 |
Tower Bridge
Tower Bridge is a bascule bridge in London over The River Thames. In the second half of the 19th century increased commercial development led to a requirement for a new river crossing downstream of London Bridge. A traditional fixed bridge could not be built because it would cut off access to the port facilities situated at that time in the Pool of London, between London Bridge and the Tower of London.
A Special Committee was formed in 1876 to find a solution to the river crossing problem. It opened the design of the crossing to public competition. Over 50 designs were submitted but it was not until 1884 that a design submitted by Horace Jones, the City Architect, was approved.
Jones' design was for a bascule bridge 800 feet in length with two towers built on piers. The central span of 200 feet between the towers is split into two equal bascules, which can be raised to allow river traffic to pass. Although each bascule weighs over 1,000 tons, they are counterbalanced to minimize the force required and allow raising in one minute. The original hydraulic raising mechanism was powered by pressurized water stored in six accumulators. Water was pumped into the accumulators by steam engines. Today the original hydraulic machinery still opens the bridge, however it has been converted to use oil instead of water and electric motors have taken the place of the steam engines and accumulators. The old mechanism is open to the public.
Construction of the bridge started in 1886 and took 8 years to complete, the bridge was opened on 30 June 1894 by the Prince of Wales, the future King Edward VII of the United Kingdom, and his wife, Alexandra of Denmark.
The high-level walkways between the towers gained an unpleasant reputation as a haunt for prostitutes and pickpockets and were closed in 1910. They have now been reopened as part of the Tower Bridge Experience.
A computer system was installed in 2000 to control the raising and lowering of the bascules remotely. Unfortunately this has proved less reliable than desired, resulting in the bridge being stuck in the open or closed positions on a number of occasions (most recently 2 June 2005). (http://en.wikipedia.org/wiki/Tower_bridge)
|
 |
