CHINESE JOURNAL OF SHIP RESEARCH， VOL.14， Supp 2，DEC 2019 To cite this article： Peng T， Li S Y， Pei Z Y， et al. Optimization study on transverse structures of deep-water drilling ship ［J/ OL ］ . Chinese Journal of Ship Research， 2019， 14 （Supp 2 ） . http://www.ship-research.com/EN/Y2019/V14/ ISupp 2/59. DOI ： 10.19693/j.issn.1673-3185. 01962 Received： 2019 - 02 - 19 Revised： 2019 - 10 - 20 Authors: Peng Tao， male, born in 1963, engineer. Research interest: ship structure design. E-mail: [email protected]Li Siyuan， male, born in 1992, master degree candidate. Research interest: ship structure and safety. E-mail： [email protected]Pei Zhiyong，male, born in 1974, Ph.D., professor. Research interest: ship structure and safety. E-mail： zhi⁃ [email protected]Wu Weiguo， male, born in 1960, professor, doctorial supervisor. Research interest: structural dynamics. E-mail： [email protected]*Corresponding author：Pei Zhiyong Optimization study on transverse structures of deep-water drilling ship Peng Tao 1 ， Li Siyuan 1 ， Pei Zhiyong *2 ， Wu Weiguo 2 1 Wuhan University of Technology Ship Co.， LTD ， Wuhan 430070， China 2 Green and Smart River-Sea-Going Ship， Cruise Ship and Yacht Research Center， Wuhan University of Technology ， Wuhan 430070， China Abstract：［Objectives ］In order to achieve safe and lightweight structural design，structural optimization is usually performed. ［Methods ］ In the present research，a structural optimization platform is developed based on ISIGHT platform and finite element method. A parameterized model of the objective deep-water drilling ship is generated and the structural optimization on transverse structures is carried out in the proposed optimization platform. The plate thickness and the stiffener size are considered as discrete variable in the optimization platform. ［Results ］ The structural weight of the transverse components of deep-water drilling ship can be reduced by 11% after the optimization.［Conclusions ］This paper shows that the structural weight can be effectively reduced by the optimized design of strong frame structure. Key words： deep-water drilling ship； transverse strength； structural optimization CLC number: U663.2 0 Introduction The transverse strength of a ship's structure repre⁃ sents its ability to resist lateral bending caused by lateral water pressure and transverse waves. General⁃ ly speaking, the total strength of a ship is mainly de⁃ termined by its total longitudinal strength. However, as a deep-water drilling ship has large dimensions in the width direction, it is prone to bearing more se⁃ vere transverse force from water pressure and trans⁃ verse bending moment. The underestimation of trans⁃ verse load in the design phase results in damage to the ship's structure under practical working condi⁃ tions. As such, transverse strength analysis and trans⁃ verse structure optimization are essential for deep-water drilling ships. Ship is a traditional transportation vehicle with complex structural system. To achieve safe and light⁃ weight structural design, structural optimization is common considering theoretical and computational tools [1-2] . The rapid development of artificial intelli⁃ gence is making the optimized design of ship struc⁃ tures faster and more intelligent. There are many kinds of intelligent optimization methods, most of which have the advantages of flexibility and conve⁃ nience. Zhang [3] studied the optimization of the mid⁃ section of a container ship by means of a simulated annealing algorithm. Kitamura et al. [4] used a genetic algorithm as their optimization method to establish a bulk cargo ship structure optimization model on which they then carried out optimization analysis. However, the intelligent algorithm also has certain disadvantages, such as a great amount of calcula⁃ tions and local optimal solutions. But a new type of structural optimization design process has emerged which uses the parametric programming language of 66 downloaded from www.ship-research.com
Transcript
CHINESE JOURNAL OF SHIP RESEARCHVOL14Supp 2DEC 2019To cite this articlePeng TLi S YPei Z Yet al Optimization study on transverse structures of deep-water drilling ship［J
OL］ Chinese Journal of Ship Research201914（Supp 2） httpwwwship-researchcomENY2019V14ISupp 259
DOI1019693jissn1673-3185 01962
Received2019 - 02 - 19 Revised2019 - 10 - 20Authors Peng Taomale born in 1963 engineer Research interest ship structure design E-mail ae8711163com
Li Siyuanmale born in 1992 master degree candidate Research interest ship structure and safety E-mail13307164876163comPei Zhiyongmale born in 1974 PhD professor Research interest ship structure and safety E-mailzhiyong_peiwhuteducnWu Weiguomale born in 1960 professor doctorial supervisor Research interest structural dynamics E-mailmailjt163com
Corresponding authorPei Zhiyong
Optimization study on transversestructures of deep-water drilling ship
Peng Tao1Li Siyuan1Pei Zhiyong2Wu Weiguo2
1 Wuhan University of Technology Ship CoLTD Wuhan 430070China2 Green and Smart River-Sea-Going ShipCruise Ship and Yacht Research CenterWuhan University of
Technology Wuhan 430070ChinaAbstract［Objectives］In order to achieve safe and lightweight structural designstructural optimization is usuallyperformed［Methods］ In the present researcha structural optimization platform is developed based on ISIGHTplatform and finite element method A parameterized model of the objective deep-water drilling ship is generated andthe structural optimization on transverse structures is carried out in the proposed optimization platform The platethickness and the stiffener size are considered as discrete variable in the optimization platform ［Results］ Thestructural weight of the transverse components of deep-water drilling ship can be reduced by 11 after theoptimization［Conclusions］This paper shows that the structural weight can be effectively reduced by the optimizeddesign of strong frame structureKey wordsdeep-water drilling shiptransverse strengthstructural optimizationCLC number U6632
0 Introduction
The transverse strength of a ships structure represents its ability to resist lateral bending caused bylateral water pressure and transverse waves Generally speaking the total strength of a ship is mainly determined by its total longitudinal strength Howeveras a deep-water drilling ship has large dimensionsin the width direction it is prone to bearing more severe transverse force from water pressure and transverse bending moment The underestimation of transverse load in the design phase results in damage tothe ships structure under practical working conditions As such transverse strength analysis and transverse structure optimization are essential fordeep-water drilling ships
Ship is a traditional transportation vehicle withcomplex structural system To achieve safe and light
weight structural design structural optimization iscommon considering theoretical and computationaltools[1-2] The rapid development of artificial intelligence is making the optimized design of ship structures faster and more intelligent There are manykinds of intelligent optimization methods most ofwhich have the advantages of flexibility and convenience Zhang [3] studied the optimization of the midsection of a container ship by means of a simulatedannealing algorithm Kitamura et al[4] used a geneticalgorithm as their optimization method to establish abulk cargo ship structure optimization model onwhich they then carried out optimization analysis
However the intelligent algorithm also has certaindisadvantages such as a great amount of calculations and local optimal solutions But a new type ofstructural optimization design process has emergedwhich uses the parametric programming language of
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finite element software to write the command flowthen combines it with mathematical optimization software to select an optimization algorithm for analysisand solutions until the final optimization plan isachieved[5] On the basis of the APDL language ofANSYS Cheng et al[6] established a parametric model of a complex structure as the research object andoptimized the discrete design variables which weredifficult to handle with considerable success
Based on the above analysis this paper adopts thefinite element method to analyze the strength of thetransverse structure in the midsection of a deep-water drilling ship according to the corresponding specifications A simulated annealing algorithm was employed as the intelligent optimization algorithm to determine the horizontal structural optimization process of the deep-water drilling ship combined withNASTRANPATRAN structural calculation andISIGHT numerical optimization The horizontal structure optimization of a deep-water drilling ship wasthen conducted making the ship greener and moreeconomical on the basis of satisfying the safety andreliability of the structure
