Tower Bridge
Tower Bridge from the North Bank at dusk
Carries	A100 Tower Bridge Road - motor vehicles, pedestrians
Crosses	Thames
Locale	London
Maintained by	Bridge House Estates
Design	Bascule bridge, suspension bridge
Longest span	61 m (200 ft)
Total length	244 m (800 ft)
Clearance below	8. The Thames ( is a major River flowing through southern England. London ( ˈlʌndən is the capital and largest urban area in the United Kingdom. The City Bridge Trust, is the working name of the grant-making arm of Bridge House Estates and was set up in 1995 The Bascule Bridge is a paved one-lane highway bridge in Westport, Massachusetts, USA. This article is concerned with a particular type of suspension bridge the suspended-deck type 6 m (closed), 42. 5 m (open)
Opening date	30 June 1894

Tower Bridge is a combined bascule and suspension bridge in London, England over the River Thames. The Bascule Bridge is a paved one-lane highway bridge in Westport, Massachusetts, USA. This article is concerned with a particular type of suspension bridge the suspended-deck type London ( ˈlʌndən is the capital and largest urban area in the United Kingdom. England is a Country which is part of the United Kingdom. Its inhabitants account for more than 83% of the total UK population whilst its mainland The Thames ( is a major River flowing through southern England. It is close to the Tower of London, which gives it its name. Her Majesty's Royal Palace and Fortress, more commonly known as the Tower of London (and historically as The Tower) is a historic monument in central London It has become an iconic symbol of London. For other uses of the term see Icon (disambiguation. For a list of icons for use on Wikipedia see WikipediaIcons. Tower Bridge is one of several London bridges owned and maintained by the City Bridge Trust, a charitable trust overseen by the City of London Corporation. The City Bridge Trust, is the working name of the grant-making arm of Bridge House Estates and was set up in 1995 The City of London Corporation (formerly known as the Corporation of London)is the municipal governing body of the City of London.

Tower Bridge is sometimes mistakenly referred to as London Bridge, which is actually the next bridge upstream. London Bridge is a Bridge between the City of London and Southwark in London, England, over the River Thames. ^[1] A popular urban legend is that, in 1968 Robert McCulloch, the purchaser of the old London Bridge which was later shipped to Lake Havasu City, Arizona, believed mistakenly that he was buying Tower Bridge, but this was denied by McCulloch himself and has been debunked by Ivan Luckin, the seller of the bridge. An urban legend or urban myth is a form of modern Folklore consisting of stories thought to be factual by those circulating them For other persons bearing this name see Robert McCulloch (disambiguation. The London Bridge, currently located in Lake Havasu City Arizona, USA, was originally constructed in London, in 1831 Lake Havasu City is a city in Mohave County, Arizona, United States. ^[2]

Design

Elevation, with dimensions

Tower Bridge under construction, 1892

In the second half of the 19th 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 in the Pool of London, between London Bridge and the Tower of London. Originally the Pool of London was the stretch of the River Thames forming the south side of the City of London.

A Special Bridge or Subway Committee was formed in 1876, chaired by A. J. Altman, 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. A civil engineer is a person who practices Civil engineering, one of the many engineering professions Sir Joseph William Bazalgette ( 28 March 1819 &ndash 15 March 1891) was one of the great English Civil engineers of 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 (who was also one of the judges),^[3] was approved. Sir Horace Jones ( 20 May 1819 - 1887 was an English Architect of the 19th century knighted in 30 July 1886

Jones' engineer, Sir John Wolfe Barry devised the idea of a bascule bridge 800 feet (244 m) in length with two towers each 213 feet (65 m) high, built on piers. Sir John Wolfe-Barry ( December 7, 1836 – January 22, 1918) was an English Civil engineer of the late 19th and early The Bascule Bridge is a paved one-lane highway bridge in Westport, Massachusetts, USA. A foot (plural feet or foot; symbol or abbreviation ft or sometimes &prime – the prime symbol) is a non-SI unit The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International The central span of 200 feet (61 m) between the towers was split into two equal bascules or leaves, which could be raised to an angle of 83 degrees to allow river traffic to pass. The bascules, weighing over 1,000 tons each, were counterbalanced to minimize the force required and allow raising in five minutes.

