3.3.4 Cables
The bridge deck, with a combined load-bearing
weight of more than 53,000 tonnes, is supported by
146 stay cables. There are 62 stay cables attached to
the South pylon (31 on each side), 54 attached to the
North pylon (27 on each side) and 30 attached to the
Central pylon (15 on each side).
The cable sheaths are helix-shaped to prevent
vibrations from wind and rain and were tested in wind
tunnels. They vary in length; with the shortest
measuring approximately 41m and the longest
measuring 226m.
Once the deck concrete reached the required
strength, the stay cables were installed. The first two
strands were threaded through the stay pipe, the
pylon crane lifted the pipe up to the anchor point in
the upper pylon where the top ends of the strands
were fixed into place.
Then a winch system within the stay pipe was used to
winch the remaining strands up one by one. Once all
of the strands were installed they sit in parallel inside
the stay pipe to form the stay cable.
The bottom ends of the strands were then attached
to the anchor point in the bridge deck and stressed
using a hydraulic system. This enabled to get the
correct level of tension needed to support that
segment of bridge deck.
More than 1300 km (810 miles) of the strands were
used for the project. The strands were delivered to
site in compact coils. Every single strand was installed
individually, combined to achieve a rate of 6 stays per
week.
Each stay cable consists of between 41 and 91
individual steel strands that sit inside a stay pipe – the
outer casing that provides protection from weather-
related corrosion. Each strand contains seven wires,
which are galvanised, waxed and coated.
Figure 12: The first stay cable being
lifted into position by a pylon crane
at the South pylon
Figure 13: Steel strands can be seen inside
the light green stay pipe, which form the
stay cable
3/2017
Figure 14: First stay