The size of the transverse members in the strongframe of a deep-water drilling ship is so large thatthe stress on the frame composed of these components is very serious and has great influence on transverse strength Therefore deep-water drilling shipshave higher requirements for transverse strengthand the strength analysis of transverse componentsmust be considered The typical transverse profile ofa deep-water drilling ship is shown in Fig 111 Calculation model and boundary
conditions
By using MSC NASTRAN and PATRAN finite element software a structural model was establishedwith a transverse range of half the width of the vertical range of the depth of the ship and a longitudinalrange from Fr 174-230 The coordinates are determined in the right-hand coordinate system Let thex y and z directions to be the longitudinal transverse and vertical directions of the ship and the posi
Peng T et al Optimization study on transverse structures of deep-water drilling ship 67
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CHINESE JOURNAL OF SHIP RESEARCHVOL14Supp 2DEC 2019tive directions of x y and z are the bow port and upward direction respectively The components of thesuperstructure main deck intermediate deck transverse bulkheads longitudinal bulkheads deck longitudinal members deck strong beams side framesand vertical girders of longitudinal bulkheads are discreted by coarse meshes with a size of 500times500 Themesh size of the transverse and vertical componentsis equal to the longitudinal spacing distance of themembers the mesh size of the longitudinal membersis the rib spacing distance and the sides are determined according to the dimensions The boundaryconditions of the A side B side central longitudinalsection(CL) are shown in Table 1 where times represents constraint δx δy δz represent constraint ofline displacement respectively θx θy θz reresentconstraint of angular displacement respectively
12 Load cases
According to the CCS Rules for the Constructionof Sea-going Steel Ships (2018) [7] in the transversestrength calculation of the transverse strong frame ofa deep-water drilling ship only the loads on thetransverse components are considered includingmain deck cargo pressure intermediate deck cargopressure ballast tank water pressure and outboardwater pressure The finite element model is shown inFig 2
Fig2 Finite element model（port side）
13 Calculation results
The allowable stress σ should not be greater thanthe value calculated by the following formula (1)
σ σS
N（1）
where σS is yield strength MPa N is safety factorThe detailed parameters in the stress criteria of
transverse strong components are σS =355 MPa N=125 Therefore the allowable synthetic stress oftransverse strength components can be obtainedas σ le284 MPa The maximum value of the normalstress of transverse strong frame components in the finite element model is 228 MPa which is lower thanthe allowable stress value2 Horizontal structural optimiza-
tion of deep-water drilling ship
The flowchart of the horizontal structural optimization process of deep-water drilling ships is shown inFig 3 This paper is mainly divided into three partsthe first part presents the finite element model of thestructure by establishing the correct finite elementmodel of the cross-section of the deep-water drillingship and introducing new design variables to form anew model the second part deals with the strengthcalculation of the ships structure and the third partcovers the optimization calculation by integrating thefirst two parts in ISIGHT then setting the elementsof the various optimization models and combiningthem with its own optimization algorithm
21 Parametric model
Optimization efficiency can be improved by parameterizing the model There are many parameter
LocationAB
CL
Line displacementδx
times
δy
times
δz
times
Angular displacementθx
times
θy
timestimes
θz
timestimestimes
Table 1 Boundary conditions
Fig3 Optimization flow chart of transverse structures ofdeep-water drilling ship
Structure design
Finite element mode 1
Calculation
The design variablesThe constraint
The objective functionOptimization algorithm
Integrate inISIGHT
Newdesignvariable
Optimization analysis
68
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ized modeling methods The PCL language of PATRAN software is adopted in this paper In the process of modeling the operation process of superstructure components and the parametric data of the model are recorded in the command flow Through mastering the command flow the model data in the command flow can be rapidly modified to change themodel The specific steps are as follows
Analyze and classify the variables that need to beoptimized in the cross-section model of the deep-water drilling ship The dimensions of the shell platesand side longitudinal members will not changewhile the design variables of the deck beams and vertical girders of longitudinal bulkheads will change
As the ship has a strong frame for every 4 ribs a4-rib mid-tank model of the deep-water drillingship should be established first and the beams material properties thickness eccentricity and otherproperties should be set The model is then dividedinto elements boundary conditions are set and external loads are applied
The command flow files in the above modeling process are stored The model can be modified by modifying the parameter values of the design variables inthese files and the subsequent optimization processonly requires the modification of the file to realize
the parameterization of the model22 Lateral structural optimization model
The lateral structural optimization of a deep-waterdrilling ship is classified as a dimension optimization problem Due to the large transverse dimensionsof the hull it is the reasonable to set the sizes oftransverse members as design variables and set thetransverse strong framework structure with the lightest weight as the objective function In accordancewith the relevant specifications for transverse sizesection modulus and stress requirements as constraint conditions a lateral structural optimizationmodel for a deep-water drilling ship can be builtThe design variables include the 9 profile designvariables shown in Fig 4 The selection of designvariables is shown in Table 23 Horizontal structural optimiza-
tion of deep-water drilling ship
First the initial values of the design variables of adeep-water drilling ship were set in ISIGHT and optimization was started according to the establishedlateral structural optimization platform The simulated annealing intelligent algorithm was then selected
Peng T et al Optimization study on transverse structures of deep-water drilling ship 69
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CHINESE JOURNAL OF SHIP RESEARCHVOL14Supp 2DEC 2019
for optimization On the premise of satisfying the constraint conditions the minimum weight of the structure was taken as the target until the final optimization plan was achieved After the final optimizationplan was achieved the change information and stressinformation of the optimized design variables were recorded31 Optimization results
The weights of optimized design variable valuesand initial values are collated as shown in Table 3
32 Analysis of optimization results
The optimized scheme was compared with the basic design scheme of the cross-section of thedeep-water drilling ship and the optimization results were sorted out and analyzed It can be seenthat
1) Optimization effect of strong beamsThe optimization of deck beams is shown in
Fig 5 In the optimization scheme the sizes of maindeck beam 1 and main deck beam 2 clearly reducedthat is the optimization effect of the main deckstrong beams was good reaching the lowest value ofthe range
2) Optimization effect of vertical girdersThe optimization of the vertical girders of longitu
dinal bulkheads and strong side ribs is shown inFig 6 The longitudinal bulkhead vertical girderswere reduced in size
3) Optimization effect of structural weight of cabinand components
The optimized value of the objective function was
Table 2 Design variable list Unitmm
Serial number
X1 X2
X3 X4 X5 X6
X7 X8
X9
Design variable
Main deck strong beam
Mid-deck strong beam
Girder for longitudinalbulkhead L10 L24
Strong side frame
Web heightWeb thickness
Wing widthWing thickness
Web heightWeb thickness
Wing widthWing thicknessWing thickness
Web heightWeb thickness
Wing widthWing thickness
Web heightWeb thickness
Wing width
Initial value1 000
1830024
70011
1501212
70011
20020
1 00014
250
Min value90017
25023
60010
1001111
60010
15013
60010
150
Max value1 100
1935025
80012
2001313
80012
25015
80012
250
Interval value501
501
501
5011
501
501
501
50
Table 3 Design variable list
Designvariable
Initial valueOptimal value
Totalweightt
684671
Strong horizontalframe weightt
131118
Maximum stress MPa228226
Fig5 Cross-sectional view of deck beams
1 000900800700600500400300200100
Strong
beams
izemm
MaindeckbeamNo1
Initial valueOptimal value
MaindeckbeamNo2
MiddeckbeamNo1
MiddeckbeamNo2
MiddeckbeamNo3
MiddeckbeamNo4
Fig6 Cross-sectional view of vertical girders
1 000900800700600500400300200100
Girder
sizemm
Initial valueOptimal value
L10 Girder L24 Girder Strong sideframe