The two side-spans are suspension bridges, each 270 feet (82 m) long, with the suspension rods anchored both at the abutments and through rods contained within the bridge's upper walkways. The pedestrian walkways are 143 feet (44 m) above the river at high tide. ^[4]

Construction started in 1886 and took eight years with five major contractors – Sir John Jackson (foundations), Baron Armstrong (hydraulics), William Webster, Sir H.H. Bartlett, and Sir William Arrol & Co.^[5] – and employed 432 construction workers. Sir John Jackson ( 4 February 1851 &ndash 14 December 1919) was a Unionist Member of Parliament for Devonport Sir William George Armstrong 1st Baron Armstrong ( November 26 1810 &ndash December 27 1900) was a Tyneside industrialist who Sir Herbert Henry Bartlett 1st Baronet ( 30 April 1842 &ndash 23 June 1921) was a civil engineer and contractor responsible for many landmark Sir William Arrol & Co was a leading Scottish Civil engineering business based in Glasgow. E W Crutwell was the resident engineer for the construction. ^[4]

Two massive piers, containing over 70,000 tons of concrete,^[6] were sunk into the river bed to support the construction. Concrete is a construction material composed of Cement (commonly Portland cement) as well as other cementitious materials such as Fly ash and Slag Over 11,000 tons of steel provided the framework for the towers and walkways. Steel is an Alloy consisting mostly of Iron, with a Carbon content between 0 ^[7] This was then clad in Cornish granite and Portland stone, both to protect the underlying steelwork and to give the bridge a pleasing appearance. Cornwall ( Kernow ˈkɛɹnɔʊ is the most southwesterly county of England, on the Peninsula that lies to the west of the River Tamar Granite (ˈɡrænɪt is a common and widely occurring type of intrusive, Felsic, igneous rock. Portland stone is a Limestone from the Jurassic period quarried on the Isle of Portland, Dorset.

Jones died in 1887, and George D. Stevenson took over the project. ^[8] Stevenson replaced Jones' original brick facade with the more ornate Victorian Gothic style that makes the bridge a distinctive landmark, and was intended to harmonise the bridge with the nearby Tower of London. Culture The Victorian fascination with novelty resulted in a deep interest in the relationship between modernity and cultural continuities The Gothic Revival is an architectural movement which began Her Majesty's Royal Palace and Fortress, more commonly known as the Tower of London (and historically as The Tower) is a historic monument in central London ^[4]

The bridge was officially opened on 30 June 1894 by the Prince of Wales, the future King Edward VII, and his wife, Alexandra of Denmark. Events 350 - Roman usurper Nepotianus, of the Constantinian dynasty, is defeated and killed by troops of the Usurper Year 1894 ( MDCCCXCIV) was a Common year starting on Monday (link will display the full calendar of the Gregorian calendar (or a Common Alexandra of Denmark (Alexandra Carolina Marie Charlotte Louise Julia 1 December 1844 – 20 November 1925 was Queen Consort to Edward VII of the United Kingdom ^[9]

The bridge connected Iron Gate, on the north bank of the river, with Horsleydown Lane, on the south – now known as Tower Bridge Approach and Tower Bridge Road, respectively. The London Inner Ring Road is the name commonly given to a route formed from a number of major Roads that encircle the centremost part of London. ^[4] It largely replaced Tower Subway, 400 m to the west, the world's first underground railway (1870). The Tower Subway is a Tunnel beneath the River Thames in central London, close — as the name suggests — to the Tower of London. Until the bridge was opened, the subway was the shortest way to cross the river from Tower Hill to Tooley Street in Southwark. Tower Hill is an elevated spot north-west of the Tower of London, just outside the limits of the City of London in the London Borough of Tower Hamlets. Tooley Street is a road in South London connecting London Bridge to St Saviour's Dock; it runs past Tower Bridge on the Southwark Southwark or The Borough is an area of south-east London in the London Borough of Southwark, situated 1

The total cost of construction was £1,184,000. ^[4]

Hydraulic system

One of the original steam engines: a 360 hp horizontal twin-tandem compound engine, fitted with Meyer expansion slide valves

The original raising mechanism was powered by pressurised water stored in six hydraulic accumulators. A hydraulic accumulator is an Energy storage device It is a Pressure storage reservoir in which a non-compressible Hydraulic fluid is held under pressure

The system was designed and installed by Sir W. G. Armstrong Mitchell & Company of Newcastle upon Tyne. Sir W G Armstrong Whitworth & Co Ltd was a major British manufacturing company of the early years of the 20th century Newcastle upon Tyne ( (often shortened to Newcastle) is a city and Metropolitan borough of Tyne and Wear, England Water, at a pressure of 750psi, was pumped into the accumulators by two 360 hp stationary steam engines, each driving a force pump from its piston tail rod. The pound per square inch or more accurately pound-force per square inch (symbol psi or lbf/in² or lbf/in²) is a unit of Stationary steam engines are fixed Steam engines used for pumping or driving mills and factories and for power generation The accumulators each comprise a 20-inch ram on which sits a very heavy weight to maintain the desired pressure.

