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reliability in design and supplement the research project on ship inspection issues under
Project SR-1355.
In support of Goal I. reliability research goals should include:
· improved methods of predicting hydrodynamic loads and structural response of
ships in extreme seas;
details;
· improved methods of predicting fatigue stresses in structural components and
· improved descriptions of matena] properties, including fracture, corrosion, and
fatigue of common marine steels; and
· development of structuraI-reliability theory, application to existing Resins, and
development of probability-based design critena.
In support of Goal 2. reliability marine activities must be based on env~ronmental-
protection criteria and procedures that wall remain effective throughout the life cycle of a
structure or project. In the past, inadequate criteria and procedures resulted in
environmental damage and loss of natural resources, public support, and productivity.
Enhanced environmental protection can be realized with improved criteria and
improved procedures for designing, fabricating, operating, inspecting, and maintaining
ships, offshore structures, and marine systems. Structural-research projects that wall
enhance environmental protection must be pursued in the areas of:
· doubJe-hull technology;
· damage-tolerant structures; and
· the effect of human factors on the reliability of marine structures.
Composites
On September 25-26, 1990, the Manne Board of the National Research Council
convened a National Conference on the Use of Composite Materials in LoacI-Beanng
Manne Structures. This conference brought together leaders Tom industry, government,
and academia to exchange ideas and lay the groundwork for future marine applications
of composite materials by U.S. industry. The conference drew enthusiastic participation
and was highly productive. Its recommendations are reported in a two volume report of
the National Research Council.t As a result, the CMS adopted a thrust area in
composites in its recommendations for FY 1994 so that the advantages of composites
may be more fully realized in marine structures.
New matenals and vanations on existing matenals offer opportunities for
improving marine structures. Content emphasis is on fiber-reinforced plastics and related
composites. In recent years, their use in the primary structures of vessels less than 60
meters long has increased substantially, and many navies are introducing a new class of
~ National Research Council, 1991. Conference on Use of Composite Matenal in Load-Beanng Marine
Structures, September 25-27, 1990; Summary Report, Volume I, and Conference Proceedings, Volume IT.
Washington, DC: National Academy Press. NTIS Report No. DTCG-23~ C-20025.
s
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fiber reinforced plastic coastal minehunters. New composite matenals may have
potential applications to larger marine structures, which would take advantage of their
increased specific stiffness and strength and resistance to corrosion. Graphite, ceramic,
and Braid composites, In addition to glass, should be evaluated for special structural
components.
The use of composite matenals presents a special challenge to the designer. The
many matenal parameters that can be vaned, including the basic fiber and matrix
matenals, require eng~neenng analysis and design evaluation to determine the most
efficient design. The use of composites and their design methodoJo~es is relatively weD
documented in the aerospace industry. Report SSC-360 provides a survey and
assessment of the uses of fiber reinforced plastic matenals. As newer generations of
matenals, such as fiber reinforced plastics, are introduced into the marine industry, new
analytical techniques need to be developed to aciciress structural ~ntegnty. The structural
integrity of novel matenals is strongly affected by processing. Understanding the
necessary interrelationships may require matenal-property data beyond that which has
been histoncally available.
To expand understanding of these interrelationships requires further evaluation of
expertise and design techniques used in aerospace and other irldustries and ways to adapt
them to marine structures. To accomplish this, the National Conference on the Use of
Composite Materials in Load-Beanng Manne Structures, which was sponsored by the
SSC as project SR-133l, enabled experts to share their knowledge of and experience with
the use, fabncation, and inspection of new marine matenals. The applicability of design
practices used in other industnes was evaluated,.and the conference proceedings were
published in 1991. The CMS prepared project descnptions in response to the
recommendations of the proceedings. The first of these, "Design Guide for Marine
Applications of Composites" (SR-1367), was recommended by the CMS as the initial
project in this thrust area.
In support of Goal I, research in composites is needed to address safety and
integrity aspects with respect to corrosion, fire, and toxicity.
In support of Goal 3, research in composites needs to be coordinated and
advanced for the determination of performance properties of anisotropic composite
matenals that wall be used increasingly by the marine industry.
Producibility/Competitiveness
The SSC Strategic Plan identified a decline in the U.S. merchant marine industry
and developed the goad to "support the U.S. maritime industry in shipbuilding,
maintenance and repair." Past recommendations of the CMS, and research projects
conducted by the SSC, included projects to increase the ease of fabrication and to
improve productivity. In the recommendations for FY 1994, the CMS developed a thrust
area in producibili~cy/competitiveness. This thrust area seeks to improve industry
competitiveness in ship design, construction, and repair. The ship design process needs
to be changed to reduce design time and cost; to improve design quality, including
6
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producibility; to reduce design errors; and to produce ships that yield enhanced
producibility, performance, and operability at lower life-cycle costs.
Recent surveys project a steady growth in world trade during the 199Os. As a
leading industna] nation, the United States win benefit from increased export arid import
of raw matenals and manufactured products. At the same time, world shipbuilding costs
have risen and new ship deliver dates have been extended as building berths have
become filled. Increasing demand for merchant ships presents an opportunity for the
United States as a shipbuilder to regain its stature as a leading maritime nation.
