Ultra Large Container Research Articles

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

This paper figures out investigations into the ultimate strength of ultra large container ships (ULCS). Both the experiment and non-linear finite element method (NFEM) are utilized to evaluate the ultimate longitudinal strength behaviors of hull girder for ULCS in this study. Firstly, an experiment regarding the similar model is carried out to examine the characteristics of the ultimate longitudinal strength of the ultra large container ship's hull girder structures. The test model is designed by similar theory to reflect the progressive collapse behaviors of actual hull girder under hogging bending moment. Secondly, the results of simulations performed by numerical analysis into hull girder ultimate strength are compared with the experimental results. The results show good agreement with model test demonstrating the reliability of NFEM. Finally, a series of non-linear finite element analysis is performed to assess the ultimate strength of hull girder taking into account the effects of initial imperfections and both material and geometric nonlinearities, in which the typical 4,000 TEU, 10,000 TEU and 20,000 TEU representing normal and ultra large container ships are adopted as study cases to clarify the ultimate strength characteristics of ULCS. This analysis can help to cognize the ultimate longitudinal strength of ULCS.

The Issue of the Masthead Lights View of Ultra Large Container Vessel from Another Vessel

The Issue of the Masthead Lights View of Ultra Large Container Vessel from Another Vessel

Design similar scale model of a 10,000 TEU container ship through combined ultimate longitudinal bending and torsion analysis

This paper firstly figures out a similar scale model regarding ultimate strength experiment of a typical ultra large container ship (ULCS) through combined ultimate longitudinal bending and torsion analysis, in which the similarity theory is proposed to design the scale model for reflecting the progressive collapse behaviors of true ships in ultimate strength model test. The present study presents the similarity between scale model and true ship in cross-section considering the height of neutral axis, the section modulus, the inertia moment about neutral axis and the polar inertia moment should fit the geometrical similarity theory, and in strength considering buckling strength and shear ultimate strength of plates and stiffened panels should fit the strength similarity theory. Numerical investigations are conducted on the ultimate strength of a 10,000 TEU container ship and the similar scale model under pure hogging bending, pure torsion and combined bending and torsion, respectively. The nonlinear finite element method (NFEM) is adopted considering the effects of initial deformations and both material and geometric nonlinearities. Finally, the numerical results are compared with each other and discussed showing a good agreement in both elastic and inelastic range during the progressive collapse behaviors, which means the similar scale model can represent the true ship regarding ultimate strength test. And the similarity theory is verified quite stable after the uncertainty analysis.

Factors affecting safety of handling ultra large container vessels in Port of Gdańsk

Paper discussed important factors affecting handling of ULCS (ultra large container ships) in Port of Gdańsk. In recent years more such vessels had been calling Gdańsk, including new generation o ULCS called Triple-E launched by Maersk. Studies conducted in Maritime University confirmed feasibility of safe handling of such large vessels but pointed to several factors needed to be taken under consideration to provide required safety level for ship handling operations. Author analysed factors responsible for safe handling ULCs in Gdańsk.

Green sea loads in irregular waves with Finite Volume method

Extreme green sea loads upon a vertical deck structure of an Ultra Large Container Ship are calculated in this paper using Finite Volume based CFD simulations in full scale, where two different approaches for the definition of the Equivalent Design Wave are used. Linear frequency–domain method is used to calculate the long–term response in terms of Relative Wave Elevation, which in turn is used to define a deterministic Equivalent Design Wave which is then used in the CFD simulation. The simulations are conducted using a newly developed flow model that takes into account air compression in violent free–surface phenomena. Regular Equivalent Design Wave and Response Conditioned Wave approaches are used and compared in terms of loads exerted on the deck structure and required computational resources. Some differences in loads are found between the methods, whilst similar computational resources are required. The Regular Equivalent Design Wave gives larger loads, making it a safer choice. However, the Response Conditioned Wave takes into account the relevant ocean wave conditions as well as the response of the ship, resulting in smaller loads which would enable smaller structural scantlings and cost savings.

Modelling the manoeuvring behaviour of an ULCS in coastal waves

Understanding the ship manoeuvring behaviour in waves is of major interest to avoid ship responses which can lead to hazardous scenarios. Waves may impair the ship's manoeuvrability by inducing hull forces and moments, and by changing the propeller and rudder performance. These are fundamental problems which require further attention.The present work aims to provide a better insight on the problem of manoeuvring in waves by investigating the change of the hull, propeller and rudder hydrodynamic behaviour with respect to calm water. Coastal waves and finite water depths, representative of the Belgian coastal zone of the North Sea, are chosen for the present study. These correspond to scenarios where Ultra Large Container Ships (ULCS) manoeuvre in waves and shallow water. The study includes experiments conducted with a scale model of an ULCS in the Towing Tank for Manoeuvres in Confined Water at Flanders Hydraulics Research (in cooperation with Ghent University). Different combinations of ship forward speeds, wave amplitudes and periods, drift angles, propeller rates and rudder angles are considered. Moreover, numerical results for the wave induced forces, moments, and motions have been computed with the software package Hydrostar and the results are compared with the experiments to evaluate their accuracy.

