ssc-367 - Ship Structure Committee

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Preparationof a table of offsets for the vessel,defining the
geometry with stations (20 or more)along the longitudinal
axis and points (15 or more) at each station (i.e. describing
the transverse section).
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Preparationof weightdistributionto define structure (steel)
and variables (ballast,cargo, fuel, etc.).
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Utilization of table of offsets and weight distribution to
compute bending moments and shear forces at each station.
The
shear force and bending moment diagrams developed along the
length of the vessel facilitate equilibrium checks.
The vessel motion anlalysis requires definition of vessel
hydrodynamic properties: For a linear strip theory based ship
motion computerprogram,the hydrodynamicpropertiesdefiningvessel
added mass and damping coefficientsmay be input based on available
data onsimilarvessels. Conforrnalmapping approach is also used to
define the added mass and damping coefficients. However, if the
vessel configuration is unique, a 2D or 3D diffraction analysis is
recommended to define the hydrodynamicproperties.
The 1inear strip theory based ship motion program, uti1izing the
hydrodynamiccoefficients,is usedto generateequilibriumsolutions
for vessel motions in six degrees of freedom. Then, the transfer
functionscan be defined for verticaland lateral bending,torsional
moments, vessel accelerations and hydrodynamic pressures at each
station along the vessel longitudinal axis.
Finite Element Stiffness Model
The load transfer function, both in-phase and out-of-phase
components, are used in the stress analyses to obtain corresponding
stress range transfer functions. The computer model and the
structural analysis used is very important to define local stress
ranges. Fatigue is a local phenomena.and it isimportant to define
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