Page 125 - Marine Structural Design

Chapter 6 mshore Siructural Analysis 101

design, fabrication or operation, their specialist knowledge in regards to the type of structure,
client recommendation, or their ability to meet cost and time budget requirements.
The rules published by CAS emphasize on safety targets and consequently give precedence to
safety factors and failure levels, along with general specifications of the design. Consequently,
all design engineers should have access to the relevant CA rules to ensure that certification
requirements are met.

6.1.5 Codes and Standards
Codes and standards provide details on how structures should be designed, built, and operated.
The difference between a code and a standard is that a code should be followed more
rigorously, while a standard sets recommended practices that should be followed. This
difference is largely ignored now with, for example, the Eurocode for steel design, which is
classified as a national standard.
The range of worldwide codes and Standards is substantial. However, the important aspect of
these documents is that they both have national, or in some cases international standing.
Examples of the codes and standards for the design of steel marine structures are the
following:
ANSVAWS D1.l, Structural Welding Code,
API RP2A (Working Stress Design or Load Resistance Factored Design, Recommended
Practice for Planning, Designing and Constructing Fixed Offshore Platforms),
Eurocode 3 (NS-ENV 1993 1-1 Eurocode 3),
IS0 Codes for Design of Offshore Structures,
NORSOK Standard N-004, Design of Steel Structures,
NS3472,
BS5750.
The design or reassessment of steel marine structures will be based on one or more of the
above mentioned documents. The software used, will be an essential program for all members
of the design team. However, with regards to the use of the finite element methods during the
design, none of these documents give a thorough assessment of the preferred or recommended
techniques.
Standards such as NS3472 and BS5750 provide the hndamental equations needed to
determine stresses in steel components, regardless of their area of application. Documents
such as NORSOK N-004 and API RP2A apply the relevant fundamental equations, along with
appropriate factors of safety corresponding to the design limit-states for particular marine
structures. NORSOK N-004 (NTS, 1998) gives state of the art specifications for designing
floating and fixed marine structures. It is based on NS3472, Eurocode 3, oil company's
specifications for the design of steel structures, and many of the best features from technical
papers.
API RP 2A (2001) has been widely applied for design and construction fixed platforms, and
serve as a basic document for offshore structural design.
API RF' 2T (1987) has been mainly used for tension leg platforms. It provides comprehensive
guidance on design criteria, environmental forces, global design and analysis, structural design