ANZAC Bridge - Sydney

Stay Cables

The western tower, along with the first three deck segments, were built at the same time and completed in mid 1993. During construction the three deck segments were supported by scaffolding and then, when tower construction was completed, the first stay cables were installed.

The sub contractor responsible for the cable stays was Austress Freyssinet Pty Ltd.

Wire strand
Single strand showing the seven galvanised steel wires
The stay cables were constructed from multiple wire strands surrounded by a black polyethylene sheath supplied by Vinidex Pty Ltd.

The individual strands, 15.7mm in diameter, consist of seven galvanised steel wires waxed and covered in polyethylene.

The number of strands in each sheath varied - increasing in number from 25 to 74 towards the centre of the bridge.
wire strands within cables
Wire strands within cables.
Stay Cable outer tubes
Polyethylene sheath ready for joining.

12m lengths of polyethylene sheath were welded together on the deck and an initial wire strand drawn in.
The sheath and strand were then winched into place and the initial strand fixed into the anchor points and tensioned to its predetermined load. 3.

Cable strands and drawing wheel
Cable strands within the polyethylene
sheath and the drawing wheel.
Stay Cable outer tube
Joined length of polyethylene sheath ready for placement.

The remaining strands were then individually drawn into place through the polyethylene sheath from the deck level using a drawing wheel.

After being secured in an adjustable anchorage point in the tower head, the strand was cut to length and fixed at deck level.

A hydraulic jack at the tower top was then used to set the final strand tension to match that of the initial strand. 1.3.8.

The cable drawing wheel
The cable drawing wheel.
Tower anchor points
Tower anchor points.
Anchor points - eastern end
Cable stay anchor points - eastern end.
Anchor points under the deck - western end
Anchor points under the deck - western end.
Stay cables are numbered - eastern end 1
Stay cables are numbered viewed from the spiral ramp eastern end
Stay cables are numbered - eastern end 2

Initially the stay cables were subject to serious vibrations. Experimentation using heavy ropes tying the stay cables diagonally back to the deck reduced the problem.

Antivibration cables
A permanent solution replaced the ropes with thin spring loaded stabilising cables between the stay cables and the deck.

The spring failure safety link shown below was added later.

From 2011 to 2013 major works were undertaken to replace the stabilising cables with hydraulic dampers.See stay cable maintenance 

Antivibration cable mounting to deck showing safety link
Antivibration cable mounting to deck

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