Rationalization of Design of Side Structure of Ice-strengthened Tankers
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The industry demand for ice-classed tankers is rapidly increasing as a result of the growing exports of oil from Russia. There has been a trend toward allowing for alternative designs using direct calculation approaches. However, no complete procedure is available. This paper presents a procedure for designing ice-strengthened structures of tankers using direct calculation approaches. It addresses the main issues, including ice load definition, material modeling, structural modeling and acceptance criteria. The paper summarizes a recent joint ABS-SHI project that will become the basis of the future, refined design practice.Keywords:
rationalization
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Abstract Double hull (DH) tankers may be more effective than single hull (SH) tankers in pollution prevention because they have a second barrier, the inner skin, to oil outflow in the event of side damage. The actual effect of DHs calls for quantitative study. This paper presents a comparative study on the side structure resistance to collisions. A DH Aframax tanker and an SH Aframax tanker of similar size were selected for the study. The two vessels were assumed to be struck by a same bulbous bow in different locations and angles. The bow was assumed to be rigid and different non-linear materials and contact models were considered for the struck tankers based on the original designs. The DH tanker was found to be superior to the SH tanker in relation to resistance to side structural damage. Finally, by using the simulation results, the distribution of damage extents for DH tankers is proposed based on the historical damage extents, which are mainly for SH tankers. Key words: Double hull tankersingle hull tankership collisioncollision damage distributionexplicit finite element analysis ACKNOWLEDGEMENT The research presented in this paper was part of the project Pollution Prevention and Control (POP&C) funded by the European Commission within the Sixth Framework Programme (2002–2006). The support is given under the scheme of STREP, Contract No. FP6-PLT-506193. The authors would like to express their gratitude for the support. The European Community and the authors shall not in any way be liable or responsible for the use of any such knowledge, information or data, or of the consequences thereof. The authors would also like to thank Mr Praveen Kumar and Dr Shengming Zhang from Lloyd's Register for kindly providing the geometric model of the DH tanker.
European commission
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This paper deals with the structural details and defines the reasoning of the side, deck, and bottom structure of a tanker ship hull. The hull structure consists 5 longitudinal girders connected mutually by transverse bulkhead stools. The orthotropic composite plates (panels) of double bottom, double side, and deck are supported by the girder system brought about in a specific way, which flows between the peaks. In the composite plate structure, the longitudinal elements are performed without break and they flow continuously throughout the ship.
Bulkhead (partition)
Orthotropic material
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An ad hoc panel on tanker stability was formed in the United States in response to concerns about the potential for lolling incidents dangerous to life, property, and the environment associated with certain double hull tankers. A working group was formed to investigate the influence of design parameters on the intact stability of double hull tankers. This report describes the results of that investigation. The value of tank arrangements utilizing centreline bulkheads in both cargo and ballast spaces was brought forth. The roles of breadth/depth ratio, specific gravity, lightship vertical centre of gravity are documented. An addendum, titled Considerations for Lolling Prevention, was prepared by the full ad hoc Panel on tanker stability.
Ballast
Addendum
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An optimum procedure of hull form design for ice ship going “Double Acting Tanker” is introduced. The procedure orderly consist of hull form design, analyses of performance of a ship in open water and ice condition, maneuverability performance, ice loading effect on propeller and torsional shaft, and economical and environmental societies. In the present study, only two topics are mainly discussed, which are hull form design and then continued with performance analysis in ice condition and open water. For the hull form design the objective parameter are considered as follows; stem and the stern angles, upper and lower fore bulbous angles, entrance angles, and spreading angles. All those angles are investigated for both full loaded and ballast condition in ahead and astern. Special concern is needed for stern part due to existing propeller effect on ice breaking performance. The hull form is firstly investigated without installation of propeller to avoid the effect of pressure from propeller and then continued by installation of propeller to find the optimum propeller design and propeller immersion. Research in ice condition is compromised with open water. The optimum hull form, propeller design and propeller immersion is when the hull form gives better performance for both open water and ice condition. The selected hull form then is compared with existing DAT tanker “Tempera”.
Open water
Stern
Ballast
Drive shaft
Naval architecture
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After a brief introduction of the structural design procedure for double hull tankers, their design features are highlighted in comparison with conventional single hull tankers. Double hull VLCCs including the use of higher tensile steel and the strut arrangement in transverse ring frames is discussed. Finally, the ultimate longitudinal strength of a hull girder under both sagging and hogging conditions is analyzed through a simplified method. Using this result, some considerations are made on the structural reliability of double hull VLCCs.
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Two energy methods for calculating the impacting loads of oil tanker on the fenders are introduced.One is the formula given in the port engineering criteria by Chinese port authority,another is the formula recommended by the international conference committee of ship navigation.A strip method is used in this paper to calculate the six degree of freedom motions of an oil tanker in waves,and the effect of the motions of the oil tanker on the impacting energy is considered.Based on the results,the maximum transverse velocity of the oil tanker is obtained,which is the allowable transverse velocity of the oil tanker under the combined action of wind,tide and the tugboat when the tanker is berthing to an offshore platform.
Port (circuit theory)
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The article describes a new ice-breaking cargo ship hull form which breaks ice from underneath instead of the conventional method which uses the weight of the ship riding up on the ice to break down and through the ice. Disadvantages of the conventional method are given, and advantages of using the new ice-breaking hull, such as an increase in the width of the channel that is broken and the reduced amount of power required to break through the ice.
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