archn jun 2 5 2013 aries

125 Pages·2013·19.67 MB·English

Cost Reduction of Polar Class Vessels:
Structural Optimization that Includes Production Factors
by
Stephen S. Normore
B.Eng., Ocean and Naval Architectural Engineering,
Memorial University of Newfoundland and Labrador, 2007
Submitted to the Department of Mechanical Engineering and the Engineering Systems
Division in Partial Fulfillment of the Requirements for the Degrees
of
Masters of Science in Naval Architecture and Marine Engineering, and
Masters of Science in Engineering and Management ARCHN
at the
MASSACHUSETTS INS E
OFTECHNOLOGY
Massachusetts Institute of Technology
JUN 2 5 2013
June 2013
© 2013 Stephen S. Normore. All rights reserved ARIES
The author hereby grants to MIT permission to reproduce and to
distribute publicly paper and electronic copies of this thesis document in whole or in part
in any medium now known or hereafter created.
Signature of Author_
Department of Mechani I Enginer an ngineering Systems Division
/ May 10, 2013)
Certified by
Daniel D. Frey
Professor of anical Engine ring and Engineering Systems
Khesis Supervisor
Accepted by__ _ __Hale
Pat Hale
Director, Systems Design and Management Fellows Program
EpginjpygSys~te Division
Accepted by W
David E. Hardt
Chair, Departmental Committee on Graduate Students
Department of Mechanical Engineering
(This Page is Intentionally Left Blank)
Cost Reduction of Polar Class Vessels:
Structural Optimization that Includes Production Factors
by
Stephen S. Normore
Submitted to the Department of Mechanical Engineering and the Engineering Systems
Division on May 10, 2013 in Partial Fulfillment of the requirements for the Degrees of
Masters of Science in Naval Architecture and Marine Engineering
and
Masters of Science in Engineering and Management
Abstract
The design of ship structures was normally optimized to reduce construction
material and maintain adequate strength while adhering to a given classification society's
rules. In the case of Polar Class vessels, where weight minimization was important,
higher fabrication labor costs occurred due to the closely spaced frames and thicker
material needed. There was a cost trade-off between minimizing material under the
traditional design method and designing a ship that was easier to construct at the
shipyard, i.e. designing for downstream processes.
Using the newly defined Unified Requirements for Polar Ships by the
International Association of Classification Societies Inc., a numerical tool was developed
to minimize construction cost of the icebreaker's hull form. This tool allowed the user to
tailor the labor and material metrics to represent a specific shipyard. The tool then
specified an optimum structural solution in terms of minimum weight and production
cost.
Thesis Supervisor: Daniel D. Frey
Title: Professor of Mechanical Engineering and Engineering Systems
(This Page is Intentionally Left Blank)
Acknowledgements
This thesis would not have been possible without the guidance and support of so many
organizations and individuals who helped the author achieve its completion. As such, the
author would like to express his sincere appreciation to the following:
- Vanessa Normore for her love, devotion, and unwavering support to the
author in helping to remove any distraction and allowing him to focus on his
studies while at MIT,
Dr. Dan Frey for his support and guidance in the development of the
optimization program and completion of this research,
* Douglas Jonart for his assistance with reviewing and editing this paper,
Pat Hale for his guidance with the SDM program and paving the way for
e
so many individuals to experience such a wonderful and educating curriculum,
e Philip Koening for his intricate knowledge of ship production and
providing invaluable information to the author during the beginning months of
research,
- Dr. Jeff Beach for his openness and willingness with to provide
information regarding production based cost estimating,
e Laurent Deschamps for providing fundamental information that without,
the author would not have been able to complete his research,
Dan McGreer and Wade Carson with STX Canada Marine for their
e
contribution of information regarding weight based cost metrics for icebreakers,
e Dan Vyselaar and John Shaw with Seaspan Marine - Vancouver Shipyards
for his assistance with outlining methods of production cost estimation for
icebreakers,
e Dr. Claude Daley for his approachable demeanor and eagerness to always
assist in any way possible,
- John Dolny with ABS for his intricate knowledge of the Steel Vessel
Rules used in the development of the program, and last but not lease,
e George Solis with NASSCO for his collaboration with developing the
author's understanding of icebreaker production metrics.