In support of Goal 1. certain producibility/competitiveness capabilities are
required:
· Improved design tools and information systems need to be developed, including
computer-aided design, design and manufacturing information, and expert systems.
· Regulations need to be continuously reviewed and upgraded to reflect
technological advances.
· Reliability-based design techniques to optimize matena] use need to be
developed.
· Pnnciples of design for production need to be adopted.
· Research on design tools, producibility, production processes, reliability-based
design, and damage-tolerant structures needs to be sponsored, and professional education
in these fields needs to be enhanced.
In support of Goal 3. the preceding as well as the follomng
producibility/competitiveness items are needed:
· Ship repair and construction capability need to be made viable. Repair time
and material costs must be reduced, and labor efficiency improved.
· The maritime industry needs to adopt the worldwide measurement standard
System International to become competitive in the world market.
· Labor hours for construction and material costs for construction need to be
drastically reduced to restore a viable production capability for new merchant ships. To
achieve this, improvements in production technology and production processes must be
developed. Examples of these improvements include laser alignment, faster welding
techniques, improved accuracy control, the use of robotics, and automated material
handling, automated storage equipment.
inspection /Ma inten a nce
The Manne Board convened a symposium and workshop on the role of design,
inspection, and redundancy in marine structures on November IRIS, 1983 2 The
workshop determined that consideration of the Design, Inspection, and Redundancy
Triangle is necessary for reliable structural systems. To strengthen the inspection leg of
the triangle, the CMS began to recommend inspection projects in its recommendations
2 National Research Council 1984. Toward an Integrated Design' Inspection, and Redundangy Research
Program. Washington, DC: National Academy Press.
7
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for FY 1986 to support reliability goals. With the increasing number of aging ships and
concomitant greater need for repair, life-cycle maintenance of ships grew to equal
importance. As a result, the CMS incorporated a thrust area on inspectiorLlmaintenance
In its recommendations for I;Y 1994.
Recommended research efforts wall focus on inspection and repair strategies for
aging ships. Development of improved inspection techniques for in-seIvice structural
monitoring is needed, as well as analytical methods for assessing the effects of corrosion,
Baws, and other strength defects. Also, development of effective localized repair
methods for cntical defect areas is needed.
In support of Goal I, inspection/maintenance research is needed in the areas of:
· determination of performance properties of coatings and other structural
presentation techniques; and
· determination of corrosion rates for matenais under venous environmental
conditions, such as bare steed in the splash zone of seawater ballast tanks filled for 10
continuous days dunug each 40-day voyage.
In support of Goal 2, inspection/mainter~ance research is needed in the areas of:
· structural monitonug; and
blasting and coating application techniques.
In support of Goal 3. the following inspection/maintenance items are needed:
· Ship repair and construction capability must be made economically viable.
Repair time and material costs must be reduced and labor efficiency improved.
· Better ship inspection and repair methods must be developed.
Table ~ relates the recommended projects for FY 1995 to the thrust areas, and
identifies the technology area under which they wall be discussed in the section on
research program development.
8
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TABLE ~ Recommended Projects in Support of Thrust Areas
Number Project Title
Primary
Technology Area
RELIABILITY PROJECTS
95- 1 Symposium/Workshop: Higher Order Prediction Methods for Loads and Response
Hydrodynamic Loadings and Response of Marine Structures
95- 5 Combined Load Effects for Design and Strength Assessment of Ship Loads and Response
Structures (94D-J)
95- 6 Weld Detail Fatigue Life Improvement Techniques Design
95- 7 Structural Design Guide for Win Hull Vessels Loads and Response
95- 8 Fatigue and Fracture Cnteria for Double-Hulled Ships Materials Criteria
95- 9 Hull Response Monitoring System Design
95-12 Rupture Resistance of Cargo Tanks of Double Hull Tankers to Low Design
Energy Impacts
95-13 Iwo-Parameter Approach to Fracture Prediction in Ship Structures Materials Criteria
COMPOSITES PROJECTS
95-14 Assessment of Fire, Smoke, and Toxicity Characteristics of
Composite Matenals Proposed for Marine Applications (94M-O)
PRODUCIBILIlY/COMPETITIVENESS PROJECTS
Materials Criteria
95-11 Alternative Stiffening Systems for Double-Skin Tankers (94-14) Design
95-15 High Productivity Welding Processes (94-13) Fabrication and
Maintenance
95-16 Evaluation of Marine Structures Education in North America Design
INSPEcllON/MAINTENANCE PROJECTS
95- 2 Methodology to Establish the Adequacy of Weld Repairs (94-8) Fabrication and
Maintenance
95- 3 Commercial Ship Design and Fabrication for Corrosion Control Materials Criteria
95- 4 Detection Probability Assessment of Visual Inspection of Ships Fabrication and
Maintenance
95-10 A Guide to Damage Tolerance Analysis of Marine Structures Materials Criteria
9
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RESEARCH PROGRAM DEVELOPMENT
Technology Areas
The CMS and its working groups—the Materials Work Group and the Design
Work Grou~recommend a multlyear plan that introduces new, long-range performance
concerns. Long-range research guidance comes from:
· the working groups' thrust-development sessions held in June 1993;
· SSC report recommendations;
· the annual joint meeting of the CMS and the SSSC;
· the SSC fad meeting; and
· the expertise of the working groups, whose members were selected for their
broad experience in the areas of concern.