In 1974, the original operating mechanism was largely replaced by a new electro-hydraulic drive system, designed by BHA Cromwell House. The only components of the original system still in use are the final pinions, which engage with the racks fitted to the bascules. These are driven by modern hydraulic motors and gearing, using oil rather than water as the hydraulic fluid. A Hydraulic motor is a mechanical actuator that converts hydraulic pressure and flow into torque and angular displacement (rotation ^[10]

Some of the original hydraulic machinery has been retained, although it is no longer in use. It is open to the public and forms the basis for the bridge's museum, which resides in the old engine rooms on the south side of the bridge. The museum includes the steam engines, two of the accumulators and one of the hydraulic engines that moved the bascules, along with other related artefacts.

The third steam engine

During World War II, as a precaution against the existing engines being damaged by enemy action, a third engine was installed in 1942. World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including ^[11] This was a 150 hp horizontal cross-compound engine built by Vickers Armstrong Ltd., at their Elswick works in Newcastle-upon-Tyne. Vickers was a famous name in British engineering that existed through many companies from 1828 until 2004 It was fitted with a 9 feet diameter flywheel weighing 9 tons, and was governed to a speed of 30 rpm. A flywheel is a mechanical device with significant Moment of inertia used as a storage device for Rotational energy.

The engine became redundant when the rest of the system was modernised in 1974, and was donated to the Forncett Industrial Steam Museum by the Corporation of the City of London.

Navigation control

To control the passage of river traffic through the bridge, a number of different rules and signals were employed. Daytime control was provided by red semaphore signals, mounted on small control cabins on either end of both bridge piers. One of the earliest forms of fixed Railway signal is the semaphore. At night, coloured lights were used, in either direction, on both piers: two red lights to show that the bridge was closed, and two green to show that it was open. In foggy weather, a gong was sounded as well. ^[4]

Vessels passing through the bridge had to display signals too: by day, a black ball at least 2 feet (0. 61 m) in diameter was to be mounted high-up where it could be seen; by night, two red lights in the same position. Foggy weather required repeated blasts from the ship's steam whistle. A steam whistle is a device used to produce Sound with the aid of Live steam. ^[4]

If a black ball was suspended from the middle of each walkway (or a red light at night) this indicated that the bridge could not be opened. These signals were repeated about 1,000 yards (910 m) downstream, at Cherry Garden Pier, where boats requiring to pass through the bridge had to hoist their signals/lights and sound their horn, as appropriate, to alert the Bridge Master. ^[4]

Some of the control mechanism for the signalling equipment has been preserved and may be seen working in the bridge's museum.

Reaction

Although the bridge is an undoubted landmark, professional commentators in the early 20th century were critical of its aesthetics. "It represents the vice of tawdriness and pretentiousness, and of falsification of the actual facts of the structure", wrote H. H. Statham,^[12] while Frank Brangwyn stated that "A more absurd structure than the Tower Bridge was never thrown across a strategic river". ^[13]

Architectural historian Dan Cruickshank selected the bridge as one of his four choices for the 2002 BBC television documentary series Britain's Best Buildings. The term architecture (from Greek αρχιτεκτονικήarchitektoniki) can be used to mean a process a profession or documentation History is the study of the past particularly the written record Those who study history as a Profession are called Historians Etymology Dan Cruickshank (born 26 August, 1949) is an architectural historian and Television presenter currently working for the BBC The year 2002 in television involved some significant eventsBelow is a list of Television -related events in 2002. Television ( TV) is a widely used Telecommunication medium for sending ( Broadcasting) and receiving moving Images, either monochromatic Documentary film is a broad category of visual expression that is based on the attempt in one fashion or another to " Document " reality Britain's Best Buildings is a BBC documentary series in which Dan Cruickshank chooses the finest examples of British architecture ^[14]

