Tower Bridge

 

Tower Bridge

Tower Bridge from the south side at dusk

is a combined bascule and suspension bridge in London, over the River Thames. It is close to the Tower of London, from which it takes its name. It has become an iconic symbol of London.

The bridge consists of two towers tied together at the upper level by means of two horizontal walkways, designed to withstand the horizontal forces exerted by the suspended sections of the bridge on the landward sides of the towers. 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. The bridge's present colour scheme dates from 1977, when it was painted red, white and blue for the Queen Elizabeth II's silver jubilee. Originally it was painted a mid greenish-blue colour.

Tower Bridge is sometimes mistakenly referred to as London Bridge, which is the next bridge upstream.

The nearest London Underground station is Tower Hill on the Circle and District lines, and the nearest Docklands Light Railway station is Tower Gateway.

Design

 

Tower Bridge viewed from the top of London City Hall.

The bridge is 800 feet (244 m) in length with two towers each 213 feet (61 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 86 degrees to allow river traffic to pass. The bascules, weighing over 1,000 tons each, are counterbalanced to minimise 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.