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Alternative Solutions to Bridge Design

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The Gateshead Millennium Bridge

The Twin Sails Bridge in Dorset

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The Twin Sails Bridge is a double leaved bascule bridge that spans the Backwater Channel in Holes Bay connecting the town center of Poole, in Dorset, England, to Hamworthy. In the closed position, the bridge lays flat over its supporting pillars, but when the two spans of the bridge are lifted to allow boats to pass, the two triangular lifting leaves resembles the sails of a yacht. The triangular shape is caused by the fact that the bridge isn’t dissected perpendicularly across its width, but at an angle, creating two long, opposing triangles that lie side by side. When the bridge is opened, they rise skyward, like a pair of masts opening their sails.

The two triangular leaves measure 23 meters each, and when lifted, they provide a clear channel 19 meters wide for boats to pass through. The lift spans are powered by two hydraulic rams which operate up to 15 times per day, and take two minutes to fully open.

The bridge was built and opened to traffic in April 2012, after nearly three decades of deliberation, approvals and cancellations. The plan for the construction of a new bridge was initiated in the 1980s. The existing bridge, which was built in 1927, was facing congestion due to increasing traffic levels. At first a fixed bridge crossing Holes Bay and linking with the A31 was suggested but it got cancelled in 1998. The concept of the second lifting bridge was put forward in 2004, and received approval in 2006, but immediately went into hold due to issues between the council and the land owners. When everything was cleared and parties had agreed, construction of the bridge commenced in 2010.

SOURCES:

Dowling, D. (2019). Engineering Your Future: An australasian guide. Milton, QLD: John Wiley and Sons Australia.

Patowary, K. (2016, January 14). The twin sails bridge. Amusing Planet. https://www.amusingplanet.com/2016/01/the-twin-sails-bridge.html

Interesting Engineering (2016, April 12). Gateshead Millennium Bridge: World’s Only Tilting Bridge. Interesting Engineering. https://interestingengineering.com/gateshead-millennium-bridge-worlds-only-tilting-bridge