ssc-367 - Ship Structure Committee

where:
u
= defined as the net velocity vector component s
UW-UG
Uw
u=
= the componentof the velocity vector of the water
= the structure velocity
Uw
= the component
water
of the acceleration vector of the
U*
cm
= the structure acceleration
= added mass coefficient is often taken to be a
variable ranging from 1.5 to 2.0. It is
recommended that Cm be taken as 2.0, which is
consistent with the potential flow solution for
added mass.
It is necessary to choose an appropriate method or analysis
technique that is compatiblewith fatigue design parameters such as
the structure configuration and its susceptibility to fatigue and
the environment. If the structure dynamics are negligible, and a
deterministicanalysis,based on the use of wave exceedence curves,
may be appropriate for initial sizing of platform components.
However, for most structures, the dynamic response should be
incorporated into the fatigue analyses as illustrated in the above
given equilibrium equations.
A rigorous analysis using a time integration method to determine
platform global and local dynamic responses at each wave height and
period is time consuming and costly. Therefore, it is desirable to
have an alternative analysis procedure. One such alternative
proposed by Serrahn (Reference5.15) consists of a hybrid time and
frequencydomain analysismethod. The analysisflow charton Figure
5-4 summarizes this analysis methodology.
Global spectral static and dynamic responses (e.g. base shear and
overturningmoment) aredeterminedat selecteddiscretewave heights
and periods. The static response is determined based on an applied
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