Incidents

At 21:35 on 30 December 1952, a crowded double-decker London bus (an RT), on route 78 to Dulwich, jumped over the gap when the bridge started to open while it was halfway across. Events 1460 - Wars of the Roses: Battle of Wakefield. 1816 - The Treaty of St Year 1952 ( MCMLII) was a Leap year starting on Tuesday (link will display full calendar of the Gregorian calendar. The AEC Regent III RT was a variant of the AEC Regent III. It was a Double-decker bus produced jointly between AEC and London Transport. ^[15]

On 5 April 1968 a Hawker Hunter FGA. Events 456 - St Patrick returns to Ireland as a missionary bishop Year 1968 ( MCMLXVIII) was a Leap year starting on Monday (link will display full calendar of the Gregorian calendar. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout 9 jet fighter from No. 1 Squadron RAF, flown by Flt Lt Al Pollock, flew under Tower Bridge. Unimpressed that senior staff were not going to celebrate the RAF's 50th birthday with a fly-past, Pollock decided to do something himself. Without authorisation, Pollock flew the Hunter at low level down the Thames, past the Houses of Parliament, and continued on to Tower Bridge. He flew the Hunter beneath the bridge's walkway, remarking afterwards it was an afterthought when he saw the bridge looming ahead of him. Pollock was placed under arrest upon landing, and discharged from the RAF on medical grounds without the chance to defend himself at a court martial. A court-martial (plural courts-martial) is a Military court. These military courts can determine Punishments for members of the Military subject ^[16][17] (See also: Hawker Hunter Tower Bridge incident. The Hawker Hunter Tower Bridge incident occurred 1968 - the fiftieth anniversary of the founding of the Royal Air Force. )

In May 1997,^[18] the motorcade of United States President Bill Clinton was divided by the 'unexpected' opening of the bridge. The President of the United States is the Head of state and Head of government of the United States and is the highest political official in United States by William Jefferson "Bill" Clinton (born William Jefferson Blythe III, August 19 1946 served as the forty-second President of the United States Thames sailing barge Gladys, on her way to a gathering at St Katharine Docks, arrived on schedule and the bridge was duly opened for her. A Thames sailing barge was a type of commercial Sailing boat common on the River Thames in London in the 19th century St Katharine Docks, in the London Borough of Tower Hamlets, were one of the commercial docks serving London, on the north side of the river Thames Returning from a Thames-side lunch at Le Pont de la Tour restaurant, with UK Prime Minister Tony Blair, President Clinton was less punctual, and arrived just as the bridge was rising. The Prime Minister of the United Kingdom of Great Britain and Northern Ireland is the political leader of the United Kingdom Anthony Charles Lynton "Tony" Blair (born 6 May 1953 is a British Politician who was Prime Minister of the United Kingdom from 2 May 1997 to The bridge opening split the motorcade in two, much to the consternation of security staff. A spokesman for Tower Bridge is quoted as saying, 'We tried to contact the American Embassy, but they wouldn't answer the 'phone. ' ^[19]

On 19 August 1999, Jef Smith, a Freeman of the City of London, drove a 'herd' of two sheep across the bridge. Events 43 BC - Octavian, later known as Augustus compels the Roman Senate to elect him Consul. Year 1999 ( MCMXCIX) was a Common year starting on Friday (link will display full 1999 Gregorian calendar) Freedom of the City is an honour bestowed by some municipalities in Australia, Canada, Ireland, France, Italy, New Zealand He was exercising an ancient permission, granted as a right to Freemen, to make a point about the powers of older citizens and the way in which their rights were being eroded. ^[20]

Tower Bridge today

Tower Bridge connects Borough to the heart of the City of London Financial District

Tower Bridge in its river setting, looking east from the viewing platform of The Monument. The Monument to the Great Fire of London, more commonly known as The Monument, is a 61 metre (202 ft tall stone Roman doric column in the City of London, near City Hall is the building shaped like a motorcycle helmet, and below it is HMS Belfast. City Hall is the headquarters of the Greater London Authority which comprises the Mayor of London and London Assembly. Early history The Town class cruisers were constrained to less than 10000 tons by the Washington Naval Treaty.

