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Safety evaluation of a lashed trailer on the cargo deck of ships is essential for ferry operations. Although ferry accidents have occurred worldwide, few studies have focused on the dynamic analysis of trailer motion in irregular sea states. To date, effective counterapproaches have not been established. Thus, first, ferry masters were interviewed to summarize the difficulty in cargo management during rough sea voyages. Second, a modified simulation model of lashed trailer motions was constructed to evaluate the safety of cargo management, considering wave, seakeeping, and trailer motion simulations. Few studies apply the model to the irregular sea state in actual seas, using a combination of three different kinds of models. A simulation was conducted to analyze the collapse of a trailer loaded on a ferry in high waves owing to rapidly developing atmospheric pressures. Essentially, the model can reproduce the collapse of trailers, especially when a shift in the center of gravity is considered when accelerations occur in loaded cargo inside trailers. The model enables the estimation of trailer motions and lashing wire tensions in ferry operations, considering suitable lashing arrangements. • Dynamic analysis of lashed trailer motions in irregular sea state is focused. • A complete simulation model of lashed trailer motions was newly constructed. • The model can reproduce the collapse of 100 trailers for the accident in 2009. • Lashing arrangement with longer breast lines can be effective to reduce motions. • A shift in the center of gravity for cargo in large motions could be occurred. [ABSTRACT FROM AUTHOR]

Accurate estimation of ship motions is inevitable for safe, economical, and environmentally friendly ship routing. Onboard measurements have been conducted for a bulk carrier in 2010–2016, including eight rough seas in the Northern and Southern Hemispheres. Rough sea conditions were reproduced using a wave model, WaveWATCH III, with wind inputs from meteorological organizations. Ship performances were evaluated using traditional seakeeping theories, with the main focus being on transverse motion. The 3D frequency-domain Rankine Panel Method (RPM), New Strip Method (NSM), and Enhanced Unified Theory (EUT) were compared. First, roll decay tests and simplified Ikeda's methods of roll damping were applied in each method. Second, the results of the model tests in oblique seas in regular waves were additionally considered for the accurate estimation of ship motions in actual seas. These were validated with measured ship motions in eight rough sea voyages. It was found that errors are smaller in the RPM than those in the EUT and NSM for measured roll and pitch motions in actual seas. The favorable results obtained using the proposed methods may provide a new alternative for optimal ship routing to predict ship roll and pitch motions in rough seas with reliable accuracy and computational efficiency. • Ship motions in actual seas are analyzed for 28,000DWT bulk carrier. • Frequency-domain Rankine panel method is used to estimate ship motions. • New strip method and enhanced unified theory are used for comparison. • Roll damping is estimated by decay tests and simplified Ikeda's methods. • Ship motion computations are validated by model tests and actual seas. [ABSTRACT FROM AUTHOR]

The present global society has made the development of a safe and efficient maritime transportation system more imperative than ever before. Of particular impetus is the steep rise in the price of crude oil, which has required shipping companies to minimize the fuel consumption of their ships. Moreover, the emission of carbon dioxide has been restricted by the EEDI (Energy Efficiency Design Index) issued by the IMO (International Maritime Organization). Weather routing services have become more important to shipping companies. However, there are accuracy deficiencies in the numerical models employed by such services for purposes such as weather forecast and the ship speed loss phenomenon. Moreover, the development of weather routing models has been hampered by insufficient accumulation of continuous data on ship motions, and the navigation, engine, and weather parameters. The data used for this study was collected over one year from a 20,000 DWT class bulk carrier on worldwide voyages. Some new relationships regarding ship motions, speed loss, and wave conditions were developed, which were verified by experimental data and numerical simulations of the frequency response of the ship motion and of the weather and ocean. [ABSTRACT FROM AUTHOR]

The analysis of ocean surface waves is essential to ensure safe navigation. Since 2010, different on-board observation data from bulk carriers, including those navigating high-risk shipping regions in the southern hemisphere with strong ocean currents, have been collected for 6 years. High-resolution numerical simulations of ocean waves for four rough sea cases, considering the effect of wave-current interaction on ship navigation, have been performed using the WAVEWATCH III model. The simulations considered the ocean surface wind force from the widely used reanalysis database of the National Centers for Environmental Prediction Final and European Center for Medium-range Weather Forecasts Interim Reanalysis. To provide practical suggestions for safe navigation by avoiding possible high-risk ocean regions and construct a more effective and efficient optimum ship routing system, the model results were validated based on on-board observations, followed by discussions on the responses of ship motion and navigation to sea states at different levels. Finally, early warning criteria, including various operational ocean parameters for ballast and loaded ships sailing in rough seas were identified. • Shipboard measurement data with detailed navigation information has been collected for two different years and ship loading conditions. • Four rough seas have been focused on covering important maritime transportation ocean regions. • Wave simulations have been done with a high resolution to obtain detailed sea states. • Statistical approaches has been used to quantitatively study the ship responses to ocean waves. • Ship responses to ocean states are given, quantitatively showing the relationship among ship navigational parameters with ocean parameters. [ABSTRACT FROM AUTHOR]

The increasing demand for efficient, safe, and economic operation of ships has drawn attention to practical maneuvering behaviors for developing autonomous ships. Actual sailing conditions are reproduced to determine the relationship between environmental factors and ship steering records in rough seas. First, we generate realistic ocean environmental fields and analyze actual sea data. Then, we derive a modular maneuvering model reflecting environmental disturbances for further simulations. The correlation and multi regression analyses are performed based on measured data and environmental factors, which illustrate that the abnormal rudder angles are caused by reduced steering effectiveness. Finally, an attenuation function acting on the rudder normal forces is proposed to simulate this type of reduction. The time histories of maneuvering difficulties are selected as verification datasets. The maneuvers are simulated by adopting the attenuation function, and the simulation results show fair agreement with the measured data. The significant wave height, wind speed, mean wave period, current speed, wind apparent direction, and wave encounter angles are found to be the most statistically significant factors of rudder attenuation in the studied cases. The results and conclusions obtained from this study are of great significance for the further exploration of actual ship maneuvering behaviors in seas. • Problems to maintain course in actual sailing are investigated. • Data from spatiotemporally varying environmental fields are collected. • Measured data are utilized to reproduce realistic fields. • Rudder attenuation under severe weather is found by a statistical analysis. [ABSTRACT FROM AUTHOR]

Abstract: Sea states, such as waves, tidal currents, and wind are important factors for safe and economic ship navigation. In previous papers of Xia et al. (2006a, 2006b) single factor generated by low pressure was studied independently. The objective of this paper is to study how ship navigation is affected by the combined effects of these factors. For clarification, simulations of two representative typhoons were conducted, and the results were compared. Numerical simulations of tidal currents, waves, and wind were applied to provide high-resolution information, which was then used to simulate ship navigation. Estimation of ship position was found effectively by comparing the results from these two cases and using the proposed numerical navigation simulation method. [Copyright &y& Elsevier]