The Evolution of Bridges Presentation)

8/8/2019 The Evolution of Bridges Presentation)

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The Evolution of Bridges

For as long as man has lived upon thisearth he has expressed through bridges his

will to overcome any obstacles

encountered on the road to his goal.


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Outline

History of Bridges

Design Style Perceived Environments

Patterns of innovation

Technology Push Market Pull


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History of Bridges Pre-civilisation bridges: Beams fallen across a stream. ->

Rope bridges

2000 BC: According to Chinese tradition, stationarybridges existed in this period.

493 BC: Timber (pontoon) bridges used during Persianmilitary campaign.

Early Roman: Stone arch bridges, wooden framework

used to hold the incomplete bridge. Use of concrete. 16th18th Century: After the collapse of Roman empire,

no advance in bridge building. During the Renaissanceadvances in architecture and engineering.


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History of Bridges (2) 18th19th 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. Firstsuspension bridge which used steel cables by JohannRoebling. 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 Cantileverconstruction and Travelling formwork techniques.

1940 Tacoma Narrows Bridge disaster in city ofTacoma due to wind-induced oscillation.


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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 constructionand 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 asaesthetically 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 onelane 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 checkupsand 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 fromrope 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 andstronger. Spans of 1km may be achieved.

The Evolution of Bridges Presentation)

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