Road traffic

Tower Bridge is still a busy and vital crossing of the Thames: it is crossed by over 40,000 people (motorists and pedestrians) every day. ^[21] The bridge is on the London Inner Ring Road, and (as of 2007) is on the eastern boundary of the London congestion charge zone. The London Inner Ring Road is the name commonly given to a route formed from a number of major Roads that encircle the centremost part of London. The London congestion charge is a fee for some motorists travelling within those parts of London designated as the Congestion Charge Zone (CCZ (Drivers do not incur a charge by crossing the bridge. )

In order to maintain the integrity of the historic structure, the City of London Corporation have imposed a 20 miles per hour (32 km/h) speed restriction, and an 18 ton weight limit on vehicles using the bridge. The City of London Corporation (formerly known as the Corporation of London)is the municipal governing body of the City of London. A sophisticated camera system measures the speed of traffic crossing the bridge, utilising a number plate recognition system to send fixed penalty charges to speeding drivers.

A second system monitors other vehicle parameters. Induction loops and piezo-electric detectors are used to measure the weight, the height of the chassis above ground level, and the number of axles for each vehicle.

Bridge open to admit
HMS Northumberland (F238)

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

River traffic

The bascules are raised around 1000 times a year. Service history Construction She was built by Swan Hunter in 1992 at Wallsend, was launched by her sponsor Lady Kerr in April 1992 and was accepted ^[22] River traffic is now much reduced, but it still takes priority over road traffic. Today, 24 hours' notice is required before opening the bridge.

A computer system was installed in 2000 to control the raising and lowering of the bascules remotely. Unfortunately it proved less reliable than desired, resulting in the bridge being stuck in the open or closed positions on several occasions during 2005, until its sensors were replaced. ^[21]

Tower Bridge Exhibition

The high-level walkways between the towers gained an unpleasant reputation as a haunt for prostitutes and pickpockets and were closed in 1910. Prostitution is the act of performing Sexual activity in exchange for Money. This article is about the crime For the Robert Bresson film see Pickpocket (film. In 1982 they were reopened as part of the Tower Bridge Exhibition, an exhibition now housed in the bridge's twin towers, the high-level walkways and the Victorian engine rooms. The walkways boast stunning views of the River Thames and many famous London sites, serving as viewing galleries for over 380,000 tourists who visit each year. The exhibition also uses films, photos and interactives to explain why and how Tower Bridge was built. Visitors can access the original steam engines that once powered the bridge bascules, housed in a building close to the south end of the bridge. A steam engine is a Heat engine that performs Mechanical work using Steam as its Working fluid.

A Behind the Scenes tour can be booked in advance, during which it is possible to see the bridge's command centre, from where the raising of the bascules is controlled for a vessel to pass through, and go down into the bascule chambers too.

2008-2012 facelift

In April 2008 it was announced that the bridge will undergo a 'facelift' costing £4m, and taking four years to complete. The Pound Sterling ( symbol £; ISO code: GBP) subdivided into 100 pence (singular penny) is the Currency The work entails stripping-off the existing paint and repainting in blue and white. Each section will be enshrouded in scaffolding to prevent the old paint falling into the Thames causing pollution. Starting in summer 2008, contractors will work on a quarter of the bridge at a time to minimise disruption, but some road closures are inevitable. The bridge will remain open until winter 2010, but is then expected to be closed for several months. It is hoped that the completed work will last 25 years. ^[23]

Gallery

Tower Bridge at night	Tower Bridge area from the air	A slave ship moored by Tower Bridge to mark 200 years since the Slave Trade Act 1807 (April 2007)	Close-up of opened bascules
South view at dusk	Tower Bridge in a night setting with HMS Belfast (2007)	Tower Bridge viewed from St Paul's Cathedral	The south tower, showing pier at river level. See also Atlantic slave trade, Abolitionism The Slave Trade Act (citation 47 Geo III Sess Early history The Town class cruisers were constrained to less than 10000 tons by the Washington Naval Treaty.

See also

• Sequence showing the bridge opening
• Crossings of the River Thames
• Historic places adjacent to Tower Bridge:
  • Tower of London
  • St Katharine Docks
  • Shad Thames

References

External links

• Official website
• Bridge Lifting / Opening Dates and Times
• Technical article on the building of Tower Bridge

• The third steam engine (includes photo) – now at Forncett Industrial Steam Museum, Forncett St Mary, Norfolk
• Tower Bridge in the Structurae database
• 1878 article on Tower Bridge
• Tower Bridge information and photography
• Tower Bridge PhotoEssay
• Some Old Postcards of The Tower and Tower Bridge