Transcript Document

Rogue Waves 2004
Ship design rules and regulations – an
overview of major themes
Gil-Yong Han
Int’l Association of Classification Societies
An overview of major themes
Risk-Based
Approach
IMO GoalBased
Standards
IACS Common
Structural Rules
* Freak Waves
Role of IACS
•SETTING
RULES’
Hull
structure +
machinery
engineering
•IMPLEMENTING
•MONITORING
What are the class rules
Complying with Class Rules:
- Provision of adequate global strength;
(ships capable of withstanding still water and wave induced
loads with the specified stress criteria)
- Provision of adequate local strength of
individual components
(steel material requirements and scantling formulations are
to ensure that ships resist modes of buckling, fatigue,
yielding, brittle fracture)
- Rules provide direct calculations
procedures for determination of
scantlings.
Relation with IMO and flag States
IMO Conventions – Statutory Requirements
SOLAS Convention states that in addition to the Conventions requirements,
ships shall be designed, constructed and maintained in compliance with
class rule requirements of a classification society which is recognized by
the Administrations;
Many of the flag States authorize class societies to apply the IMO
Conventions (statutory req.) on their behalf by design appraisals and
surveys.
What IACS can not do
A strength of “classification” concept is
that the Societies act as independent
bodies, giving an independent and
unbiased assessment of the status of
ship’s hull and machinery;
However, they are not guarantors of the
safety as they have no control over how
a ship is operated and maintained.
The current regulatory
framework – shipping safety
International
Conventions &
Regulations
Flag State
Regulations
Classification
Rules
Chartering &
Vetting
Criteria
Coastal State
Regulations
Underwriting
Clauses
Port State
Controls
Operational
Procedures
Industry
Standards
Safety & Quality
Management
Systems
Risk-Based Approach in shipping
In many cases, enhancing the safety rules (structure
incl.) were driven by accidents;
Following high profile accidents (Herald of Free
Enterprise, Exxon Valdez, Piper Alpha), a risk-based
approach in ship design and operation was
introduced;
IMO, supported by IACS, recommends FSA to be
applied, to examine potential areas and introduce
risk reduction measures before a tragedy happens.
Bulk Carriers – top priority.
Example: BC Accidents Trend
LOSS OF LIVES
0
10
20
30
200
180
Collision
No. lives lost
160
140
Grounding
120
100
80
Structural
60
40
20
Flooding
20
02
20
00
19
98
19
96
19
94
19
92
19
90
0
Machinery
fire/explosion
Years
Machinery failure
BULK CARRIER LOSSES
Cargo
loading/unloading
Cargo
fire/explosion
Cargo
shift/capsize
25
No. vessels lost
20
15
10
5
Contact object
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
1991
1990
0
Years
Source: INTERCARGO Annual Report 2002
Unknown
1993-2001
2002
Changes
• A systematic method is put in place to establish the ship
safety rules of the basis of assessment of risks, costs and
benefits – final decisions are now robust and defensible.
• However, this risk-based approach “supplements” the
traditional prescriptive rule-making, allowing variation from
prescriptive rules, provided that the ship (system) risks are
maintained at acceptable levels.
Widespread consensus Make ships durable and fit-for purpose
Expectations
Regulatory
Expectation
Safe
Environmentally
friendly
Easy for inspection
and maintenance
Industry
Expectation
Robust and Reliable
Fit for purpose
User friendly
Goal-Based Standards
Common Rules
New regulatory framework
REGULATION
Safety
objectives
Risk
acceptance
criteria
2
3
Prescriptive rules
Operational requirements
SELFREGULATION
Policies, management systems and best practices
Objectives – Common Structural
Rules
• To eliminate competition between class
societies on standards
• To embrace the intentions of the anticipated
IMO requirements for Goal-Based Standards
for new buildings
• To ensure that a ship meeting these new
standards will be recognised by industry as
being safe, robust and fit for purpose as would
have been required
• To employ the combined experience of all class
societies to develop an agreed standard, or set
of Rules
IACS Common Structural Rules
Net scantling approach
Buckling and ultimate limit state of the hull girder
Dynamic loading
Fatigue life
Coating life
Transparency and ease of use: (Under the old rules, the
corrosion margin is given as a percentage, now an
absolute min figure corrosion margin)
Draft Rules:
–
–
–
–
–
Fatigue life [ 25 years ]
Coating life [ 10 years ]
Corrosion additions
[ 25 years ]
Structural strength
intact conditions
Residual strength
assumed damaged
Principal new elements
• Net scantling approach is used throughout the
new Rules
• Inclusion of procedures for the assessment of
buckling and ultimate limit state of the hull girder
• Inclusion of new methods for describing dynamic
loading
• Inclusion of new methods for determination of the
fatigue life
• Development of a Rule format that provides
transparency and ease of use
New regulatory framework
IMO
Goal-Based
Standards
Safety
objectives
Risk
acceptance
criteria
Prescriptive rules
Operational requirements
SELFPolicies, management systems and best practices
REGULATION
Goal-Based Framework
GBS represents the top tiers of framework, against which the ships safety
is verified both at design and construction stages and during the operation
Tier II
Goal Based Functional
Requirements
Tier III
Goal Based Verification of
Compliance Criteria
Tier IV
IACS Common Rules,
Technical Procedures and Guidelines
Tier V
Industry Standards, Codes of Practice and Safety and
Quality Systems for Shipbuilding, Ship Operation,
Maintenance, Training, Manning, etc.
