Search Results (43)

Deep-sea navigation represents the future trend of maritime navigation; however, complex seakeeping conditions often lead to unconventional ship attitudes. Conventional calculation methods are insufficient for accurately assessing hull performance under heeled or extreme trim conditions. Drawing inspiration from Bonjean curve principles, this study proposes a Quasi-Bonjean (QB) method to compute ship performance elements in arbitrary attitudes. Specifically, the QB method first constructs longitudinally distributed hull sections from the Non-Uniform Rational B-Spline (NURBS) surface model, then simulates arbitrary attitudes through dynamic waterplane adjustments, and finally calculates performance elements via sectional integration. Furthermore, an Adaptive Surface Tessellation (AST) method is proposed to optimize longitudinal section distribution by minimizing the number of stations while maintaining high geometric fidelity, thereby enhancing the computational efficiency of the QB method. Comparative experiments reveal that the AST-generated 100-station sections achieve computational precision comparable to 200-station uniform distributions under optimal conditions, and the performance elements calculated by the QB method under multi-attitude conditions meet International Association of Classification Societies accuracy thresholds, particularly excelling in the displacement and vertical center of buoyancy calculations. These findings confirm that the QB method effectively addresses the critical limitations of traditional hydrostatic tables, providing a theoretical foundation for analyzing damaged ship equilibrium and evaluating residual stability. Full article

The maritime sector is under pressure to increase ship energy efficiency and reduce greenhouse gas (GHG) emissions as a part of global decarbonization goals. Various innovative technologies are being adopted in recent years, raising concerns not only about technological feasibility but also about the economic viability of such technologies in the context of sustainable maritime practices. This study evaluates the operational performance, potential to increase energy efficiency, and economic feasibility of wind-assisted propulsion technologies such as rotor sails across different vessel types and operational profiles. As a contribution to cleaner and more efficient shipping, energy savings produced by rotor thrust were analyzed in relation to vessel dimensions and rotor configuration. The results derived from publicly available industry data including shipowner reports, manufacturer case studies, and classification society publications on 25 confirmed rotor sail installations between 2010 and 2025 indicate that savings typically range between 4% and 15%, with isolated cases reporting up to 25%. A simulation model was developed to assess payback time based on varying fuel consumption, investment cost, CO₂ pricing, and operational parameters. Monte Carlo analysis confirmed that under typical assumptions rotor sail investments can reach payback in three to six years (as the ship is also liable for CO₂ payments). These findings offer practical guidance for shipowners and operators evaluating wind-assisted propulsion under current and emerging environmental regulations and contribute to advancing sustainability in maritime transport. The research contributes to bridging the gap between simulation-based and real-world performance evaluations of rotor sail technologies. Full article

Ships are designed to withstand various types of hull structure damage, including corrosion, fatigue, damage, crack, fouling, etc., throughout their projected life cycle of 25 years. In this study, we used a database of 25 different bulk carriers aged from five to twenty-five years, consisting of a total of 1920 thickness measurements of girder plate damage across 110 fuel tanks. Thickness measurements of longitudinal girder plate were conducted by certified technicians and approved company. Ultrasound thickness gauging equipment was used to collect data in accordance with the developed methodology and gauging scheme. Based on the classification societies’ rules, the values of the reduction in steel plate thickness due to corrosion over time fall into three categories: acceptable corrosion, substantial corrosion, and extensive corrosion. While classification societies prescribe permissible thickness reductions between 15 and 30%, in this study, the authors considered the excessive corrosion values to be above 20% reduction in initial thickness. Measurements indicating more than 20% reduction were classified as failures, necessitating the replacement of the corroded surfaces. After applying the multistate approach to the reliability analysis of longitudinal girder plates and improving reliability after reaching the critical state, the results show that usability dropped significantly between ten and fifteen years of service for upper girder plating and between twenty and twenty-five years of service for lower girder plates. These findings highlight the crucial impact of gauging location on reliability analysis. Full article

