The first stay cable connecting the south pylon to the main bridge deck has been installed on the £600 million Mersey Gateway Project.
The 52-metre long cable at the south pylon in the Mersey estuary is one of 146 stay cables that will support the 1,000-metre long reinforced concrete bridge at Halton.
Gareth Stuart, Project Director of the Merseylink construction joint venture, which comprises Kier, Samsung and FCC, said: “This marks a momentous occasion for the project.
“The stay cables will be an iconic feature of this landmark structure making it one of the most recognisable bridges in the UK. We’re now entering a new, very visual phase of the bridge construction, where people will be able to see the stay cables connected to the bridge deck as it emerges across the river week by week.
“??Form traveller machines are casting the deck segments from each side of the three pylons and once the concrete has reached the required strength the stay cables will be installed along the bridge.”
More than 810 miles of the strands will be used on the project – equivalent to the same distance from John O’Groats to Land’s End – with each cable installed individually.
Each stay cable consists of up to 91 individual steel strands that sit inside an outer casing known as a stay pipe, which provides protection from weather-related corrosion.
Merseylink’s Design Manager, George Moir, explains. “The first two strands are threaded through the stay pipe then the tower crane lifts the pipe up to the anchor point in the upper pylon where the top ends of the strands are fixed into place.
“The bottom ends of the strands are then attached to the anchor point in the bridge deck and stressed using a hydraulic system. This enables us to get the correct level of tension needed to support that segment of bridge deck.
“We then use a winch system through the stay pipe to winch the remaining strands up one by one. Once all of the strands have been installed they sit in parallel inside the stay pipe to form the stay cable.”
The combined load bearing capacity of the 146 stay cables is about 53,500 tonnes, which is heavier than the QE2 ocean liner.