IMO Goal Based Standards
Tier I
Goal Based Safety
Objectives
Mechanism
The mechanism by which the goal-based
standards will be put in place is:
• IMO sets the goal;
• IACS develops class rules that meet
the so-determined goals;
• Industry and IACS develop detailed
guidelines and recommendations for
wide application in practice.
Main ship
functions
Major systems and
equipment
Optional sub
systems and components
Detailed rule requirements
Class
Rules
Overall
objectives
IMO
Functional Requirements
Goals
Goal Based Standards + IACS
Rules
Example: Safety Objectives
Goal Based Safety
Objectives
Tier II
Design
Life
Goal
Based Functional
Requirements
Environmental Conditions
Tier III
Goal Based Verification of
Compliance Criteria
Structural Safety
IV
StructuralTierAccessibility
Technical Procedures and Guidelines, IACS
Common Rules
Quality of Construction
Tier V
Industry Standards, Codes of Practice and Safety
and Quality Systems for Shipbuilding, Ship
Operation, Maintenance, Training, Manning, etc.
IMO Goal Based Standards
Tier I
Example: Functional
Requirements
Goal Based Safety
Objectives
Tier II
Goal Based Functional
Requirements
Tier III
Fatigue
Life of
Goal
Based Verification
Compliance Criteria
Coating Life
Tier IV
Technical Procedures and Guidelines, IACS
Common Rules
Corrosion Additions
Tier VCriteria
Strength
Industry Standards, Codes of Practice and Safety
and Quality Systems for Shipbuilding, Ship
Operation, Maintenance, Training, Manning, etc.
IMO Goal Based Standards
Tier I
Verification Criteria
 Compliance with the goal-based standards during shipbuilding
 Plan review and approval
 Structural calculations
 Surveys during construction
 Compliance with the goal-based standards on ships-in-service
 Periodic surveys and thickness measurements
 Structural reassessment based on survey and thickness measurements
Deliverables
• A new complete set of Rule covering the
structural requirements for oil tankers and bulk
carriers for new construction and for those ships
subsequently in service.
• Supporting guidance to amplify the Rules,
including the procedures for carrying out direct
calculations and for fatigue life assessment.
• Background documents explaining the implicit
safety levels, design principles and assumptions
on which the Rules are based.
• IACS Common Structural Rules will be in line
with the IMO Goal-Based Standards.
Freak Waves Findings
• Traditionally, this type of waves have been observed only
occasionally under unexpected conditions. However, by
virtue of an advance mode of measurement and data
analysis techniques, such an occurrence is analyzed;
• Better understanding of the mechanism generating such
waves has been gained;
• The analysis of casualty database and the forecast of
such waves can lead to the development of a mechanism
by which masters can be alerted so as to enable them to
take precautionary action;
Freak Waves Findings
For future study:
•
The design practice is moving a more consistent probablistic
method, e.g. Extremes are determined for a given return period –
expected lifetime of the structure. For consideration in ship
design, the probability of occurrence and also the probability of a
ship encountering such waves are needed. This involves a rigirous
analysis of shipping casualty data. Lack of information of the core
causes of the reported casualties can lead to a misleading or
unfounded conclusion.
•
According to the Maxwave study, due to their extreme steepness,
they last for very short period of time before breaking. Hence, the
probability of a ship meeting such waves is even lower that the
actual occurrence of freak waves in open ocean;
•
Shape of freak wave profiles in space and time including their
kinematics and ship responses to freak waves are to be
documented.
Freak Waves Findings
•
A distinction between the offshore platform and moving ships
•
The validity of a non-linear theory and mathematical model for
freak waves needs be verified. END
CSR + GBS