Regulatory Framework
3.7 Goal Based Standards
The new item on the agenda for the International Maritime Organisation’s (IMO) Maritime Safety Committee (MSC) – ‘Goal-Based New Ships Construction Stan- dards’ – was introduced at the MSC78 in May 2004 and it has been an MSC agenda item ever since, with a dedicated Working Group in place. GBS is expected to stay on the IMO agenda for the next years. This agenda item was introduced by the Bahamas and Greece in a paper to the IMO Council (Bahamas and Greece 2002).
In this paper, the Bahamas and Greece argue that the IMO should play a greater role in determining the construction standards to which new ships are built, a role tradi- tionally delegated to the classification societies, and that this should be incorporated into the IMO Strategic Plan. Many flag states opposed the proposal as they did not see any compelling need for it. However, the Bahamas and Greece prevailed.
The initiative was also surprising, as FSA also will tend to result in goal based standards, as the goal (or the safety objective of a regulation) is made explicit. By making the goal explicit it is also easier to deal with innovative and risk based de- sign, as the prescriptive rules are seen as a means to achieve the goal (for standard design solutions), but in principle the goal may be achieved by any other design solution that can be documented to meet the goal (the risk acceptance criteria). This would open opportunities for risk based design. Some classification societies had already started to use the FSA guidelines as basis for own rule development, and saw clear benefits of having more well-defined criteria to relate to.
There are also new elements introduced in the regulatory process, by formalizing a Goal Based Approach. This relates to the style of writing regulations: Rather than stating in prescriptive form how ships should be built and equipped, the regulations focus on the goals, the purpose of the regulation, what should be achieved, rather than how to achieve it. This affects the structure of the regulations, and helps keeping a well-defined structure to the regulation. This is an attractive idea, as the current regulatory system is extremely complicated, and is becoming ever more complicated due to a continuous amendment process.
The structure of the goal based regulatory system as tentatively agreed at MSC84 (May 2008) is shown in Fig. 3.4. It is noted that Tiers I, II and III represents the GBS to be maintained at IMO level, and includes a verification process that e.g. classifi- cation rules, being an example of Tier IV, should be verified to meet the goals for one or more functional requirements.
Fig. 3.4 Goal based standards framework
3.7.1 Definition of GBS
According to the current definition, IMO goal-based standards are:
1. broad, over-arching safety, environmental and/or security standards that ships are required to meet during their lifecycle;
2. the required level to be achieved by the requirements applied by class societies and other recognized organizations, Administrations and IMO;
3. clear, demonstrable, verifiable, long standing, implementable and achievable, ir- respective of ship design and technology; and
4. specific enough in order not to be open to differing interpretations.
3.7.2 Tier I: Goals
Currently a draft text is available only for ship construction and the goals (Tier I) are expressed as follows:
Ships are to be designed and constructed for a specified design life to be safe and environmentally friendly, when properly operated and maintained under the specified operating and environmental conditions, in intact and specified damage conditions, throughout their life.
1. Safe and environmentally friendly means the ship shall have adequate strength, integrity and stability to minimize the risk of loss of the ship or pollution to the marine environment due to structural failure, including collapse, resulting in flooding or loss of watertight integrity.
2. Environmentally friendly also includes the ship being constructed of materials for environmentally acceptable dismantling and recycling.
3. Safety also includes the ship’s structure being arranged to provide for safe access, escape, inspection and proper maintenance.
4. Specified operating and environmental conditions are defined by the operating area for the ship throughout its life and cover the conditions, including interme- diate conditions, arising from cargo and ballast operations in port, waterways and at sea.
5. Specified design life is the nominal period that the ship is assumed to be exposed to operating and/or environmental conditions and/or the corrosive environment and is used for selecting appropriate ship design parameters. However, the ship’s actual service life may be longer or shorter depending on the actual operating conditions and maintenance of the ship throughout its life cycle (End quote).
Many have proposed to simply add a reference to the ALARP principle, and the FSA Guidelines to make these goals risk based (and possible to understand in prac- tical application to rule development). Since the FSA Guidelines already contains the risk evaluation criteria this would be sufficiently clear to a rule developer.
3.7.3 Tier II: Functional Requirements
The first three of the so-called functional requirements, are given below:
Tier II (Functional Requirements)
(Applicable to new oil tankers and bulk carriers in unrestricted navigation) Design
II.1 Design life
The specified design life is not to be less than 25 years.
II.2 Environmental conditions
Ships should be designed in accordance with North Atlantic environmental conditions and relevant long-term sea state scatter diagrams.
II.3 Structural strength
Ships should be designed with suitable safety margins:
1. to withstand, at net scantlings, in the intact condition, the environmental conditions anticipated for the ship’ design life and the loading conditions
appropriate for them, which should include full homogeneous and alternate loads, partial loads, multi-port and ballast voyage, and ballast management condition loads and occasional overruns/overloads during loading/unloading operations, as applicable to the class designation; and
2. appropriate for all design parameters whose calculation involves a degree of uncertainty, including loads, structural modelling, fatigue, corrosion, mate- rial imperfections, construction workmanship errors, buckling and residual strength.
The structural strength should be assessed against excess deformation and failure modes, including but not limited to buckling, yielding and fatigue. Ulti- mate strength calculations should include ultimate hull girder capacity and ul- timate strength of plates and stiffeners. The ship’s structural members should be of a design that is compatible with the purpose of the space and ensures a degree of structural continuity. The structural members of ships should be de- signed to facilitate load/discharge for all contemplated cargoes to avoid dam- age by loading/discharging equipment which may compromise the safety of the structure.
II.4 Fatigue life
The design fatigue life should not be less than the ship’s design life and should be based on the environmental conditions in II.2 (end quote).
Already at this stage, there are many challenges, as seen from a risk perspective.
1. 25 years design life. In practice this is strongly dependent on maintenance, and outside control of the regulator; but in any case most ships are designed to have an economic life of 25 years. But the actual life depends on many commercial issues, like e.g. the market situation: At times with high day-rates there is no scrapping. The term ‘design life’ does not play any important role in classifi- cation rules. The 25 years used in classification rules rather refers to the return period for extreme loads (which is a different concept than the design life).
2. Bulk Carriers and Tankers are today designed to 20 years North Atlantic ex- tremes loads. To change this to 25 years has almost no effect.
3. Suitable safety margin? This is where a risk based approach becomes useful, as Structural Reliability Analysis could be used to calibrate the Rules to the relia- bility level defined.
4. Fatigue life equal to design life. This statement must be based on a non-standard definition of fatigue life (corresponding to about 2.27% probability of failure for each ‘hot spot’). With hundreds of hot spots this probability appears too high.
These few examples demonstrate that rules today should be better based on a risk based approach. It is not possible to seriously discuss safety, without using risk concepts. The example relating to hull girder ultimate strength was prepared based on work of Hørte et al. (2007) and internal work in DNV for IACS (2006).
The role of FSA and Structural Reliability Analysis in the GBS Framework is a rational way for the justification of the rules and regulations. These analyses can be subject to verification. The final formulation of the rules and regulations is, however, usually not possible to be verified. The tendency for those supporting a prescriptive
approach to GBS is to write detailed verification requirements (in Tier III), rather than leaving it to the developer of the rules/regulation to justify their development.