Read the text and make a pencil drawing of Old London Bridge.

The River Thames in London is graced with a score of bridges and a barrier. Historical evidence proves that London Bridge is the earliest in Great Britain and dates back to the time when the Roman Emperor Claudius invaded Britain. The Romans built the first London Bridge by AD 60. It replaced the wooden Celtic structure, but the Danes destroyed the first London Bridge in 805. The bridge was rebuilt but collapsed in 1091, and its next replacement burned down in 1136.

By 1209, the Old London Bridge was rebuilt by a self-taught builder who used rather simple building techniques. It was the first great stone arch bridge built in Europe, after the Romans. Its total length was about 300 m and the spans were 20 m high above the water. The bridge consisted of 19 pointed arches, each with a span of approximately seven metres built on piers six metres wide; a 20^th opening was a wooden drawbridge. The stone foundations of the piers were built inside cofferdams made by driving timber piles into the riverbed; these in turn were surrounded by starlings (loose stone filling enclosed by piles). As a result, the arch spans actually varied from five to ten metres and the width of the protective starlings was so great that the total waterway was reduced to a quarter of its original width and the bridge looked as if it were a dam on the river. It caused essential water level differences, which was very dangerous for boats and “running the rapids” became one of the thrills of Londoners.

Almost immediately Old London Bridge became renowned throughout Europe for its chapel, many-storied houses, built above the shops, which lined both sides of the roadway between the fortified gates at either end, and the heads of traitors which were stuck on the gate spikes until the 17^th century. The bridge became not only a residential site but also an important commercial crossing on the river. It was an overcrowded village with walkways between the buildings. From time to time, it suffered from fires though everything and the bridge itself were built in stone. In 1282, five arches of the Old London Bridge collapsed under the pressure of winter ice.

By 1762 all the houses were removed, the carriageway was widened to 14 m, and the two central arches were replaced by one great arch at mid span. The removal of the central pier led to serious erosion of the riverbed, and gravel was constantly poured to protect the remaining piers. Finally the maintenance became too much of a burden, and a new granite structure was built several yards upstream by Sir John Rennie. He proposed five semi elliptical stone arches, with central span reaching 46 m, the next two 43 m, and the two shore spans 40 m. In 1831, the new bridge was opened, and the ancient structure disappeared. Rennie’s bridge survived less than 140 years. Between 1968 and 1971, its stone facing was dismantled and sold to an American company, which shipped the old bridge stone-by-stone across the Atlantic Ocean to the USA. There it was re-erected in a theme park in Arizona.

Harold Knox King built the modern London Bridge in 1972. He replaced Rennie’s stone arches with beams of pre-stressed concrete reaching 104 m in overall span length. Construction was carried out using the cantilever method with segments being built outward from piers. In the centre, the two cantilevers did not meet leaving a space into which the builders placed a concrete beam to complete the span. The design represents a major post-World War II innovation in bridge engineering.

Part II