e-mosty September 2018 Vessels and Equipment Used for Bridge Construction | Page 8

VESSELS AND MARITIME EQUIPMENT
USED FOR BRIDGE CONSTRUCTION
Hans Tompot – naval architect
I.
I. INTRODUCTION
This article gives a general overview of vessels and
maritime equipment which are used in the
construction of bridges over rivers, canals, bays,
fjords, etc. The first part focuses mainly on sheerlegs.
The Second part gives examples of vessels and
maritime equipment in bridge construction and the
third part comprises major equipment specification
tables.
The equipment most commonly used in bridge
construction can be divided into four major groups:
 Floating sheerlegs (cranes) / Heavy Lift Vessels
 Pontoons and barges, towed by a tug
 Heavy transport vessels
 Special purpose vessels
II.
III.
II. FLOATING SHEERLEGS
possible under favourable conditions with limited
wind speed, current, wave height and ship
movements. Open water lifting operations are
therefore reserved for the larger units subject to their
construction and longitudinal strength.
To select a floating sheerleg for a lifting operation the
following criteria are pertinent:




Mass and dimensions of object
Required lifting height
Required outreach
Operational conditions
In general, sheerlegs are fitted with an A-frame and a
jib on top of the A-frame. The A-frame and jib are
each provided with at least two hoisting tackles.
Instead of a jib some units can be equipped with a
long boom to increase the lifting height.
A floating sheerleg is a vessel with a crane (the
sheerleg), which in contrast with a crane vessel is not
capable of rotating its crane independently of its hull.
Sheerlegs are mostly used for salvaging ships,
assistance with shipbuilding, loading and unloading of
large loads in ships and in bridge construction.
The lifting capacity and dimensions have increased
considerably in recent decades and have been
adapted to deal with the ever increasing dimensions
of ships, cargoes and structures for the offshore
industry, civil engineering, marine salvages.
The largest floating sheerlegs are self-propelled and
have accommodation facilities on board, while the
smaller units are often propulsion-assisted for
manoeuvring and need to be towed to their operation
area.
Most lifting operations using floating sheerlegs take
place in sheltered waters, like ports, estuaries, river
deltas, etc. Lifting operations in open waters are only
Figure 1: Diagram of a typical sheerleg
(based on ´Uglen´ of Ugland Construction AS
3/2018