The autonomy of transport systems presents a transformative opportunity to enhance logistics efficiency, improve safety, and support decarbonization. In the maritime sector, the International Maritime Organization (IMO) has been working since 2016 to develop a mandatory regulatory framework for Maritime Autonomous Surface Ships (MASSs), aiming to finalize a comprehensive code. Simultaneously, pilot projects are underway in national waters under the oversight of national administrations. Naval applications of autonomous ships demonstrate their potential, as emerging doctrines highlight their strategic and operational advantages. Although the military sector is not governed at the international level, safely managing interactions between military and commercial MASSs is crucial for ensuring safe navigation. Classification societies play a vital role in achieving high safety standards and ensuring regulatory compliance. This study aims to propose a framework for certifying maritime autonomous vessels. Through a thorough analysis of the existing literature and by identifying gaps, this study outlines a structured pathway to facilitate the certification and operation of MASSs, addressing key technical, operational, and safety considerations. This research contributes to designing a risk-informed approach for the development of autonomous surface vehicles. Full article

Lloyd’s Register became the first classification society to mandate reliability testing for insulation degradation in rotating electrical machinery. As the maritime industry shifts toward eco-friendly practices, high-voltage rotating electrical machinery on ships increasingly features higher voltages and larger capacities. However, incidents involving insulation systems have also become more frequent. Additionally, testing facilities with the necessary equipment to perform such reliability tests are lacking, and standardized testing methods are yet to be established. This study proposes test items, methods, and evaluation criteria for the reliability testing of high-voltage rotating electrical machinery. The testing methods are broadly categorized into four types: thermal, electrical, multifactor, and thermomechanical degradation reliability testing. The proposed methods were validated by conducting long-term testing over approximately one year. Key results showed a breakdown time of 7056 h in thermal evaluation, 5040 h in electrical evaluation, and 258.5 d in multifactor evaluation, as well as a 63rd percentile value of 245.7 h in thermomechanical evaluation, all of which fulfill the required criteria. The study offers practical guidelines for ensuring the durability and safety of high-voltage electrical machinery, aligning with the sustainability and safety goals of the maritime industry. Full article

This study investigates the design and potential failure modes of a marine propeller shaft using computational and analytical methods. The aim is to assess the structural integrity of the existing design and propose modifications for improved reliability and service life. Analytical calculations based on classification society rules determined acceptable shaft diameter ranges, considering torsional shear stress limits for SAE 1030 steel. A Campbell diagram analysis identified potential resonance issues at propeller blade excitation frequencies, leading to a recommended operating speed reduction for a safety margin. Support spacing was determined using both the Ship Vibration Design Guide and an empirical method, with the former yielding more conservative results. Finite element analysis, focusing on the keyway area, revealed stress concentrations approaching the material’s ultimate strength. A mesh sensitivity analysis ensured accurate stress predictions. A round-ended rectangular key geometry modification showed a significant stress reduction. Fatigue life analysis using the Goodman equation, incorporating various factors, predicted infinite life under different loading conditions, but varying safety factors highlighted the impact of these conditions. The FEA revealed that the original keyway design led to stress concentrations exceeding allowable limits, correlating with potential shaft failure. The proposed round-ended rectangular key geometry significantly reduced stress, mitigating the risk of fatigue crack initiation. This research contributes to the development of more reliable marine propulsion systems by demonstrating the efficacy of integrating analytical methods, finite element simulations, and fatigue life predictions in the design process. Full article

Sorting out the requirements for intelligent functions is the prerequisite and foundation of the top-level design for the development of intelligent ships. In light of the development of inland intelligent ships for 2030, 2035, and 2050, based on the analysis of the division of intelligent ship functional modules by international representative classification societies and relevant research institutions, eight necessary functional modules have been proposed: intelligent navigation, intelligent hull, intelligent engine room, intelligent energy efficiency management, intelligent cargo management, intelligent integration platform, remote control, and autonomous operation. Taking the technical realization of each functional module as the goal, this paper analyzes the status quo and development trend of related intelligent technologies and their feasibility and applicability when applied to each functional module. At the same time, it clarifies the composition of specific functional elements of each functional module, puts forward the stage goals of China’s inland intelligent ship development and the specific functional requirements of different modules under each stage, and provides reference for the Chinese government to subsequently formulate the top-level design development planning and implementation path of inland waterway intelligent ships. Full article

