UFC 4-159-03
3 October 2005
CHAPTER 8
EXAMPLE PROBLEMS
8-1
INTRODUCTION. The design of mooring systems is illustrated through
the use of several examples in this section. The emphasis of this UFC is on statics, so
static results are shown. However, the marine environment can be dynamic, so
dynamic effects are illustrated in the examples.
8-2
SINGLE POINT MOORING - BASIC APPROACH. Design of single point
fleet moorings (SPMs) is illustrated here.
Let us first assume that the wind is coming from a specified direction and
has stationary statistical properties. The current speed and direction are constant. In
this case there are three common types of ship behavior, shown in Figure 8-1, that a
vessel at a single point mooring can have:
a) Quasi-static. In this case the ship remains in approximately a fixed
position with the forces and moments acting on the ship in balance. For quasi-static
behavior, the tension in the attachment from the ship to mooring will remain
approximately constant. Quasi-static analyses can be used for design in this case.
b) Fishtailing. In this case the ship undergoes significant surge, sway,
and yaw with the ship center of gravity following a butterfly-shaped pattern. The
mooring can experience high dynamic loads, even though the wind and current are
constant.
c) Horsing. In this case the ship undergoes significant surge and sway
with the ship center of gravity following a U-shaped pattern. The mooring can
experience high dynamic loads.
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