Flexible pipes are often a technically attractive alternative to
the traditional steel pipe. Often commercial utilisation of
oil/gas fields depends on the use of flexible pipes. An example is
when floating production vessels are used, where the flexible pipe
follows the wave induced motions and thus resists the loading from
the environment in a more suitable way.A flexible pipe is a
composite structure, built up of several layers each having a
specific function. Due to the flexibility, the response of the
pipe in wave induced motions are governed by a complex
hydroelastic set of differential equations.An important part in
the design of flexible pipes is the end fitting. The purpose of
the end fitting is mainly to connect pipe units, but it also
combines and terminates the different layers of the flexible pipe.
The end fitting system contains a bending stiffener and an end
fitting. The bending stiffener is installed to prevent damages
caused by bending concentrations at the connection. The bending
stiffener is designed to optimise the curvature distribution from
the flexible riser to the vessel and to minimise the support
forces at the vessel.Today, when end-fitting system are designed
FEM programs are normally used to determine the stresses in the
end fitting system. It is a timeconsuming procedure due to large
non-linearities and therefore costly. The purpose of this study is
to generate design curves for the tension andaxial force in a
flexible riser as function of different riser parameters.The idea
is to divide the riser system of riser and end fitting system into
a global system including the riser and a local system of the
bending stiffener and the end fitting. The forces at top of the
riser shall be used as input for the design of the local
system.This report introduces a non-dimensional description of
these forces, a force design basis. This description is
non-dimensional curves where the tension and the bending moment
can be estimated at top of the riser when input data like water
depth, weight per length, inner diameter andpressure (for tension)
and current velocity (for bending moment) are given.
| Number of pages | 67 |
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| Publication status | Published - 1996 |
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