Table of Contents
Acknowledgem ents ....................................................................................................... 5
Table of Contents......................................................................................................... 6
Table of Figures ................................................................................................................. 8
1.0 Introduction..................................................................................................... 10
2.0 Background ....................................................................................................... 12
2.1 Countries Operating Ice-capable Ships.................................................. 12
2.2 Icebreaking Process .............................................................................. 13
2.3 Classification of Ice Type ...................................................................... 15
2.4 Icebreaking Hull Form s .......................................................................... 16
2.4.1 Hull Form Geom etry Nom enclature .......................................... 16
2.4.2 Developm ent of Icebreaking Hull Form s .................................. 18
2.5 Structure of Ice-Capable Ships ............................................................ 22
2.5.1 Hull Structure N om enclature ................................................... 22
2.5.2 Icebreaking vs. Ice-strengthened Vessels ................................. 24
2.6 Developm ent of Polar Code.................................................................. 26
2.6.1 Classification Societies ............................................................. 26
2.6.2 IACS and the Polar Code .......................................................... 27
2.6.3 IACS, ABS, and the Polar Code ............................................... 31
2.7 Current M ethod of Design ...................................................................... 33
2.8 M otivation of Thesis............................................................................. 35
2.8.1 Developm ent of Research Concept........................................... 35
2.8.2 Current Cost Estim ation Techniques ........................................ 36
3.0 Program Developm ent........................................................................................ 41
3.1 Goal of Program .................................................................................... 41
3.2 Initial Program Setup ................................................................................ 42
3.3 Optim ization Setup .............................................................................. 44
3.4 A ssum ptions.......................................................................................... 46
3.4.1 General A ssum ptions .................................................................. 46
3.4.2 Costing A ssum ptions ................................................................. 47
3.4.3 Structural Assum ptions............................................................. 50
3.5 Test Hull U sed ........................................................................................ 52
4.0 Program Description .......................................................................................... 53
4.1 User Inputs and Variable Assignment Description............................... 55
4.1.1 U ser Inputs ................................................................................. 55
4.1.2 Calculate Region Pressures........................................................ 59
4.1.3 Assign Global Variables.............................................................59
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4.2 Optimization Setup and Run Loop Description.................................... 60
4.2.1 Set-up of Bounds and Initial Guess .......................................... 60
4.2.2 Set Optimization Algorithm Options ........................................ 60
4.2.3 Run Loop Optimization Routine............................................... 61
4.3 Program Output Description..................................................................... 62
4.3.1 Determine Best Solution .......................................................... 62
4.3.2 Round-up Design Variables......................................................63
4.3.3 Output / Display Solution .......................................................... 63
5.0 Results, Discussion, and Validation............................................................... 66
5 .1 R esults................................................................................................... . 66
5.1.1 Mild Steel Results ...................................................................... 67
5.1.2 Grade-32 High Strength Steel Results ...................................... 70
5.2 Discussion of Results............................................................................. 72
5.2.1 Metrics Used and Concern with Cost Scale............................... 72
5.2.2 Cost versus Weight Trade-off.................................................... 73
5.2.3 Bow Frame Spacing .................................................................... 74
5.2.4 Upper and Lower Bounds .......................................................... 75
5.2.5 Sensitivity Analysis ................................................................... 76
5.2.6 Family of Solutions.................................................................... 76
5.3 Validation of Program........................................................................... 76
6.0 Areas for Future W ork & Program Development........................................ 78
7.0 Conclusions...................................................................................................... 81
B ib lio gra p h ...................................................................................................................... 82
Appendix A List of Acronyms ................................................................................... 84
Appendix B Program Code ........................................................................................ 85
Section 1 Main Program ................................................................................. 85
Section 2 Production Cost Objective Function................................................. 103
Section 3 W eight of Material Objective Sub-Function..................................... 104
Section 4 Cost of Labor Objective Sub-Function ............................................. 106
Section 5 Constraints ........................................................................................ 114
Appendix C Hull Form Geometry Used in Calculations ............................................ 121
Appendix D Production Metrics Used in Calculations ............................................... 123
Appendix E Structural Choices Made in Calculations................................................ 124
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Table of Figures
