e-mosty December 2018 e-mosty December 2018 | Page 45

For these manoeuvres, ALE utilised barges on the
Swan River to float the wishbones to the designated
piers and used the Mega Jack as temporary 50m high
towers to pull the wishbones up.
After successfully lifting the first wishbone using
strand jacks, the second wishbone was lifted and
concurrently the both wishbones were successfully
docked within two weeks’ time.
The fourth stage was the lifting of the five bridge
decks, which formed the pedestrian and cycle path
crossing the river.
III. SPMT TRANSPORT
The two wishbones were transported from the
assembly area onto the barges using SPMTs.
The SPMTs were prepared under ALE supervision in
the required configurations, and temporary supports
were installed and lashed on the trailer deck.
Following the assembly, the trailers were positioned
under the wishbones and concurrently transported to
the quay side for load-out.
As the two wishbones had a unique design, the
configuration of the temporary supports was changed
under ALE supervision allowing the trailers to be
positioned and the wishbone to be transported for
load-out.
IV. MARINE TRANSPORT
The marine transport was executed using two barges.
These barges were connected with a truss system
causing the barges to act as a single floating system.
V. INSTALLATION OF MEGA JACK TOWERS
During the SPMT and the water transportation, ALE
personnel executed the installation of the Mega Jack
system concurrent on each pier.
The main structure of the Mega Jack system and the
lifting construction was built as low level as possible.
This was to reduce the amount of heavy crane works
required, and, more importantly, to reduce the
amount of working at height hours.
Following the installation of the Mega Jack system,
the towers were individually jacked-up to a height of
65 m above the level of the assembly area of the
wishbones.
After docking the wishbone(s), the strand wires were
connected from the top lifting construction with the
wishbone(s) using Dyneema slings. This gave the
necessary flexibility, eased the connections of the
strand lift system, and reduced lead times required
for connections.
Finally, the main lifts were executed and each
wishbone was lifted to an over rotated stage to allow
the final docking of the wishbones to take place.
The final docking took place with a strand jack
operator on each side of the river, which were able to
lower the wishbone(s).
The full connection in the top of the wishbone was
established using camera systems and geometrical
survey.
VI. INSTALLATION OF THE BRIDGE DECKS
The load-out followed the pre-determined procedure
which involved coordination between three parties
and the use of crawler cranes and SPMTs. Concurrent the final docking of the wishbones, the
barge system was floated back to the assembly area.
There, the old transport construction was modified
and the barges were connected together.
When the load-out was completed, all mooring lines
were installed to allow the float-in itself to
commence. This allowed the bridge decks to be lifted on top of
the new barge system using a 650t crawler crane.
Due to the assembly restrictions, one of the
wishbones required a 180° rotation on the water,
which required the repositioning of all mooring lines
during this rotation.
Following the float-in of each wishbone, the
wishbones were docked on their designated
foundation and secured for unwanted movements.
As no ballasting of the barges was involved in any of
the operations, the tidal compensation and any
required height changes for docking were executed by
using hydraulic cylinders. These were able to lift and
lower the wishbone individually on each barge.
4/2018
In the new barge system, also hydraulic cylinders
were present to overcome any barge draft and
compensate tidal levels.
The bridge decks were floated one by one under the
main arch and connected to the cables hanging from
the arch.
After installation, each bridge deck was lifted
individually to allow the pretensions adjustment of
the cables. When all works were finished, all
equipment was removed from the site and
demobilised.