Ultra Large Container Research Articles

Dynamic ultimate strength of a ultra-large container ship subjected to realistic loading scenarios

When technically specifying ships for the future, the following aspects are examples of what we will have even more focus on than today: bigger, lighter, and faster. Thereby, the hydroelastic type of structural response will be more and more significant. Furthermore, it is well-known that the whipping-induced stresses are having a higher frequency than the ordinary wave-induced stresses; hence, some doubts are cast on the probability that the dynamic effects may provide additional strength reserves. Therefore, this research aims to analyze the dynamic ultimate capacity of ultra-large container ships under realistic loading scenarios. The hull-girder is subjected to a combined bending moment, resulting from a long-term hydroelastic analysis, with the lateral loads and to local loads given by different cargo loading cases. The numerical results are discussed, and the dynamic load factors are derived as the ratio between the dynamic capacity and the quasi-static one. Finally, it is shown that the strain rate effect is negligible in the analysis of the ultimate strength of ship structures subjected to whipping-induced stresses.

Analysis of the scatter in fatigue life testing of thick thermal cut plate edges

ABSTRACT Structural elements of ships are subjected to a high number of cyclic loads, which are critical to fatigue life. Especially for ultra-large container ships the cutting of thick steel plates with high finishing quality and good fatigue life is important, e.g. located at openings in walls and decks of ships. This study presents a series of fatigue tests with 50 mm thick S355 specimens that are thermally gas cut on different shipyards. The obtained stress-life (S-N) curve contains significant horizontal scatter which often occurs for specimens that spend a high number of cycles on crack initiation. However, it is found that both the local stress concentrations and the origin of failure affect the number of load cycles significantly. Accounting for local stress concentrations provides an explanation for the initially encountered scatter in the S-N curves and indicates possible limitations of the nominal stress approach for thermal cut edges.

Effectiveness of surface-based detection methods for vessel strike mitigation of North Atlantic right whales

Increasing commercial and recreational use of the world’s oceans has led to growing concerns about vessel and marine mammal encounters. For endangered species such as the North Atlantic right whale Eubalaena glacialis, reducing the number of vessel strikes is key to improving their protection. In this study, we developed an agent-based model to assess the efficacy of thermal imaging systems as a surface-based whale detection method for vessel strike mitigation. We found that the detection range of such systems is the determining factor for their efficacy and needs to be chosen according to vessel characteristics, such as speed and maneuverability. Furthermore, we found that combining large-scale (e.g. protected zones) and small-scale (e.g. on-board detection systems) mitigation strategies increases protection. Finally, technological improvements are needed to achieve reliable detection ranges beyond what is currently possible so that fast and poorly maneuverable vessels such as ultra-large container ships could benefit from on-board detection systems.

Impact of the Thruster Jet Flow of Ultra-large Container Ships on the Stability of Quay Walls

As the size of ships increases, the size and output power of their thrusters also increase. When a large ship berths or unberths, the jet flow produced from its thruster has an adverse effect on the stability of quay walls. In this study, we conducted a numerical analysis to examine the impact of the thruster jet flow of a 30,000 TEU container ship, which is expected to be built in the near future, on the stability of a quay wall. In the numerical simulation, we used the fluid–structure interaction analysis technique of LS-DYNA, which is calculated by the overlapping capability using an arbitrary Lagrangian Eulerian formulation and Euler–Lagrange coupling algorithm with an explicit finite element method. As the ship approached the quay wall and the vertical position of the thruster approached the mound of the quay wall, the jet flow directly affected the foot-protection blocks and armor stones. The movement and separation of the foot-protection blocks and armor stones were confirmed in the area affected directly by the thruster jet flow of the container ship. Therefore, the thruster jet flows of ultra-large ships must be considered when planning and designing ports. In addition, the stability of existing port structures must be evaluated.

Nonlinear bending moments of an ultra large container ship in extreme waves based on a segmented model test

The paper presents an experimental investigation on the nonlinear bending moments of an ultra large container ship over 300 m long in rough waves. The design and calibration procedure of the scaled segmented ship model with variable cross-section backbone beam is introduced. Transfer functions of vertical bending moments at different Froude numbers, wave headings and wave heights are analyzed. Ship responses in harsh waves are analyzed and the largest wave height to wavelength ratio exceeds 1/10. It is interesting and significant to analyze the strongly nonlinear behaviors of the ship in such high waves. The resonance frequencies, proportion of high-order harmonic components, asymmetry of hogging and sagging moments as well as the phase differences between wave-frequency and high-order harmonics in extreme waves are investigated systematically.

