How bridges are built?

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“Every bridge should join two shores. Utility and beauty”.

These are the words used by the Polish poet Stanisław Jerzy Lec to define the very essence of this type of infrastructure.
Bridges, since ancient times, have always met Man's need to connect his settlements with the surrounding territory. First in wood, and then in stone. And then, after the industrial revolution, in metal.
Bridges allowed Man to cross rivers, lakes, or any other type of natural or artificial obstacle, to go beyond. Bringing together places and peoples. To exceed every limit.

Let's discover, in this collection, the types of bridges, their parts, the materials used to build them, the phases required to build them.
A visual story dedicated to some of the world's most iconic bridges.

The simplest structure made of a horizontal beam and two or more vertical supports called piers.
The beam supports vertical loads, flexing and being subject to a horizontal compression on the top part, while the part under is subject to horizontal tension.
The supports do not flex but are only subject to compression.
When the bridge has more than one support it is called a "continuous beam bridge".

It features an arched deck. This type of bridge supports compression loads, transferring horizontal and vertical side forces that the foundations must contrast, to the sub-structure. This is why the foundation project presents greater complexity, while the structure above can generally require less material compared to a beam bridge of the same extension.

Featuring cables under tension and other rigid elements to which the deck hangs to.
Loads are transferred from the cables to the supporting towers that transfer the vertical thrust to the soil, and to the anchoring elements that mainly support traction towards the inside. Being suspended in the air, the deck must not move excessively under loads.

A suspended bridge whose deck is supported by stays connected to the supporting towers.
Stays are a series of cables under tension that are almost diagonal and that transfer vertical thrusts to the foundations through the towers, also keeping the deck horizontally compressed.

Which materials are used for bridges?

Bridges can be made with wood, masonry, metal or concrete.
The most ancient bridges are built with wood or stone. Metal and concrete bridges were possible after the Industrial Revolution, which brought to an extraordinary production of concrete and steel. These different materials are used today in various combinations: i.e. using reinforced concrete for the piles and steel for the deck.

The most ancient material that is though subject to quicker wear and deterioration, which is the reason why other materials were used. This is why there are not many wooden bridges today left to admire.

Stone is also a material that has been used since ancient times, probably even since pre-Roman Italy.

Since the 18th century, with the progresses made in working materials introduced during the
Industrial Revolution, the first cast iron bridges started to appear, which later on were made with wrought iron, and towards the end of the 19th century, in steel.

The most recent material to be used when building bridges is concrete that, with the use of reinforced steel, creates reinforced concrete.

The materials used to build bridges can also be used in different combinations building mixed bridges.

The foundation piles are built, which are the base upon which the entire bridge rests with its entire weight. The piles fix directly in depth in the rock substrate, going beyond the alluvial soil to ensure that they can resist the weight sufficiently.
The foundation piles are built by excavating deep holes where the cylindrical cages made of steel are subsequently filled with a jet of concrete.

Plinths are the reinforced concrete bases that connect piles to the sub-foundations and upon which the piles that support the entire weight of the deck, rest. To build the plinths, it is first important to proceed to excavate around the foundation piles; then, the steel reinforcement cages are positioned, which are subsequently covered by a jet of concrete. Quality tests and control activities are carried out during these first phases, in addition to the tests on the underground works.

Piles are pillars that support the concrete segments and the deck and that deliver the entire weight onto the sub-foundations. The progressive construction of the shaft of the reinforced concrete piles is done by using climbing formworks, special formworks that are raised as the structure develops in height, where the metal cages are consolidated with special concrete that performs excellently in terms of resistance.

The bridge deck is prepared, arranging and assembling the various elements of the spans that will then be raised in height.

The deck spans are raised at height, and then they are connected to the elements that have been already previously raised at height. Welding and bolting activities are then done according to the project requests. All raising activities can be carried out with high-reaching lattice cranes, SPMT trucks, hydraulic jacks and Strand Jacks.

Once the deck is finished, the reinforced concrete slab is then built. The asphalt and the safety elements and all the elements that make up the final road surface will be placed on it.

The bridge is completed by laying the asphalt paving, placing the safety elements of the bridge, the horizontal and vertical signalling systems and by creating the lighting system.

Tests requested by regulations are carried out to verify how the works perform in operating conditions.

