ssc-367 - Ship Structure Committee

others. Extensive analytical and experimental work provides
validation of techniques used to generate the loads.
Fcrstandard vesselswith aforward speed, stripmethods often
provide the desirable accuracy. Although the diffraction
methods are still considered largely a research tool by many,
they are now used as an analyses and design tool by others.
Limited amount of available data on wave-induced and dynamic
impact (i.e. slawaning)loading on vessels and the vessel
responsedo not facilitatecalibrationof analysesmodels. It
is necessary to obtain sufficient data for various vessel
types for an extended period. Boylston and Stambaugh
(Reference 9.10) recommended program to obtain loading
computer records, based on vessel strains for at least three
vessel types over a five-year period, should provide
sufficient data on probabilistic loadings and the vessel
response.
b)
Mass. Motions and Stiffness Models
There are few uncertainties in developing an accurate mass
model. The motionsmodel, however, is largely affected by the
assumptions made to define the motions and stiffness models
and the analyses techniques chosen. The uncertainties built
into these models that allow the definition of nominal
stresses are:
linearizationof drag term
definitionof joint releases,complexityof joint, joint
flexibility etc.
definition of strongbacks and global versus local
distribution of loads
added mass
appurtenancesmodelling
structuraldamping (for bottom-supported structures)
foundationmatrix (for bottom-supportedstructures)
9-16