Tower Bridge
History
Tower Bridge 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. The bridge was built between 1886 and 1894. 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. The design was a result of a public competition, and the winning design was submitted by Sir Horace Jones, the City Architect, in collaboration with Sir John Wolfe Barry.
The bridge's construction was a response to increased commercial development in the East End of London, which required a new river crossing downstream of London Bridge. The design had to allow for the passage of tall ships while maintaining road traffic flow. The solution was a bascule bridge, with two leaves that could be raised to allow river traffic to pass.
Design and Construction
The bridge's design combines elements of both bascule and suspension bridge engineering. The central span of the bridge is split into two equal bascules or leaves, which can be raised to an angle of 86 degrees to allow ships to pass. Each bascule weighs over 1,000 tons and is counterbalanced to minimize the effort required to raise them. The bascules are operated by hydraulic power, originally using steam engines, but now powered by oil and electricity.
The two towers are constructed on piers, providing stability for the bridge. The towers are connected by two horizontal walkways at the top level, designed to withstand the horizontal forces exerted by the suspended sections of the bridge. These walkways also provide pedestrian access when the bascules are raised.
The bridge is clad in Cornish granite and Portland stone to protect the underlying steel structure and to give it a more aesthetically pleasing appearance. The bridge's total length is 244 meters (800 feet), with the longest span measuring 61 meters (200 feet). The height of the towers is 65 meters (213 feet).
Technical Specifications
Tower Bridge is a marvel of Victorian engineering, incorporating both bascule and suspension bridge elements. The bascules are raised using a sophisticated hydraulic system, originally powered by steam and now by oil and electricity. The hydraulic system uses accumulators to store energy, which can be released quickly to raise the bascules.
The bridge's suspension elements consist of two main chains, anchored at each end and passing over the tops of the towers. These chains support the central span and distribute the load to the towers and anchorages. The chains are made of wrought iron, a common material for bridge construction in the 19th century.
The bridge's roadways are made of timber, supported by a steel framework. The walkways at the top of the towers are also constructed of steel, with timber decking. These walkways provide a unique vantage point for viewing the river and the city.
Maintenance and Modifications
Over the years, Tower Bridge has undergone several modifications and maintenance projects to ensure its continued operation. In the 1970s, the original steam-powered hydraulic system was replaced with an electro-hydraulic system, which is more efficient and easier to maintain. The bridge's roadways have also been resurfaced several times to accommodate modern traffic loads.
In 2008, a major renovation project was undertaken to clean and repaint the bridge, as well as to replace the timber decking on the walkways. The project took four years to complete and cost over £4 million. The bridge is now painted in a blue and white color scheme, which was chosen to commemorate the Queen's Silver Jubilee in 1977.
Cultural Significance
Tower Bridge is one of London's most iconic landmarks and a symbol of the city's industrial heritage. It is a popular tourist attraction, with visitors able to explore the towers, walkways, and engine rooms. The bridge is also a vital part of London's transport infrastructure, carrying thousands of vehicles and pedestrians each day.
The bridge has appeared in numerous films, television shows, and advertisements, further cementing its status as a cultural icon. It is often used as a backdrop for events and celebrations, such as the annual London Marathon and the New Year's Eve fireworks display.