| Summary: | This thesis investigates two slender body problems,
namely the static and dynamic analysis of submarine pipeline
spans and the dynamic analysis of marine risers. In view of
structural and environmental similarities, these problems
are closely related and where possible common analysis
procedures have been developed.
For the problem of pipe spanning, attention is focused
on the possibility of vortex induced vibration and the
associated question of span assessment. This situation
arises when following the discovery of a span, an assess-
ment is required to determine if any remedial repair work
required. To assist in this assessment, and also to
provide a more fundamental understanding of span behaviour,
number of mathematical models are developed.
First linear beam-column theory is used to determine
the span natural frequencies and buckling load for a single
span supported continuously on either side by an elastic
foundation. The effects of internal/external pressures and
product temperature are included and the results presented
terms of two independent nondimensional parameters.
Next the effects of pipe/soil friction and change in
geometry are considered utilising a nonlinear Finite Element
model. Theories are developed for a nonlinear pipe element
with axial/bending coupling and a nonlinear nonconservative
pipe/soil friction element. The effects of initial seabed
geometry and finite amplitude vibration are included and it
shown that span frequencies are sensitive to both end
friction constraints and seabed geometry.
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For marine riser dynamics, an attempt is made to
synthesise the best parts from the many and varied analysis
methods developed to date, into a simple but flexible design-orientated program. The riser is represented using
a Finite Element model similar to that employed for the
pipeline spans, and a reduced set of equations obtained
using a component mode synthesis method. Several riser/
articulated column designs are considered and the results
found to agree with published data.
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