8.1 Berthing structures and jetties
Cargo jetties consist of a berthing head at which the ships are moored to receive or
discharge their cargo and an approach structure connecting the berthing head to the shore
and carrying the road or rail vehicles used to transport the cargo. Where minerals are
handled in bulk the approach structure may carry a belt conveyor or an aerial ropeway. In
addition to its function in providing a secure mooring for ships, the berthing head carries
cargo-handling cranes or special equipment for loading and unloading dry bulk cargo
and containers.
Berthing structures or jetties used exclusively for handling crude petroleum and its
products are different in layout and equipment from cargo jetties. The tankers using the
berths can be very much larger than the cargo vessels. However, the hose-handling equip-
ment and its associated pipework are likely to be much lighter than the craneage or dry bulk-
loading equipment installed on cargo jetties serving large vessels. The approach from the
shore to a petroleum loading jetty consists only of a trestle for pipework and an access road-
way. Where the deep water required by large tankers commences at a considerable distance
from the shore-line, it is the usual practice to provide an island berthing structure connected
to the shore by pipelines laid on the sea bed.
In spite of the considerable differences between the two types of structure, piling is an
economical form of construction for cargo jetties as well as for berthing structures and pipe
trestles for oil tankers. The berthing head of a cargo jetty is likely to consist of a heavy deck
slab designed to carry fixed or travelling cranes and the imposed loading from vehicles
and stored cargo. The berthing forces from the ships using the berths can be absorbed by
fenders sited in front of and unconnected to the deck structure (Figure 8.1a), but it is more
usual for the fenders to transfer the berthing impact force to the deck and in turn to the rows
of supporting piles. The impact forces may be large and because the resistance of a vertical
pile to lateral loading is small the deck is supported by a combination of vertical and raking
piles (Figure 8.1b). These combinations can also be used in structures of the open trestle
type such as a jetty head carrying a coal conveyor (Figure 8.2).
The piles in the berthing head of a cargo jetty are required to carry the following
loadings:
(1) Lateral loads from berthing forces transmitted through fendering
(2) Lateral loads from the pull of mooring ropes
(3) Lateral loads from wave forces on the piles
(4) Current drag on the piles and moored ships
Chapter 8