The Evolution of Bridges

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The Evolution of Bridges

• For as long as man has lived upon this earth he
  has expressed through bridges his will to
  overcome any obstacles encountered on the road to
  his goal.

2
Outline

• History of Bridges
• Design Style
• Perceived Environments
• Patterns of innovation
• Technology Push
• Market Pull

3
History of Bridges

• Pre-civilisation bridges Beams fallen across a
  stream. -gt Rope bridges
• 2000 BC According to Chinese tradition,
  stationary bridges existed in this period.
• 493 BC Timber (pontoon) bridges used during
  Persian military campaign.
• Early Roman Stone arch bridges, wooden framework
  used to hold the incomplete bridge. Use of
  concrete.
• 16th 18th Century After the collapse of Roman
  empire, no advance in bridge building. During the
  Renaissance advances in architecture and
  engineering.

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History of Bridges (2)

• 18th 19th Century Use of iron cables in
  suspension bridges and iron beams also used for
  the first time.
• 19th - 20th Century Mass production of steel
  begun. First suspension bridge which used steel
  cables by Johann Roebling. Use of concrete begun.
• 1879 Tay Bridge disaster at Firth of Tay at
  Dundee.
• 20th Century Steel replaced iron. Reinforced
  concrete bridges became common. Development
  Cantilever construction and Travelling formwork
  techniques.
• 1940 Tacoma Narrows Bridge disaster in city of
  Tacoma due to wind-induced oscillation.

5
Design Style

• The design of bridges has been mostly
  evolutionary with some revolutionary design.
• Evolutionary Timber bridges covered in order to
  protect them from the weather.
• Revolutionary Introduction of use of stone.

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Perceived Environments (1)

• Intrapsychic Environment
• Concept of bridges readily available in nature.
• Will to overcome obstacles.
• Rope bridges predecessors of modern suspension
  bridges.

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Perceived Environments (2)

• Construction/Manufacture Environment
• Early rope bridges were easy to build as they
  only required a rope to be secured at both ends.
• As the demands for more sophisticated bridges
  increased, construction techniques evolved.
• Wooden framework, Cantilever construction and
  travelling formwork.

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Perceived Environments (3)

• Adoption Environment
• Bridges, in general, were needed by communities,
  countries and empires, so they were easily
  salable.
• Initially, reinforced concrete bridges failed in
  this environment as they were not as
  aesthetically pleasing as stone bridges.

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Perceived Environments (4)

• Use Environment
• Bridge builders can design bridges for todays
  use.
• However, it has been difficult to predict
  bridges future use. For example, increased loads
  and, particularly, the change from one lane
  traffic to two lane traffic due to invention of
  automobiles.

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Perceived Environments (5)

• Failure Environment
• Bridges cannot fail!
• Possibly, severe loss of life and money.
• Collapse of Tacoma Narrows Bridge
• Loss of 6.4 million and death of a dog.
• The Tay Bridge disaster
• Loss of train full of 75 passengers.
• Maintenance in the form of regular checkups and
  paint for iron and steel bridges.

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Perceived Environments (6)

• Scrapping Environment
• Material from the bridges can be used again.
• Or the bridge itself can be recycled. (DHV Dutch
  office)
• Political/Ecological environment
• May ruin beauty of countryside.

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Patterns of Innovation

• More of the same
• Increased spans, heavier loads, and reducing
  wastage of materials and construction time.
• Passing over of quantity into quality
• Evolution of modern suspension bridges from rope
  bridges.
• Knights move
• Roman stone arch bridges.

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Technology Push

• Charm
• Will to overcome obstacles.
• Feasibility
• Full support from people as bridges have been
  vital in early and modern civilisation. Wood and
  stone naturally available.
• Belief that market exists
• Initially, small communities. Then, whole
  countries and empires.

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Market Pull

• There has always been a market pull for bridges.
  They were invented because there was need to
  cross an obstacle.
• Market pull has been increasingly rapidly due to
• Exploration
• Trade
• Colonisation
• Railroads
• Automobiles and motorways.

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Conclusion

• Unlike other inventions, bridges always had a
  market pull from the beginning.
• From trees and logs fallen across a stream to
  modern suspension bridges. Where now?
• Use of composite materials and polymers may make
  bridges lighter, longer and stronger. Spans of
  1km may be achieved.