70
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compared with that before optimization From the optimization results it can be seen that the weight ofthe optimized cabin decreased from 684 to 671 tonsrepresenting a reduction of 19 The weight of thetransverse strong frame structure decreased from 131to 118 tons representing a reduction of 10 Theweight of the structure was reduced on the premisethat the strength meets the specifications The optimization results are shown in Fig 7
4) Optimization effect of maximum stressThe change in the maximum value of stress is
shown in Fig 8 In the optimized scheme the stresses of the girders and strong beams increased up to114 but still meet the requirements of the specifications The stresses in the cabin decreased
By comparing the initial scheme and optimizedscheme the following conclusions can be drawn
1）A total of 729 schemes were formed The maximum stress value of the optimized finite elementmodel of the ship is 226 MPa which is lower thanthe allowable stress value and meets the transversestrength requirements of the specifications
2） The optimization effects of the main deckstrong beams and the vertical girders of longitudinalbulkheads are better The maximum stress occurs atthe joint of the main deck strong beam and verticalgirder of L10 bulkhead which is 114 higher than
the maximum stress before optimization3）After optimization the cross-sectional area of
the cabin increased and the ballast cabin increasedfrom 2464 to 2688 m2 representing an increase of908 The mud tank between the inner floor andmiddle lower deck increased from 4459 to 46 m2representing an increase of 316 The cabin between the middle lower deck and main deck increased from 3549 to 368 m2 representing an increase of 37
4）The structural weight of the cabin decreasedfrom 684 to 671 tons representing a decrease of19 The weight of the transverse strong framestructure decreased from 131 to 118 tons representing of decrease of 104 Conclusions
In this paper in order to reach the lightweight design goal of a deep-water drilling ship the transverse structure of the ship was optimized and analyzed The discrete design variables were consideredin the optimization process The constraint conditions were considered to be the requirements of member size and the modulus of member section in thecustoms specifications The objective function wasthe lightest weight of the cabin structure
NASTRAN and PATRAN were combined with themathematics optimization platform ISIGHT to complete a horizontal structural optimization process forthe deep-water drilling ship and the basic designscheme of the ship was optimized In the optimization plan compared with the basic design plan of thedeep-water drilling ship on the premise that thestrength meets the specifications the maximumcross-sectional area of the cabin increased by908 the structural weight of the cabin decreasedby 19 the weight of the transverse strong framestructure decreased by 10 (from 131 to 118 tons)and the maximum stress of the transverse strongframe increased by 114References［1］ YANG D S Hull strength and structural design［M］
BeijingNational Defense Industry Press1981 （inChinese）
［2］ ZENG G W Calculation and optimization design ofship structure strength［M］ WuhanHuazhong Institute of Technology Press1985（in Chinese）
［3］ ZHANG L Research on optimum design of containership structures［D］ ShanghaiShanghai Jiaotong University2008（in Chinese）
［4］ KITAMURA MNOBUKAWA HYANG F X Appli
Fig7 Optimum results of section and strong frame weight
700600500400300200100
0
Weigh
tt
Total weight strong frame weight
Initial valueOptimal value
Fig8 Stress optimization diagramInitial plan Optimal plan
260250240230220210200190180
Vonmis
esMPa
Von misesBeamGrider
Peng T et al Optimization study on transverse structures of deep-water drilling ship 71
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CHINESE JOURNAL OF SHIP RESEARCHVOL14Supp 2DEC 2019cation of a genetic algorithm to the optimal structuraldesign of a ships engine room taking dynamic constraints into consideration［J］ Journal of Marine Science and Technology20005131-146
［5］ ZHAO L PZHAN D WCHENG Y Set al Reviewon optimum design methods of ship structures［J］ Chinese Journal of Ship Research20149（4）1-10（inChinese）
［6］ CHENG Y SXIA X LTIAN X Jet al Structural op
timization of a non-axisymmetric cone-cylinder shellstiffened with tapered thick plate and longitudinals［J］Shipbuilding of China201152（3）36-45（in Chi
nese）［7］ China classification society Comprehensive text of
classification code for steel seagoing ships released in2018［J］ Ship standardization engineer2018（4）67（in Chinese）
finite element software to write the command flowthen combines it with mathematical optimization software to select an optimization algorithm for analysisand solutions until the final optimization plan isachieved[5] On the basis of the APDL language ofANSYS Cheng et al[6] established a parametric model of a complex structure as the research object andoptimized the discrete design variables which weredifficult to handle with considerable success
Based on the above analysis this paper adopts thefinite element method to analyze the strength of thetransverse structure in the midsection of a deep-water drilling ship according to the corresponding specifications A simulated annealing algorithm was employed as the intelligent optimization algorithm to determine the horizontal structural optimization process of the deep-water drilling ship combined withNASTRANPATRAN structural calculation andISIGHT numerical optimization The horizontal structure optimization of a deep-water drilling ship wasthen conducted making the ship greener and moreeconomical on the basis of satisfying the safety andreliability of the structure
The size of the transverse members in the strongframe of a deep-water drilling ship is so large thatthe stress on the frame composed of these components is very serious and has great influence on transverse strength Therefore deep-water drilling shipshave higher requirements for transverse strengthand the strength analysis of transverse componentsmust be considered The typical transverse profile ofa deep-water drilling ship is shown in Fig 111 Calculation model and boundary
conditions
By using MSC NASTRAN and PATRAN finite element software a structural model was establishedwith a transverse range of half the width of the vertical range of the depth of the ship and a longitudinalrange from Fr 174-230 The coordinates are determined in the right-hand coordinate system Let thex y and z directions to be the longitudinal transverse and vertical directions of the ship and the posi
Peng T et al Optimization study on transverse structures of deep-water drilling ship 67
downloaded from wwwship-researchcom
CHINESE JOURNAL OF SHIP RESEARCHVOL14Supp 2DEC 2019tive directions of x y and z are the bow port and upward direction respectively The components of thesuperstructure main deck intermediate deck transverse bulkheads longitudinal bulkheads deck longitudinal members deck strong beams side framesand vertical girders of longitudinal bulkheads are discreted by coarse meshes with a size of 500times500 Themesh size of the transverse and vertical componentsis equal to the longitudinal spacing distance of themembers the mesh size of the longitudinal membersis the rib spacing distance and the sides are determined according to the dimensions The boundaryconditions of the A side B side central longitudinalsection(CL) are shown in Table 1 where times represents constraint δx δy δz represent constraint ofline displacement respectively θx θy θz reresentconstraint of angular displacement respectively
12 Load cases
According to the CCS Rules for the Constructionof Sea-going Steel Ships (2018) [7] in the transversestrength calculation of the transverse strong frame ofa deep-water drilling ship only the loads on thetransverse components are considered includingmain deck cargo pressure intermediate deck cargopressure ballast tank water pressure and outboardwater pressure The finite element model is shown inFig 2
Fig2 Finite element model（port side）
13 Calculation results
The allowable stress σ should not be greater thanthe value calculated by the following formula (1)
σ σS
N（1）
where σS is yield strength MPa N is safety factorThe detailed parameters in the stress criteria of
transverse strong components are σS =355 MPa N=125 Therefore the allowable synthetic stress oftransverse strength components can be obtainedas σ le284 MPa The maximum value of the normalstress of transverse strong frame components in the finite element model is 228 MPa which is lower thanthe allowable stress value2 Horizontal structural optimiza-
tion of deep-water drilling ship
