Continued...
Without the project it is estimated that
traffic weight restrictions on the bridge will have to be introduced as early as
2013.
To enable access for work on the main
cables to take place Bennett Associates have designed a 28m long lightweight,
steel gantry. Two gantries have been made which will travel along and up the
main cables to the top of the towers, 100m above deck level. Linear elastic
analysis software was used to design the structure for a variety of different
support configurations and harsh loading conditions.
The platform moves along the cable from one set of hangers, which
the bridge deck is suspended from, to the next. At this point the platform is
secured to the main cable ready for work to commence on that section.
Access is via a small man rider cradle, which suspends off the side of the
platform and hoists the men and equipment up and down as necessary to carryout
the works.
The work from the platform involves wrapping the whole cable with
a plastic wrap, which is heat sealed to form an impermeable coating. The cable
bands, which support the deck hangers, are sealed using various polymers to
ensure there is no way for air to escape.
At several locations along the cables, air injection sleeves,
designed by Bennett Associates, are installed along with the necessary pipework
and air condition sensors to carryout the dehumidifying task.
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