Eco-efficient marine power system with cooled air ventilation by waste LNG cold energy for reefer holds in an ultra-large container ship

This study investigates dissipated heat removal from the internal cargo holds of an ultra-large container ship utilizing an LNG waste cold source. The reefer containers in the cargo hold dissipate heat to maintain certain freight conditions. While the extracted air from the atmosphere absorbs cold energy during LNG vaporization, it prevents a temperature increase inside the cargo holds by supplying cooled air. Herein, the marine power system is an electric propulsion type with a combined gas turbine electric and steam system. The cooled-airflow-ventilation system linked to the power system is evaluated regarding energy and exergy flows and greenhouse gas emissions. Cooled-airflow-ventilation performs efficiently as its coefficient-of-performance becomes twice that of atmospheric-airflow-ventilation when the reefer container box temperature is above zero and heat dissipation is high. Moreover, cooled-airflow-ventilation reduces the maximum-continuous-rating and improves the exergy efficiency. LNG waste cold source utilization benefits the response to the enforced regulation of ship greenhouse gas emissions. However, a high atmospheric temperature makes dissipated heat removal difficult. Consequently, cold energy cannot be provided to all cargo holds. The lower the box temperature is; the more cargo holds that can utilize cold energy.

Review and Analysis of Blockage of Suez Canal Region Due to Giant Container Ship

Abstract Navigation through narrow waterways always requires expertise and help from local authorities to facilitate safer and faster navigation. The recent Suez Canal blockage by the ultra-large container ship Ever Given running aground has resulted in a temporary halt and extended delay in goods transportation. Blockage of such a critical waterway has raised major concerns about the risk involved in navigation. This commentary attempts to analyze the background and chain of events leading up to the blocking of the Suez Canal. In this process, the issues related to navigation and following up salvage efforts are analyzed to identify the critical areas of improvement. Based on these identifications, suggestions for future improvement of navigation and better preparedness to optimize the salvage efforts have been identified. These suggestions include digitalization, prediction-based navigation capabilities, development of tugboats and associated tools, and so forth.

Operational cost analysis for a container shipping network integrated with offshore container port system: A case study on the West Coast of North America

The number of mega containerships operated by the major container shipping operators has reached a significant level in their fleet. However, the technical and physical insufficiencies of container ports do not allow handling of the latest generation mega containerships. The challenges of handling ultra-large container vessels (ULCV), especially in the main container lines, force port authorities to produce new port solutions. Offshore container port system (OCPS) is one of the recently proposed solutions to deal with the challenges of handling ULCVs more efficiently. These structures provide flexibility in eliminating operational difficulties arising from ULCV dimensions, while also helping to eliminate navigational constraints such as bridge and canal passages, and water draft. This article applies a research approach designed to evaluate the application of an OCPS in a particular geographical region. Based on this application, this research focuses on economic changes likely to arise as a result of the integration of ULCVs and OCPS into the existing container transport network. Accordingly, the developed container transport network model covers both the main route and the short sea shipping (SSS) leg, considering the offshore container port as a hub. In essence, this research is proposing an alternative port system and its associated container transportation network, for those ports that are currently unable to handle ULCV. To solve the problem, the paper presents a mixed- integer linear program model. It utilises a number of different decision variables and constraints in the process of making the model more realistic. Extensive numerical experiments based on realistic Asia-North America (West Coast) container shipping operations show that the model can be solved by Excel Solver. A case study for a container shipping network, using a set of 10 North America (West Coast) container ports linked to Asian markets, is presented herein. However, the robustness of the conclusions is subject to the uncertainty of the used values and the hypotheses made. Even though, the results can serve as an argument to strengthen the belief that the offshore container port concept can be considered as an alternative to conventional container ports.