The flowchart of the horizontal structural optimization process of deep-water drilling ships is shown inFig 3 This paper is mainly divided into three partsthe first part presents the finite element model of thestructure by establishing the correct finite elementmodel of the cross-section of the deep-water drillingship and introducing new design variables to form anew model the second part deals with the strengthcalculation of the ships structure and the third partcovers the optimization calculation by integrating thefirst two parts in ISIGHT then setting the elementsof the various optimization models and combiningthem with its own optimization algorithm
21 Parametric model
Optimization efficiency can be improved by parameterizing the model There are many parameter
LocationAB
CL
Line displacementδx
times
δy
times
δz
times
Angular displacementθx
times
θy
timestimes
θz
timestimestimes
Table 1 Boundary conditions
Fig3 Optimization flow chart of transverse structures ofdeep-water drilling ship
Structure design
Finite element mode 1
Calculation
The design variablesThe constraint
The objective functionOptimization algorithm
Integrate inISIGHT
Newdesignvariable
Optimization analysis
68
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ized modeling methods The PCL language of PATRAN software is adopted in this paper In the process of modeling the operation process of superstructure components and the parametric data of the model are recorded in the command flow Through mastering the command flow the model data in the command flow can be rapidly modified to change themodel The specific steps are as follows
Analyze and classify the variables that need to beoptimized in the cross-section model of the deep-water drilling ship The dimensions of the shell platesand side longitudinal members will not changewhile the design variables of the deck beams and vertical girders of longitudinal bulkheads will change
As the ship has a strong frame for every 4 ribs a4-rib mid-tank model of the deep-water drillingship should be established first and the beams material properties thickness eccentricity and otherproperties should be set The model is then dividedinto elements boundary conditions are set and external loads are applied
The command flow files in the above modeling process are stored The model can be modified by modifying the parameter values of the design variables inthese files and the subsequent optimization processonly requires the modification of the file to realize
the parameterization of the model22 Lateral structural optimization model
The lateral structural optimization of a deep-waterdrilling ship is classified as a dimension optimization problem Due to the large transverse dimensionsof the hull it is the reasonable to set the sizes oftransverse members as design variables and set thetransverse strong framework structure with the lightest weight as the objective function In accordancewith the relevant specifications for transverse sizesection modulus and stress requirements as constraint conditions a lateral structural optimizationmodel for a deep-water drilling ship can be builtThe design variables include the 9 profile designvariables shown in Fig 4 The selection of designvariables is shown in Table 23 Horizontal structural optimiza-
tion of deep-water drilling ship
First the initial values of the design variables of adeep-water drilling ship were set in ISIGHT and optimization was started according to the establishedlateral structural optimization platform The simulated annealing intelligent algorithm was then selected
Peng T et al Optimization study on transverse structures of deep-water drilling ship 69
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CHINESE JOURNAL OF SHIP RESEARCHVOL14Supp 2DEC 2019
for optimization On the premise of satisfying the constraint conditions the minimum weight of the structure was taken as the target until the final optimization plan was achieved After the final optimizationplan was achieved the change information and stressinformation of the optimized design variables were recorded31 Optimization results
The weights of optimized design variable valuesand initial values are collated as shown in Table 3
32 Analysis of optimization results
The optimized scheme was compared with the basic design scheme of the cross-section of thedeep-water drilling ship and the optimization results were sorted out and analyzed It can be seenthat
1) Optimization effect of strong beamsThe optimization of deck beams is shown in
Fig 5 In the optimization scheme the sizes of maindeck beam 1 and main deck beam 2 clearly reducedthat is the optimization effect of the main deckstrong beams was good reaching the lowest value ofthe range
2) Optimization effect of vertical girdersThe optimization of the vertical girders of longitu
dinal bulkheads and strong side ribs is shown inFig 6 The longitudinal bulkhead vertical girderswere reduced in size
3) Optimization effect of structural weight of cabinand components
The optimized value of the objective function was
Table 2 Design variable list Unitmm
Serial number
X1 X2
X3 X4 X5 X6
X7 X8
X9
Design variable
Main deck strong beam
Mid-deck strong beam
Girder for longitudinalbulkhead L10 L24
Strong side frame
Web heightWeb thickness
Wing widthWing thickness
Web heightWeb thickness
Wing widthWing thicknessWing thickness
Web heightWeb thickness
Wing widthWing thickness
Web heightWeb thickness
Wing width
Initial value1 000
1830024
70011
1501212
70011
20020
1 00014
250
Min value90017
25023
60010
1001111
60010
15013
60010
150
Max value1 100
1935025
80012
2001313
80012
25015
80012
250
Interval value501
501
501
5011
501
501
501
50
Table 3 Design variable list
Designvariable
Initial valueOptimal value
Totalweightt
684671
Strong horizontalframe weightt
131118
Maximum stress MPa228226
Fig5 Cross-sectional view of deck beams
1 000900800700600500400300200100
Strong
beams
izemm
MaindeckbeamNo1
Initial valueOptimal value
MaindeckbeamNo2
MiddeckbeamNo1
MiddeckbeamNo2
MiddeckbeamNo3
MiddeckbeamNo4
Fig6 Cross-sectional view of vertical girders
1 000900800700600500400300200100
Girder
sizemm
Initial valueOptimal value
L10 Girder L24 Girder Strong sideframe
70
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compared with that before optimization From the optimization results it can be seen that the weight ofthe optimized cabin decreased from 684 to 671 tonsrepresenting a reduction of 19 The weight of thetransverse strong frame structure decreased from 131to 118 tons representing a reduction of 10 Theweight of the structure was reduced on the premisethat the strength meets the specifications The optimization results are shown in Fig 7
4) Optimization effect of maximum stressThe change in the maximum value of stress is
shown in Fig 8 In the optimized scheme the stresses of the girders and strong beams increased up to114 but still meet the requirements of the specifications The stresses in the cabin decreased
By comparing the initial scheme and optimizedscheme the following conclusions can be drawn
1）A total of 729 schemes were formed The maximum stress value of the optimized finite elementmodel of the ship is 226 MPa which is lower thanthe allowable stress value and meets the transversestrength requirements of the specifications
2） The optimization effects of the main deckstrong beams and the vertical girders of longitudinalbulkheads are better The maximum stress occurs atthe joint of the main deck strong beam and verticalgirder of L10 bulkhead which is 114 higher than
the maximum stress before optimization3）After optimization the cross-sectional area of
the cabin increased and the ballast cabin increasedfrom 2464 to 2688 m2 representing an increase of908 The mud tank between the inner floor andmiddle lower deck increased from 4459 to 46 m2representing an increase of 316 The cabin between the middle lower deck and main deck increased from 3549 to 368 m2 representing an increase of 37
4）The structural weight of the cabin decreasedfrom 684 to 671 tons representing a decrease of19 The weight of the transverse strong framestructure decreased from 131 to 118 tons representing of decrease of 104 Conclusions
In this paper in order to reach the lightweight design goal of a deep-water drilling ship the transverse structure of the ship was optimized and analyzed The discrete design variables were consideredin the optimization process The constraint conditions were considered to be the requirements of member size and the modulus of member section in thecustoms specifications The objective function wasthe lightest weight of the cabin structure
NASTRAN and PATRAN were combined with themathematics optimization platform ISIGHT to complete a horizontal structural optimization process forthe deep-water drilling ship and the basic designscheme of the ship was optimized In the optimization plan compared with the basic design plan of thedeep-water drilling ship on the premise that thestrength meets the specifications the maximumcross-sectional area of the cabin increased by908 the structural weight of the cabin decreasedby 19 the weight of the transverse strong framestructure decreased by 10 (from 131 to 118 tons)and the maximum stress of the transverse strongframe increased by 114References［1］ YANG D S Hull strength and structural design［M］