Multidimensional examination of the performances of a liner shipping network: trunk line/route operated by conventional (Panamax Max) and mega (ULC - ultra large container) ships

This paper deals multidimensional examination of performances of a trunk line/route of liner container-shipping network serving an intercontinental supply chain by the conventional (Panamax Max) and mega (ULC - Ultra Large Container) ships. The trunk line/route of the network includes the supplier and the customer seaport of freight shipments consolidated into containers (TEU (Twenty Foot Equivalent Unit)), and the container ships operated by liner shipping carriers and/or their alliances providing transport services between them. The supplier and the customer seaport can be either the main seaports of the line or the hubs of the H&S (Hub-and-Spoke) network of particular liner container-shipping carriers.The multidimensional examination implies defining and developing the analytical models of indicators of the trunk line’s infrastructural, technical/technological, operational, economic, environmental, and social performances and their application to the selected real-life case. The infrastructural performances relate to the characteristics of infrastructure (berths) and container terminals in the seaports at both ends of the line. The technical/technological performances reflect the characteristics of facilities and equipment for loading/unloading and storing TEU shipments in these terminals, and that of the container ships transporting them. The operational performances include the transport service frequency, size, transport work and technical productivity of the deployed container ship fleet while serving a given volume of TEU flows during the specified time. The economic performances contain the inventory, handling, transport, and external costs of handling the TEU flows. The environmental performances relate to the fuel consumption and consequent emissions of GHG (Green House Gases). Finally, the social performances in terms of impacts generally refer to noise, congestion, and safety.The models of indicators of performances have been applied to the liner container-shipping trunk line/route connecting the East Asia and North Europe operated exclusively by two above-mentioned categories of ships according to the “what-if” scenario approach. The results have indicated the very high sensitivity of all considered indicators of performances to the category of deployed ships under given conditions. As well, they have shown to be dependent on each other – the operational on the technical/technological, and the economic, environmental, and social on the technical/technological and operational.

Experimental investigations on extreme bow-flare slamming loads of 10,000-TEU containership

Bow-flare slamming is issue that must be considered in ship design because it affects the local strength and fatigue life of a ship. In this paper, the experimental study of the spatial distribution of slamming load was conducted, which acts on the bow flares of ultra-large containerships. For a model test, 10,000 TEU container ship model with 1/60-scale ratio divided into six segments was applied. Fifteen force sensors were placed on the bow flare surface to measure slamming load. The slamming loads were measured in regular and irregular waves at various ship speeds, wave lengths, wave heights, and heading angles. In a regular wave test, the slamming load was larger in oblique sea than in head sea because the relative angle of the wave and bow flare is smaller in oblique sea. In an irregular wave test, extremely large slamming loads were measured at the centre line at the bow, which is influenced by the horizontal relative velocity such as the ship speed and surge. In an analysis of the slamming load of the ship, the direction of wave and forward speed of the ship should be carefully considered. These are difficult to consider in 2D analysis.

Structural Reliability Analysis of Container Ships under Combined Wave and Whipping Loads

A practical methodology for structural reliability assessment of ultra large container ships is proposed in the article. The commonly used limit state function for structural reliability analysis of oil tankers and bulk carriers was extended to take into account the whipping response due to the bow flare slamming. The ultimate vertical bending moment capacity of hull girder was considered as a fundamental safety variable in the limit state function, whereas the stochastic model of the loads consists of static still-water bending moments (SWBMs), low-frequency rigid body vertical wave bending moments and high-frequency whipping bending moments. The stochastic model of SWBM for one of the studied ships was obtained from actual bending moments recorded by the onboard loading computer in 2 years of operation. Linear vertical wave bending moment was calculated by a 3D panel seakeeping code, using International Association of Classification Societies (IACS) recommendation No. 34 for the computation of extreme global wave loads. The nonlinear correction of linear wave bending moment was obtained from the recent IACS Unified Requirement S11A for longitudinal strength of container ships. Impulsive loading was modeled by von Karman added mass variation method, whereas transient dynamic hull girder response was analyzed by Timoshenko beam finite elements. Load combinations between extreme still-water and vertical wave bending moments, and between extreme low- and high-frequency vertical wave bending moments are considered. The structural reliability analysis of two container ships of different sizes was performed using the first-order reliability method, to observe differences in safety levels due to different ship sizes. Safety indices are compared with the International Maritime Organization recommendations for double-hull oil tankers to have credible basis for assessing the obtained results. An extensive sensitivity and parametric study was performed, accounting for various operational, environmental, and modeling uncertainties, as well as for corrosion degradation. The presented study may be useful for classification societies in further development of recently introduced IACS Unified Requirements for longitudinal strength of container ships.

