In a delightful show of Scottish engineering, a new moveable bridge to span the Clyde River works like a drawbridge but horizontally.
It’s one of the world’s first large “double-leaf swing bridges,” to use the proper term, which opens to allow boat traffic to pass by swinging each half of the bridge like the paddles in a pinball machine.
The New Clyde River Bridge is the centerpiece of a $140 million revitalization project for the communities on each side: the Clyde Waterfront and Renfrew Riverside. It will consist of a motorway, bike path, and pedestrian walkways, and will be the first new crossing point for vehicles since 2006.
“The connectivity and opportunities it will create for businesses, workers, and communities to locate here is going to bring visible economic benefits to Renfrewshire and the Glasgow City Region,” said Renfrewshire Council leader Iain Nicolson.
In particular, the bridge replaces an outdated car ferry service and will allow direct road access to the Glasgow airport.
Rotating on vast cylindrical bearings on either riverbank, the bridge’s two decks measure 213 feet, and meet in the middle of the river. Their 88-foot-long back spans, or the part of the bridge that projects over the land behind it, incorporate 500 metric tons of counterweights to pair with three stressed staying cables on either side of a central pylon.
“I would say it’s the most complicated moveable bridge I’ve ever designed, and I’ve designed a lot of these things,” says Florida-based Jim Phillips, lead bridge designer with Hardesty & Hanover LLC (H&H).
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Phillips told ENR that the local port authority required 90 meters by 45 meters of space under any prospective bridge for vessels to access offshore oil rigs nearby. Countering, the airport set a height ceiling on vertical structures at 40 meters, and space restrictions on both banks of the Clyde prevented a more traditional single-leaf swing bridge.
But if necessity is the mother of invention, Phillips and others involved innovated their hard hats off.
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“In a lot of swing bridges, the bridge is balanced so the total dead load center of gravity is right at the pivot point,” explains Phillips. Peter Reina at ENR added that Philllips’ solution to redesign requirements was actually to unbalance it.
The project is jointly funded by the UK and Scottish governments through the £1.13bn Glasgow City Region—a coalition of 8 local governments around Glasgow.
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A proven concept has now been created and implemented on each bank rather than the center of the river.
The first swing bridge was built in Chicago, IL, USA in 1857. Others were built in that general area around the same time. The concept had been copied to Europe and implemented in many locations with a hydraulically powered bridge making life easier in 1873.