Design methodology in transverse webs of the torsional box structure in an ultra large container ship

Container ships has a transverse section in the form of an open profile, making it very sensitive to torsion phenomena. To minimize this effect, a structure known as a torsion box exists, which is subject to high stresses influenced by the fatigue phenomenon and the existence of cut-outs, for the passage of the longitudinal stiffeners, acting as stress concentrators. The aim of this study is to propose a two-stage design methodology to aid designers in satisfying the structural requirements and contribute with to a better understanding of the considered structure. The transverse webs of a torsional box structure are examined by comparing different cut-out geometries from numerical models with different regular load conditions to obtain the variables of the fatigue safety factor through linear regression models. The most appropriate geometry of the torsion box is established in terms of minimum weight, from nonlinear multivariable optimization models.

Ultimate strength envelope of a 10,000TEU large container ship subjected to combined loads: From compartment model to global hull girder

The main objective of this research is to figure out the relationship of the ultimate strength characteristics between the compartment hull girder and the global hull girder, especially focusing on the ultimate strength envelope of the global hull girder of a 10,000TEU ultra large container ship subjected to combined loads, which is one of the most important indexes to quantify the safety margin of the container ship. To achieve these aims, both the compartment hull girder and the global hull girder are modeled based on true ship hull girder's configurations. A series of full-scale nonlinear finite element analyses are performed. In addition, to examine the reliability of the elastic-perfectly plastic material models employed in FEA, similar scale model collapse experiments of a compartment hull girder subjected to pure hogging and pure torsion are also presented. Finally, the ultimate strength envelope of the global hull girder of the 10,000TEU ultra large container ship subjected to combined vertical bending and torsion is quantitatively obtained, which can characterize the container ship hull girder's ultimate strength interactions between vertical bending and torsion and quantify the safety margin of the global hull girder of the container ship subjected to combined vertical bending and torsion.

Investigation on effects of springing and whipping on fatigue damages of ultra-large container ships in irregular seas

Springing and whipping play an important role in determining the fatigue damages of ultra-large container ships in waves, and it is widely acknowledged that the separation of the contributions of springing and whipping on fatigue damages is difficult. In this paper, the effects of springing and whipping on a targeted 21,000 TEU container ship are numerically investigated. The springing responses are calculated based on the linear 3D frequency domain hydroelasticity theory, while a 3D nonlinear time domain hydroelasticity formulation which couples the 3D hydrodynamic theory, 1D Timoshenko beam theory, 2D generalized Wagner method and 1D green water theory, is adopted to obtain the slamming-induced whipping response. Spectral analysis method is analyzed and compared with an indirect time domain method. Through investigating the characteristics of the accumulated fatigue damages with respect to the significant wave heights and characteristic wave periods of short-term sea states, the contributions from springing and whipping to the accumulated fatigue damages are generally separated for most short-term sea states. In addition, several short-term sea states are chosen to present detailed information on the extents to which springing and whipping increase the fatigue damages relative to the low-frequency structural responses counterpart.

Ultimate strength characteristics of as-built ultra-large containership hull structures under combined vertical bending and torsion

ABSTRACT The aim of the present paper is to investigate the ultimate strength characteristics of as-built ultra-large containership hull structures under combined vertical bending and torsional moments with varying the ship size. The intelligent supersize finite element method (ISFEM) is employed for the ultimate hull girder strength analyses. A total of three as-built containerships carrying 9,300 TEU, 13,000 TEU, and 22,000 TEU are studied. Based on the computations, ultimate strength interaction relationships of containership hull girders under combined vertical bending and torsional moments are also formulated by a curve fitting. Insights and structural design recommendations obtained from the study are summarised, which will be useful to not only enhance the ultimate limit state capacity of containership hull structures in existing sizes but also achieve the robust structural design of ultra-larger containerships which have never been built before.

Experimental and numerical investigation on the scaled model of lashing bridge coupled with hull structure and container stack

ABSTRACT Huge progress has been made in the design innovation for ultra-large container ships, instead of in cargo securing systems. The mechanical behaviour characteristics of the lashing bridge were studied statically and dynamically. Firstly, the static and dynamic characteristics of the prototype structure were obtained via finite element analysis. Then, the coupling effect between the lashing bridge and hull structure was considered and analysed. Secondly, the scaled model of the lashing bridge, hull structure and container stack was constructed by Similarity Theory and finite element analysis. Lastly, several experiments (static and dynamic) and numerical simulations were conducted, and the experiment results were compared with the finite element analysis. It reveals that the numerical model built is a promising tool, and the coupling effect of the hull structure on the lashing bridge cannot be ignored. Moreover, the mechanical behaviour of the full-scale lashing bridge can be conveniently derived from the scaled model.