Feasibility study on applying the mist-spraying cooling to improve the capacity of ultra-large container ships for loading reefers

This work proposed a novel hybrid cooling system that applies the mist-spraying technology to improve the thermal conditions and loading capacity of refrigerated containers (reefers) in the cargo holds of ultra-large container ships. Thorough studies were carried out via both experiments and simulations. First, effects of the air supply rate and the mist spray rate on the reefer's exhaust temperature and the ambient temperature of the reefer Lab. were investigated in comparison with the simulation models. Then the possible operating conditions of the air and mist flow rates were clarified and the cargo hold from a practical container ship was adopted as the example to verify their feasibility. Finally, the possible capacity improvement for loading reefers was discussed while the method of determining the operating range of mist spray rates and air supply rates was also established. It was found that great benefits were generated by the proposed system in lowering the reefer's exhaust temperature and improving the thermal conditions inside the cargo hold. In addition, a substantial capacity improvement for loading reefers in the cargo hold was also achieved in the present study. The study will help in enhancing the efficiency and economic benefits for the reefer transportation.

Research of Springing and Whipping Influence on Ultra-Large Containerships’ Fatigue Analysis

Rules of Classification Societies all around the world have made changes on design wave loads’ value and fatigue influence factor modification due to the influence of springing and whipping on ultra-large containerships. The paper firstly introduced 3-D linear hydroelastic theory in frequency domain and 3-D nonlinear hydroelastic theory in time domain, considering large amplitude motion nonlinearity and slamming force due to the severe relative motion between ship hull and wave. Then the spectrum analysis method and time domain statistical analysis method were introduced, which can make fatigue analysis under a series of standard steps in frequency and time domain, respectively. Finally, discussions on the influence factor of springing and whipping on fatigue damages of 8500TEU and 10000TEU containerships with different loading states were made. The fatigue assessment of different position on the midship section was done on the basis of nominal stress. The fatigue damage due to whipping can be the same as the fatigue damage due to springing and even sometimes can be larger than the springing damage. Besides, some suggestions on calculating load case selection were made to minimize the quantity of work in frequency and time domain. Thus, tools for fatigue influence factor modification were provided to meet the demand of IACS-UR.

Numerical prediction of slamming on bow-flared section considering geometrical and kinematic asymmetry

Asymmetric impacting phenomenon is quite common for the sailing ship when it encounters oblique waves. The asymmetrical water entry problem of a full scale bow-flared section from Ultra Large Container Ship (ULCS) was investigated using CFD method in commercial code FLUENT. A two-phase flow model was established based on N-S equations, which were discretized through the finite volume method and the free surface was captured by VOF model. The body motion was achieved in the dynamic mesh model with prescribed dynamic boundary condition. The impacting forces were obtained through direct numerical integration on the body surface. The validation and convergence were carried out through comparing experimental data and other numerical methods in already published literature. Two kinds of asymmetry, heel angle as geometrical asymmetry and horizontal velocity as the kinematic asymmetry, were comprehensively considered in numerical simulation and significant attention is given into the discussion of their effects on impacting hydrodynamics including pile-up water, pressure and slamming forces. The results show the geometrical asymmetry is important on these hydrodynamics if the flow separation does not happen. Otherwise, the kinematic asymmetry can significantly influence pile-up water form and further determines the pressure and slamming forces.

The Building of Latest Ultra-Large Container Ship

The Building of Latest Ultra-Large Container Ship

Numerical investigation of three-dimensional hull girder ultimate strength envelope for an ultra large container ship

Ultra large container ship (ULCS) structures feature large deck openings and low torsional rigidity. It is essential to accurately evaluate the maximum loading carrying capacity of ship structures. When the ship sails at an oblique heading in rough sea, the horizontal and torsional moments may approach or even exceed the magnitude of vertical bending moment. In such cases, hull girder ultimate strength assessment of container ships under load combinations comprising of vertical bending moment, horizontal bending moment and torsion is necessary in their structural design stage. In this paper, special attentions are thus paid to the hull girder ultimate strength of an ULCS (i.e., a typical 10,000 TEU container ship) subjected to combined three load components mentioned above, which is also a common load case in ships and ship-shaped offshore structures and it is assumed that the three kinds of main loads can be combined each other freely. A series of nonlinear finite element analyses (NFEA) is carried out. Effects of fabrication related initial imperfections are investigated in the present study. Based on the computed numerical results, the 3D hull girder ultimate strength envelope considering initial deformation and incorporating the interaction relationships among three kinds of load components mentioned above is established.

