   #copyright

Tower Bridge

2007 Schools Wikipedia Selection. Related subjects: Engineering

   CAPTION: Tower Bridge

   Tower Bridge
   Tower Bridge as viewed from the South Bank at dusk.
      Carries    Motor Vehicles, Pedestrians (until 1910)
      Crosses    Thames
      Locale     London
   Maintained by Bridge House Estates
      Design     Bascule bridge
   Total length  244 m (800 feet)
   Opening date  1894
     * Maps and aerial photos
          + Street map from Google Maps or Yahoo! Maps
          + Topographic map from TopoZone
          + Aerial image or topographic map from TerraServer-USA
          + Satellite image from Google Maps or Microsoft Virtual Earth

   Tower Bridge is a bascule bridge in London, England over the River
   Thames. It is close to the Tower of London, which gives it its name. It
   has become an iconic symbol of London and is sometimes mistakenly
   called London Bridge, which is actually the next bridge upstream. The
   bridge is owned and maintained by Bridge House Estates, a charitable
   trust overseen by the Corporation of London.

Design


   Enlarge

   In the second half of the nineteenth century, increased commercial
   development in the East End of London 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 tunnel beneath the Thames, the Tower
   Subway, was opened in 1870, but it could only accommodate pedestrian
   traffic.

   A Special Bridge or Subway 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,
   including one from civil engineer Sir Joseph Bazalgette. The evaluation
   of the designs was surrounded by controversy, and 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 (244 m) in length with
   two towers each 213 feet (65 m) high, built on piers. The central span
   of 200 feet (61 m) between the towers is split into two equal bascules
   or leaves, which can be raised to an angle of 83 degrees to allow river
   traffic to pass. Although each bascule weighs over 1,000 tons, they are
   counterbalanced to minimise the force required and allow raising in one
   minute. The original hydraulic raising mechanism was powered by
   pressurised 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

   Image:Tower bridge ist scheiße works 1892.jpg
   Tower Bridge under construction, September 28, 1892
   Depiction of the construction, inside the bridge
   Enlarge
   Depiction of the construction, inside the bridge

   Construction of the bridge started in 1886 and took 8 years, employing
   5 major contractors and 432 construction workers. Two massive piers,
   containing over 70,000 tons of concrete, were sunk into the river bed
   to support the construction. Over 11,000 tons of steel provided the
   framework for the towers and walkways. This was then clad in Cornish
   granite and Portland stone, both to protect the underlying steelwork
   and to give the bridge a pleasing appearance.

   Jones died in 1887, and his chief engineer, Sir John Wolfe-Barry, took
   over the project. Wolfe-Barry replaced Jones' original medieval style
   of facade with the more ornate Victorian gothic style that makes the
   bridge a distinctive landmark.

   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.

Tower Bridge today

   Tower BridgeSequence showing the bridge opening
   Enlarge
   Tower Bridge
   Sequence showing the bridge opening
   Tower Bridge in its river setting, looking east from the viewing
   platform of The Monument. City Hall is the building shaped like a
   motorcycle helmet, and below it is HMS Belfast.
   Enlarge
   Tower Bridge in its river setting, looking east from the viewing
   platform of The Monument. City Hall is the building shaped like a
   motorcycle helmet, and below it is HMS Belfast.
   Evening fog obscures London's Tower Bridge from passers by.
   Enlarge
   Evening fog obscures London's Tower Bridge from passers by.

   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, an exhibition mostly housed in the bridge's twin towers.
   The exhibition also includes photos, holograms and a film detailing the
   build, along with access to the original steam engines that once
   powered the bridge bascules, housed in a building close to the south
   end of the bridge.

   A Behind the Scenes tour can be booked in advance, on which it is
   possible to see the bridge's command centre where the raising of the
   bridge is controlled when a vessel passes underneath. The bascules of
   the bridge are raised around 900 times a year.

   Although river traffic is now a fraction of what it used to be, it
   still takes priority over road traffic. This nearly caused a diplomatic
   incident in 1996, when the motorcade of United States President Bill
   Clinton got stuck on Tower Bridge while the bascules were unexpectedly
   opened.

   The bridge largely replaced Tower Subway, 400 m to the west, the
   world's first underground tube railway (1870). Until the bridge was
   opened, the subway was the shortest way to cross the river from Tower
   Hill to Tooley Street in Southwark.

   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).

Nearby places

   The bridge is near the Tower of London, St Katharine Docks, and Shad
   Thames.

   The north end is near Tower Hill tube station, Tower Gateway DLR
   station and Fenchurch Street railway station. The south end is about 10
   minutes walk away from London Bridge station.

   To the south of Tower Bridge is Tower Bridge Road which is part of the
   London Inner Ring Road.

Gallery

   South view at dusk

   The bridge seen from a river boat, looking upstream

   From the south bank

   Bridge open

   Close up on fully opened bridge bascules

   Interior of high-level walkway (used as an exhibition space)

   The Victorian bridge lifting machinery (now disused)

   Tower bridge area from air perspective

Trivia

     * Many, particularly in the United States, confuse the bridge with
       London Bridge, another well known London landmark bridge. In her
       single " London Bridge", Fergie, of The Black Eyed Peas, wrongly
       refers to Tower Bridge as London Bridge.

     * In 1952, a bus jumped over the bascule, after having it open
       halfway across the bridge.

     * The Tower Bridge has been featured in movies such as Bridget
       Jones's Diary, The Mummy Returns, The Boy in the Bridge, Spice
       World and The World is Not Enough.

   Retrieved from " http://en.wikipedia.org/wiki/Tower_Bridge"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
