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Transcript of Arch Bridges
design by Dóri Sirály for Prezi
Why is the basic structure unique?
This arch bridge structure is not only unique in design but holds vital advantages. Obviously, arch bridges are shaped in an arch, which means this semicircular structure offers very high resistance to forces that bend.
Another important benefit is the adaptability of the materials used in making the basic structure of the arch. Builders can use materials such as, brick and stone, when building the arch bridge. These materials allow to span a distance that materials other bridges use, will never be able to do.
And a significant convenience of having the basic structure of the bridge is because the arch is one of the most strongest structures to build and requires the least amount of materials.
When and where was the arch bridge first used?
One of the first arch bridge that is still in existence dates back to around 1300 BC and is was situated in Greece. The bridge was called Arkadiko Bridge, also known as the Mycenaean Arkadiko Bridge or the Kazarma Bridge. This particular bridge is a corbel, stone arch bridge which is a type of bridge that each higher set of material made for the bridge projects more towards the center to create a rough, arch shape. It is then craved to create the perfect arch. The Arkadiko Bridge is found in the southern area of Greece in Peloponnese. In Peloponnese, you will find the bridge near the road to Epidaurus from Tiryns.
What material is an arch bridge commonly constructed out of?
Arch bridges in the early past had been commonly constructed out of brick or stone. However, as of nowadays, builders use reinforced concrete or steel mostly to build these arch bridges. Out of the concrete and steel used, the most commonly used is the reinforced concrete.
For example, the Alcántara Bridge was built out of stone and had finished construction in 106 CE (Common Era) and the Arkadiko Bridge was also made out of stone and had finished construction at around 1300 BC (Before Christ). The Plougastel Bridge was constructed out of reinforced concrete, was finished in 1930 and the Schwandbach Bridge was assembled out of the same concrete, was finished in 1933.
So in the past, the material most used was stone and nowadays it would be reinforced concrete.
What are the limitations of the Arch Bridge
Over all the advantages of the Arch Bridge there are, of course, some limitations that can be crucial in some situations. One of which is, if you were to build a bridge crossing a large vast distance over the ocean (such as the Rio-Antirrio Bridge) and that bridge was to be built as an arch bridge, the bridges can be stuck in between the small degree where the start of the arch is on the sea meets the water.
Another one would be, arch bridges need a VERY stable and rigid foundation on the sides, abutments. If these aren't, then EVERYTHING would fall apart. All the tension of the bridge is directed to these supports which is why they need to be ultra firm. Plus, builders and engineers need to pay vital attention to these and must calculate the result after million of cars have gone over the road. One miscalculation can conclude to many deaths and severe injuries.
Finally, when building an arch bridge, you have a specific of span distance before the bridge is over weighed with weight and it isn't far compared to other bridges. The longest arch bridge is 1,741 m long and the longest bridge in general is 164,800 m. As you can see, the arch bridge is VERY far behind in the span distance.
The basic structure
Many bridges have been designed based on the arch bridge's structure. The structure consists of a rounded and semicircular design. The arch bridge is built in such a way that the weight of the bridge is diverted to the abutments at the sides of the bridge.
Abutments are constructions built to withstand the load of an arch. These abutments have the whole responsibility of making the bridge still and invulnerable to fall.
The support the abutments hold, first comes from the load on the central keystone. The keystone pushes down the adjacent rocks or materials and creates a firm path for traveling to the abutments on either side. From the abutments, the ground surrounding them pushes back the support to the central keystone. The support is then released there and pushed outward to help hold the load.
Famous Arch Bridge
A famous example of an arch bridge would be the Pont du Gard, which is an ancient aqueduct bridge that is situated in Vers-Pont-du-Gard, Gard in France. The bridge was constructed by Romans dating back to the 1st century AD. It crosses the Gardon River and is made out of shelly limestone. The Pont du Gard is the tallest of all the Roman bridges. Along with the Aqueduct of Segovia, the arch bridge is the most well preserved as well. The bridge has three levels of arches, with the top one being the smallest of them, the lowest being the tallest and the middle arch the middle of them both.
Why is it an arch bridge?
As I mentioned before the Pont du Gard is an ancient aqueduct and crosses the Gardon River. The bridge aqueduct was to carry waters from the spring located at Uzès. The waters of the spring were then carried to the Roman colony of Nîmes. But why is it an arch bridge? Well, most bridges that were created and constructed for the use of an aqueduct are arch bridges. Bridges could of course be not only in the structure and design of the arch bridge but they are the most commonly used when building an arch bridge aqueduct.