methods. In this paper, while establishing the nonlinear mathematical model of a ship's motion, environmental factors such as wind, waves, currents and system parameter uncertainties were considered. The model is a type of affine nonlinear system, and the sliding mode variable structure (SMVS) control method was selected to obtain the SMVS controller. Through a MATLAB simulation, the results showed that the SMVS control had the advantages of a small overshoot, fast response and strong anti-disturbance ability.

Numerical simulation of the maneuvering performance of ships in broken ice area

This article presents preliminary design formulas developed using a database of container ships built since 2015. Artificial neural networks and multiple nonlinear regressions with randomly searched functions were used to develop these formulas. The use of random search for nonlinear functions in a Multiple Nonlinear Regression model gave estimates which were just as precise as estimates created by the artificial neural network. All equations presented in this paper could have practical application for the estimation of dimensions, such as: length between perpendiculars, breadth, draught moulded and side depth. The equations were developed in relation to deadweight, TEU capacity and ship speed. These kinds of relationships have not been demonstrated before in ship theory. A statistical analysis showed that the main dimensions of the container ships can be estimated highly accurately by using the equations presented in the paper. The study showed that taking into account deadweight, TEU capacity and ship speed as three input parameters can improve the accuracy of an estimation by up to 44 percent, than when compared to the estimate accuracy of the design equations which are based on one input parameter.

A wake will appear behind the ship with long continuous time when the ship sail in the sea. The apparent wake can be detected with infrared imaging device. By analyzing infrared imaging characterization of the wake, many parameters of the ship can be gained in principle, such as ship's dimensions, course and speed. Combined JONSWAP wave spectrum with Kelvin wake model based on hydrodynamics, the simulation of Kelvin wake in the maritime environment is achieved. Meanwhile, a physics based model of infrared imaging for ship wake is proposed. Then the infrared characterization of ship Kelvin wake in different detection conditions is obtained, considering sky background radiation, atmospheric transmission, and other environmental factors. The results show that ship speed range can be estimated by using the infrared imaging characterization of ship wake. The detection and recognition probability of ship can be improved with appropriate detection azimuth.

In this paper, the course keeping control problem of a 5446TEU container ship is considered, a ship mathematical model is set up based on MMG modeling theory, the model’s validity is verified through a comparison study of turning simulation. A LADRC method is applied to the ship motion model, the simulation results illustrate the effectiveness of the control method.KeywordsCourse keepingContainer shipMMG modelLADRC method

Influence of the vertical seismic component on the response of continuous RC bridges

Estimation of the extreme values of wave-induced ship motions and accelerations for the First Nuclear Ship in Japan