This paper investigates the change in hull girder failure probabilities and partial safety factors caused by the implementation of the new procedure for direct computation of wave loads recommended by the International Association of Classification Societies (IACS). Differences between new and previous procedures are primarily related to the different associated scatter diagrams, and secondarily due to the assumptions on wave spectrum, wave energy spreading, and ship speed. This study performs a comparative structural reliability analysis of the global longitudinal bending of five oil tankers of different sizes between two procedures for wave load computation. Firstly, failure probabilities are compared, and secondly, modified partial safety factors are proposed, resulting in similar failure probabilities according to two separate procedures. It is found that implementation of the new revision of the IACS procedure for direct computation of wave loads results in a reduction of the minimum required ultimate vertical bending capacity of a ship hull by 10%. In addition to the novel investigation of the safety of oil tankers using a revised wave scatter diagram, this study offers a new rapid method for calculation of extreme vertical wave bending moments based on the regression of the parameters of the Weibull function, used for the long-term probability distribution of wave-induced loads. Full article

Port State Control (PSC) inspections conducted under the Paris Memorandum of Understanding (MoU) agreement have become a crucial tool for maritime administrations in European Union countries to ensure compliance with international maritime safety standards by ships entering their ports. This paper analyses all PSC inspections conducted in 10 major European ports belonging to the Paris MoU between 2012 and 2019. For its study, a multivariate HJ-Biplot statistical analysis is carried out, which facilitates the interpretation and understanding of the underlying relationships in a multivariate data set by representing a synthesis of the data on a factorial plane, with an interpretation that is very intuitive and accessible for readers from various fields. Applying this method with ship characteristics as explanatory variables, several classifications were derived. These classifications align with the annual performance lists published by the Paris MoU and the International Association of Classification Societies list, suggesting that this method could serve as a reliable classification approach. It provides maritime authorities with an additional indicator of a ship’s risk profile, aiding in the prioritising of inspections. The method also effectively categorises ports and types of ships used for cargo transport, offering insights into the specific maritime traffic each port experiences. Furthermore, this study identifies characteristics associated with substandard ships, which is a primary objective of PSC inspections. Beyond revealing these traits, this research underscores the existence of several readily applicable techniques to enhance maritime safety and reduce the risk of ocean pollution. Full article

The intricate nature of ships and floating structures presents a significant challenge for ship designers when determining suitable structural dimensions for maritime applications. This study addresses a critical research gap by focusing on a three-cargo hold model for a multipurpose cargo ship. The complex composition of these structures, including stiffening plates, deck plates, bottom plates, frames, and bulkheads, necessitates thorough structural analysis to facilitate effective and cost-efficient design evaluation. To address this challenge, the research utilises FEMAP-integrated NX NASTRAN software (2021.2) to assess hull girder stress. Furthermore, a novel approach is introduced, integrating the Design of Experiments (DOE) principles within Minitab 21.4.1 software to identify critical parameters affecting hull girder stress and production costs. This method determined the top five key parameters influencing hull girder stress: Hatch coaming plate, Hatch coaming top plate, Main deck plate, Shear strake plate, and Bottom plate, while also highlighting key parameters that impact production costs: the inner bottom plate, Inner side shell plate, Bottom plate, Web frame spacing, and Side shell plate. Ship design optimisation is then carried out by incorporating regression equations from Minitab software into the Non-dominated Sorting Genetic Algorithm II (NSGA-II), which is managed using Python software (PyCharm Community Editon 2020.3.1). This optimisation process yields a significant 10% reduction in both ship weight and production costs compared to the previous design, achieved through prudent adjustments in plate thickness, web frame positioning, and stiffener arrangement. The optimally designed midship section undergoes rigorous validation to ensure conformity with industry standards and classification society regulations. Necessary adjustments to inner bottom plates and double bottom side girders are made to meet these stringent requirements. This research offers a comprehensive framework for the structural optimisation of ship hulls, potentially enhancing safety, sustainability, and competitiveness within the maritime engineering industry. Full article

This paper addresses the growing concern over air pollutant emissions (NOx, SOx, PM, CO₂) from ocean-going vessels in harbor areas and the role of Onshore Power Supply (OPS) systems in mitigating these emissions during vessel berthing. However, the slow progress in global shore power facilities is attributed to safety- and specification-related concerns. Our study conducts a comprehensive analysis, comparing international shore power regulations, with a specific focus on the IEC/IEEE 80005-1 standard and guidelines from various ship classification societies. We introduce checklists, scoring tables, and spider diagrams to evaluate the regulatory content, highlighting the strengths and weaknesses of each approach. Furthermore, this paper emphasizes the significance of a well-defined operational process for high-voltage shore connection (HVSC) to ensure the safety of OPS operations. We present process diagrams for key operational stages, based on IEC/IEEE 80005-1 specifications and evaluation criteria. The ultimate goal of this research is to drive the global adoption of shore power and foster the establishment of shore power facilities worldwide. This aligns with the broader environmental protection objectives of achieving cleaner ports and reducing emissions for a sustainable future. Full article

