Pile Design and Construction Practice, Fifth edition

416 Piling for marine structures
Dredgect
seabed
Ice rubble
Current direction
Ice floe
Figure 8.14 Conical structure for resisting ice forces.
As already noted the face of a timber fender pile can be protected by a renewable timber rubbing
strip. The type of timber used for fender piles is governed by considerations of the attack by
organisms present in the sea water. Suitable types of timber are described in Chapter 10.
For jetties and berthing structures in deep water serving large vessels, either steel or
prestressed concrete tubular piles can be used. Steel piles have the advantage that they can
withstand rough handling while being loaded onto barges and lifted into the leaders of the
floating piling frame or jack-up platform (Figure 3.7). They can withstand hard driving to
attain the penetration depths necessary to achieve the required uplift and lateral resistance.
However, they require expensive cleaning and coating treatment above the soil line, supplemented
by cathodic protection to enable them to resist corrosion in sea water. Losses in
thickness of the pile section over the design life of the structure caused by corrosion need to
be considered in relation to the working stresses under operating conditions. The types of
steel suitable for piling in marine structure are discussed in Section 2.2.6.
Prestressed concrete piles also possess considerable resilience, but repair is a difficult problem
if they are subjected to accidental heavy impact damage. Prestressed concrete piles are suitable
for approach structures and for jetty heads protected by independent berthing structures.
Problems of sea-water attack on steel and concrete structures are discussed in Chapter 10.
8.2 Fixed offshore platforms
Water
filling
Support piles
Ballast
RC caisson
Rock rubble
mattress
Because of their location, frequently in deep water exposed to severe wave action, the forces
acting on fixed platform structures are different in character from those on jetties in