Архитектура Аудит Военная наука Иностранные языки Медицина Металлургия Метрология
Образование Политология Производство Психология Стандартизация Технологии
Text 6: George P. Coleman Bridge
Location: Yorktown, Virginia, USA
Completion Date: 1952 (original), 1995 (reconstruction)
Cost: $9 million (original), $76.8 million (reconstruction)
Length: 3,750 feet
Type: Movable (double swing span)
Materials: Steel, concrete
Longest Single Span: 500 feet
Engineer(s): Parsons Brinckerhoff, Inc.
In the spring of 1995, the largest double-swing-span bridge in the United States was dismantled and replaced in only nine days. The George P. Coleman Bridge in Virginia was originally constructed in 1952 as a two-lane highway designed to carry no more than 15,000 vehicles a day. By 1995, the population around the bridge had increased so much that the structure was carrying in excess of 27,000 vehicles a day.
To make matters worse, the machinery that rotated the massive swing spans often experienced mechanical problems. In short, the bridge was a major headache. Engineers considered several designs to ease congestion -- from building a tunnel to constructing a new bridge upstream -- but the least expensive option proved to be reconstruction of the existing bridge. So between May 4 and May 13, 1995, about 2,500 feet of truss and swing spans -- complete with pavement, lightpoles, and barrier walls -- were floated in six sections over 40 miles from Norfolk, Virginia, to the bridge site. It marked the first time in engineering history that such an enormous bridge was assembled off site and floated into place.
The new four-lane bridge is three times wider than the original bridge and can now carry up to 50,000 vehicles daily.
· The George P. Coleman Bridge is the largest double-swing-span bridge in the United States and the second largest in the world.
· The new bridge weighs only 25 percent more than the original because the new spans are made of lightweight, high-strength steel.
· The two main river piers contain mechanisms that lift the swing spans to different elevations so they don’t hit each other when they rotate.
I. Answer the following questions:
1. How can you prove that the George P. Coleman Bridge is the second largest double-swing-span bridge in the world?
2. Do you agree that before the reconstruction the bridge was a major headache?
3. What is peculiar about the George P. Coleman Bridge?
4. How many vehicles can it carry nowadays?
5. How is it possible that swing spans don’t hit each other while rotating?
II. Match the meanings of these terms with their definition:
III. Fill in the correct prepositions:
to find a solution … the river crossing problem, to be assembled … site and floated … place , the central span … 200 feet … the towers, the structure carries … excess … 27,000 vehicles … a day, to propose a design … a bascule bridge 244 m … length … two towers each 65 m … high, to be raised … an angle …86 degrees
IV. Say in other words:
Tower Bridge was built because of the demand for access across the Thames. A tunnel under the Thames could only carry pedestrian traffic. Although each leave of the bridge weighs quite much, they are counterbalanced to limit the force and time necessary to raise them. Two heavy piers were put into the river bed to support the structure. Victorian gothic style makes the bridge a distinguishing landmark.
V. Reconstruct the following texts and title them:
1. London … (noun) is a bridge …(adverb) the River … (proper noun) in London, connecting the …(adjective) centre of the city to the district of Southwark. … (preposition) 1750 it was the only bridge … (participle 1) the Thames in London. The present bridge , … (participle 11) in 1973, replaced one that was sold to a US businessman and rebuilt in Arizona.
2. … (noun) bridge is a bridge across the … (noun) Thames and is one of the most … (adjective) structures in London. It was … (participle 11) between 1886 and 1894 and is close to London … (noun) and the Tower of London. Its towers are in … (adjective) style and the part of the bridge with the road on … (pronoun) can be … (participle 11) to allow ships to pass through.
Последнее изменение этой страницы: 2016-03-16; Просмотров: 36; Нарушение авторского права страницы