As the shipbuilding industry has emerged from an extended recession, orders for high-value-added ships, such as LNG and ultra-large container ships, are increasing. For ultra-large container ships, high-strength, thick materials are applied. Because the possibility of brittle fracture increases owing to the application of thick steel plates, the related regulations of the International Association of Classification Societies have been strengthened to prevent brittle fracture. To secure brittle fracture stability, it is necessary to secure crack arrest toughness ($K_{ca}$) through large ESSO experiments or to secure a crack arrest temperature (CAT) value. Because large-scale experiments require considerable costs and efforts, efforts have increased to examine brittle fracture stability through small-scale tests. In the present study, a technology was developed to predict CAT with small specimens. The CAT prediction formula developed with small specimens makes it possible to accurately predict CAT using data obtained through large-scale experiments. Full article

Cargo ships with wide hatches usually have thin walls and limited torsional rigidity. Consequently, conducting a comprehensive torsional analysis is important because these loads can exert a significant impact. In this paper, the structural response of a multipurpose cargo ship to combined bending and torsional loads is studied using finite element analysis. The bending and torsional moments are calculated following the rules and standard regulations followed by the classification society. The ship’s 3D finite element model was verified using beam theory and direct calculations. In contrast, the accuracy of torsional stress was confirmed by comparing thin wall girder theory with direct calculation results. This study thoroughly examined the impacts of the still water bending moment, the vertical wave bending moment, and the wave-induced torsional moment on the structural response of ships. Furthermore, it scrutinised the impact of torsion on both open-deck and closed-deck ships. Hull girder normal stresses at midship due to still water and the vertical wave bending moment are shown to contribute to almost 70% of total stress in an inclined condition; stresses resulting from the horizontal wave bending moment contribute nearly 10%, while warping stresses contribute approximately 20% in open-deck ships. It is also shown that torsion has little impact on closed-deck ships. Finally, a buckling analysis was conducted to assess the ship’s buckling criteria, confirming that the linear buckling criteria were satisfied. Full article

General cargo ships are the most numerous in the merchant fleet. In these vessels, the stowage and securing of non-standardized cargo must be designed prior to being shipped. Furthermore, during sea navigation, the shipmaster must be confident that the secured cargo is safe in any weather conditions. One of the goals of the present research is to provide helpful guides to ship operators about the optimal navigational parameters. Despite different criteria being followed by the shipping industry to calculate the rolling motion accelerations, relevant accidents and losses related to an inadequate securing arrangement still occur. Firstly, this paper analyzes and compares the IMO’s and classification societies’ criteria, obtaining relevant results about the different safety levels along the ship’s dimensions. Secondly, it obtains a novel mathematical model of angular transverse acceleration, considering the sea state conditions and navigational parameters. For this reason, it investigates the combinations of optimization of these parameters. Finally, it proposes novel 3D surface graphs as being easy, useful, and quick to be interpreted by shipmasters when sailing in certain sea state conditions, to know if the limits of the maximum securing arrangement are exceeded and predict the ship’s optimal speed and heading in order to set out. Full article

International Association of Classification Societies (IACS) is responsible for many of the ship strengthrules including both generally applicable Unified Strength Requirements (UR-S) and other rules specific for various ship types. For historical reasons, there have been different structural strength requirements regarding hatch covers, hatch coamings, and related structures in IACS UR S21, S21A, and CSR (Common Structural Rules for bulk carriers and oil tankers). This paper presents the work carried out to improve the related rules and thereby the development of the unified strength requirements for hatch covers. Firstly, related IACS rules are reviewed and compared, and some major improvements to the buckling formulations are proposed for improved accuracy. Secondly, with UR S35 being developed as a unified buckling toolbox, the unified strength requirements for hatch covers—UR S21 (Rev.6, complete revision)—are developed with a standardized interface of reference to UR S35 for buckling assessment. Finally, the numerical calculations of typical stiffened panels and full hatch covers are carried out for rule verification and consequence assessment, which demonstrates that more rational hatch cover designs can be achieved based on UR S21 (rev 6). Full article