Numerical analysis and experimental study on the scaled model of a container ship lashing bridge

Most existing studies and standards for containers and lashing equipment correspond to static conditions, which stresses current imperfections in the design specifications of the lashing bridge structure and gaps in experimental research. In this paper, an approach is proposed to study the mechanical behavior of the ultra-large containership lashing bridge structure. Based on Buckingham's Theorem and the Froude scaling laws, a scaled model test system with a container stack and twist lock is developed for a systematic experimental study of the lashing bridge. Additionally, the numerical analysis of the static, modal and dynamic response were carried out under the typical motion of the lashing bridge. Also, the coupling effect of the lashing bridge and hull structure is considered to design the system. The physical (size, mass, and moment of inertia) and structural characteristics (longitudinal, lateral, and torsional stiffness) of the proportional model are determined by two dimensionless numbers: Froude's number and Cauchy's number. The results suggest that the mechanical behavior of the ultra-large containership lashing bridge structure can be easily obtained from the reduced model. This can help to achieve the structural design and optimization, and the substructure coupling analysis of ultra-large lashing bridges.

The role of port authorities in the promotion of logistics integration between ports and the railway system: The Italian experience

This paper aims at deepening the knowledge about the traits and characteristics of the evolution of the intermodality quest in Italy by carrying on two distinct as well as correlated benchmark analyses. The first is performed on the approaches resulting by the Port Authorities (PAs) of Centre-Northern Italy and the second on the schemes adopted by the PAs of Southern Italy.The context of the analysis is characterized by the growing power of alliances, the vast diffusion of Ultra-Large Container Vessels both in container and Ro/Ro markets and the need for port systems to act in a logic of transport integration and sustainability.PAs of Center-Northern Italy have developed an active role in the transition to intermodality, promoting the participation in railways companies, focusing on the digitalization and integration with hinterlands. We show that the role of these PAs has proved fundamental in the acceleration of the process and there are various best practices that could be replicated in other contexts.PAs of Southern Italy's role, instead, is being hampered by the lack of suitable infrastructures, therefore their role has a different nature than in Center-Northern Italy. Southern Italy's PAs are also at the heart of various policies of fiscal incentives promoted by local and national governments, e.g. Special Economic Zones and Logistics Integrated Areas. Nonetheless, we show how they have been less effective in contrasting the growing power of other Mediterranean ports and have not been able to extend and diversify their port activities.The results of this work point in the direction of a more integrated cooperation between PAs and local and national governments, but also highlight that PAs alone cannot pursue such a complex transition in today's competitive market. Nevertheless, the current role of PAs in Italy has been reformed in 2016, therefore suggesting to treat results of this work as preliminary and in need of further research especially on the potential collaboration between public authorities and private operators. The work concludes with some food for thoughts and policy implications.

Dimensional precision controlling on out-of-plane welding distortion of major structures in fabrication of ultra large container ship with 20000TEU

Ultra large container ship as an essential role during international trade, is required for precision fabrication due to highly efficient TEU loading and unloading. In this study, two major structures, so called watertight transverse bulkhead structure and torsion box structure of ultra large container with 20000TEU were examined for out-of-plane welding distortion prediction and mitigation with measurement and computational analysis. Based on the welding inherent deformation theory, typical welded joints of two major structures were systematically classified with the different material, thickness, welding condition and joining form; and the relationships between welding heat input and inherent deformations were also presented. Elastic FE analysis with shell elements model and welding inherent deformation as input loading was employed for welding distortion prediction. Not only the distributions but also the magnitudes of predicted out-of-plane welding distortions of considered major structures have a good agreement comparing to the measurements. Furthermore, welding sequence influence was considered for dimensional precision controlling during the watertight transverse bulkhead structure fabrication, and welding groove optimization of thick plate was examined for out-of-plane welding distortion mitigation during the torsion box structure fabrication. Computational results show that welding distortions of both ship block structures can be significantly reduced for requirement of fabrication precision.

