Page 124 - Marine Structural Design

100 Part I Siructural Design Principles

Chapters relating to loads and safety factors, which give a more detailed explanation of the
different design methods employed in these codes, should be referenced i.e., the load and
resistance factored design method, allowable stress design method, and design by testing or
observation.
6.1.3 Government Requirements
Governments set legal requirements for using their ports or territorial waters that must be
followed in the design of marine structures. Some of these laws, particularly those relating to
vessel movements, are internationally consistent to avoid problems in passing through several
national waters during transit. However, most national laws relating to the design,
construction, and operation of marine structures will differ from country to country, each
reflecting local conditions, health and safety laws, expertise and experience including that
learned from previous major incidents and accidents.
The government requirements, such as those published by:
Norwegian Petroleum Directorate (NPD),
UK Health and Safety Executive (HSE),
US Mineral Management Service (MMS).
are the legalities that need to be met rather than specific design methods and criteria to be
employed. Such rules are mainly the concern of the project manager and the client
representative who should ensure that the relevant pieces of legislation are reflected in the
Design Basis (see Section 6.2.2).
6.1.4 Certification/Classification Authorities

Historically, the CertificatiodClassification Authority (CA) acted as an independent body
between the vessel's designer, builder, owner, operator and the insurance company. The
government's interest of reducing the risks to life and the environment from marine accidents
has increased the need for CA's to also provide their expertise in government policies and
legislation.
CAS are companies such as:
American Bureau of Shipping (ABS),
Bureau Veritas (BV),
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Det Norske Veritas (DNV),
Lloyds Register of Shipping (LR),
ClassNK(NK)
Ships and mobile offshore drilling units (MODU) transit from one location to another
worldwide and thus the use of the CA's service may avoid the repetitive approvals from the
many national governments concerned. The role of the CA has become questioned in recent
years concerning the fixed (bottomed supported) structures, which will generally remain at one
location within one nation's territorial waters throughout its life.
CAS perform an independent third party assessment of the structure throughout the design of
the structure to ensure that it fits for purpose. This may include review of the design reports
and independent structural analyses, particularly with the increasing use of computer aided
FEM. The CA's may be chosen based on their office location relative to the sites for structural