Tower Bridge

A nighttime view of the historic Tower Bridge.

The bridge consists of two towers which are tied together at the upper level by means of two horizontal walkways which are designed to withstand the horizontal forces exerted by the suspended sections of the bridge to the left and the right. The vertical component of the forces in the suspended sections and the vertical reactions of the two walkways are carried by the two robust towers. The bascule pivots and operating machinery are housed in the base of each tower.

Tower Bridge is sometimes mistakenly referred to as London Bridge, which is actually the next bridge upstream. 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. Its present colour dates from 1977 when it was painted red, white and blue for the Queen's Silver Jubilee. Before this, it was painted a chocolate brown color.

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.

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. 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), was approved.

Jones' engineer, Sir John Wolfe Barry, devised the idea of a bascule bridge 800 feet in length with two towers each 213 feet high, built on piers. The central span of 200 feet 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 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 above the river at high tide.

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. - and employed 432 construction workers. E W Crutwell was the resident engineer for the construction.

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 George D. Stevenson took over the project. Stevenson replaced Jones' original brick facade with the more ornate Victorian Gothic style, which makes the bridge a distinctive landmark, and was intended to harmonise the bridge with the nearby Tower of London.

The bridge was officially opened on 30 June 1894 by The Prince of Wales (the future King Edward VII), and his wife, The Princess of Wales (Alexandra of Denmark).

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. It largely replaced Tower Subway, 400 m to the west, the world's first underground 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.

In April 2008 it was announced that the bridge will undergo a 'facelift' costing around eight million dollars, and taking four years to complete. 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.

**The bridge opened to river traffic in 1894, and is raised and lowered approx. 1,000 times per year.

**In 1952, a London bus had to leap from one bascule to the other when the bridge began to rise with the bus still on it. Luckily, no one was injured.

**The Tower Bridge is the only movable bridge of the 29 bridges on the Thames River.

The above photos are courtesy; Wikipedia, Wikimedia, Creative Commons, and public domain.
Background and design info courtesy Wikipedia.