A Self-Learning Manual - Institution of Engineers Mauritius

A Self-Learning Manual
Mastering Different Fields of Civil Engineering Works (VC-Q&A Method) Vincent T. H. CHU
Level One (Core FAQs)
Part I: Piers and Dolphins
1. Which configuration is better, finger jetty or T-shaped jetty? (P1)
Finger jetty is a more efficient pier structure because it could accommodate
vessels at both sides of the jetty. However, there should be sufficient water
depth as the berths at finger jetty is relatively close to shoreline when
compared with T-shaped jetty so that it is anticipated that vessels are
required to berth at shallower water. Moreover, there should be no cross
current to enhance berthing at both sides of finger jetty. Also, as mooring
points are often located on the jetty, leads are not ideal for larger ships.
T-shaped jetty allows higher water depth for vessels to berth. Moreover,
with the installation of breasting dolphins and mooring dolphins, it allows
the berthing of larger vessels.
Fig. Finger jetty and T-shaped jetty
2. Why is shallow bedrock condition unfavorable for open berth
piers?
The most severe load on piers generally is the horizontal load due to
berthing of large vessels. Since the widths of open berth piers are relatively
small so that they provides a short lever arm to counteract the moment
induced by berthing loads. Moreover, the dead load of open berth piers are
normally quite light and therefore the resisting moment provided by the
dead load of pier structures may not be sufficient to counteract the moment
generated by berthing loads.
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