reliability are
The working groups' specific concerns, activities, and common interest in structural
· Design Work Group—extreme wave loads, higher-order forces, and responses;
ice, groundings, and collisions; large-scale structural tests; operations-onented monitoring
systems; modeling errors in loads and responses; procedures for fatigue stress
computations; design process improvement; producibility; and reliability-based design
codes.
· Materials Work Grou~new marine structural materials; fracture mechanics;
fatigue (incIllding corrosion fatigue); corrosion and its prevention; welding; inspection;
and deep-ocean inspection and repair.
To varying degrees, these specific activities and recommendations contribute
knowledge and data needed for the SSC's overall objective of improving the structural
reliability of vessels and other marine structures.
The proposed multlyear plan addresses five technology areas that provide the
underlying technical support for the thrust areas. The technology areas are
I. matenals cntena;
2. loads and response;
3. design methods;
4. fabrication and maintenance techniques; and
5. reliability.
Individual projects were developed by the Design Work Group and the Materials
Work Group at their meeting in June 1993. Projects were prioritized as high' medium,
or low pnonty. All these projects were discussed at the joint meeting of the SSSC and
the CMS In September 1993. Al] these projects were then evaluated by the CMS at their
September 1993 meeting. Factors taken into account during discussions were the interest
10
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shown by the agencies for individual projects, the cost and time for accomplishment'
technical feasibility, t~meiiness of the project with respect to ongoing work and current
needs. The projects were originally proposed by the work groups on the basis of
technology area. The CMS considered their own thrust areas, the national goals of the
strategic plan of the SSC, but maintained an independent attitude based upon their own
professional expenence. Based on these considerations, the CMS determined an Scotia]
prioritization by ballot vote. Further discussions were then held to consider the balance
of the entire program, and revised priorities were assigned.
At the November 1993 meeting of the CMS, project priorities were again
discussed based upon the above listed factors. Final priorities for accomplishment were
then assigned.
Relationship Among Strategic Plan, Technology Areas, and Thrust Areas
The Table ~ relationships between CMS-recommended projects and thrust areas
are further expanded In Table 2 and Figure I. Table 2 relates the goals of the strategic
plan to thrust areas of the CMS and to the technology areas of the multiyear research
program. As Table 2 reflects, the research projects recommended for FY 1995 are
heavily oriented toward the CMS's traditional emphasis on safety and integrity of
structures with diverse technology areas associated with these projects. Figure ~ outlines
a multiyear research program. The CMS recommendations are organized on the basis of
the four thrust areas (reliability, composites, producibility/competitiveness, ant]
inspection/maintenance). The proposed later year projects (see Appendix A) are
included for completeness. Again, it is noted that the CMS recognizes that many
recommended research projects are related to more than one strategic goal and
objective.
The following sections of this chapter describe the technology areas of the 5-year
program plan development and the programmatic argument for the recommended
FY 1995 projects.
11
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TABLE 2 Relationships Between the Strategic Plan, Thrust Areas, and Technology
Areas in the Research Plan. Sheet I.
Research
Projects
STRATEGIC PIAN: THRUST AREA TECHNOLOGY
NATIONAL GOALS
AREAS
95- 1 Symposium/Workshop - Higher
Order Loads and Prediction Methods:
Hydrodynamic Loadings and Response
of Marine Structures
95- 2 Methodology to Establish the
Adequacy of Weld Repairs (94-8)
95- 3 Commercial Ship Design and
Fabrication for Corrosion Control
95- 4 Detection Probability
Assessment of Visual Inspection of Ships
95- 5 Combined Load Effects for
Design and Strength Assessment of Ship
Structures (94D-J)
95- 6 Weld Detail Fatigue Life
Improvement Techniques
95- 7 Structural Design Guide for
Twin Hull Vessels
95- 8 Fatigue and Fracture Critena for
Double-Hulled Ships
Safety and Integrity Reliability
Maritime Industry
Support
Safety and Integrity Inspection /
Maintenance
Maritime Industry
Support
Safety and Integrity Inspection /
Maintenance
Mantime IndustIy
Support
Safety and Integrity Inspection /
Maintenance
Environmental Risk
Mitigation
Safety and Integrity Reliability
Loads and
Response
Design
Fabrication and
Maintenance
Materials
Criteria
Design
Reliability
Loads and
Response
Design
Safety and Integrity Reliability Materials
Criteria
Maritime Industry
Support
Safety and Integrity Reliability Design
Maritime Industry
Support
Environmental Risk Reliability Materials
Mitigation Criteria
12
Representative terms from entire chapter:
materials criteria
