ssc-367 - Ship Structure Committee

the sensitivity of fabricationdefects in determining the fitnessfor-purpose
of the component. This concept, first described by
Wells (Reference 4.13), allows engineering assessment of weld
defects to determine those defects that require repair as well as
those that are considered fit-for-purposewithout a repair.
4.2
FATIGUE RULES AND REGULATIONS
The primary objective of the various recommendations, rules,
regulations and codes applicable to marine structures is to ensure
that the design and analysis process results in construction of
marine structures.that can resist both extreme loads and cyclic
operating loads and have adequate fatigue lives.
Rules and recommendations issued by classification societies and
certifying agenciesmay representthe minimum requirements based on
research and development. The hull girder design criteria given by
each of the four leading classificationsocieties (American Bureau
of Shipping, Lloyd’s Register of Shipping, Bureau Veritas and Det
Norske Veritas) is very similar and differs only in some of the
details. While the design basis primarily addresses stillwater and
wave-induced bending moments, some discussion on dynamic stress
increments and fatigue file assessment is often provided. Recent
research and development efforts have produced several recommended
fatigue design guidelines. Rules and reconunendationson offshore
structures are very specific on fatigue design. Guidelines are
provided to carry out both simplified and detailed analyses.
Commentary to
development of
such guidelines also provide background for the
fatigue design methods.
Fatigue design methods chosen vary depending on several factors,
including the owner’s design philosophy. Most fatigue design
methods are variations of a method based on application of S-N
curves representingthe fatigue strengthof similardetails/joints.
A basic S-N curve applicablefor a given detail/joint also requires
adjustments to incorporate the influence of variables. Although
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