Hey everyone!

I am an Engineer currently occupied as a research scientist for the National Technical University of Athens. I've always thought that the blockchain technology can be used to fight suppression of information, therefore I've decided to launch a series of engineering blogs, sharing my humble knowledge for free with everyone on Steemit. All information provided is taken from my notebooks, gathered throughout the years. It's a win - win situation as far as I'm concerned, as I get the chance to combine and practice two different things that I love; blogging and engineering. I also love sharing. So, this is my second blog regarding Engineering.

This time I'm taking the chance to share some technical and historical information about one of the most important and amazing types of construction.

History

The very first bridges, made of stone and logs, could be lifted and placed precisely. In cases where wider bridges were needed, engineers would construct piers as intermediate support units in certain places in the stream, in order to place beams of wood that would form a continuous bridge.

There is a number of magnificent arch bridges that were built in Mesopotamia, China and Egypt in the ancient times. However, the greatest bridge-builders of all are the Romans without a doubt, as there is a number of Roman arch bridges which were constructed using heavy piers that still exist today. For instance the bridge of Fabricius which was constructed in 62 BC. and the Sant' Angelo bridge, built in 136 AD. are reminders of the Romans' superiority in bridge construction. Both bridges are situated in Rome.

The Fabricius Bridge (62 BC.) / Source: euratlas.com

The Sant' Angelo bridge (136 AD.) / Source: aviewoncities.com

Materials & Construction

Stone, brick and wood were the most commonly used materials in the construction of bridges until approximately 1800 AD. There are several stone bridges in England that are more than 300 years old. Iron was not being used in bridge construction until the 18th century, with the first iron bridge being built in 1779. Iron would then be widely used for the construction of large bridges for over a century.

The development of transportation systems consisting of railroads and highways, along with the rapid growth in mercantile activity inevitably induced a greater need for bridges. A whole new series of technical problems occured. With progress come problems! Spans had to be stronger and more rigid in order to withstand the crossing locomotives' weight. Fortunately, engineers managed to overcome this obstacle by developing methods of producing steel affordably in the 19th century, therefore accomplishing to replace iron with the new alloy in bridge construction.

Steel, as a purified alloy of carbon and iron manufactured in the liquid state, is very pliable and ductile, and thus can be produced in a variety of different degrees of hardness. Manufacturing steel without the mining of three essential raw materials (iron ore, coal and limestone) is impossible. Measured quantities of various chemical elements are necessary as well and have to be added later in order to make alloy steels. Despite the fact that iron is the fourth most abundant element on Earth, exceeded only by oxygen, aluminium and silicon, it's rather difficult for iron to occur in nature as a pure metal. Iron hates loneliness! Therefore it is often chemically imprisoned in compounds that it forms with surrounding elements.

It's known that cast iron, wrought iron and steel are all mixtures of carbon and iron. It is also a known fact that carbon is responsible for those mixtures' strength. Inevitably, due to its properties and behaviour demonstrated in standard temperature and pressure conditions, steel not only became one of the most versatile materials of construction, but also one of the most important materials of the modern world.

Design

Nowadays bridges are made of steel and reinforced concrete, or even aluminium in certain cases. There is a noticeable range of different designs as well.

The main types are:

• Girder Bridges (using supports at either end)
• Arch(ed) Bridges (situated on arched vaults)
• Suspension Bridges (framework hung from high masts)
• Cable-Braced Bridges (framework hung from columns)
• Lattice Bridges (steel bridges)
• Pontoon Bridges (floating bridges)

Bow-String Girder Bridge in Texas./ Source: learntocivilfield.com

Arch(ed) Bridge in Burgundy, France./ Source: pixabay.com

Suspension Bridge in San Fransisco./ Source: pixabay.com

Cable-Braced Bridge in Warsaw./ Source: pixabay.com

Lattice Bridge in Portland, Oregon./ Source: pixabay.com

Pontoon Bridge in Hamburg, Germany./ Source: questionreponse.info

In addition to those different types of stationary bridges mentioned above, there are also three main types of moveable bridges, which are bridges that move in order to allow passage for boats or barges. Making bridges moveable decreases the cost significantly as there is no need for high piers, however this comes with the disadvantage of halted traffic.

Bridge movement is generally powered by electric motors, some bridges are even operated by users with boats. There are also bridges that are remotely controlled using cameras and others operated by a bridgeman. Even though moveable bridges in their entirety can be quite long, it's fair to say that their moving portions are relatively small, restricted by engineering and cost considerations.

The main types are:

• The Draw-Bridge (associated with castles and towers, surrounded by a moat)
• The Swing Bridge (moves horizontally)
• The Bascule Bridge (moves vertically on the see-saw principle)

Draw-Bridge in Sonderborg, Denmark./ Source: alamy.com

Swing Bridge in Karosta, Latvia./ Source: pixabay.com

Bascule Bridge in Schlei, Germany./ Source: pixabay.com

IMAGE SOURCES:

pixabay.com / alamy.com / euratlas.com / questionresponse.info / learntocivilfield.com / aviewoncities.com

REFERENCES:

University Textbooks and Lecture Notes:

• Getting Familiar with Technical Terms for Architects, Civil Engineers and Surveying Engineers, New Technology Publications - ELENI KOLETHRA (National Technical University of Athens, School of Civil Engineering university textbook)

• Συστήματα Σιδηροδρομικών Μεταφορών (Υποδομή, Τροχαίο Υλικό, Εκμετάλλευση), Εκδόσεις ΖΗΤΗ. / Rail Transport Systems (Infrastructure, Materials, Exploitation Rates), ΖΗΤΗ Publications. - PIRGIDIS CHRISTOS (National Technical University of Athens, School of Rural & Surveying Engineering university textbook.)

• Tεχνικά Υλικά / Technical Materials - MICHAEL SAKELLARIOU (National Technical University of Athens, School of Rural & Surveying Engineering course lectures)

• Δημόσια Έργα, Εκδόσεις Παπασωτηρίου / Public Constructions, Papasotiriou Publications. - CHATZOPOULOU ALIKI (National Technical University of Athens, School of Civil Engineering university textbook.)

• Τεχνική Μηχανική (Αντοχή των Υλικών), Εκδόσεις Συμμετρία / Technical Engineering (Strength of Materials), Symmetria Publications. - MARKETOS EVANGELOS (National Technical University of Athens, School of Rural and Surveying Engineering university textbook.)

Internet Links:

• https://en.wikipedia.org/wiki/Bridge

• https://www.steelconstruction.info/Steel_material_properties

• https://en.wikipedia.org/wiki/Strength_of_materials

• http://www.bridgedesign.org.uk/parts/pier.html

• http://www.engineering-timelines.com/scripts/engineeringItem.asp?id=319

• https://en.wikipedia.org/wiki/Moveable_bridge

Thank you for your attention!
Hope you enjoyed this post and did learn a thing or two.
Follow me and stay tuned for more engineering blogs every day.

Highest Regards
@lordneroo