BeijingNational Defense Industry Press1981 （inChinese）
［2］ ZENG G W Calculation and optimization design ofship structure strength［M］ WuhanHuazhong Institute of Technology Press1985（in Chinese）
［3］ ZHANG L Research on optimum design of containership structures［D］ ShanghaiShanghai Jiaotong University2008（in Chinese）
［4］ KITAMURA MNOBUKAWA HYANG F X Appli
Fig7 Optimum results of section and strong frame weight
700600500400300200100
0
Weigh
tt
Total weight strong frame weight
Initial valueOptimal value
Fig8 Stress optimization diagramInitial plan Optimal plan
260250240230220210200190180
Vonmis
esMPa
Von misesBeamGrider
Peng T et al Optimization study on transverse structures of deep-water drilling ship 71
downloaded from wwwship-researchcom
CHINESE JOURNAL OF SHIP RESEARCHVOL14Supp 2DEC 2019cation of a genetic algorithm to the optimal structuraldesign of a ships engine room taking dynamic constraints into consideration［J］ Journal of Marine Science and Technology20005131-146
［5］ ZHAO L PZHAN D WCHENG Y Set al Reviewon optimum design methods of ship structures［J］ Chinese Journal of Ship Research20149（4）1-10（inChinese）
［6］ CHENG Y SXIA X LTIAN X Jet al Structural op
timization of a non-axisymmetric cone-cylinder shellstiffened with tapered thick plate and longitudinals［J］Shipbuilding of China201152（3）36-45（in Chi
nese）［7］ China classification society Comprehensive text of
classification code for steel seagoing ships released in2018［J］ Ship standardization engineer2018（4）67（in Chinese）
CHINESE JOURNAL OF SHIP RESEARCHVOL14Supp 2DEC 2019tive directions of x y and z are the bow port and upward direction respectively The components of thesuperstructure main deck intermediate deck transverse bulkheads longitudinal bulkheads deck longitudinal members deck strong beams side framesand vertical girders of longitudinal bulkheads are discreted by coarse meshes with a size of 500times500 Themesh size of the transverse and vertical componentsis equal to the longitudinal spacing distance of themembers the mesh size of the longitudinal membersis the rib spacing distance and the sides are determined according to the dimensions The boundaryconditions of the A side B side central longitudinalsection(CL) are shown in Table 1 where times represents constraint δx δy δz represent constraint ofline displacement respectively θx θy θz reresentconstraint of angular displacement respectively
12 Load cases
According to the CCS Rules for the Constructionof Sea-going Steel Ships (2018) [7] in the transversestrength calculation of the transverse strong frame ofa deep-water drilling ship only the loads on thetransverse components are considered includingmain deck cargo pressure intermediate deck cargopressure ballast tank water pressure and outboardwater pressure The finite element model is shown inFig 2
Fig2 Finite element model（port side）
13 Calculation results
The allowable stress σ should not be greater thanthe value calculated by the following formula (1)
σ σS
N（1）
where σS is yield strength MPa N is safety factorThe detailed parameters in the stress criteria of
transverse strong components are σS =355 MPa N=125 Therefore the allowable synthetic stress oftransverse strength components can be obtainedas σ le284 MPa The maximum value of the normalstress of transverse strong frame components in the finite element model is 228 MPa which is lower thanthe allowable stress value2 Horizontal structural optimiza-
tion of deep-water drilling ship
The flowchart of the horizontal structural optimization process of deep-water drilling ships is shown inFig 3 This paper is mainly divided into three partsthe first part presents the finite element model of thestructure by establishing the correct finite elementmodel of the cross-section of the deep-water drillingship and introducing new design variables to form anew model the second part deals with the strengthcalculation of the ships structure and the third partcovers the optimization calculation by integrating thefirst two parts in ISIGHT then setting the elementsof the various optimization models and combiningthem with its own optimization algorithm
21 Parametric model
Optimization efficiency can be improved by parameterizing the model There are many parameter
LocationAB
CL
Line displacementδx
times
δy
times
δz
times
Angular displacementθx
times
θy
timestimes
θz
timestimestimes
Table 1 Boundary conditions
Fig3 Optimization flow chart of transverse structures ofdeep-water drilling ship
Structure design
Finite element mode 1
Calculation
The design variablesThe constraint
The objective functionOptimization algorithm
Integrate inISIGHT
Newdesignvariable
Optimization analysis
68
downloaded from wwwship-researchcom
ized modeling methods The PCL language of PATRAN software is adopted in this paper In the process of modeling the operation process of superstructure components and the parametric data of the model are recorded in the command flow Through mastering the command flow the model data in the command flow can be rapidly modified to change themodel The specific steps are as follows
Analyze and classify the variables that need to beoptimized in the cross-section model of the deep-water drilling ship The dimensions of the shell platesand side longitudinal members will not changewhile the design variables of the deck beams and vertical girders of longitudinal bulkheads will change
As the ship has a strong frame for every 4 ribs a4-rib mid-tank model of the deep-water drillingship should be established first and the beams material properties thickness eccentricity and otherproperties should be set The model is then dividedinto elements boundary conditions are set and external loads are applied
The command flow files in the above modeling process are stored The model can be modified by modifying the parameter values of the design variables inthese files and the subsequent optimization processonly requires the modification of the file to realize
the parameterization of the model22 Lateral structural optimization model
The lateral structural optimization of a deep-waterdrilling ship is classified as a dimension optimization problem Due to the large transverse dimensionsof the hull it is the reasonable to set the sizes oftransverse members as design variables and set thetransverse strong framework structure with the lightest weight as the objective function In accordancewith the relevant specifications for transverse sizesection modulus and stress requirements as constraint conditions a lateral structural optimizationmodel for a deep-water drilling ship can be builtThe design variables include the 9 profile designvariables shown in Fig 4 The selection of designvariables is shown in Table 23 Horizontal structural optimiza-
tion of deep-water drilling ship
First the initial values of the design variables of adeep-water drilling ship were set in ISIGHT and optimization was started according to the establishedlateral structural optimization platform The simulated annealing intelligent algorithm was then selected
Peng T et al Optimization study on transverse structures of deep-water drilling ship 69
downloaded from wwwship-researchcom
CHINESE JOURNAL OF SHIP RESEARCHVOL14Supp 2DEC 2019
for optimization On the premise of satisfying the constraint conditions the minimum weight of the structure was taken as the target until the final optimization plan was achieved After the final optimizationplan was achieved the change information and stressinformation of the optimized design variables were recorded31 Optimization results
The weights of optimized design variable valuesand initial values are collated as shown in Table 3
32 Analysis of optimization results
The optimized scheme was compared with the basic design scheme of the cross-section of thedeep-water drilling ship and the optimization results were sorted out and analyzed It can be seenthat
1) Optimization effect of strong beamsThe optimization of deck beams is shown in
Fig 5 In the optimization scheme the sizes of maindeck beam 1 and main deck beam 2 clearly reducedthat is the optimization effect of the main deckstrong beams was good reaching the lowest value ofthe range
2) Optimization effect of vertical girdersThe optimization of the vertical girders of longitu
dinal bulkheads and strong side ribs is shown inFig 6 The longitudinal bulkhead vertical girderswere reduced in size
3) Optimization effect of structural weight of cabinand components
The optimized value of the objective function was
Table 2 Design variable list Unitmm
Serial number
X1 X2
X3 X4 X5 X6
X7 X8
X9
Design variable
Main deck strong beam
Mid-deck strong beam
Girder for longitudinalbulkhead L10 L24
Strong side frame
Web heightWeb thickness
Wing widthWing thickness
Web heightWeb thickness
Wing widthWing thicknessWing thickness
Web heightWeb thickness
Wing widthWing thickness
Web heightWeb thickness
Wing width
Initial value1 000
1830024
70011
1501212
70011
20020
1 00014
250
Min value90017
25023
60010
1001111
60010
15013
60010
150
Max value1 100
1935025
80012
2001313
80012
