ssc-367 - Ship Structure Committee

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analysis process is often initiated after the initial structure
configuration has been defined, but while its components are still
being designed and modified.
3.2.3
Stress Model Parameters
A generalized stress model representsall of the steps necessary to
define the local stress ranges throughout the structure due to the
structure’s global response to excitation loads. These parameters
are as follows:
Motions [Hydrodynamics)Model
Amotions (hydrodynamics)model includesvariousmodels necessaryto
determine the applied excitation forces, response of the structure
to these forces, and the resultant loads on the system. The choice
of a model primarilydepends on the structureconfiguration. While
a continuous finite element model may be used for ship-shaped
structuresor semisubmersibleswith orthotropicallystiffenedplate
system (i.e. continuoussystems),a discrete space frame consisting
of strut members are typically used for the analyses of an offshore
platform.
Floating structures,whether ship-shaped,twin-hulledor of another
configuration,may requirethe use of diffractionanalysesto define
the hydrodynamiccoefficients. Diffractionpressuresgenerated are
transformed intomember wave loadswhile the radiationpressuresare
transformedintoaddedmass and dampingcoefficients. This approach
is valid to obtain hydrodynamic coefficients for non-conventional
geometries,the motion analysisutilizinghydrodynamiccoefficients
does account for the effects of member interaction and radiation
damping components.
Bottom-supportedstructuresare generallymade up of small-diameter
tubulars, and their drag and inertia coefficients can be defined
based on previous analytical and model basin work on tubulars.
However, some componentsare frequency-dependentfor arange ofwave
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