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 IMO Goal- Based Standards IACS Common Structural Rules * Freak Waves Risk-Based Approach

Role of IACS SETTING SETTING IMPLEMENTING IMPLEMENTING MONITORING MONITORING RULES’ Hull structure + machinery engineering

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 Coastal State Regulations Flag State Regulations Underwriting Clauses Operational Procedures Industry Standards Classification Rules International Conventions & Regulations Safety & Quality Management Systems Port State Controls Chartering & Vetting Criteria

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 Source: INTERCARGO Annual Report 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 User friendly Goal-Based Standards Common Rules

New regulatory framework 2 3 REGULATION SELF- REGULATION Safety objectives Risk acceptance criteria Prescriptive rules Policies, management systems and best practices Operational requirements

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 strengthintact conditions – Residual strengthassumed damaged

Principal new elements Net scantling approach Net scantling approach is used throughout the new Rules buckling and ultimate limit state Inclusion of procedures for the assessment of buckling and ultimate limit state of the hull girder dynamic loading Inclusion of new methods for describing dynamic loading fatigue life Inclusion of new methods for determination of the fatigue life transparency and ease of use Development of a Rule format that provides transparency and ease of use

New regulatory framework SELF- REGULATION Safety objectives Risk acceptance criteria Prescriptive rules Policies, management systems and best practices Operational requirements IMO Goal-Based Standards

Goal-Based Framework Goal Based Safety Objectives Goal Based Functional Requirements Goal Based Verification of Compliance Criteria Tier I Tier II Tier III Industry Standards, Codes of Practice and Safety and Quality Systems for Shipbuilding, Ship Operation, Maintenance, Training, Manning, etc. Tier V IACS Common Rules, Technical Procedures and Guidelines Tier IV IMO Goal Based Standards GBS represents the top tiers of framework, against which the ships safety is verified both at design and construction stages and during the operation

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.

Goal Based Standards + IACS Rules

Example: Safety Objectives Goal Based Safety Objectives Goal Based Functional Requirements Technical Procedures and Guidelines, IACS Common Rules Industry Standards, Codes of Practice and Safety and Quality Systems for Shipbuilding, Ship Operation, Maintenance, Training, Manning, etc. Goal Based Verification of Compliance Criteria Tier I Tier II Tier III Tier IV Tier V IMO Goal Based Standards Design Life Environmental Conditions Structural Safety Structural Accessibility Quality of Construction

Example: Functional Requirements Goal Based Safety Objectives Goal Based Functional Requirements Technical Procedures and Guidelines, IACS Common Rules Industry Standards, Codes of Practice and Safety and Quality Systems for Shipbuilding, Ship Operation, Maintenance, Training, Manning, etc. Goal Based Verification of Compliance Criteria Tier I Tier II Tier III Tier IV Tier V IMO Goal Based Standards Fatigue Life Coating Life Corrosion Additions Strength Criteria

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; 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; 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; 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. 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; 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. 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 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 The validity of a non-linear theory and mathematical model for freak waves needs be verified. END

CSR + GBS