25015
80012
250
Interval value501
501
501
5011
501
501
501
50
Table 3 Design variable list
Designvariable
Initial valueOptimal value
Totalweightt
684671
Strong horizontalframe weightt
131118
Maximum stress MPa228226
Fig5 Cross-sectional view of deck beams
1 000900800700600500400300200100
Strong
beams
izemm
MaindeckbeamNo1
Initial valueOptimal value
MaindeckbeamNo2
MiddeckbeamNo1
MiddeckbeamNo2
MiddeckbeamNo3
MiddeckbeamNo4
Fig6 Cross-sectional view of vertical girders
1 000900800700600500400300200100
Girder
sizemm
Initial valueOptimal value
L10 Girder L24 Girder Strong sideframe
70
downloaded from wwwship-researchcom
compared with that before optimization From the optimization results it can be seen that the weight ofthe optimized cabin decreased from 684 to 671 tonsrepresenting a reduction of 19 The weight of thetransverse strong frame structure decreased from 131to 118 tons representing a reduction of 10 Theweight of the structure was reduced on the premisethat the strength meets the specifications The optimization results are shown in Fig 7
4) Optimization effect of maximum stressThe change in the maximum value of stress is
shown in Fig 8 In the optimized scheme the stresses of the girders and strong beams increased up to114 but still meet the requirements of the specifications The stresses in the cabin decreased
By comparing the initial scheme and optimizedscheme the following conclusions can be drawn
1）A total of 729 schemes were formed The maximum stress value of the optimized finite elementmodel of the ship is 226 MPa which is lower thanthe allowable stress value and meets the transversestrength requirements of the specifications
2） The optimization effects of the main deckstrong beams and the vertical girders of longitudinalbulkheads are better The maximum stress occurs atthe joint of the main deck strong beam and verticalgirder of L10 bulkhead which is 114 higher than
the maximum stress before optimization3）After optimization the cross-sectional area of
the cabin increased and the ballast cabin increasedfrom 2464 to 2688 m2 representing an increase of908 The mud tank between the inner floor andmiddle lower deck increased from 4459 to 46 m2representing an increase of 316 The cabin between the middle lower deck and main deck increased from 3549 to 368 m2 representing an increase of 37
4）The structural weight of the cabin decreasedfrom 684 to 671 tons representing a decrease of19 The weight of the transverse strong framestructure decreased from 131 to 118 tons representing of decrease of 104 Conclusions
In this paper in order to reach the lightweight design goal of a deep-water drilling ship the transverse structure of the ship was optimized and analyzed The discrete design variables were consideredin the optimization process The constraint conditions were considered to be the requirements of member size and the modulus of member section in thecustoms specifications The objective function wasthe lightest weight of the cabin structure
NASTRAN and PATRAN were combined with themathematics optimization platform ISIGHT to complete a horizontal structural optimization process forthe deep-water drilling ship and the basic designscheme of the ship was optimized In the optimization plan compared with the basic design plan of thedeep-water drilling ship on the premise that thestrength meets the specifications the maximumcross-sectional area of the cabin increased by908 the structural weight of the cabin decreasedby 19 the weight of the transverse strong framestructure decreased by 10 (from 131 to 118 tons)and the maximum stress of the transverse strongframe increased by 114References［1］ YANG D S Hull strength and structural design［M］
BeijingNational Defense Industry Press1981 （inChinese）
［2］ ZENG G W Calculation and optimization design ofship structure strength［M］ WuhanHuazhong Institute of Technology Press1985（in Chinese）
［3］ ZHANG L Research on optimum design of containership structures［D］ ShanghaiShanghai Jiaotong University2008（in Chinese）
［4］ KITAMURA MNOBUKAWA HYANG F X Appli
Fig7 Optimum results of section and strong frame weight
700600500400300200100
0
Weigh
tt
Total weight strong frame weight
Initial valueOptimal value
Fig8 Stress optimization diagramInitial plan Optimal plan
260250240230220210200190180
Vonmis
esMPa
Von misesBeamGrider
Peng T et al Optimization study on transverse structures of deep-water drilling ship 71
downloaded from wwwship-researchcom
CHINESE JOURNAL OF SHIP RESEARCHVOL14Supp 2DEC 2019cation of a genetic algorithm to the optimal structuraldesign of a ships engine room taking dynamic constraints into consideration［J］ Journal of Marine Science and Technology20005131-146
［5］ ZHAO L PZHAN D WCHENG Y Set al Reviewon optimum design methods of ship structures［J］ Chinese Journal of Ship Research20149（4）1-10（inChinese）
［6］ CHENG Y SXIA X LTIAN X Jet al Structural op
timization of a non-axisymmetric cone-cylinder shellstiffened with tapered thick plate and longitudinals［J］Shipbuilding of China201152（3）36-45（in Chi
nese）［7］ China classification society Comprehensive text of
classification code for steel seagoing ships released in2018［J］ Ship standardization engineer2018（4）67（in Chinese）
ized modeling methods The PCL language of PATRAN software is adopted in this paper In the process of modeling the operation process of superstructure components and the parametric data of the model are recorded in the command flow Through mastering the command flow the model data in the command flow can be rapidly modified to change themodel The specific steps are as follows
Analyze and classify the variables that need to beoptimized in the cross-section model of the deep-water drilling ship The dimensions of the shell platesand side longitudinal members will not changewhile the design variables of the deck beams and vertical girders of longitudinal bulkheads will change
As the ship has a strong frame for every 4 ribs a4-rib mid-tank model of the deep-water drillingship should be established first and the beams material properties thickness eccentricity and otherproperties should be set The model is then dividedinto elements boundary conditions are set and external loads are applied
The command flow files in the above modeling process are stored The model can be modified by modifying the parameter values of the design variables inthese files and the subsequent optimization processonly requires the modification of the file to realize
the parameterization of the model22 Lateral structural optimization model
The lateral structural optimization of a deep-waterdrilling ship is classified as a dimension optimization problem Due to the large transverse dimensionsof the hull it is the reasonable to set the sizes oftransverse members as design variables and set thetransverse strong framework structure with the lightest weight as the objective function In accordancewith the relevant specifications for transverse sizesection modulus and stress requirements as constraint conditions a lateral structural optimizationmodel for a deep-water drilling ship can be builtThe design variables include the 9 profile designvariables shown in Fig 4 The selection of designvariables is shown in Table 23 Horizontal structural optimiza-
tion of deep-water drilling ship
First the initial values of the design variables of adeep-water drilling ship were set in ISIGHT and optimization was started according to the establishedlateral structural optimization platform The simulated annealing intelligent algorithm was then selected
Peng T et al Optimization study on transverse structures of deep-water drilling ship 69
downloaded from wwwship-researchcom
CHINESE JOURNAL OF SHIP RESEARCHVOL14Supp 2DEC 2019
for optimization On the premise of satisfying the constraint conditions the minimum weight of the structure was taken as the target until the final optimization plan was achieved After the final optimizationplan was achieved the change information and stressinformation of the optimized design variables were recorded31 Optimization results
The weights of optimized design variable valuesand initial values are collated as shown in Table 3
32 Analysis of optimization results
The optimized scheme was compared with the basic design scheme of the cross-section of thedeep-water drilling ship and the optimization results were sorted out and analyzed It can be seenthat
1) Optimization effect of strong beamsThe optimization of deck beams is shown in
Fig 5 In the optimization scheme the sizes of maindeck beam 1 and main deck beam 2 clearly reducedthat is the optimization effect of the main deckstrong beams was good reaching the lowest value ofthe range
2) Optimization effect of vertical girdersThe optimization of the vertical girders of longitu
dinal bulkheads and strong side ribs is shown inFig 6 The longitudinal bulkhead vertical girderswere reduced in size
3) Optimization effect of structural weight of cabinand components
The optimized value of the objective function was
Table 2 Design variable list Unitmm
Serial number