Figure 1: Concept of a Ship's Hull Breaking Ice ........................................................ 13
Figure 2: Depiction of Ice Being Submerged Under a Vessel..................................... 13
Figure 3: Picture of Typical Broken Ice Flows........................................................... 14
Figure 4: Depiction of Glancing Impact of Ice on Hull Forms ................................... 14
Figure 5: Ice Categories and Typical Thickness Range .............................................. 15
Figure 6: Development of Sea Ice and Classification.................................................. 16
Figure 7: Hull Geometry Terms for Hull Bows........................................................... 16
Figure 8: Categories of Icebreaking Hull Forms ........................................................ 19
Figure 9: Evolution of Ice Breaker Hull Forms Identifying Specifically the
"White bow" and the "Spoon Bow".......................................................... 20
Figure 10: Evolution of Ice Breaker Hull Forms Identifying Specifically the
"F lat F am ily".............................................................................................. 20
Figure 11: Bow Picture of PolarS ea.......................................................................... 21
Figure 12: Side Picture of Polar Sea .......................................................................... 21
Figure 13: Bow Picture of Oden ................................................................................. 21
Figure 14: Side Picture of Oden ................................................................................. 21
Figure 15: Depiction of Structural Members of Hull Forms ...................................... 23
Figure 16: Depiction of Simple Transversely and Longitudinally Framed Hulls ..... 24
Figure 17: Depiction of Strengthened Structure for "Ice-strengthened" Vessels........ 25
Figure 18: Depiction of Strengthened Structure for Icebreakers ................................. 26
Figure 19: IACS Polar Classes and Descriptions ........................................................ 29
Figure 20: Defined Regions for Strengthening of Polar Class Hull Forms................. 30
Figure 21: ABS Notations for Vessels that Operate in Ice .......................................... 32
Figure 22: Typical Icebreaker Hull Form Structure ................................................... 33
Figure 23: Typical Design Process for Ice Class Vessels........................................... 34
Figure 24: Example of SWBS Format........................................................................ 37
Figure 25: Example of PWBS Format ........................................................................ 37
Figure 26: Illustration of a Plate with an Attached Frame........................................... 48
Figure 27: Illustration of Intermediate Frames ............................................................. 51
Figure 28: Views of Test Hull used in Program Development.................................... 52
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Figure 29: Flow Chart of Program ............................................................................... 54
Figure30: Illustration of Program's Run Loop Optimization Routine ....................... 62
Figure31: Exam ple of Program Output ..................................................................... 64
Figure32: Weight Vs. Polar Class For Comparison of Both Optimization
M ethods using M ild Steel.......................................................................... 67
Figure 33: Cost Vs. Polar Class For Comparison of Both Optimization Methods
using Grade-32 High Strength Steel.......................................................... 68
Figure 34: Cost Savings Vs. Weight Increase for Production Cost Minimization
compared to Weight Minimization using Mild Steel................................ 69
Figure 35: Weight Vs. Polar Class For Comparison of Both Optimization
Methods using Grade-32 High Strength Steel........................................... 70
Figure 36: Cost Vs. Polar Class For Comparison of Both Optimization Methods
using Grade-32 High Strength Steel.......................................................... 71
Figure 37: Cost Savings Vs. Weight Increase for Production Cost Minimization
compared to Weight Minimization using Grade-32 High Strength
S teel.......................................................................................................... .. 7 1
Figure 38: Base W elding Cost M etrics Used............................................................... 72
Figure 39: Fram e Spacing Factor U sed ....................................................................... 72
Figure 40: Frame Spacing for Polar Class 1 Identifying a Larger Bow Frame
Spacing than the Bow Intermediate Region ............................................... 75
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1.0 Introduction
Traditionally, the first step of ship design has been for the owner to choose a
classification society, prescribing the rules to which his or her vessel will adhere. Next,
the design firm would create a vessel that both met the owner's desires and complied
with existing standards and regulations. In this phase, the design of a vessel was
normally optimized to reduce the amount of material for the vessel's hull form without
compromising strength. When completed, the vessel's design was then given to a
shipyard where the ship was to be constructed. The shipyard alone determined the true
costs associated with material, labor, overhead, and profit, most often transferring them to
the owner.
An interesting aspect of this traditional method would arise when, for example, a
disconnect developed between the engineering firm's design and the construction
methods used at the shipyard for fabrication of the vessel. One possible scenario that
might have developed involved the design, optimized by the design firm to have
increased strength and minimum material, forcing the shipyard to procure a particularly
high strength material uncommon to the work force. The resulting cost increase with
material and labor identified one way by which optimization in one phase could
negatively impact later design/construction phases.
In the cases of ice-class or Polar Class vessels, with strengthened hull structure for
operation in ice-covered water or in the polar regions of the globe, these disconnects
could be even greater. However, instead of the disconnect being with material and
strength, it often developed between the density of hull structure in the design phase and
the labor effort expended during the construction phase. This was due to the fact that ice-
class and Polar Class vessels have more strengthening structure in a given foot print area
compared to an open-water hull form not intended to come in contact with ice. The high
density of the structure reduced the accessibility for welders to easily access joints for
welding. Therefore extra effort was expended, resulting in higher labor costs to the
shipyard, and ultimately to the owner of the vessel.
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