Rome, Italy, 109 BC, Arch Bridge, stone and bricks
One of the oldest bridges in Rome

_{Photo by Livioandronico2013 - Own work, CC BY-SA 4.0, from WikCommons}

Vers-Pont-du-Gard, France, 17 BC, Arch Bridge, stone
UNESCO World Heritage

_{Photo by Patrick Clenet - Own work, CC BY-SA 3.0, from WikiCommons}

Lucerne, Switzerland, 1408 AC, Beam bridge, wood (deck) and stone (piles), stone and bricks (arch)
One of the oldest wooden bean bridges

_{Photo by Dennis Jarvis from Halifax, Canada, CC BY-SA 3.0, from WikiCommons}

Venice, Italy, 1591 AC, Arch bridge, stone

_{Photo by Wolfgang Moroder, CC BY-SA 3.0, from WikiCommons}

Paris, France, 1607 AC, Arch bridge, stone

_{Photo by gnuckx , CC BY-SA 3.0, from Flickr}

Iwakuni, Japan, 1633 AC, Arch bridge, wood (deck) and stone (piles)

_{Photo by Jakub Hałun - Own work, CC BY-SA 4.0, from WikiCommons}

Cambridge, UK, 1749 AC, Arch bridge, wood

_{Photo by Hadrianus1959 , CC BY-SA 4.0, from WikiCommons}

Ironbridge Gorge, UK, 1779 AC, Arch bridge, steel
First metal bridge in history - UNESCO World Heritage

_{Photo by Roantrum - Flickr, CC BY-SA 4.0, from WikiCommons}

Amarapure, Myanmar, 1851 AC, Beam bridge, wood
Longest wooden bridge, worldwide

_{Photo by mohigan, CC BY-SA 4.0, from WikiCommons}

New York City, New York, USA, 1883 AC, Suspended Bridge, steel (deck), stone (piles and towers)
Forst Steel bridge worldwide

_{Photo by Postdlf, CC BY-SA 4.0, from WikiCommons}

Edinburgh, Scotland, 1890 AC, Cantilever Bridge, steel
Heritage of humanity UNESCO

_{Photo by Unknown, Public Domain}

London, UK, 1894 AC, Suspended Bridge, mixed material

_{Photo by Fred Romero, CC BY-SA 4.0, from WikiCommons}

Landwasser, Switzerland, 1902 AC, Arch Bridge, stone

_{Photo by Kabelleger / David Gubler, CC BY-SA 4.0, from WikiCommons}

Québec, Canada, 1904 AC, Cantilever Bridge, steel
Longest bridge worldwide for several years

_{Photo by Musidoz, CC BY-SA 4.0, from WikiCommons}

Schiers, Switzerland, 1930 AC, Arch Bridge, concrete

_{Photo by Musidoz, CC BY-SA 4.0, from WikiCommons}

Sydney, Australia, 1930 AC, Arch bridge, steel

_{Photo by Rama, CC BY-SA 4.0, from WikiCommons}

San Francisco, California, USA, 1937 AC, Suspended Bridge, steel
Longest suspended bridge worldwide for several years

_{Photo by David Ball, CC BY-SA 4.0, from WikiCommons}

Italy, 1972 AC, Pushing arch bridge, mixed material
It’s the tallest pushing arch bridge worldwide

_{Webuild Image Library – Photo by Moreno Maggi}

Argentina, 1973 AC, Cable-stayed bridge, concrete
First example of large pre-composed concrete span

_{Webuild Image Library}

Alstahaug/Leirfjord, Norway, 1991 AC, Cable-Stayed Bridge, concrete

_{Photo by Heiko Hübscher, CC BY-SA 4.0, from WikiCommons}

Copenhagen/Malmö, Denmark/Sweden, 1998 AC, Cable-Stayed Bridge (section), steel (deck), concrete (towers)
Longest bridge in Europe

_{Photo by Nick-D, CC BY-SA 4.0, from WikiCommons}

Argentina, 2003 AC, Cable-stayed bridge, mixed media

_{Webuild Image Library – Photo by Moreno Maggi}

Millau, Francia, 2004 AC, Cable-Stayed Bridge, steel (deck and antennas), concrete (piles)
One of the tallest bridges worldwide

_{Photo by Nick-D, CC BY-SA 4.0, from WikiCommons}

Chonngqing, China, 2009 AC, Arch bridge, Steel

_{Photo by Graeme Bray, CC BY-SA 4.0, from WikiCommons}

Istanbul, Turkey, 2016 AC, Cable-Stayed Breidge, Steel (deck and antennas), concrete (towers)
Largest bridge worldwide in his category (59 m)

_{Photo by Rolfcosar , CC BY-SA 4.0, from WikiCommons}

Sydney, Australia, 2018 AC, Cable-stayed bridge, concrete
“2018 Project of the Year” - Engineering News-Record (ENR) “2018 Global Best Project” settore ferroviario / railway sector

_{Photo by Jonathan Pope from Glenbrook , CC BY-SA 4.0, from WikiCommons}