As already noted, the facilities provided at the berthing head of an oil jetty or island
berthing structure are limited to hose-handling gear and pipework. A relatively small deck
area is required and the berthing structure can take the form of two main fenders spaced at
a distance equal to about 0.3 times the length of the largest tanker using the berth, with two
or more secondary fenders having a lower energy-absorbing capacity sited between them to
accommodate smaller vessels (Figure 8.7). Frequently, the main and secondary fenders are
sited in front of the hose-handling platform and pile trestles to allow them to take the full
impact of the tanker without transmitting any thrust to these structures. The independent
breasting dolphins, as shown in Figure 8.7, are designed so that their collapse load is not
exceeded by the thrust due to the maximum berthing velocity expected.
The type of piling required for independent breasting dolphins depends on the soil
conditions. Where rock, stiff clay or granular soils offering a good resistance to lateral loads
are present at or at a short distance below the sea bed, the dolphin can consist of a group
of large-diameter circular or box-section vertical steel piles, linked together by horizontal
diaphragms (Figure 8.8) and carrying a timber fender with rubber cushion blocks on
the front face of the group. The face area of the fender should be large enough to prevent
concentrated loading from damaging the hull of the ship. The horizontal bracing members
are not rigidly connected to the pile group. This is to allow the piles to deflect freely to the
maximum possible extent while performing their function of bringing the ship to rest.
The layout shown in Figure 8.7 can sometimes restrict the size and numbers of vessels
using the berth. It can be more economical to adopt a berthing structure of the type used for
cargo handling (Figure 8.1b). The berthing forces are transmitted directly to the deck so
404 Piling for marine structures
Figure 8.6Pile-supported fendering systems (a) Rubber cushion fender (b) Link-suspended clump
fender.
Rubber blocks
Main bearing frameFender
FenderR. C. clumpHardwood
guideSuspension links(a) (b)