London, England

Tower Bridge was completed in 1894, after eight years of construction. It is a combined bascule ("draw") and suspension bridge. Total length, including approaches, is 2,680 feet.

The bascule bridge is 800 feet (244 m) in length, with each of the two towers being 213 feet (65 m) high. The central span of 200 feet (61 m) is split into two equal bascules, which can be raised to an angle of 83 degrees to allow river traffic to pass.

The two side spans are suspension bridges, with the suspension rods anchored both at the abutments and through rods contained within the bridge's upper walkway. Each side span is 270 feet long.

History

London Bridge was the first crossing over the Thames River at London. As London grew, more bridges were added, but always to the west of London Bridge. By the 19th century, however, the east end of London had become so densely populated that public pressure mounted for a bridge to the east of London Bridge.

In 1876, the City of London Corporation formed the "Special Bridge or Subway Committee," and opened the design of a new river crossing to public competition. Over 50 designs were submitted, but it wasn't until October 1884 that Horace Jones, the City Architect, in collaboration with John Wolfe Barry, offered the design which resulted in the Tower Bridge.

Operation

When it was completed, Tower Bridge was the largest and most sophisticated bascule ("draw") bridge ever built. It was a hydraulically operated bridge, using steam to power the enormous pumping engines. The energy created was then stored in six massive accumulators so that, as soon as power was required to lift the bascules, it was readily available. The accumulators fed the driving engines, which in turn drove the bascules up and down.

Nowadays the bascules are stilled operated by hydraulic power, but since 1976 they have been driven by oil and electricity rather than steam.

The Tower Bridge Exhibition

The high-level walkways between the bridge's main towers were designed so that the public could still cross the Bridge when it was raised, but they were closed to the public in 1910 due to lack of use -- most people preferred to wait at the bottom and watch the bascules rise and fall.

In 1982, the walkways and towers were opened to the public for the first time since 1910, with a permanent exhibition inside called the Tower Bridge Exhibition. In 1993, the Tower Bridge Experience opened, featuring animatronic models telling the story of Tower Bridge. The current Tower Bridge Exhibition, focusing on the magnificent views from the Walkways and the history of the Bridge, opened in 2002.

The Tower Bridge Exhibition website is located at www.towerbridge.org.uk.

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