X1 X2
X3 X4 X5 X6
X7 X8
X9
Design variable
Main deck strong beam
Mid-deck strong beam
Girder for longitudinalbulkhead L10 L24
Strong side frame
Web heightWeb thickness
Wing widthWing thickness
Web heightWeb thickness
Wing widthWing thicknessWing thickness
Web heightWeb thickness
Wing widthWing thickness
Web heightWeb thickness
Wing width
Initial value1 000
1830024
70011
1501212
70011
20020
1 00014
250
Min value90017
25023
60010
1001111
60010
15013
60010
150
Max value1 100
1935025
80012
2001313
80012
25015
80012
250
Interval value501
501
501
5011
501
501
501
50
Table 3 Design variable list
Designvariable
Initial valueOptimal value
Totalweightt
684671
Strong horizontalframe weightt
131118
Maximum stress MPa228226
Fig5 Cross-sectional view of deck beams
1 000900800700600500400300200100
Strong
beams
izemm
MaindeckbeamNo1
Initial valueOptimal value
MaindeckbeamNo2
MiddeckbeamNo1
MiddeckbeamNo2
MiddeckbeamNo3
MiddeckbeamNo4
Fig6 Cross-sectional view of vertical girders
1 000900800700600500400300200100
Girder
sizemm
Initial valueOptimal value
L10 Girder L24 Girder Strong sideframe
70
downloaded from wwwship-researchcom
compared with that before optimization From the optimization results it can be seen that the weight ofthe optimized cabin decreased from 684 to 671 tonsrepresenting a reduction of 19 The weight of thetransverse strong frame structure decreased from 131to 118 tons representing a reduction of 10 Theweight of the structure was reduced on the premisethat the strength meets the specifications The optimization results are shown in Fig 7
4) Optimization effect of maximum stressThe change in the maximum value of stress is
shown in Fig 8 In the optimized scheme the stresses of the girders and strong beams increased up to114 but still meet the requirements of the specifications The stresses in the cabin decreased
By comparing the initial scheme and optimizedscheme the following conclusions can be drawn
1）A total of 729 schemes were formed The maximum stress value of the optimized finite elementmodel of the ship is 226 MPa which is lower thanthe allowable stress value and meets the transversestrength requirements of the specifications
2） The optimization effects of the main deckstrong beams and the vertical girders of longitudinalbulkheads are better The maximum stress occurs atthe joint of the main deck strong beam and verticalgirder of L10 bulkhead which is 114 higher than
the maximum stress before optimization3）After optimization the cross-sectional area of
the cabin increased and the ballast cabin increasedfrom 2464 to 2688 m2 representing an increase of908 The mud tank between the inner floor andmiddle lower deck increased from 4459 to 46 m2representing an increase of 316 The cabin between the middle lower deck and main deck increased from 3549 to 368 m2 representing an increase of 37
4）The structural weight of the cabin decreasedfrom 684 to 671 tons representing a decrease of19 The weight of the transverse strong framestructure decreased from 131 to 118 tons representing of decrease of 104 Conclusions
In this paper in order to reach the lightweight design goal of a deep-water drilling ship the transverse structure of the ship was optimized and analyzed The discrete design variables were consideredin the optimization process The constraint conditions were considered to be the requirements of member size and the modulus of member section in thecustoms specifications The objective function wasthe lightest weight of the cabin structure
NASTRAN and PATRAN were combined with themathematics optimization platform ISIGHT to complete a horizontal structural optimization process forthe deep-water drilling ship and the basic designscheme of the ship was optimized In the optimization plan compared with the basic design plan of thedeep-water drilling ship on the premise that thestrength meets the specifications the maximumcross-sectional area of the cabin increased by908 the structural weight of the cabin decreasedby 19 the weight of the transverse strong framestructure decreased by 10 (from 131 to 118 tons)and the maximum stress of the transverse strongframe increased by 114References［1］ YANG D S Hull strength and structural design［M］
BeijingNational Defense Industry Press1981 （inChinese）
［2］ ZENG G W Calculation and optimization design ofship structure strength［M］ WuhanHuazhong Institute of Technology Press1985（in Chinese）
［3］ ZHANG L Research on optimum design of containership structures［D］ ShanghaiShanghai Jiaotong University2008（in Chinese）
［4］ KITAMURA MNOBUKAWA HYANG F X Appli
Fig7 Optimum results of section and strong frame weight
700600500400300200100
0
Weigh
tt
Total weight strong frame weight
Initial valueOptimal value
Fig8 Stress optimization diagramInitial plan Optimal plan
260250240230220210200190180
Vonmis
esMPa
Von misesBeamGrider
Peng T et al Optimization study on transverse structures of deep-water drilling ship 71
downloaded from wwwship-researchcom
CHINESE JOURNAL OF SHIP RESEARCHVOL14Supp 2DEC 2019cation of a genetic algorithm to the optimal structuraldesign of a ships engine room taking dynamic constraints into consideration［J］ Journal of Marine Science and Technology20005131-146
［5］ ZHAO L PZHAN D WCHENG Y Set al Reviewon optimum design methods of ship structures［J］ Chinese Journal of Ship Research20149（4）1-10（inChinese）
［6］ CHENG Y SXIA X LTIAN X Jet al Structural op
timization of a non-axisymmetric cone-cylinder shellstiffened with tapered thick plate and longitudinals［J］Shipbuilding of China201152（3）36-45（in Chi
nese）［7］ China classification society Comprehensive text of
classification code for steel seagoing ships released in2018［J］ Ship standardization engineer2018（4）67（in Chinese）
CHINESE JOURNAL OF SHIP RESEARCHVOL14Supp 2DEC 2019
for optimization On the premise of satisfying the constraint conditions the minimum weight of the structure was taken as the target until the final optimization plan was achieved After the final optimizationplan was achieved the change information and stressinformation of the optimized design variables were recorded31 Optimization results
The weights of optimized design variable valuesand initial values are collated as shown in Table 3
32 Analysis of optimization results
The optimized scheme was compared with the basic design scheme of the cross-section of thedeep-water drilling ship and the optimization results were sorted out and analyzed It can be seenthat
1) Optimization effect of strong beamsThe optimization of deck beams is shown in
Fig 5 In the optimization scheme the sizes of maindeck beam 1 and main deck beam 2 clearly reducedthat is the optimization effect of the main deckstrong beams was good reaching the lowest value ofthe range
2) Optimization effect of vertical girdersThe optimization of the vertical girders of longitu
dinal bulkheads and strong side ribs is shown inFig 6 The longitudinal bulkhead vertical girderswere reduced in size
3) Optimization effect of structural weight of cabinand components
The optimized value of the objective function was
Table 2 Design variable list Unitmm
Serial number
X1 X2
X3 X4 X5 X6
X7 X8
X9
Design variable
Main deck strong beam
Mid-deck strong beam
Girder for longitudinalbulkhead L10 L24
Strong side frame
Web heightWeb thickness
Wing widthWing thickness
Web heightWeb thickness
Wing widthWing thicknessWing thickness
Web heightWeb thickness
Wing widthWing thickness
Web heightWeb thickness
Wing width
Initial value1 000
1830024
70011
1501212
70011
20020
1 00014
250
Min value90017
25023
60010
1001111
60010
15013
60010
150
Max value1 100
1935025
80012
2001313
80012
25015
80012
250
Interval value501
501
501
5011
501
501
501
50
Table 3 Design variable list
Designvariable
Initial valueOptimal value
Totalweightt
684671
Strong horizontalframe weightt
131118
Maximum stress MPa228226
Fig5 Cross-sectional view of deck beams
1 000900800700600500400300200100
Strong
beams
izemm
MaindeckbeamNo1
Initial valueOptimal value
MaindeckbeamNo2
MiddeckbeamNo1
MiddeckbeamNo2
MiddeckbeamNo3
MiddeckbeamNo4
Fig6 Cross-sectional view of vertical girders
1 000900800700600500400300200100
Girder
sizemm
Initial valueOptimal value
L10 Girder L24 Girder Strong sideframe
70
downloaded from wwwship-researchcom
compared with that before optimization From the optimization results it can be seen that the weight ofthe optimized cabin decreased from 684 to 671 tonsrepresenting a reduction of 19 The weight of thetransverse strong frame structure decreased from 131to 118 tons representing a reduction of 10 Theweight of the structure was reduced on the premisethat the strength meets the specifications The optimization results are shown in Fig 7
4) Optimization effect of maximum stressThe change in the maximum value of stress is
shown in Fig 8 In the optimized scheme the stresses of the girders and strong beams increased up to114 but still meet the requirements of the specifications The stresses in the cabin decreased
By comparing the initial scheme and optimizedscheme the following conclusions can be drawn