Quasi-Static Response of a 19,000 TEU Class Ultra Large Container Ship with a Novel Mobile Deckhouse for Maximizing Cargo Capacity

Quasi-Static Response of a 19,000 TEU Class Ultra Large Container Ship with a Novel Mobile Deckhouse for Maximizing Cargo Capacity

Prediction of extreme loads on ultra-large containerships with structural hydroelasticity

Design rules for very large seagoing vessels are undergoing changes owing to the hydroelasticity of the ship. The hydroelasticity of the ship is in the form of wave-induced vibrations such as springing and whipping, which are known to aggravate fatigue and extreme loads. The present study deals with a method for the estimation of extreme loads. The method consists of a preliminary analysis of linear responses of motions and loads, and a sequential analysis of the nonlinear extreme load. First, a full-time series of the linear response is obtained using response amplitude operators and wave spectra. Next, the candidate waves of extreme event are extracted from the full-time series based on the linear response. The linear response may be a motion or a load depending on the target value of the sequential analysis. Finally, the sequential analysis is conducted using a fully coupled model of the three-dimensional Rankine panel method, three-dimensional finite-element method, and two-dimensional generalized Wagner model with the candidate waves. The method is validated for a nonlinear hogging moment in a short-term sea state and applied for a long-term prediction of an extreme hogging moment on an ultra-large containership. The extreme values of linear and nonlinear loads are compared in terms of the most probable value and probabilistic distribution.

Effect of ship size on EEDI requirements for large container ships

The Energy Efficiency Design Index (EEDI) is a technical measure introduced by International Maritime Organization (IMO) aiming to improve energy efficiency of ships. The Attained EEDI of a ship has to be calculated for every new ship and lower than the Required EEDI determined by the EEDI reference line, which represents world fleet average for a certain ship type, and an appropriate reduction factor. Nowadays ultra large container ships (ULCS) are being built, and for the time being they are not accounted for in the Required EEDI formulation for container ships. Consequently, in most cases, it makes existing EEDI criteria relatively irrelevant for the design of ULCS. In this paper, the effect of ship size on the EEDI requirements for large container ships is elaborated in details. Several important issues are addressed: updating of existing baseline formulation with new ULCS data available in the IHS Fairplay database; extending the EEDI reference line into the EEDI reference surface for container ships as a function of ship capacity and speed; establishing a relation between the deadweight used in the EEDI calculation and the real ship capacity measured in TEU which enables more practical data handling in overall container ship design procedure.

Application of a Free-Surface-Type Antirolling Tank on an Ultralarge Container Ship

Application of a Free-Surface-Type Antirolling Tank on an Ultralarge Container Ship

Hydroelastic response of 19,000 TEU class ultra large container ship with novel mobile deckhouse for maximizing cargo capacity

This paper is related to structural design evaluation of 19,000 TEU ultra large container ship, dealing with hydroelastic response, i.e. springing and whipping. It illustrates application of direct calculation tools and methodologies to both fatigue and ultimate strength assessment, simultaneously taking into account ship motions and her elastic deformations. Methodology for springing and whipping assessment within so called WhiSp notation is elaborated in details, and in order to evaluate innovative container ship design with increased loading capacity, a series of independent hydroelastic computations for container ship with mobile deckhouse and conventional one are performed with the same calculation setup. Fully coupled 3D FEM – 3D BEM model is applied, while the ultimate bending capacity of hull girder is determined by means of MARS software. Beside comparative analysis of representative quantities for considered ships, relative influence of hydroelasticity on ship response is addressed.

Containership port time: The bay time factor

Containership size has been increasing in length, width (beam), and height. The introduction of Ultra Large Containerships results in a much larger number of containers stowed in a cargo bay. The objective of this paper is to determine the impact of the increasing containership bay size on the economies of scale at berth. We develop the concept of bay time, the amount of time it takes to load and discharge the largest cargo bay of a containership based on bay size, in order to determine the minimum amount of time it takes to discharge and load a containership. The analysis establishes that bay time is the foundation and critical path of the minimum amount of time a containership must stay at berth and in port. The study notes that, inherently, an increase in containership bay size involves diseconomies of scale in cargo handling operations, at a given level of gantry crane productivity. We find that there are increasing diseconomies of scale for large containerships at berth. The study also establishes that: as beam/bay size increases, the average cargo handling time of two bays increases by an average of 4.5 h at any productivity level. Bay time declines as crane productivity increases up to the crane’s technological constraint. Furthermore, the larger the beam/bay, the larger the marginal benefits when productivity increases. The diseconomies of scale are stable and predictable at every gantry crane productivity level. The study recommends using bay time as the fundamental measure for containership performance at berth and in port, as well as for voyage planning.