Arches
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11 years ago

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Arches have been significant throughout history with their ability to hold tension in the structures as well as providing beauty to the building. They have been dated as far back as 200 A.D and there on wards have been used throughout different times and eras. From wood to stone, arches have graced churches, castles, houses and bridges. Arches have different types and form that are used for different purposes and with different materials. We would be discussing in details the types and construction of arches and where exactly can they be used.

Although arches have been dated back to 200 A.D and proof of them being used has been found in Mexico and the Levant (Lebanon, Syria, Jordan, Palestine, Israel, Cyprus, Hatay Province) but the Romans were the first to use arches to their full potential. There is a rare exception though in the form of Bronze Age arched city gate of Ashkelon which is modern Israel now, it dates back to 1850 B.C. The entire Roman Empire has a rich history of bridges, aqueducts and gates made from arches. The most common type of arch seen in the Roman Empire was the Vault, which were used for larger roofing and especially for the interiors. When a vault was used underground the floor provided all the resistance but when above ground thicker walls were used to give the resistance needed.

Triumphal, segmental and semicircular arches were also introduced by the romans as well. They explored every inch of an arch and knew that to eliminate tensile stresses in spanning a large amount of open spaces arches were the only solution. All the forces acting are resolved into compressive stresses. Their research and experiments also showed them that materials such as stone, cast iron and concrete strongly resist compression but they turn very weak when torsional stress and tension is applied to them. Using an arch makes the compressive forces stay together in equilibrium and this method can also be applied on frictionless surfaces. The only drawback the arches have in them is that the arch has an outward push at the base; this has to be restrained using angled cuts, bedrock or friction.

Building an arch, the most important thing to keep in mind is if the elements of arch will hold together or fall apart. One of the answers among many is to build a frame (historically always made of wood) which is in flow with the underside of the arch. This is called centering, and then voussoirs are laid in the shape until it is complete in self-support. For a much higher arch, scaffolding is required and it can be combined with the arch support.

The Basic arch is labeled below as:

Arches come in four basic shapes that frame and support windows, doors, porches and other wall openings.

(a)    Flat Arch

(b)   Triangular Arch

(c)    Round Arch

(d)   Pointed Arch

(a)Flat Arch:  An arch that has a horizontal intrados (Inner line of the arch) and a chamber to provide settling to the structure. This is also called a Jack Arch.

French Arch: This particular arch has the voissoirs inclined in the same angle on both sides of the center. This particular arch is considered weak.

(b) Triangular Arch: The material used is either wood or stone, is placed diagonally to support one another over an opening in the wall. Depending on the materials available the size is mostly limited, but with evolution materials to support and hold for years to come has increased the size and the spanning.

Corbel Arch:  each side until they meet in the center, a capstone (keystone) is placed to     complete the work.

(c) Round Arch:  They are normally either four centered or single centered. There are different types though.

Roman Arch: Intrados in this arch is semicircular and they are strongly rounded.

Segmental Arch: These arches have one more centers below the springing point, a
curve or an eyebrow is formed. It is called a segmental arch as it is made from
a  segment of a circle. This is the most common form and can be made both
from brick and stone.

Stilted Arch: The imposts act as the resting of the arch which acts as the continuous down
flow of the archivolt.

Bell Arch: Corbels are places for the arch to rest upon it and the faces of these corbels are curved.

Horse Show Arch: Also knows as the Moorish arch has an intrados which extends beyond
the springing line before it narrows down to form a rounded crown.

Basket Handle: The radius of the crown in this arch is much greater than the outer pair of curves,it is a three centered arch and it is also called Anse De Panier.

 Florentine Arch: The extrados of these arches are fixed from the central vertical axis than the intrados.

(d) Pointed Arch:  The center keystone of these arches is pointed rather than having a flat service.

Gothic arch: These arches have two centers and equal radii. They are pointed and were used a lot.

Lancent Arch:  These arches have two centers but the radius is greater than the
total span.

Drop /Depressed Arch: The radius is less than the span in these arches and the centers are two.

Ogee Arch:  The haunches in these arches are double in curve with a concave side.

Apart from these men made arches our nature has provided us with natural arches all across the globe. The definition of a natural arch would be

“A natural arch is a rock exposure that has a hole completely through it formed by the natural, selective removal of rock, leaving a relatively intact frame.”

Societies and organizations have dedicated years of experience and research studying these natural pieces of wonder that are perfection within themselves. These arches have been formed by wind or water erosion. Of course other natural elements also have a role to play with these arches.

If you like to construct arches, please contact Amer Adnan Associates today.

Below are the lists that have only a few manmade and natural arches from all across the globe.