Tower Bridge (1894) London, England
Tower Bridge is a combined bascule and suspension bridge over the River Thames in London and takes its name from the nearby Tower of London. Frequently mistaken for London Bridge, the next bridge upstream, it has become an iconic symbol of the city and a very popular tourist attraction.
In 1876 the City of London Corporation held a competition for the design of a much needed new river crossing downstream of London Bridge but it was essential that the new bridge would not disrupt river traffic. More than 50 designs were submitted for consideration and it wasn’t until 1884 that the bascule and suspension design of Sir Horace Jones and Sir John Wolfe Barry was chosen.
Construction began in 1886 and 8 years later Tower Bridge was officially opened on 30th June 1894.
Tower Bridge, London at night © By Diliff (Own work) [CC-BY-SA-3.0) via Wikimedia Commons
The bridge is 244m (800 ft) long between two 65m (213 ft) tall towers constructed on piers. The central span of 61m (200 ft) between the towers is split equally into two bascules or leaves, which can be raised to an angle of 83 degrees to allow river traffic to pass through. The bascules weigh over 1,100 tons each and are counterbalanced to minimize the force required to raise them, an operation which takes just five minutes. They are raised by huge hydraulic pumps which were first powered by coal burning steam engines which were replaced by electricity and oil in 1976. The two side-spans are suspension bridges, each being 82m (270 ft) in length.
Between the towers are two high level walkways which allow pedestrians to cross the river even when the bridge deck is raised. These walkways were closed to the public in 1910 due to lack of use but were reopened as fully covered passages in 1982 as part of the then newly launched Tower Bridge Exhibition.
The bridge is made from more than 11,000 tons of steel, and covered with Cornish granite and Portland stone. More than 70,000 tons of concrete were sunk into the riverbed to support the piers. The total construction cost was £1.184 million.
Links: Wikipedia | Tower Bridge Exhibition