1）A total of 729 schemes were formed The maximum stress value of the optimized finite elementmodel of the ship is 226 MPa which is lower thanthe allowable stress value and meets the transversestrength requirements of the specifications
2） The optimization effects of the main deckstrong beams and the vertical girders of longitudinalbulkheads are better The maximum stress occurs atthe joint of the main deck strong beam and verticalgirder of L10 bulkhead which is 114 higher than
the maximum stress before optimization3）After optimization the cross-sectional area of
the cabin increased and the ballast cabin increasedfrom 2464 to 2688 m2 representing an increase of908 The mud tank between the inner floor andmiddle lower deck increased from 4459 to 46 m2representing an increase of 316 The cabin between the middle lower deck and main deck increased from 3549 to 368 m2 representing an increase of 37
4）The structural weight of the cabin decreasedfrom 684 to 671 tons representing a decrease of19 The weight of the transverse strong framestructure decreased from 131 to 118 tons representing of decrease of 104 Conclusions
In this paper in order to reach the lightweight design goal of a deep-water drilling ship the transverse structure of the ship was optimized and analyzed The discrete design variables were consideredin the optimization process The constraint conditions were considered to be the requirements of member size and the modulus of member section in thecustoms specifications The objective function wasthe lightest weight of the cabin structure
NASTRAN and PATRAN were combined with themathematics optimization platform ISIGHT to complete a horizontal structural optimization process forthe deep-water drilling ship and the basic designscheme of the ship was optimized In the optimization plan compared with the basic design plan of thedeep-water drilling ship on the premise that thestrength meets the specifications the maximumcross-sectional area of the cabin increased by908 the structural weight of the cabin decreasedby 19 the weight of the transverse strong framestructure decreased by 10 (from 131 to 118 tons)and the maximum stress of the transverse strongframe increased by 114References［1］ YANG D S Hull strength and structural design［M］
BeijingNational Defense Industry Press1981 （inChinese）
［2］ ZENG G W Calculation and optimization design ofship structure strength［M］ WuhanHuazhong Institute of Technology Press1985（in Chinese）
［3］ ZHANG L Research on optimum design of containership structures［D］ ShanghaiShanghai Jiaotong University2008（in Chinese）
［4］ KITAMURA MNOBUKAWA HYANG F X Appli
Fig7 Optimum results of section and strong frame weight
700600500400300200100
0
Weigh
tt
Total weight strong frame weight
Initial valueOptimal value
Fig8 Stress optimization diagramInitial plan Optimal plan
260250240230220210200190180
Vonmis
esMPa
Von misesBeamGrider
Peng T et al Optimization study on transverse structures of deep-water drilling ship 71
downloaded from wwwship-researchcom
CHINESE JOURNAL OF SHIP RESEARCHVOL14Supp 2DEC 2019cation of a genetic algorithm to the optimal structuraldesign of a ships engine room taking dynamic constraints into consideration［J］ Journal of Marine Science and Technology20005131-146
［5］ ZHAO L PZHAN D WCHENG Y Set al Reviewon optimum design methods of ship structures［J］ Chinese Journal of Ship Research20149（4）1-10（inChinese）
［6］ CHENG Y SXIA X LTIAN X Jet al Structural op
timization of a non-axisymmetric cone-cylinder shellstiffened with tapered thick plate and longitudinals［J］Shipbuilding of China201152（3）36-45（in Chi
nese）［7］ China classification society Comprehensive text of
classification code for steel seagoing ships released in2018［J］ Ship standardization engineer2018（4）67（in Chinese）
compared with that before optimization From the optimization results it can be seen that the weight ofthe optimized cabin decreased from 684 to 671 tonsrepresenting a reduction of 19 The weight of thetransverse strong frame structure decreased from 131to 118 tons representing a reduction of 10 Theweight of the structure was reduced on the premisethat the strength meets the specifications The optimization results are shown in Fig 7
4) Optimization effect of maximum stressThe change in the maximum value of stress is
shown in Fig 8 In the optimized scheme the stresses of the girders and strong beams increased up to114 but still meet the requirements of the specifications The stresses in the cabin decreased
By comparing the initial scheme and optimizedscheme the following conclusions can be drawn
1）A total of 729 schemes were formed The maximum stress value of the optimized finite elementmodel of the ship is 226 MPa which is lower thanthe allowable stress value and meets the transversestrength requirements of the specifications
2） The optimization effects of the main deckstrong beams and the vertical girders of longitudinalbulkheads are better The maximum stress occurs atthe joint of the main deck strong beam and verticalgirder of L10 bulkhead which is 114 higher than
the maximum stress before optimization3）After optimization the cross-sectional area of
the cabin increased and the ballast cabin increasedfrom 2464 to 2688 m2 representing an increase of908 The mud tank between the inner floor andmiddle lower deck increased from 4459 to 46 m2representing an increase of 316 The cabin between the middle lower deck and main deck increased from 3549 to 368 m2 representing an increase of 37
4）The structural weight of the cabin decreasedfrom 684 to 671 tons representing a decrease of19 The weight of the transverse strong framestructure decreased from 131 to 118 tons representing of decrease of 104 Conclusions
In this paper in order to reach the lightweight design goal of a deep-water drilling ship the transverse structure of the ship was optimized and analyzed The discrete design variables were consideredin the optimization process The constraint conditions were considered to be the requirements of member size and the modulus of member section in thecustoms specifications The objective function wasthe lightest weight of the cabin structure
NASTRAN and PATRAN were combined with themathematics optimization platform ISIGHT to complete a horizontal structural optimization process forthe deep-water drilling ship and the basic designscheme of the ship was optimized In the optimization plan compared with the basic design plan of thedeep-water drilling ship on the premise that thestrength meets the specifications the maximumcross-sectional area of the cabin increased by908 the structural weight of the cabin decreasedby 19 the weight of the transverse strong framestructure decreased by 10 (from 131 to 118 tons)and the maximum stress of the transverse strongframe increased by 114References［1］ YANG D S Hull strength and structural design［M］
BeijingNational Defense Industry Press1981 （inChinese）
［2］ ZENG G W Calculation and optimization design ofship structure strength［M］ WuhanHuazhong Institute of Technology Press1985（in Chinese）
［3］ ZHANG L Research on optimum design of containership structures［D］ ShanghaiShanghai Jiaotong University2008（in Chinese）
［4］ KITAMURA MNOBUKAWA HYANG F X Appli
Fig7 Optimum results of section and strong frame weight
700600500400300200100
0
Weigh
tt
Total weight strong frame weight
Initial valueOptimal value
Fig8 Stress optimization diagramInitial plan Optimal plan
260250240230220210200190180
Vonmis
esMPa
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CHINESE JOURNAL OF SHIP RESEARCHVOL14Supp 2DEC 2019cation of a genetic algorithm to the optimal structuraldesign of a ships engine room taking dynamic constraints into consideration［J］ Journal of Marine Science and Technology20005131-146
［5］ ZHAO L PZHAN D WCHENG Y Set al Reviewon optimum design methods of ship structures［J］ Chinese Journal of Ship Research20149（4）1-10（inChinese）
［6］ CHENG Y SXIA X LTIAN X Jet al Structural op
timization of a non-axisymmetric cone-cylinder shellstiffened with tapered thick plate and longitudinals［J］Shipbuilding of China201152（3）36-45（in Chi
nese）［7］ China classification society Comprehensive text of
classification code for steel seagoing ships released in2018［J］ Ship standardization engineer2018（4）67（in Chinese）
CHINESE JOURNAL OF SHIP RESEARCHVOL14Supp 2DEC 2019cation of a genetic algorithm to the optimal structuraldesign of a ships engine room taking dynamic constraints into consideration［J］ Journal of Marine Science and Technology20005131-146
［5］ ZHAO L PZHAN D WCHENG Y Set al Reviewon optimum design methods of ship structures［J］ Chinese Journal of Ship Research20149（4）1-10（inChinese）
［6］ CHENG Y SXIA X LTIAN X Jet al Structural op
timization of a non-axisymmetric cone-cylinder shellstiffened with tapered thick plate and longitudinals［J］Shipbuilding of China201152（3）36-45（in Chi
nese）［7］ China classification society Comprehensive text of
classification code for steel seagoing ships released in2018［J］ Ship standardization engineer2018（4）67（in Chinese）
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