Features of an Ultra-large Container Ship Mathematical Model Adjustment Based on the Results of Sea Trials

Features of an Ultra-large Container Ship Mathematical Model Adjustment Based on the Results of Sea Trials

Experimental and numerical investigations of the ultimate torsional strength of an ultra large container ship

Structures of ultra large container ships (ULCS) are characterized by large deck openings and low torsional rigidity. It is essential to comprehensively figure out their collapse behaviors under pure torsion with both model experiments and numerical simulations, making an evaluation of their ultimate torsional strength. In this paper, a similar scale model of a 10,000TEU container ship has been designed and manufactured first, in which both geometric similarity and strength similarity are taken into account. Next the collapse behaviors of the test model are detailedly illustrated with both experimentally and numerically obtained results. Then discussions on warping or shear buckling deformations involved in the collapse process of the structure are conducted with extended numerical simulations. Finally, the ultimate torsional strength of the true ship is evaluated according to the similarity theory. Results show that it is the yielding and shear buckling of the side shells that causes the failure of the hull girder under pure torsion. Further nonlinear finite element analysis demonstrates that it may either have warping or shear buckling deformations in the torsional collapse process of the hull girder with a large deck opening, depending on the local rigidity distribution of side shells, which has a significant effect on the ultimate torsional strength of the hull girder.

An experimental study on Kca value to arrest a running brittle crack in structural model specimens with steel plate of 100 mm thickness for container ships

With demand for ultra-large container ships, high-strength steel plates with extremely large thicknesses are applied to the structural elements around hatch side structures. The two longitudinal plates of the upper deck and hatch side coaming are the main structural elements that support bending stress during hogging of the ship structure, and brittle crack arrest toughness as well as crack initiation toughness are required in these steel plates to avoid the catastrophic ship damage. Although the International Association of Classification Societies prescribes a unified requirement for brittle crack arrest steel plates providing the value of brittle crack arrest toughness Kca at − 10 °C for plate thicknesses of 80 mm or less, ultra-large container ships using steel plates with thicknesses exceeding 80 mm are continuously required and built. In the present work, brittle crack arrest tests with large scale structural model specimens which simulate the structural element of the hatch side structure were performed to investigate the Kca value required to arrest a running brittle crack for steel plates with the thickness of 100 mm. The present investigation suggested that the test plate simulating upper deck could arrest a running brittle crack at the plate Kca of 6000 N/mm3/2, nevertheless the Kca value of 8000 N/mm3/2 was needed in the test plate simulating hatch side coaming. The different Kca values required to arrest a running crack between the test plates simulating the upper deck and the hatch side coaming are also discussed from the viewpoint of the arrested crack size and shape.

Towards 25,000 TEU vessels? A comparative economic analysis of ultra-large containership sizes under different market and operational conditions

The introduction of ever-larger containerships is a much-discussed topic in academic and business circles. The largest containership size has evolved from about 5500 TEU in 1995 to more than 23,000 TEU in 2019. The economic rationale for further scale increases in ship size is largely dependent on the current and future market conditions in the container shipping market, the adaptive capacity of ports and terminals (both economically and technologically) and, more recently, environmental requirements and considerations. This paper evaluates under which economic, operational and environmental conditions and expectations, shipping companies are likely to push the ultra-large containership (ULCS) size from 18,000 to 20,000 TEU to 25,000 TEU. Differences in both annual container slot cost and more comprehensive cost–benefit measures are assessed under different key market-based and operational conditions. The basic cost parameters for 20,000 TEU and 25,000 TEU vessels were estimated using a regression analysis applied to actual data of vessels up to 18,000 TEU. Our findings show that a further scale increase to a 25,000 TEU ULCS still generates economies of scale. However, very low freight rates, i.e. even below the poor freight rates of 2016–2017, and low load factors would not be conducive to the economic viability of 25,000 TEU ships, compared to smaller ULCSs. This study complements and updates the findings of previous studies (which focused on much smaller ship sizes) and contributes to the ongoing academic and corporate discussion on drivers and impediments of scale increases in vessel size by explicitly incorporating time- and context-dependent factors affecting optimal ship size.