What is an arch/arch definition?
In architectural and civil engineering, an arch is a curved member that is used to span an opening and support loads from above.
It can be constructed using many different materials like stone brick RCC etc. Arches are also constructed in different shapes, giving us the same motive.
Function of arches
- Create opening
- Give light & ventilation
- Reduces the weight of the building
- Good looking
Arch history / who invented the arch?
Q) Who invented the arch?
Ans:- Arch have invented in the second thousand years BC in Mesopotamian block architecture, & their precise utilization began with the old Romans, who were the primary ones to use the procedure of large scope of construction.
Since it’s an unadulterated pressure structure, the arch is effective in the actual fact that a lot of structure materials, including un-reinforced concrete, can oppose pressure, however, are frail when malleable pressure is applied to them.
History of arches
- Ture arches, as opposed to corbel arches, were known by a number of civilizations in the Ancient Near East, the Levant, and Mexico, but their use was infrequent & mostly confined to underground structures like drains where the matter of lateral thrust is greatly diminished.
- A rare exception is the bronze age arched city gate of Ashkelon, dating to ca. 1850 B.C.
- An early example of the Voussoir arch appears in the Greek Rhodes Footbridge.
- In 2010, a robot discovered a long arch-roofed passageway underneath the pyramid of Quetzalcoatl which stands in the ancient city of Teotihuacan north of Mexico City, dated to around 200AD
- The ancient Romans learned about the arch from the Etruscans, refined it & were the first builders to tap its full potential for above-ground buildings.
- Throughout the Roman empire, their engineers erected arch structures such as bridges, aqueducts & gates.
- They also introduced the triumphal arch as a military monument.
- Vault began to be used roofing large interior spaces such as assumed by domed structures from the first century BC onwards.
Parts of an arch
The different parts of an arch are given below:
- Intrados:- Intrados is the inner curve of the arch.
- Soffit:- The inner surface of the arch is called a soffit. Sometimes, intrados and soffit are treated as synonymous.
- Extrados or back:- The outer surface of an arch or the outer curve of the arch ring is known as extrados.
- Voussoirs or arch blocks:- Voussiors are the wedge-shaped units forming the courses of an arch.
- Crown:- The highest point of the extrados is known as the crown.
- Key-stone:- The highest central wedge-shaped block of an arch is called key-stone.
- Arcade:- A row of arches supporting a wall above and being supported by the piers is called an arcade.
- Abutment:- The end support of an arcade is called an abutment.
- Piers:- The intermediate supports of an arcade is called piers.
- Springing points:- Springing points are the points from which the curve of arch springs.
- Springing line:- Springing line is an imaginary line joining the two springing points.
- Skewback:- Skewback is the inclined or splayed surface on the abutment.
- Springer:- Springer is the first voussoir level on either side of an arch and it is adjacent to the skewback.
- Span:- The clear horizontal distance between the supports is known as span.
- Rise:- Rise is the vertical distance between the springing line & highest point on the intrados.
- Centre:- The geometrical center of the curve of an arch is called center of arch.
- Ring:- The circular course forming an arch is called a ring.
- Depth or height:-The perpendicular distance between the intrados and extrados is known as depth or height.
- Spandrel:- The irregular triangular space formed between the intrados and extrados is known as a spandrel.
- Haunch:- The lower half portion of the arch between the crown and the skewback.
- Thickness or breadth of soffit:- This is the horizontal distance measured perpendicular to the front and back faces of an arch.
- Impost:- This is the projecting course at the upper part of a pier or an abutment to stress the springing line.
Types of arches
A) Types of arches based on the shape
1) Flat arches:- In this arch, the intrados is apparently flat and it acts as a base of an equilateral triangle which was formed by the horizontal angle of 60 degrees by skewbacks. Extrados is also horizontal & flat. These flat arches are generally used for light loads & for spans up to 1.5 m.
2) Segmental arch:- Segmental arch is the basic type of arch. This arch is used for buildings in which the center of the arch lies below the springing line. The thrust transferred in an inclined direction to the abutment in a segmental arch.
3) Semi-circular arch:- The shape of the semi-circular arch curve is semi-circle & the thrust transferred to the abutment is perfectly vertical direction since the skewback is horizontal. The center in the semi-circular arch lies exactly on the springing line.
4) Horseshoe arch:- The shape of this arch is a horseshoe that curves more than a semi-circle. This is taken in account for architectural provisions.
5) Pointed arch:- Pointed arch is also called a Gothic arch. Two arcs of circles are met at the apex hence triangle is created. This could be either isosceles or equilateral.
6) Stilted arch:- This arch consists of a semi-circular arch within2 vertical portions at the springing. The arc center lies on the horizontal line through the tops of vertical portions.
B) Types of arches based on the number of centers
1) One-centered arch:- Segmental, semi-circular, flat, horse-shoe arches & stilted arches are called one-centered arches. In some cases, a perfectly circular arch is provided for circular windows & is known as a bull’s eye arch also come under this category.
2) Two centered arches:- Pointed or gothic or lancet arches come under this type.
3) Three centered arches:- Semi elliptical & Florentine arches are generally having three numbers of centers.
4) Four-centered arches:- Venetian & Tudor arches are typical examples of four-centered arches.
5) Five-centered arch:- A good arch having a semi-elliptical in shape contains five centers.
C) Types of arches based on construction materials
1) Stone arches:- In this type of arches, the stones are cut in proper shape and fully dressed, joined with cement mortar. It is also used to make flat arches.
2) Brick arches:- Brick arches are sub-divided into:
3) Rough brick arches:- These arches are constructed with ordinary bricks without cutting to the shape. The arch curves are formed by wedge-shaped joints with greater thickness at extrados & smaller thickness at intrados. So, this type of arch looks unattractive.
4) Axed brick arches:- In this arch, the bricks are cut with the help of a brick axe into a wedge shape. So, these are roughly depressed in size & shape. Thus, the axes brick arch is not very pleasant.
5) Gauged brick arches:- In this arch, bricks are cut to the required shape & size with the help of a wire saw. The bricks are finely dressed & joined by lime putty.
6) Purpose-made brick arches:- The bricks are manufactured, matching with the required shape & size to get a very finely workmanship.
7) Concrete arches:- Concrete arches are two types:
8) Precast concrete block arches:- In these arches, the blocks are cast in molds to exact shape & size. For keystone & skewbacks, special molds are prepared. The appearance of this arch is good because of its exact shape & size. M15 grade of concrete is used.
9) Monolithic concrete block arches:- Monolithic arches are suitable for a longer span. It is constructed from cast-in-situ concrete. It may be plain or reinforced concrete, depending upon the span & magnitude of loading.
An arched structure, usually made of brick, stone, or concrete, is used as a ceiling or canopy or as a support for the roof.
Masonry walls are composed of wedge-shaped pieces called voussoirs, which are held in place by the pressure of the neighboring pieces. A temporary supporting structure must be erected in the vaulted area in the construction.
A tunnel vault or barrel vault, maybe a tunnel-like, semi-cylindrical extension of an arch, can be thought of as an unbroken series of arches pressed together, one behind the other.
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